FEDERAL RESEARCH, TECHNOLOGY, AND DEMONSTRATION
PROGRAMS IN AVIATION NOISE
Prepared by the
Federal Interagency Aviation Noise Research Panel
March 1978
U.S. Environmental Protection Agency
Office of Noise Abatement and Control
Washington, D.C. 20460
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PREFACE
The Noise Control Act of 1972 directs EPA to establish
the effective coordination of Federal research and develop-
ment activities in noise control, and to compile and publish
periodic reports on the status and progress of these actions.
The Federal noise research coordination activity was
initiated in early 1974. Four interagency research panels
were established in the areas of:
(1) Aviation
(2) Surface transportation
(3) Machinery
(4) Noise effects.
The panels issued reports in the March-June 1975 time
period summarizing the fiscal year 1973 through 1975 on-
going and planned noise research, technology, and demonstra-
tion (RT&D) programs within the various agencies of the
Federal Government.
During 1976, the four panels were reestablished to
develop an up-to-date summary of Federally-sponsored noise
RT&D programs, to assess their adequacy to meet national
objectives for noise abatement, and to identify technology
needs to support a national noise abatement strategy.
The Federal Interagency Aviation Noise Research Panel
included representatives of the agencies principally con-
cerned with aviation noise abatement and research. They
include the National Aeronautics and Space Administration
(NASA); the Department of Defense (DOD), Departments of
the Air Force, Army, and Navy; and the Environmental Pro-
tection Agency (EPA/ONAC). The Department of Housing and
Urban Development (HUD) was also represented because of
their interest in aircraft noise abatement through land
use planning and noise attenuating building practices.
HUD sponsors no research in aircraft source noise reduction.
Mr. Harry W. Johnson, Director of NASA's Aeronautical Pro-
pulsion Division, served as chairman of the panel. NASA
currently sponsors the bulk of aviation noise research pro-
grams within the Federal Government. EPA served as the
secretariat.
The information, assessments, conclusions, and recom-
mendations in this report are the consensus of the panel
members and are not necessarily the official views of the
agencies.
iii
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PREFACE BIBLIOGRAPHY
These reports are available from the National Technical Information
Service, Springfield VA. 22151.
1. First Report on Status and Progress of Noise Research and Control
Programs in the Federal Government, Volumes I and II, U.S.
Environmental Protection Agency, June 1975, NTIS No. PB-243447/AS
(Vol. 1), PB-243448/AS (Vol. 2).
2. Federal Surface Vehicle Noise Research, Development and Demonstration
Programs; FY73-FY75, U.S. Environmental Protection Agency, March
1975, NTIS No. PB-234992/AS.
3. Federal Aircraft Noise Research, Development and Demonstration Pro-
grams: FY73-75, U.S. Environmental Protection Agency, March 1975,
NTIS No. PB-244904/LK.
4. Federal Machinery Noise Research, Development and Demonstration Pro-
grams: FY73-FY75, U.S. Environmental Protection Agency, May 1975,
NTIS No. PB-243523/LK.
5. Federal Noise Effects Research: FY73-FY75, U.S. Environmental
Protection Agency, March 1975, NTIS No. PB-241751/LK.
6. An Assessment of the Federal Noise Research, Development and Demon-
stration Activities: FY73-75, U.S. Environmental Protection Agency
June 1975, NTIS No. PB-246894/LK.
IV
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FEDERAL INTERAGENCY AVIATION NOISE
RESEARCH PANEL MEMBERSHIP
Chairman: Harry W. Johnson
Director, Aeronautical Propulsion Division
National Aeronautics and Space Administration
Gordon Banerian NASA
Thomas R. Dashiell DOD
Robert J. Koenig DOT/FAA
John D. Powers DOT/FAA
William C. Sperry EPA/ONAC
George E. Winzer HUD
Secretariat: Harvey J. Nozick, EPA/ONAC
Roger W. Heymann
Thomas L. Quindry
ACKNOWLEDGMENTS
In addition to the formal members, Messrs. J. Gary
Hicks (NASA) and John E. Wesler (DOT/FAA) contributed sub-
stantially to the inputs to this report. Assistance in
preparation of the report was provided by Dr. R. J. Kevala
and Mr. G. L. McLennan of the consulting firm of Booz,
Allen Applied Research.
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TABLE OF CONTENTS
Page
Number
PREFACE iii
FEDERAL INTERAGENCY AVIATION NOISE RESEARCH
PANEL MEMBERSHIP V
INDEX OF TABLES ix
INDEX TO AVIATION NOISE PROJECTS xi
1.0 INTRODUCTION 1-1
1.1 Purpose and Scope of the Report 1-1
1.2 Organization of. the Report 1-1
2.0 SUMMARY 2-1
3.0 AGENCY PROGRAMS 3-1
3.1 National Aeronautics and Space
Administration 3-3
3.2 Department of Defense 3-9
3.3 Department of Transportation 3-17
3.4 Environmental Protection Agency 3-19
3.5 Department of Housing and Urban
Development 3-21
Vll
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Page
Number
4.0 ASSESSMENT
4.1 Introduction 4-L
4.2 Techniques Available for Aircraft Noise
Abatement 4-3
4.3 Source Noise Abatement Technology Use
Considerations 4-5
4.4 National Aviation Noise Abatement Goals 4-7
4.5 Summary and Analysis of Agency Programs 4-11
4.6 Program Assessment 4-21
4.7 Conclusions and Recommendations 4-25
APPENDICES
A Summary Tables of Aviation Noise
RT&D Funding and Manpower A-l
B National Aeronautics and Space
Administration Aviation Noise
RT&D Program B-l
C Department of Defense (Air Force,
Army, and Navy) Aviation
Noise RT&D Program C-l
D Department of Transportation
(Federal Aviation Administration)
Aviation Noise RT&D Program D-l
E Environmental Protection Agency
Aviation Noise RT&D Program E-l
F Bibliography F-l
Vlll
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INDEX OF TABLES
Page
Number
1-1 Aviation Noise RT&D Program Categories 1-2
3-1 Funding and Manpower Summary, National
Aeronautics and Space Administration 3-7
3-2 Funding Summary, Department of Defense
(Air Force, Army, and Navy) 3-10
3-3 Funding Summary, Department of the Air
Force 3-12
3-4 Funding Summary, Department of the Army 3-14
3-5 Funding Summary, Department of the Navy 3-15
3-6 Funding and Manpower Summary, Department
of Transportation (Federal Aviation
Administration) 3-18
3-7 Funding and Manpower Summary,
Environmental Protection Agency 3-20
A-l Summary of Aviation Noise RT&D Funding and
Manpower by Agency A-3
A-2 Summary of Aviation Noise RT&D Funding and
Manpower by Program Category and Agency A-5
B-l Funding and Manpower Summary, National
Aeronautics and Space Administration B-2
C-l Funding Summary, Department of Defense
(Air Force, Army, and Navy) C-3
C-2 Funding Summary, Department of the Air
Force C-4
IX
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Page
Number
C-3 Funding Summary, Department of the Army C-5
C-4 Funding Summary, Department of the Navy C-6
D-l Funding and Manpower Summary, Department
of Transportation (Federal Aviation
Administration) D~3
E-l Funding and Manpower Summary, Environmental
Protection Agency E-3
x
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INDEX TO AVIATION NOISE PROJECTS
Page
Number
RESEARCH AND TECHNOLOGY PROGRAMS
PROPULSION NOISE
Combustion Noise Characterization B-4
Jet Noise and Suppressors B-6
Forward Velocity Effects on Jet Engine
Exhaust Noise B-8
Fan/Compressor/Turbine Noise Reduction B-10
Forward Velocity Effects on Fan Noise B-13
Internal Noise Transmission Through
Turbines and Nozzles B-15
Duct Acoustic Treatment Projects B-17
Propeller Studies B-20
Supersonic Jet Exhaust Noise Investigation
(Density Model) C-7
Supersonic Jet Exhaust Noise Investigation
(Velocity Model) C-8
Sound Transmission Through Supersonic Jets C-9
Duct Acoustics Research C-ll
Noise Suppression in Jet Inlets C-13
Propulsion System Noise C-24
Jet Engine Ground Run-up Noise Suppression C-28
XI
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Page
Number
Jet Noise Research D-4
Core Engine Noise Control D-5
Small Propeller Technology E-4
ROTOR NOISE
Helicopter Rotor Noise Control B-22
Helicopter Rotor Noise C-25
INTERIOR NOISE
General Cabin Noise Research B-24
Sound/Structure Interaction B-26
AIRFRAME NOISE
General Airframe Noise B-28
Aerodynamic Noise B-30
Flow Interaction/Propulsive Noise B-34
Acoustics Research C-14
Noise and Sonic Fatigue of High Lift
Devices C-16
Anechoic Flow Facility Airframe Noise
Experiment C-30
NOISE PREDICTION TECHNOLOGY
Noise Prediction Techniques B-36
Validation of Aircraft Noise Exposure
Predictive Procedures C-18
Xll
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Page
Number
Excess Sound Attenuation Model C-19
Measurement, Prediction, and Evaluation
of Bioenvironmental Noise from Air Force
Systems and Operations C-21
Computerized Procedure To Assess Turbine
Engine Noise/Performance Tradeoffs C-22
Helicopter Noise Propagation, Prediction,
and Mitigation C-27
Naval Air Facilities Noise Prediction C-31
Aircraft Noise Source Data Base D-6
ATMOSPHERIC PROPAGATION AND GROUND EFFECTS
Noise Propagation B-38
Atmospheric Attenuation, Data Acquisition D-7
OTHER
Acoustic Instrumentation/Measurement
Techniques B-40
Noise Shielding B-41
DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CTOL (SUBSONIC)
Refan Program B-42
Advanced Acoustic Composite Nacelle
Flight Program B-45
New Propulsion Systems Studies B-46
Flight Operational Procedures B-47
Jet Noise Suppression D-8
Kill
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Page
Number
CTOL (SUPERSONIC)
New Propulsion System Studies B-49
New Aircraft Studies B-54
STOL
Aircraft Operational Systems B-55
Quiet, Clean, Short-Haul Experimental
Engine (QCSEE) B-57
Systems and Design Studies B-60
Quiet, Propulsive Lift Technology B-61
ROTORCRAFT/VTOL
Aircraft Operational Systems B-63
Rotor Systems Research Aircraft (RSRA) B-65
Tilt Rotor Research Aircraft (TRRA) B-67
GENERAL AVIATION
Quiet, Clean General Aviation Turbofan
(QCGAT) B-68
xiv
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1. INTRODUCTION
1.1 PURPOSE AND SCOPE OF THE REPORT
The United States Government, through a number of its
agencies and departments, conducts and sponsors research,
technology, and demonstration (RT&D) activities related to
aviation noise abatement and control. Agency program objec-
tives vary according to overall agency charters, statutory
authorities, and priorities. Individual programs also vary
in size and complexity.
With the reconvening of the Federal Interagency Avia-
tion Noise Research Panel, each member agency has reexamined
its noise programs in the light of national noise abatement
goals. This report summarizes each of the Federal agency
RT&D programs in aviation noise abatement and control re-
search since FY 75, and the plans for FY 78. It includes a
qualitative assessment of the adequacy of these activities
for developing technology needed for the eventual achieve-
ment of aircraft noise levels compatible with the health
and welfare needs of the nation, and it notes the recommenda-
tions of the panel.
The scope of this report is limited to RT&D activities,
and thus it does not include summaries of aviation noise regu-
latory standards, regulatory proposals, and studies specifi-
cally related to the development of standards; neither does
it summarize or assess noise abatement practices, procedures,
and technology applications implemented by industry and by
national or local authorities.
1.2 ORGANIZATION OF THE REPORT
Agency aviation noise program projects are categorized
into principal areas as presented in Table 1-1.
The remainder of this report includes the summary in
Chapter 2, an overview of each agency's program in Chapter 3,
and an assessment of the agency and overall Federal aviation
noise RT&D programs in Chapter 4. Appendices A through E
include summary tables of program funding and descriptions
of the individual projects comprising each agency's aviation
noise RT&D program. Appendix F is a bibliography.
1-1
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TABLE 1-1
Aviation Noise RT&D Program Categories
RESEARCH AND TECHNOLOGY
Propulsion Noise
Rotor Noise
Interior Noise
Airframe Noise
Noise Prediction Technology
Atmospheric Propagation and Ground Effects
Other
DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES*
CTOL (Subsonic)
CTOL (Supersonic)
STOL
Rotorcraft/VTOL
General Aviation
Includes flight operational procedures
1-2
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2. SUMMARY
This report is a compilation of the research, technology,
and demonstration (RT&D) activities of Federal agencies and
departments in the area of aviation noise during the period
FY 75-77, and planned activities for FY 78. This report
also contains assessments of these activities as well as
recommendations for future areas of work.
Federal agencies and departments with programs in avia-
tion noise RT&D during this time period are as follows:
National Aeronautics and Space Administration (NASA)
Department of Transportation (DOT)
- Federal Aviation Administration (FAA)
Department of Defense (DOD)
Department of the Air Force
Department of the Army
Department of the Navy
Environmental Protection Agency (EPA)
Aviation noise RT&D activities reported herein are grouped
into two types of programs to facilitate review. The first
group comprises Research and Technology Programs. It encom-
passes acoustic fundamentals and noise generation, suppres-
sion, transmission, and prediction. It includes both analyti-
cal and experimental activities supporting the development of
practical technology for aircraft noise abatement. The second
group is that of Demonstration Programs and Systems Studies.
Programs in this group are intended to explore the actual
effectiveness and appropriateness of applied technology for
aircraft noise abatement with realistic hardware.
Agency aviation noise program projects are categorized
further according to the scheme presented in Table 1-1.
Total Federal aviation noise RT&D funding and manpower are
shown in Figure 2-1 from FY 75 through FY 78. Funding levels
shown for DOD includes manpower costs. Manpower costs for
2-1
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- 300
- 250
- 200
1C
DC
DC
150 <
5
DC
<
100 2
co
- 50
1975
1976 1977
FISCAL YEAR
1978
* DOD FUNDING DATA INCLUDE MANPOWER COSTS
t MANPOWER COSTS ARE TREATED SEPARATELY BY NASA, DOT/FAA,
AND EPA
FIGURE 2-1
Total Federal Fiscal Year Funding and Manpower
for Aviation Noise RT&D
2-2
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NASA, DOT/FAA and EPA are accounted for separately and are
listed in manyears. As shown in Figure 2-1, total Federal
funding and manpower allocated to aviation noise RT&D have
not varied more than approximately + $1.5M and +20 man-
years within the period FY 15 - 78. Major variations are
primarily related to the magnitude of the more expensive
demonstration programs. The NASA program accounts for 80 to
85 percent of the funding and approximately 98 percent of the
civil service manpower indicated. NASA's aviation noise RT&D
programs are conducted by the Langley, Lewis, and Ames Re-
search Centers; Dryden Flight Research Center; Wallops Flight
Center; and the Jet Propulsion Laboratory. The Langley Re-
search Center is the primary NASA center for acoustic and air-
craft noise reduction research. All of these NASA centers
occasionally co-sponsor research programs with each other to
fulfill NASA's noise research responsibilities depending upon
the expertise needed. NASA's noise research efforts include
source noise phenomena, transmission and path phenomena, re-
ceiver (community) reaction phenomena, operational techniques,
and aircraft interior noise reduction.
The aviation noise RT&D activities of the Department of
Defense are conducted by the Air Force, Army, and Navy. Air
Force programs generally comprise research and techno-
logy studies" relative to propulsion, airframe, high-lift
or thrust-augmentation devices, and the development of noise
prediction technologies. Army programs are principally con-
cerned with helicopters. The Army's studies include propul-
sion noise, rotor noise, noise prediction technology, and
atmospheric propagation. Navy programs are primarily in jet
engine noise suppression and also airframe noise.
DOT's responsibilities relative to aviation noise RD&D
are carried out by the Federal Aviation Administration (FAA).
FAA's efforts are in the areas of propulsion and rotor noise,
noise prediction technology, and acoustic propagation. FAA
also has activities that are conducted principally to support
the regulatory process for aircraft. These activities in-
clude aircraft classification and certification procedures,
technology assessment, flight path control, land use studies,
and establishment of a source .noise data base for regulatory
use.
EPA's one aviation noise RT&D program is a joint project
with NASA to determine the noise emission levels of production
propeller-driven aircraft and to demonstrate the technological
feasibility and economic reasonableness of advanced-
concept propeller designs. This activity is jointly funded
2-3
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with NASA in FY 78 to augment NASA's general aviation
propeller noise investigations. EPA's other aviation
noise efforts directly support regulations and are not
included in this report.
The Panel's assessment and recommendations (elabo-
rated in Section 4) are, briefly:
• Achieving near-term and longer-range national
aviation noise abatement goals will require the
exercise of all four noise abatement options
(source and path control, airport operations
and compatible land use), not merely source con-
trol. A systems approach for greatest cost
effectiveness and earliest applicability is
needed. Systems studies of feasible alterna-
tives are recommended.
• There has been no undesirable duplication of
effort among the different Agency programs.
Interagency coordination is satisfactory, but
continuing coordination functions of the Panel
should continue. Each Agency undertakes good
program review and planning.
• Scope, content and priorities of current RT&D
program seem basically adequate. Additional
efforts in source noise control should include
flight effects, jet nozzles and suppressors.
Additional effort on operational techniques
is also recommended. In all areas, emphasis
should be on cost effectiveness and compatibili-
ty with competing aviation economic requirements,
environmental constraints and other national
priorities such as energy conservation.
• Timing of noise reduction RT&D is important to
support future new type aircraft development
decisions (STOL, VTOL, advanced SST), and pro-
grams should be reviewed in this light.
• Noise "floors" should be better assessed to
guide planning of RT&D and goals.
• Relative roles and importance of single event
vs cumulative noise exposures should be re-
examined .
2-4
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3.0 AGENCY PROGRAMS
Noise research programs conducted or sponsored by
each agency, while contributing to the national objectives
of noise reduction in general, are primarily focused on
the specific agency's needs for complying with its basic
mission and/or subsidiary legislative mandates. This sec-
tion discusses the overall noise program objectives of
each agency.
3-1
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3.1 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
The National Aeronautics and Space Administration
(NASA) was established by the National Aeronautics and
Space Act of 1958 (PL 85-568). This Act requires NASA to
conduct aeronautical research and technology activities.
Among the stated purposes of such activities is the objec-
tive that they contribute materially to the improvement of
the usefulness, performance, speed, safety, and efficiency
of aeronautical vehicles. This responsibility encompasses
aircraft noise research and technology because of the im-
portance of noise reduction to the future usefulness of
aviation and because of the interactions of aircraft per-
formance, safety, and efficiency with noise reduction
technology.
NASA's aircraft noise projects include research into
noise source characteristics, transmission and path pheno-
mena, prediction techniques, operational noise abatement
techniques, aircraft interior noise reduction, and receiver
(community) reaction phenomena (this latter area is re-
ported in the Noise Effects Panel report). The NASA pro-
gram represents about 85 to 90 percent of the Federal
government's activities in aviation noise RT&D. All program
results are made available to the industry as well as regula-
tory agencies.
NASA's objectives in noise research are to increase
the basic understanding of the physics of aircraft noise
characteristics, generation, propagation, transmission and
suppression; to evolve practical technologies to reduce
noise in aircraft; and to selectively demonstrate techno-
logical advances in source noise reduction and aircraft
noise abatement believed to have high application potential.
The NASA facilities involved in aviation noise RT&D
during the relevant period include Langley, Lewis, and Ames
Research Centers, the Jet Propulsion Laboratory, and the
Wallops Flight Center.
Langley Research Center, Hampton, Virginia, has the
primary responsibility for research on acoustic fundamen-
tals, aircraft noise research (excluding engine internal
noise creneration) , and human effects (subjective response) .
Research and technology programs reported herein for which
Langley has lead responsibility include:
3-3
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Research and Technology
Forward Velocity Effects on Fan Noise
Duct Acoustic Treatment Projects
Propeller Studies
General Cabin Noise
Sound/Structure Interaction
General Airframe Noise
Aerodynamic Noise of Airframes
Noise Prediction Techniques
Noise Propagation Studies
Acoustic Instrumentation and Measurement
Techniques.
In addition, Langley has the responsibility for con-
ducting the following demonstration and systems programs:
Demonstration Programs and Systems Studies
Advanced Acoustic Composite Nacelle Flight
Program
Flight Operational Procedures
New CTOL (Supersonic) Aircraft Studies
STOL Systems and Design Studies
Langley Research Center is also managing the joint
EPA/NASA Small Propeller Technology project.
Lewis Research Center, Cleveland, Ohio, has the pri-
mary responsibility for propulsion noise source research,
engine noise suppression technology, and engine system
noise reduction technology demonstrations. RT&D programs
include:
3-4
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Research and Technology
Combustion Noise Characterization
Jet Noise Suppressors
Forward Velocity Effects on Jet Engine
Exhaust Noise
Fan/Compressor/Turbine Noise Reduction
Internal Noise Transnissicn through Tur-
bines and Nozzles
Flow Interaction/Propulsive-Lift Noise
Demonstration Programs and Systems Studies
Re fan Program
New CTOL (Subsonic11 Propulsion Studies
Quiet, Clean, Short-Haul Experimental
Engine (QCSEE)
Quiet, Clean General Aviation Turbofan
(QCGAT).
Ames Research Center, Mountain View, California, has
the responsibility for investigating unique noise problems
associated with STOL, VTOL and rotorcraft. In addition,
unique test facilities at Ames, primarily the 40 x 80 ft.
low speed tunnel, make possible large scale tests simulat-
ing flight effects on noise. RT&D Programs for which
Ames is taking the lead include:
Research and Technology
Helicopter Rotor Noise Control
Noise Shielding
Demonstration Programs and Systems Studies
STOL Aircraft Operational Systems
Quiet Propulsive Lift Technology
Rotorcraft/VTOL Aircraft Operational Systems
3-5
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Rotor Systems Research Aircraft (RSRA)
Tilt Rotor Research Aircraft (TRRA).
Jet Propulsion Laboratory, Pasadena, California, con-
ducts noise research in the areas of jet noise fundamentals,
correlation of far field measurements with internal noise
sources, and flight effects on jet noise. In the time
frame of this report, JPL is involved with NASA's Combus-
tion Noise Characterization program, which is also being
conducted at Lewis Research Center and also with NASA's
Aerodynamic Noise of Airframes program in conjunction with
Langley and Ames Research Centers.
Wallops Flight Center, Wallops Island, Virginia, has no
noise research responsibilities, but is a convenient base for
flight noise measurements and has an instrumented noise range
used for this purpose primarily in connection with Langley
Research Center flight research programs. Currently, the
CTOL (Subsonic) Flight Operational Procedures program is
being conducted at Wallops.
Dryden Flight Research Center, Edwards, California,
also has no noise research responsibilities at present,
but has served to support full scale flight experiments
in which noise suppressors were tested. The YF-12 research
aircraft was tested with an advanced noise suppressor in
FY 76. In the past Dryden has studied approach and take-
off noise levels of business jets for a number of opera-
tional procedures and airframe noise investigations for
various size aircraft in full scale flight experiments.
Noise RT&D activities at the several NASA Research
Centers are complementary and coordinated, utilizing avail-
able research personnel and research facilities to greatest
advantage. Funding and manpower of the NASA aviation RT&D
program is summarized in Table 3-1 for the entire agency,
rather than by Research Center. Appendix B describes the
principal noise research, technology and demonstration proj-
ects and associated resources.
3-6
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Table 3-1
Category
Research and
Technology
Propulsion Noise
Rotor Noise
Interior Noise
Airframe Noise
Noise Prediction
Technology
Atmospheric Propagation
and Ground Effects
Other
Subtotal
and Manpower Summary,
tics and Space Administration
Fiscal Year Funding in $1,000
(Agency Manpower in Man- Years)
1975
2,
1,
6,
(
943
(80)
178
(7)
617
(7)
324
(20)
228
(8)
489
(12)
321
(3)
100
137)
1976
3,433
(106)
1,300
(11)
339
(6)
2,371
(44)
172
(4)
369
(12)
276
(6)
8,260
(189)
1977
3,982
(116)
1,141
(19)
701
(9)
2,702
(59)
410
(8)
549
(14)
317
(3)
9,802
(228)
1978
4,460
(118)
1,272
(13)
653
(14)
2,815
(53)
283
(6)
481
(16)
293
(7)
10,257
(227)
3-7
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Table 3-1 (Continued)
Category
CTOL (Subsonic)
CTOL (Supersonic)
STOL
Rotorcraft/VTOL
General Aviation
Subtotal
TOTAL
Fiscal
(Agency
1975
Year Funding
Manpower in
in $1,000
Man- Years)
1976 1977 1978
rams and Systems Studies
3,500
(50)
-
(-)
7,000
(98)
-
(-)
-
(-)
10,500
(148)
732
(1)
662 1,
(10)
2,107
(30)
790
(11)
808 1,
(11)
5,099 3,
(63)
16,600 13,359 13,
(285)
(252) (
148
(1)
409 2,
(8)
644
(39)
110
(7)
100 1,
(8)
411 4,
(63)
213 14,
291) (
163
(1)
729
(8)
303
(33)
130
(2)
327
(8)
652
(52)
909
279)
3-8
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3.2 DEPARTMENT OF DEFENSE
The Department of Defense (DOD) is the successor
agency to the National Military Establishment created by
the National Security Act of 1947 (61 Stat. 495). It was
established as an executive department of the Federal
Government by the National Security Act Amendments of 1949,
with the Secretary of Defense as its chief administrator
(63 Stat. 578; 5 U.S.C. 101).
Military aircraft ©Derations are not required to meet
civil aircraft noise certification requirements and can-
not always be consistent with guidelines on noise control.
DOD has, however, recognized its responsibility to develop
cleaner burning, quieter operating aircraft that do not
compromise performance requirements and thus do not sacri-
fice military mission capability and efficiency.
The most pressing DOD problem regarding national avia-
tion noise research and that given the highest priority is
the reduction of aircraft noise where community reaction is
unfavorable. DOD is including increasing community involve-
ment in its decision-making process to realign base flying
missions and bed down newly operational aircraft at existing
bases. This has required DOD to develop standardized meth-
odologies for dealing with and predicting environmental,
economic, and social parameters of such mission decisions.
Considerable research and development funds have been in-
vested in attempting to resolve community impact problem
areas associated with aircraft. Research in community reaction
to noise has become a mature technology resulting in noise
prediction models that are routinely applied to environmental
assessments. These models have been successfully adopted by
the civilian sector and will be applied eventually on an
international basis, thus providing a technical-legal base-
line for assessing aircraft noise impact.
Aviation activities, and the concern relative to noise
emissions resulting from these activities, are a significant
aspect of the missions of the three component military de-
partments of DOD, the Departments of the Air Force, the Army,
and the Navy (which includes the Marine Corps). The aviation
noise RD&D programs of each of these departments are presented
in the following subsections. A funding summary for DOD which
includes the Army, Navy and Air Force is shown in Table 3-2.
Program activities and funding for the DOD aviation noise
RT&D are included in Appendix C. Discussions of the com-
ponent organizations of DOD follow.
3-9
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TABLE 3-2
Funding Summary, Department of Defense
(Air Force, Army, and Navy)
Fiscal Year Funding ($1,000)
CATEGORY
RESEARCH AND TECHNOLOGY
PROPULSION NOISE
ROTOR NOISE
AIRFRAME NOISE
NOISE PREDICTION TECHNOLOGY
TOTAL
1975
1,510
63
22
1,595
1976
874
14
208
410
1,506
1977
433
695
76
703
1,907
1978
319
610
32
658
1,619
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Department of the Air Force
During the report period, the Air Force has undertaken
the following aviation noise RT&D programs:
Research and Technology
Supersonic Jet Exhaust Noise Investigation
(Density Model)
Supersonic Jet Exhaust Noise Investigation
(Velocity Model)
Sound Transmission through Supersonic Jets
Duct Acoustics Research
Noise Suppression in Jet Inlets
Validation of Aircraft Noise Exposure Pre-
diction Procedures
Excess Sound Attenuation Model
Measurement, Prediction and Evaluation of
Bioenvironmental Noise in Support of Air
Force Systems and Operations
Computerized Procedure to Assess Turbine
Engine Noise/Performance Tradeoffs
Acoustics Research
Noise and Sonic Fatigue of High Lift Devices
Acoustics of Transonic Walls.
Funding levels for these activities are listed in
Table 3-3, while Appendix C describes the programs, which
are conducted largely under university grants and industry
contracts.
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TABLE 3-3
Funding Summary, Department of the Air Force
Fiscal Year Funding ($1,000)
1975 1976 1977 1978
Research and Technology
Propulsion Noise 315 76 62 68
Airframe Noise 63 188 66 22
Noise Prediction Technology 22 378 383 366
TOTAL 400 642 511 456
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Department of the Army
The Army depends upon helicopter operations to provide
a significant part of the firepower and mobility required
to win the land battle. Helicopter noise, however, poses a
major limitation in the effectiveness of certain types of
combat operations, degrades crew performance and is a source
of environmental noise pollution at Army installations.
During the report period the Army has undertaken avia-
tion noise RT&D in the following areas:
Research and Technology
Propulsion System Noise
Helicopter Rotor Noise
Helicopter Noise Propagation, Prediction
and Mitigation.
Funding levels for these activities are shown in
Table 3-4 while Appendix C describes the investigations.
Department of the Navy
During the report period the Navy has undertaken avia-
tion noise RT&D in the following areas:
Research and Technology
Jet Engine Ground Run-up Noise Suppression
Airframe Noise Investigation, using an
Anechoic Flow Facility
Naval Air Facilities Noise Prediction.
Funding levels for these activities are shown in
Table 3-5, while Appendix C describes the investigations.
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TABLE 3-4
Funding Summary, Department of the Army
CATEGORY
RESEARCH AND TECHNOLOGY
PROPULSION NOISE
ROTOR NOISE
NOISE PREDICTION
TECHNOLOGY
Fiscal Year Funding ($1,000)
1975 1976 1977 1978
14
32
71
695
160
86
610
172
TOTAL
46
926
868
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TABLE 3-5
Funding Summary, Department of the Navy
CATEGORY
RESEARCH AND TECHNOLOGY
PROPULSION NOISE
AIRFRAME NOISE
NOISE PREDICTION
TECHNOLOGY
TOTAL
Fiscal Year Funding ($1,000)
1975 1976 1977 1978
1,195
798
20
1,195
818
300
10
160
470
165
10
120
295
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3.3 DEPARTMENT OF TRANSPORTATION
The Department of Transportation (DOT) was created by
the authority of the Department of Transportation Act of
1966 (PL 89-670, Oct9ber 15. 1966). Section 4 of the Act
outlines the responsibilities of the Secretary of Transpor-
tation, which include those to
"promote and undertake research and
development relating to transportation,
including noise abatement. ..."
To accomplish these basic mission goals and other specific
congressional mandates, DOT is expected to integrate noise
control into its policy, program criteria, and project
requirements.
DOT's responsibilities relative to aviation noise
RT&D programs are presently carried out by the Federal
Aviation Administration (FAA). The FAA derives its authority
to conduct aircraft noise research from the Federal Aviation
Act of 1958. This Act was amended in July 1968 by Public
Law 90-411, which established the responsibility of the FAA
for control and abatement of aircraft noise.
In addition to its responsibility for the development,
promulgation, and enforcement of Federal aircraft noise
regulations, FAA funds selected aviation noise research
activities and noise technology demonstration programs.
During the report period the FAA has undertaken the follow-
ing aviation noise RT&D programs:
Research and Technology
Jet Noise Research
Core Engine Noise Control
Aircraft Source Noise Data Base
Atmospheric Attenuation, Data Acquisition
Demonstration Programs and Systems Studies
Jet Noise Suppression for CTOL (Subsonic)
Funding levels for these activities are listed in
Table 3-6r while Appendix D describes each project.
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TABLE 3-6
Funding and Manpower Summary,
Department of Transportation
(Federal Aviation Administration)
Fiscal Year Funding ($lyOOO
(Agency Manpower in Man-Years)
CATEGORY
RESEARCH AND TECHNOLOGY
PROPULSION NOISE
NOISE PREDICTION TECHNOLOGY
1975
700
95
1976
917
86
1977
770
1978
DEMONSTRATION PROGRAMS AND
SYSTEMS STUDIES
CTOL (SUBSONIC)
164
250
950 1,730
TOTAL
959 1,253
(6) (5)
1,720
(5)
1,730
(4)
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3.4 ENVIRONMENTAL PROTECTION AGENCY
The Environmental Protection Agency (EPA) was established
in the Executive Branch of the Federal Government as an inde-
pendent agency pursuant to Reorganization Plan No. 3 of 1970.
EPA's mission is to abate and control pollution systematically
by integration of a variety of research, monitoring, standard-
setting, and enforcement activities.
EPA derives its noise control authority primarily from
the Noise Control Act of 1972 (PL 92-574, October 1972).
The Noise Control Act of 1972 amends Section 611 of the
Federal Aviation Act of 1958 (49 U.S.C. 1431; 82 Stat. 395)
to include the concept of "health and welfare" and to define
the responsibilities of and interrelationships between the
Federal Aviation Administration (FAA) and EPA in the control
and abatement of noise. Under Section 7 of the Noise Control
Act, EPA is required to study the adequacy of present air-
craft noise emissions standards (including recommendations on
retrofit); implications of achieving levels of cumulative
noise exposure around airports; and additional measures
available to airport operators and local governments to con-
trol noise. The FAA's power to prescribe and amend aircraft
noise measurement and noise emission regulations under Sec-
tion 611 of the Federal Aviation Act of 1958 is preserved.
However, EPA is required to submit recommendations for regu-
lations to FAA that EPA feels necessary to protect the pub-
lic health and welfare. A detailed process for public dis-
semination of information regarding FAA's action on EPA's
recommendations is specified. Section 14 of the Noise Con-
trol Act defines EPA's primary responsibilities relative to
noise abatement and control research programs and authorizes
the Administrator of EPA to complement as necessary the noise
research efforts of other Federal agencies by conducting and
financing research on the effects, measurement, and control
of noise.
EPA has the responsibility, in accordance with its
mandate, to propose aviation noise regulatory actions, to be
aware of, to encourage, and to conduct, as appropriate, re-
search on aviation noise evaluation and control for the pur-
pose of providing protection to the public health and wel-
fare. The agency does not plan to undertake aviation noise
RT&D on a broad scale, relying instead on other Federal
agencies to conduct the necessary activities. Accordingly,
the EPA has no aviation noise RT&D program as such at this
time; its sole action in this area has been to transfer funds
and provide guidance to NASA to accelerate research and
demonstration of advanced low-noise propeller concepts for
general aviation aircraft. Funding is shown in Table 3-7,
while Appendix E describes the activity.
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TABLE 3-7
Funding and Manpower Summary,
Environmental Protection Agency
Fiscal Year Funding ($1,000)
(Agency Manpower in Man-Years)
CATEGORY 1975 1976 1977 1978
RESEARCH AND TECHNOLOGY
PROPULSION NOISE - 100
(-)*
TOTAL 100
(-)*
Less than 1 manyear.
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3.5 DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT
The Department of Housing and Urban Development (HUD)
was established by the Department of Housing and Urban
Development Act, effective November 9, 1965 (79 Stat. 667;
42 U.S.C. 3531-3537). Its overall purpose was to assist
in providing for rational development of the nation's
communities and metropolitan areas.
Enhancement of environmental quality and environmental
planning activities are conducted by HUD in implementation
of the National Environmental Policy Act of 1969 (NEPA),
which requires that environmental impacts resulting from
Federal actions be assessed and considered as decision-
making factors of equal import with economic, technical,
and other considerations of national policy.
The Housing and Community Development Act of 1974
(PL 93-383; 42 U.S.C. 5301), Title I, Community Develop-
ment, provides further authority for HUD's activities in im-
proving neighborhood and community environments. The objec-
tive of this act is the achievement of a national housing
goal of a decent home and a suitable living environment
(including acoustical environment) for every American
family.
Aviation noise is a significant factor in the contem-
porary urban environment across the nation. Local govern-
ments and legal institutions have frequently proved inadequate
to deal with the expanding and intensified impact of aircraft
noise. The Federal Government has funded research directed
toward developing quieter aircraft engines for many years and
the results have been promising. However, the new, more
powerful engines still generate sufficient noise, particular-
ly in light of increasing air traffic volumes, to create a
serious impact in surrounding communities.
HUD has set noise standards applicable to its program
approvals, the most recent of which are published in HUD
Circular 1390.2, dated August 4, 1971, which established
standards for new residential construction. Under this
standard HUD discourages building structures in noise im-
pacted areas by withholding funding support for structures
planned on sites that are subject to unacceptable noise
exposure.
The Department's activities in the area of environmen-
tal quality and environmental planning include development
and implementation of HUD environmental policies and
3-21
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procedures, development of environmental assessment cri-
teria, and coordination with other Federal departments and
agencies with the Council on Environmental Quality (CEQ).
Other environmental functions encompass development of
strategies for the amelioration of environmental problems
such as noise pollution. Emphasis is placed on environmen-
tal and land-use planning and environmental management
practices. In the area of research, HUD is concerned with
developing policies and techniques for land use and building
construction practices.
HUD is not currently funding any research activities
related directly to aviation noise abatement and control.
HUD's current research activities in noise abatement
through compatible land use planning and noise attenuating
building practices are described in another report,
Federal Research Development and Demonstration Programs in
Transportation Noise, EPA 550/9-78-305, February, 1978.
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4.0 ASSESSMENT
4.1 Introduction
This section contains the Panel's views on the federally
sponsored aircraft noise abatement research, technology and
technology demonstration (RT&D) program summarized in this
report. It encompasses activities during Fiscal years 1975-
1978 and future program plans. The Federal program has been
examined as a whole and not merely by individual department
or agency activities.
The Panel's primary objective was to assess the total
program's adequacy and its contribution to basic knowledge
and technology for aircraft noise abatement beyond that which
could be realized by the application of existing technology.
In this connection, the relationship and value of the program
to the achievement of national aviation noise abatement goals
was considered. Other Panel objectives were to evaluate
research priorities within the program, and to decide whether
there were deficiencies in scope or pace or any unnecessary
duplication of effort. The product of the Panel's assessment
is the group of conclusions and recommendations included in
this section.
It is appropriate to note again here, as in the Introduc-
tion to this report, that the Panel confined its attention to
research, new technology evolution and technology demonstra-
tion activities--in short, to those activities which provide
a new or better technical basis for improvements in aircraft
noise abatement. Other aspects of aircraft noise abatement,
notwithstanding their great importance, were considered to
be beyond the scope of this Panel assignment and were not
addressed. Thus excluded were matters specifically related to
the development and promulgation of regulations for aircraft
noise certification and noise abatement procedures, as well as
any actions taken by municipalities, airport operators, air-
lines and aircraft manufacturers to abate noise during the
report period, inasmuch as these matters are not research,
technology evolution nor technology demonstration.
4-1
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4.2 Techniques Available for Aircraft Noise Abatement
The Panel accepted the conventional view of the different
techniques available for aircraft community noise abatement:
1. Source control consisting of the application of
basic design principles or special hardware to the
engine/airframe combination which will minimize the
generation and radiation of noise;
2. Path control consisting of the application of flight
operational procedures which will minimize the
generation and propagation of noise;
3. Airport Operations Control (Receiver control) consist-
ing of the application of procedures at the airport
or noise exposed communities including restrictions
on the type and use of aircraft, preferential runway
use and curfews on operations to reduce community
noise exposure surrounding airports; and
4. Land use control consisting of the development or
modification of airport surroundings for maximum
noise compatible usage.
It was noted by the Panel that the largest portion of aviation
noise abatement RT&D over the years has emphasized source
control, although it was agreed that all four techniques
together represent a system for noise abatement and that all
techniques must be used in a balanced, cost-effective manner.
4-3
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4.3 Source Noise Abatement Technology Use Considerations.
A considerable body of aircraft noise technology has
been developed, much of it based on government sponsored RT&D.
The actual use of this technology is governed by regulations
and economics, and as in many technical areas, there is usually
a significant time lag--frequently as much as ten years--
between the emergence of new noise technology and its appear-
ance in commercial aircraft service.
Industry has used noise reduction technology for compli-
ance with Federal noise regulations and has embodied it in
their design of derivative aircraft and new aircraft types to
the maximum extent they believe economically justifiable in
the competitive marketplace. Except for the introduction of
the by-pass turbofan engine (which improved both noise and
fuel economy) other source noise control technology used to
date has been accompanied by additional costs, weight, and
performance penalties. Furthermore, any noise margins between
certification noise requirements and lower noise levels which
may have been achieved in new aircraft types can be expected
to be used up in derivative aircraft growth.
These practices are natural of course; it would be unrea-
sonable to expect the aviation industry to apply noise technology
beyond that needed for noise rule compliance when to do so would
result in economic penalties of any magnitude. Therefore, greater
noise reduction through more extensive use of existing noise
reduction technology can be expected to occur only when required
to meet more stringent noise regulations.
The Panel recognized that the growing importance of
fuel conservation and rising fuel costs, together with con-
tinuing needs for emission reductions, increased safety and
greater system reliability, are factors which must be properly
accounted for in considering the suitability of noise tech-
nology applications. These factors also highlight the impor-
tance of seeking source noise control technology which enhance,
not degrade performance.
The Panel noted the great importance of noise technology
timing to support future aviation market needs and opportunities.
To illustrate this, it was noted that future advanced aircraft
types, particularly STOL, VTOL and the next generation SST air-
craft, may eventually be developed for commercial use depending
on the proper combination of circumstances. While it is diffi-
cult to predict when that time might come for any of these
vehicle types, it is evident that the necessary prerequisite
RT&D must be in hand before development decisions can be made.
4-5
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In each case, strict requirements will exist for noise control
and compatibility with noise environments where these aircraft
would operate. Noise reduction technology will be vital for
their successful development, and in the Panel's view thorough
early RT&D planning and implementation is necessary in these
areas to facilitate future development program decision making.
4-6
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4.4 National Aviation Noise Abatement Goals
The Panel decided that in order to place the role of
aviation noise abatement RT&D in correct perspective, it
would be necessary to relate these activities to national
aviation noise abatement goals or objectives. Both near
term and longer range objectives (stated below) were there-
fore selected which are consistent with previously published
recommendations by both EPA and FAA. It must be noted here
that goals selected by the Panel for purposes of their as-
sessment do not constitute an official position of the Fed-
eral government.
• Near term objective - To confine severe aircraft
noise exposure contours (NEF >40 or L,.jn>75) around
U0S. airports to those areas included in the air-
port boundary or under the direct control of the
airport proprietor by 1985.
• As a longer range objective - To confine aircraft
noise exposure contours (NEF> 30 or L(jn>65) within
compatible land-use areas around airports by the
end of this century.
The Panel considered the question of whether these ob-
jectives could be achieved. It was recognized that a thor-
ough examination of this question would require an extensive
analysis of a variety of scenarios with many variables inclu-
ding Federal noise regulations, airport boundaries and com-
patible land use assumptions, operational constraints includ-
ing curfews, fleet size and composition by aircraft type,
the availability and utilization of noise abatement techno-
logy, projections of air traffic growth, distribution and
control, and a careful evaluation of the economic factors
involved. Analyses of all these variables were not avail-
able to the Panel, so rather than attempt a quantitative
evaluation, the Panel only considered probable trends and
limiting assumptions.
The following observations and conclusions were made
with respect to achieving the near term goal.
1. Present regulations (FAR 36) require that by 1985
all civil aircraft operating in the U.S.A. must comply with
Stage 2 or Stage 3 noise levels, depending on aircraft type
and certification application date.
2. As an upper limit case, it was observed that if
the fleet noise were reduced simply by bringing current
4-7
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noisy (Stage 1) aircraft into compliance with Stage 2 lev-
els, this would have the effect of reducing by approximately
40 percent the noise impacted area at the NEF 40 level out-
side current boundaries of the country's aircarrier airports
today. This action alone would therefore not achieve the
near-term goal.
3. The FAA has projected moderate growth of civil
aviation, by 1985, in the number of aircraft and the number
of operations at airports. In this fleet growth, the frac-
tion of aircraft meeting Stage 3 requirements would also
increase relative to 1978. However, in the cumulative
noise exposures used here to represent noise impact and
goals, the increase in forecast operations would largely
offset the effect of individual-event aircraft noise reduc-
tions, and result in no significant reduction in noise im-
pacted area outside current airport boundaries compared to
the upper limit case (2, above).
4. Noting the time lag between new technology emer-
gence and application, the Panel considers it unlikely
that any new technology for noise reduction made available
within the last several years would find its way to any sig-
nificant degree into the commercial aircraft fleet by 1985.
And, if it should be introduced in new aircraft in the next
few years, such new technology would have to affect a large
fraction of existing aircraft in order to reduce projected
cumulative noise exposure levels in 1985 to any significant
extent.
5. The clear conclusion from the above considerations
is that if the near-term noise abatement goal is to be
achieved, it must require a combination of the four tech-
niques described in Section 4.2, above, in a systems sense,
not merely source noise control achieved by aircraft meet-
ing Stage 2 and Stage 3 noise levels, or by any near-term
applications of other new technology now available.
Panel observations and conclusions regarding the longer
range goal are as follows;
1. The FAA has projected increases of more than 50
percent by the end of the century in the numbers of civil
commercial aircraft, including substantial increases of
commuter carrier operations. FAA has also projected up
to 25 percent increases in the number of aircraft used in
general aviation, including more than a five-fold increase
in high performance turbojet/turbofan powered general avia-
tion aircraft, and more than a two-fold increase in heli-
copters. Little major new airport construction is antici-
4-8
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pated by the end of the century. Predictions of military
aircraft fleet numbers and composition at the end of the
century are more speculative, and no estimates of change
were made for this assessment.
2. It is expected that the majority of aircraft added
to the commercial fleet after 1985 will meet FAR 36 Stage 3
requirements and that by the end of the century a substan-
tial portion of the entire civil fleet would meet those
levels. No revisions to FAR 36 were assumed which would
require lower noise levels for certification, or for opera-
tion. Such changes were not ruled out, but were recognized
as being dependent on future assessments of all the factors
involved in rule making including considerations of economic
reasonability and appropriateness of using any improved
new noise reduction technology which may become available.
It is noted again (as in Section 4.3 above) that a more
extensive use of available and future source noise abate-
ment technology is not predicted unless regulations require
it or unless it can be utilized without significant economic
penalties.
3. Based on the foregoing considerations and assumptions,
the Panel recognized that cumulative noise exposure indices
within a given geographical area around busy U.S. airports
could actually increase by the end of the century to values
greater than those of 1985 due to increased aircraft operations,
even if most aircraft met current FAR 36 Stage 3 noise re-
quirements. As in the case of near-term goal, it was con-
cluded that achieving the longer-range noise goal would
require systematic use of all noise abatement techniques,
not merely source noise control. A more thorough study of
this issue is clearly in order.
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4.5 Summary and Analysis of Agency Programs
4.5.1 NASA
The NASA program represents over 85 percent of the total
Federal program. Source noise control of engines and airframes
is the primary objective, with activities ranging from funda-
mental understanding of basic phenomena through engineering
technology. Annual funding and in-house manpower levels have
not varied substantially during the report period, but there
have been shifts of emphasis, with a larger fraction of the
effort now on research and technology evolution rather than
large scale technology demonstrations.
1. Research and Technology Program Accomplishments in
the report period are noted in the detailed program descriptions
in Appendix B. Some of the major highlights are noted below:
Jet Noise. Wind tunnel tests of core and fan stream
mixer nozzles indicate the potential for noise reduction
with modest performance improvements on some existing
engine types. Tests with a P&W JT8D engine indicated a
noise reduction potential of approximately 4 dB.
An inverted velocity profile co-annular flow nozzle
has been identified as a promising concept for future SST
type applications. An empirical model prediction method
for calculating the noise from co-annular jets, including
flight effects, has been developed. The model also takes
into account shock noise from both streams and the mixing
noise from the merged and premerged regions.
In-flight jet exhaust noise predictions now can be
performed more accurately by taking into account engine
internally generated noise radiating from the exhaust.
Recent experience in which data were collected with
multiple phase-match microphones have produced new
insight into the generation, propagation and prediction
of jet exhaust noise. There is evidence to indicate that
the noise arises from a large number of highly directive,
short duration sources in motion. These results have had
an important influence on recent aeroacoustic noise theory
development.
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Fan Noise. The major cause of the difference between
the noise signatures of fans tested statically on the
ground and those obtained during flight has been found
to be due to ingestion of turbulence that is near the
ground. Inlet screens have been tested that show that
ground test results now can be more accurately extra-
polated to flight conditions. This research will lead
to improved fan and acoustic treatment designs with
less reliance on expensive flight tests.
Duct Liners. Acoustic liners with noise absorption
properties which vary either in an axial direction
or around the periphery of the duct are found to provide
more noise reduction for a given weight or volume of
liner than current liners which have uniform acoustical
properties.
Core Noise. Combustor far-field noise from an engine
was measured directly for the first time using correla-
tion and coherence techniques. In addition, correlation
measurements within an engine combustor were used to show
that far-field combustor noise is related to the second
time derivative of the combustor pressure.
Atmospheric Absorption. A study on atmospheric absorp-
tion was completed, verifying an existing analytical
model up to 100,000 Hertz.
Noise Prediction of Aircraft. A computerized method
for predicting flyover noise based on a knowledge
of the aircraft configuration and its operating conditions
is being developed for a wide variety of aircraft. A
complete working system is now available for jet powered
CTOL aircraft. Component noise sources can be modeled
and then summed at the ground to obtain an estimate of
the overall noise signature.
Acoustic Range. An acoustic range at Wallops Island
has been developed for making a large number of
simultaneous, time-synchronized acoustic measurements
during aircraft flyover. It is being used for defining
the ground noise footprint for evaluation of various
noise abatement flight procedures and for validation of
noise prediction methods.
Rotor Noise. Research to reduce helicopter blade slap
noise showed that tip air-mass injection and ogee tip
shape modifications have some noise -reduction potential.
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2. Technology Demonstration Program Highlight Accomplish-
ments are noted below:
QCSEE. The Quiet, Clean, Short-Haul Experimental Engine
(QCSEE) program objective is the evolution and demonstra-
tion of short-haul STOL propulsion technology for the
1980's but technology applications for conventional
aircraft may exist. Test stand noise measurements for
the QCSEE upper surface blowing engine configuration
indicate high potential for the noise reduction features
of the engine. Test data indicate, for example, that
a 150,000 Ib. STOL aircraft, fully utilizing the QCSEE
technology, may achieve a noise footprint area less than
3 percent of a current CTOL aircraft of the same size.
Tests on the QCSEE Under-the-Wing blown flap engine
configuration are still in progress.
REFAN. The Refan program was completed, demonstrating
the effectiveness of major modifications to the P&W
JT8D engine in combination with balanced sound suppres-
sion nacelles, as a noise abatement retrofit option.
Ground tests in a B-727 aircraft and flight tests in
a DC9 aircraft were accomplished. This program provided
the basis for subsequent industry-proposed derivative
engine and airframe combinations.
Noise Abatement Landing Approach. A program demonstrating
the effectiveness of two-segment landing path approach
for community noise abatement was completed, involving
the demonstration of the necessary airborne and ground
electronics and realistic operational flight procedures
in both DC-8 and B-727 aircraft. Any potential future
applications will require satisfactory resolution of
terminal area safety-related issues and terminal area
instrument landing system decisions.
3. Current and planned activities.
Research and technology activities are continuing in
each of the basic areas as outlined in Appendix B, and several
areas of investigation deserve special comment.
In-flight effects on fan noise. A major augmenta-
tion of work in this area is being undertaken
following the discovery, noted above, that inlet
turbulence in ground static tests is a major factor
introducing basic differences between ground and
flight engine noise measurements. The current and
projected effort includes a flight test program to
provide new information on noise characteristics.
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Correlation on the same engine with wind tunnel
tests and with carefully controlled ground tests
with turbulence controlling inlet screens will
be investigated.
• Helicopter transmission noise. Design techniques
for minimizing this noise source will be investigated
in a cooperative program with the Army.
• Variable Cycle Engine technology. Previous system
studies for defining superior advanced SST
configurations emphasized noise reduction and fuel
efficiency objectives. Variable cycle engine critical
component testing has been initiated, and will provide
major tests of co-annular inverted velocity profile
noise suppression jet nozzles.
4. Areas requiring further emphasis:
• Forward velocity effects. The present effort
emphasizes fan noise phenomena, but also needed
is an extension of prior work related to jet
noise (including suppressors) and core noise effects.
• Jet nozzles and noise suppressors. Additional
effort on both subsonic and supersonic jet nozzles
and noise suppressors is needed, particularly for
mixer type and co-annular inverted velocity profile
nozzles.
• Noise abatement operational techniques. Systems
research in terminal area procedures involving
advanced avionics and operational techniques should
include additional emphasis on noise abatement.
4.5.2 POD
The DOD program in aviation noise research and
development has shown a relatively constant level of funding
since FY 1975. The individual projects are directed at the
priority areas of DOD activity including military mission
capability and the effect of base operations on the community.
Emphasis has been placed on source control of propulsion and
rotor noise, and on problems relating to unique STOL designs.
The earlier work addressed noise fundamentals and prediction
methods, while a major emphasis currently is in Army sponsored
research on helicopter rotor noise. During the report period
studies related to path control, receiver control and land
use were also undertaken.
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1. Accomplishments during the report period are
summarized in Appendix'C. Several highlights are noted
below:
Department of the Air Force
Jet Noise. Research on sound transmission from within
a supersonic jet to the surroundings yielded informa-
tion on directivity factors needed for evaluation of
acoustical theories.
Duct Acoustics. Dependence of sound levels within
aircraft engines upon duct geometry and sound absorbing
properties, type of noise source, and flow within the
duct were evaluated. Results are being used to develop
mathematical models.
Noise Prediction. Techniques applicable to operational
problems were developed. System studies of seven air-
craft types were completed, and several RPV's were
evaluated.
Department of the Army
Helicopter Transmission Noise. Tests completed to date
evaluating propulsion system noise have shown that
substantial reductions in transmission noise can be
made by selective stiffening of present transmission
cases and proper design of new cases.
Rotor Noise. In the area of rotor noise, methodology
has been developed for calculating high frequency noise
and a simplified scaling law based upon geometric
parameters of the rotor. Prediction of helicopter
noise is being assessed in a preliminary model. This
model incorporates terrain effects and measured frequency
signatures of various helicopters.
Department of the Navy
Ground Runup Suppressors. Two noise suppression systems
for jet engine ground runup noise have been developed,
the COANDA equipment and the Brauburgh dry system. These
systems are being tested to meet the pressing problem
associated with jet engine ground runup operations both
in and out of airframes.
Rotor Noise. In cooperation with the U.S. Army,
laboratory tests on 70 samples of helicopter noise have
been completed.
4-15
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2. Current and planned activities.
• Source control efforts need to be continued to
support environmental as well as tactical mission
needs.
• The DOD has a large inventory of helicopters in
each of the departments and is likely to continue to
maintain a large force. It is in their interest,
for both personnel protection and mission security,
to expand their activity in helicopter noise RT&D.
Accomplishments in the helicopter and VSTOL areas
could eventually lead to spin-offs to the commercial
market.
• Continued aviation noise research in the path,
receiver, and land-use control areas is required
to support both tactical mission and environmental
needs. Encroachment of civilian communities
towards DOD aviation facilities as well as excessive
noise of aircraft can pose a threat to the existence
of present operational facilities.
3. Applications and actions.
This report is not intended to address applications
of aviation noise RT&D. Nevertheless, the unique problem of
the DOD military departments (maintaining effective military
capabilities while minimizing environmental impact on
communities) and their response to this problem warrant comment
because this issue is somewhat different from that of civil
aviation noise abatement, to which most of the work covered
by Federal programs is directed. During the report period the
DOD has developed noise measurement and noise isolation
techniques and has predicted changes in operational procedures
through the use of computer models, including the Air
Installations Compatibility Use Zone (AICUZ). Through utiliza-
tion of land use planning and cooperative programs with local
jurisdictions, DOD has effectively modified operational
procedures to meet standards. In the area of ground engine
maintenance the use of engine test cells has received
considerable attention.
4.5.3 DOT (FAA)
FAA under DOT, sponsors aviation noise research in
support of regulatory responsibilities. Emphasis is placed
on providing a data base from which to develop rulemaking,
certification procedures, and compliance techniques for the
4-16
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control of aviation noise. The FAA has conducted jointly
funded programs with industry to demonstrate the technological
feasibility and economic reasonableness of specific projects
which may be effective for the near term reduction of aircraft
generated noise. Program funding during the reporting period,
while increasing, reflects the high cost of a current demonstra-
tion project.
1. Accomplishments during the report period are summarized
in Appendix D. Highlights from the various program elements
are listed below:
Jet Noise. Results of contract research on high velocity
jet noise have contributed to the data base used in
developing proposed noise requirements for civil super-
sonic transport aircraft (NPRM 77-23).
Scale model tests of mixer nozzles (complimentary to
the NASA work noted previously) showed favorable results.
These tests were precursors to a mixer nozzle demonstra-
tion program with the P&W JT8D engine now being planned.
Core Noise. Engine core noise research provided data
used in the development of FAR 36 Stage 3 noise level
requirements for new aircraft type certification.
Helicopter Rotor Noise. Flight noise measurements are
being used in current development of noise certification
requirements.
2. Current and planned activities.
• With completion of recent core and jet noise research
contracts, FAA plans to depend more heavily on NASA
for future research and technology in these areas,
but will continue to review and study available
technology on source noise control in search of
methods which are economically reasonable, technically
practical and suitable for air worthiness certification.
Practical application and demonstration of such
technology will be considered.
• Expansion of aircraft noise data base and aircraft
noise prediction capabilities will be continued.
• A full scale static and flight test technology
demonstration program for mixer nozzles is planned
with the JT8D engine in FY 78/79. Objectives
include both reduction and performance improvement.
4-17
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• With respect to path control options, efforts
to improve the FAA Integrated Noise Model accuracy
by use of improved atmospheric and ground effects
data will be continued. NASA propagation research
results will be integrated with the work.
4.5.4 EPA
The EPA, through its Office of Noise Abatement and
Control (ONAC), is principally a user of the research and
technology results generated by the other Federal agencies.
These results help provide the basis for the aviation noise
regulatory actions proposed to the FAA. In this respect,
studies are sponsored or conducted by ONAC to support its
regulatory proposals and to identify future needs. These
regulatory support noise control studies are not described
in this panel report since they are not considered to be
research or technology development programs.
Section 14 of the Noise Control Act authorized EPA
to conduct or finance research by contract to complement, as
necessary, the noise research programs of other agencies.
In the past, EPA has elected not to request RT&D funding but
to depend upon the resources and research commitments of
other agencies (NASA, DOT, DOD, and HUD) to provide support
for their regulatory activities. A recent exception stemmed
from their anticipation of future noise problems from
propeller driven general aviation aircraft. Because of this,
EPA initiated a joint program with NASA in FY 1978 for
research and demonstration testing of low noise, efficient
propellers for future aircraft. This program supplements
previous work done by NASA and provides for an accelerated
demonstration program. Despite this exception, EPA believes
that RT&D programs pertaining to the source, path, and receiver
control of aircraft noise should be the responsibility of the
agencies having the most experience and direct involvement
in the particular subject matter. However, EPA believes that
they should continue to be involved in an advisory capacity
in the planning, monitoring, and evaluation of the RT&D
programs.
4.5.5 HUD
HUD has been de-emphasizing noise research. However,
there is a role for HUD in the aviation noise control picture.
This is particularly so in light of the recognized limitations
to source control technology. HUD has the potential for
influencing land use and building construction. Major changes
in building construction techniques will occur as a result of
4-18
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energy utilization requirements. These changes must be
compatible with aviation noise requirements and goals.
Cost-effective building construction and land-use policies
and practices must be developed if there is to be adoption
into the marketplace.
The only RT&D aircraft noise control programs that
appear appropriate to HDD's mission would lie within the
receiver control option, and would pertain to land use
controls and to noise-insulation and vibration-isolation
techniques in building construction. However, that type
of noise technology research would be pertinent not only
to aircraft but to surface transportation, construction
equipment, factories, etc., as well. HUD is conducting
such RT&D, and the programs are described and assessed
in the Federal Interagency Surface Transportation Noise
Research Panel report and will not be repeated here.
4-19
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4.6 Program Assessment
In reviewing the Federally sponsored aviation noise research
technology evolution and technology demonstration program as a
whole, the Panel made the following assessment:
1. Scope: All areas of source noise that have been
identified are being investigated in the various
research and technology programs.
2. Priorities: In terms of application importance, noise
reduction for commercial aviation should continue to
have the highest priority, followed by general aviation,
rotary wing and VSTOL aircraft requirements. Although
the priorities of the present program are not specifi-
cally stated nor always clearly seen, the priorities
as evidenced by internal program emphasis and funding
seem reasonable. The needs for military aircraft
noise abatement should be accorded high priority by
DOD to insure ever-improved compatibility with
community noise requirement around military install-
ations.
• With respect to noise control option priorities,
the Panel judged that highest priority should
still be given to source noise control, since
it appears that there are still significant
needs and opportunities for reducing source
noise. These include propulsion system
improvements and also airframe noise reduc-
tion benefits (at least for large aircraft).
Path control including atmospheric propagation
and ground effects phenomena should also be
continued with high priority.
• With respect to specific source noise control
topics, flight effects on noise, core noise
phenomena, airframe noise, and helicopter
rotor and transmission noise were viewed
as having highest priorities.
3. Timing: As noted previously, noise RT&D planning
and implementation timing is essential to prepare
for future new aircraft type development decisions.
The panel felt that this fact is, in general, prop-
erly accounted for in the Federal program (which is
largely the NASA program in this regard), parti-
ularly with respect to the advanced SST and for STOL,
though less evident for VTOL.
4-21
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4. Duplication: It is apparent that NASA, DOT/FAA
and DOD have pursued similiar objectives within
several of the same areas of noise RT&D, particu-
larly in jet noise and helicopter noise. Examina-
tion of the individual activities did not reveal
any repetition or actual duplication in the work,
however. Many of these are cooperative programs.
Insofar as could be determined all projects in
areas of common interest have been complementary,
each seeking incremental knowledge or specific
technology for a special agency purpose.
5. Planning and Review; Each of the Federal agencies,
NASA, DOD, and FAA, uses a number of processes to
identify aviation noise RT&D needs and to establish
RT&D plans. As an example, NASA solicits the ideas
of industry, universities, and the other Federal
agencies and holds technology workshops on special
topics to bring experts together to discuss future
needs. All three Federal organizations develop
future research plans which are regularly reviewed
and updated.
6. Interagency Coordination; Interagency coordination
of programs was judged to be satisfactory, at least
in areas of common interest or mutual high priority
for more than one agency. Two instances of good
coordination are noteworthy. The first is in the
area of jet noise research which has been undertaken
by NASA, DOT/FAA and the Air Force. The second
is in helicopter rotor research which is being
investigated cooperatively by NASA and the Army.
• It was also noted that the reactivated Federal
Interagency Aviation Noise Research Panel itself
has, through the current review, fulfilled an
important need for interagency program coordina-
tion, and it is recommended that the function be
continued in the future.
7. Technical Assesment; On balance, the Panel judged
the aviation noise RT&D program to have been basic-
ally adequate during the report period, and the
reported accomplishments were considered good.
No breakthroughs in understanding or technology
came to light during the report period which will
in themselves provide major changes in future
expectations for aircraft noise abatement.
4-22
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Accomplishments were generally more of an evolutionary
nature and added to the country's ability to
achieve incremental noise abatement for the future
more efficiently and economically than in the past.
The Panel endorsed ongoing programs and plans with
certain recommendations which are noted in the
following Section.
4-23
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4.7 Conclusions and Recommendations
The Panel concluded its assessment with the follow-
ing conclusions and recommendations:
1. If the postulated near-term and longer-range
national aviation noise abatement goals are to be achieved
circa 1985 and 2000, respectively, they will not likely
be achieved merely by projected individual aircraft com-
pliance with FAR 36 Stage 2 and Stage 3 levels, nor by
additional improvements in source noise reductions affect-
ing only a limited number of aircraft making up the total
fleet. Instead, noise goal achievement will require the
exercise of all four noise control options (source, path,
airport operations and compatible land use), ideally in an
optimal systems sense, so that maximum benefits can be
achieved soonest with lowest costs. Systems studies, of
the type FAA is now undertaking, are strongly endorsed,
since these can explore the nature of optimal solutions
considering a range of scenarios and variables. Such
studies are important for future agency planning of noise
abatement RT&D as well as future regulatory and implemen-
tation requirements, and to place the relative roles and
importance of the four noise control options in better
perspective.
2. It is important that aviation source noise reduc-
tion RT&D be pursued vigorously, not just because of the
major role source control will probably continue to play,
but also in recognition of the inevitable time-lag which
exists between technology discoveries and technology imple-
mentation. The Panel noted that RT&D costs are minor com-
pared to the costs of noise regulation compliance and to
the potential costs of court judgments rendered against
noise offenders.
3. Current and future noise reduction RT&D activities
must continue to strive for results which bring maximum
cost effectiveness or minimum economic penalties in their
applications, to make the technology more attractive for
voluntary use by industry as well as for noise rulemaking
by government. The growing importance of fuel conservation
and rising fuel costs, together with continuing needs for
emission reductions, increased safety and greater system
reliability, are factors which must be properly accounted
for in considering the suitability of noise technology
applications.
4-25
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4. The Panel noted that the scope and content of
the total program seemed basically adequate, but that
there were several areas in which additional resources
should be applied. While recognizing the usual problem of
fiscal budgetary limitations, they recommend augmentations
in the areas of flight effects on noise, jet noise and
suppressors, and aircraft operational techniques for noise
abatement.
5. Timing of noise research to support future develop-
ment decisions on possible new civil aircraft types, includ-
ing STOL, VTOL and an advanced SST, is very important. The
agencies (principally NASA and DOT/FAA) should carefully
examine projected noise RT&D planning against desired tech-
nology readiness goals for future aircraft types.
6. The Panel recommends that NASA more completely
study the question of feasible "noise floors" which repre-
sent, at any particular time, assessments of the limits of
practicability of achievement in source noise control; and
that they update their assessment periodically. It was
recognized that statements of "noise floors" can be mis-
understood or misused by those not familiar with the
physical bases involved; nevertheless such estimates could
have great value for long range planning and realistic
assessment of future goals.
7. The relative roles and significance of single-
event noise exposures versus cumulative exposures in
assessing aviation noise impact and in setting noise abate-
ment research goals should be re-examined.
4-26
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APPENDIX A
SUMMARY TABLES
AVIATION NOISE RT&D FUNDING AND MANPOWER
This appendix presents summary tables of aviation
noise RT&D program funding for the National Aeronautics
and Space Administration; the Department of Defense, in-
cluding the Departments of the Air Force, the Army, and
the Navy; the Department of Transportation; and the
Environmental Protection Agency for fiscal years 1975
through 1978. The Department of Housing and Urban De-
velopment reported no ongoing aviation noise RT&D programs
in the relevant period. Aviation noise funding is summarized
first by agency in total and then by program category and
agency in Tables A-l and A-2.
Funding figures for the National Aeronautics and Space
Administration (NASA), the Department of Transportation
(DOT), and the Environmental Protection Agency (EPA), are
exclusive of agency manpower. Consequently, Table A-l
includes manpower figures for these agencies in paren-
theses, and these manpower figures should be considered
additional to the funding figures shown. Manpower figures
for NASA are also shown in parentheses in Table A-2. DOT,
however, reported total manpower only, and, as a result,
their manpower could not be identified by program category
in Table A-2.
Funding for FY 76 includes the transition quarter
(July 1, 1976 to September 30, 1976) . Funding cited for
FY 77 and FY 78 includes estimates. Projects for FY 78
have not been finalized.
A-l
-------
TABLE A-l
SUMMARY OF AVIATION NOISE RT&D FUNDING
AND MANPOWER BY AGENCY
Fiscal Year Funding in $1,000*
AGENCY
NATIONAL AERONAUTICS AND
SPACE ADMINISTRATION
(Agency
1975
16,600
(285)
Manpower
1976
13,359
(252)
in Man-Years)
1977
13,213
(291)
1978
14,909
(279)
DEPARTMENT OF DEFENSE
•
DEPARTMENT OF THE AIR FORCE
DEPARTMENT OF THE ARMY
DEPARTMENT OF THE NAVY
SUBTOTAL: DEPARTMENT OF
DEFENSE
DEPARTMENT OF TRANSPORTATION
400
1,195
1,595
959
(6)
642
46
818
1,506
1,253
(5)
511
926
470
1,907
1,720
(5)
ENVIRONMENTAL PROECTION AGENCY
TOTAL
19,154
(291)
16,118
(257)
16,840
(296)
456
868
295
1,619
1,730
(4)
100
18,358
(283)
DOD funding data includes manpower costs.
Less than 1 man-year
A-3
-------
TABLE A-2
SUMMARY OF AVIATION NOISE RT&D FUNDING
AND MANPOWER BY PROGRAM CATEGORY AND AGENCY
Fiscal Year Funding in $1000
(Agency Manpower in Man-Years)
1975
1976
SUBTOTAL: PROPULSION NOISE
1977
CATEGORY
RESEARCH AND TECHNOLOGY
PROPULSION NOISE
. NATIONAL AERONAUTICS AND 2,943 3,433 3,982
SPACE ADMINISTRATION (80) (106) (116)
. DEPARTMENT OF DEFENSE 1,510 874 433
. DEPARTMENT OF TRANSPORTATION 700 917 770
. ENVIRONMENTAL PROTECTION
AGENCY
5,153 5,224 5,185
(80) (106) (116)
1978
4,460
(118)
319
100
(-)*
4,879
(118)
ROTOR NOISE
. NATIONAL AERONAUTICS AND
SPACE ADMINISTRATION
DEPARTMENT OF DEFENSE
SUBTOTAL: ROTOR NOISE
178
(7)
178
(7)
1,300
(11)
14
1,314
(11)
1,141
(19)
695
1,836
(19)
1,272
(13)
610
1,882
(13)
Less than 1 man-year.
A-5
-------
TABLE A-2 (Continued)
Fiscal Year Funding in $1000
CATEGORY
INTERIOR NOISE
. NATIONAL AERONAUTICS AND
SPACE ADMINISTRATION
AIRFRAME NOISE
. NATIONAL AERONAUTICS AND
SPACE ADMINISTRATION
. DEPARTMENT OF DEFENSE
SUBTOTAL: AIRFRAME NOISE
NOISE PREDICTION TECHNOLOGY
. NATIONAL AERONAUTICS AND
SPACE ADMINISTRATION
DEPARTMENT OF DEFENSE
DEPARTMENT OF TRANSPORTATION
SUBTOTAL: NOISE PREDICTION
TECHNOLOGY
ATMOSPHERIC PROPAGATION AND
GROUND EFFECTS
. NATIONAL AERONAUTICS AND
SPACE ADMINISTRATION
OTHER.
. NATIONAL AERONAUTICS AND
SPACE ADMINISTRATION
SUBTOTAL: RESEARCH AND TECHNOLOGY
(Agency Manpower in Man-Years)
1975
617
(7)
1,324
(20)
63
1,387
(20)
228
(8)
22
95
345
(8)
489
(12)
321
(3)
1976
339
(6)
2,371
(44)
208
2,579
(44)
172
(4)
410
86
668
(4)
369
(12)
276
(6)
1977
701
(9)
2,702
(59)
76
2,778
(59)
410
(8)
703
1,113
(8)
549
(14)
317
(3)
1978
653
(14)
2,815
(53)
32
2,847
(53)
283
(6)
658
941
(6)
481
(16)
293
(7)
5,490 10,769 12,479 11,976
(137) (189) (228) (227)
A-6
-------
TABLE A-2 (Continued)
CATEGORY
DEMONSTRATION PROGRAMS AND
SYSTEMS STUDIES
CTOL (SUBSONIC)
. NATIONAL AERONAUTICS AND
SPACE ADMINISTRATION
. DEPARTMENT OF TRANSPORTATION
S UBTOTAL: CTOL (SUBSONIC)
CTOL (SUPERSONIC)
. NATIONAL AERONAUTICS AND
SPACE ADMINISTRATION
Fiscal Year Funding in $1000
(Agency Manpower in Man-Years)
1975
1976
1977
1978
3,500
(50)
164
3,664
(50)
732
(1)
250
982
(1)
148
(1)
950
1,098
(1)
163
(1)
1,730
1,893
(1)
662 1,409 2,729
(10) (8) (8)
STOL
. NATIONAL AERONAUTICS AND
SPACE ADMINISTRATION
ROTORCRAFT/VT PL
. NATIONAL AERONAUTICS AND
SPACE ADMINISTRATION
GENERAL AVIATION
. NATIONAL AERONAUTICS AND
SPACE ADMINISTRATION
SUBTOTAL: DEMONSTRATION PROGRAMS
AND SYSTEMS STUDIES
TOTAL: ALL RT&D PROJECTS
7,000 2,107
(98) (30)
790
(-) (ID
808
(11)
10,664 5,349
(148) (163)
19,154 16,118
(291)* (257)*
644
(39)
110
(7)
1,100
(8)
4,361
(63)
16,840
(296)*
303
(33)
130
(2)
1,327
(8)
6,382
(52)
18,358
(283)*
Includes total manpower for DOT/FAA; individual project manpower
was not reported.
A-7
-------
APPENDIX B
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
AVIATION NOISE RT&D PROGRAMS
This appendix describes NASA's aviation noise program
in terms of research and technology and demonstration pro-
grams and systems studies projects. Where more than one NASA
research center is listed as a project sponsor, the first
named is the primary sponsor.
NASA funding figures are exclusive of manpower; there-
fore, manpower figures, in man-years, are included in paren-
theses below the fiscal year funding for each project and
should be recognized as additional costs. Funding for FY 76
includes the transition quarter (July 1, 1976 to September
30, 1976). Funding cited for FY 77 and FY 78 includes es-
timates. Projects for FY 78 have not been finalized.
B-l
-------
FUNDING AND MANPOWER SUMMARY,
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
Fiscal Year Funding in $1000
(Agency Manpower in Man-Years)
CATEGORY
RESEARCH AND TECHNOLOGY
PROPULSION NOISE
ROTOR NOISE
INTERIOR NOISE
AIRFRAME NOISE
NOISE PREDICTION TECHNOLOGY
ATMOSPHERIC PROPAGATION
AND GROUND EFFECTS
OTHER
1975
2,943
(80)
178
(7)
617
(7)
1,324
(20)
228
(8)
489
(12)
321
(3)
1976
3,433
(106)
1,300
(11)
339
(6)
2,371
(44)
172
(4)
369
(12)
276
(6)
1977
3,982
(116)
1,141
(19)
701
(9)
2,702
(59)
410
(8)
549
(14)
317
(3)
1978
4,460
(118)
1,272
(13)
653
(14)
2,815
(53)
283
(6)
481
(16)
293
(7)
SUBTOTAL: Research and
Technology
6,100 8,260 9,802 10,257
(137) (189) (228) (227)
B-2
-------
NASA FUNDING AND MANPOWER SUMMARY (Continued)
Fiscal Year Funding in $1000
(Agency Manpower in Man-Years)
CATEGORY 1975
DEMONSTRATION PROGRAMS AND SYSTEMS
STUDIES
CTOL (Subsonic) 3,500
(50)
CTOL (Supersonic)
STOL
ROTORCRAFT/VTOL
GENERAL AVIATION
1976
1977
1978
732 148 163
(1) (1) (1)
662 1,409 2,729
(10) (8) <3)
7,000
(98)
-
(-)
-
(-)
2,107
(30)
790
(11)
808
(11)
644
(39)
110
(7)
1,100
(8)
303
(33)
130
(2)
1,327
(8)
SUBTOTAL: Demonstration
Programs 10,500 5,099 3,411 4,652
(148)
(63)
(63)
(52)
TOTAL: All Programs
16,600 13,359 13,213 14,909
(285) (252) (291) (279)
B-3
-------
NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - COMBUSTION NOISE
Combustion Noise Characterization
The nature of combustion generated noise is being investigated
through suitably designed experiments on engine combustors operating
both in-situ and in development test facilities. This is a relatively
new technology area, and a significant aspect of the current program is
the design of the experiments and instrumentation to make meaningful
measurements. Also, because of the complexity of combustor systems and
of the physics of the combustion process therein, mathematical modeling
is virtually impossible. This makes the work inherently experimental.
Need for Study; Existing experimental data indicate that for many pro-
pulsion systems the engine core can be a significant contributor to the
total engine noise signature after fan and jet noise are reduced, and in
the case of some unique systems such as a duct burner. Work in this
area is necessary to improve the prediction methodology and to under-
stand the nature of the generation process with an ultimate goal of
effecting noise reduction.
Approach: The work is conducted both in-house and by contract. The
most pertinent data are obtained from in-situ engine tests. In-situ
engine tests are expensive due to the problems of installing probes in
the combustor, and because of the high operational costs of engines.
Combustor noise tests are therefore often piggybacked onto other engine
and component research tests. Because component tests are less expen-
sive and more suited to parametric investigations, significant attention
is being paid to the relationship between measurements made in-situ and
in component development rigs.
Engine tests are used to contribute to a reliable data base on far-
field noise generation. Pioneering measurements are also being made
using signal analysis (correlation, coherence) techniques between pairs
of simultaneously obtained signals within the combustor and between the
combustor and far-field.
If the relationship between engine internal measurements and com-
ponent rig measurements can be reliably established, it will become
possible to conduct component rig parametric investigations into the
nature and physics of combustor noise generation. This in turn may lead
to an assessment of the possibility of combustor noise reduction through
design.
Schedule: Combustion noise studies were initiated in 1973 with a grant
to the Georgia Institute of Technology. This was followed by contracts
to both General Electric and Pratt and Whitney Aircraft for component
rig tests.
B-4
-------
NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Combustion Noise Characterization (Continued)
Contract procurement was initiated in FY 78 for combustor noise
tests on a CF6 engine. These tests will entail simultaneous internal
and far-field measurements.
Accomplishments: Extensive combustor noise measurements in component
test rigs have been obtained by General Electric and by Pratt and
Whitney by contract addenda to the Experimental Clean Combustor Program
(ECCP) .
An in-house program has been completed using the Lycoming YF-102
engine wherein simultaneous internal and far-field measurements were
made. This program saw the successful development of instrumentation
technology to obtain combustor fluctuating internal pressures in-situ.
Correlation and coherence signal analysis techniques were used in
pioneering measurements to discriminate combustor-associated noise in
the total engine far-field noise signature. Such signal analysis
techniques have also shed new light on the nature of the combustor noise
source characteristics.
Acoustic data have also been obtained with the YF-102 combustor in
the Lycoming component test rig. These data presently are being
analyzed and will be compared with the previously obtained engine data
using identical near-field instrumentation and air flow rates. The
results of these investigations have influenced and guided the procure-
ment of the CFG test program.
Sponsor: Lewis Research Center and Jet Propulsion Laboratory
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 82 160 100 96
Agency Manpower (Man-Years): 2 5 3 3
B-5
-------
NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Jet Noise and Suppressors
This program is directed at building the technology base for re-
ducing aircraft jet engine exhaust noise. The emphasis is on basic
research into the relationships between jet flow processes and the near-
and far-field jet flow noise characteristics. Improved understanding of
basic mechanisms is expected to lead to new noise reduction concepts.
Need for Study: In present subsonic aircraft, the propulsion noise
sources (engine inlet, combustor and exhaust) are roughly in balance.
Further advances in jet noise reduction technology are needed as these
aircraft already utilize all currently available technology. Signifi-
cant advances in supersonic jet exhaust noise control technology are
also needed if an economically viable supersonic transport is ever to
become a reality.
Jet exhaust noise has been the subject of intense research since
1950. Further advances in technology at this stage can only come through
invention or basic research aimed at improving our understanding of the
fundamental noise generation mechanisms.
Approach: The traditional approach of coordinated experiments, numeri-
cal analysis and theoretical development is being followed. Carefully
controlled scale model experiments are used for validating theory and
suppressor concepts. Several innovative concepts such as the inverted
flow coannular jet, plug nozzles, and porous nozzles with boundary layer
control are under study in addition to standard nozzle configurations.
Precision measurements describe the flow and its correlation with the
near- and far-field noise components.
Forward motion effects and the effect of engine mounting on jet
noise are studied by means of high speed ground vehicles, free flight
aircraft tests in an anechoic wind tunnel, and through theoretical
analysis.
Schedule: The research in this area is of a continuing nature with the
experimental verification of promising approaches at appropriate stages.
Over the next fiscal year the plans are to: conduct experiments on
jet/body combination (static and moving) to validate theory, complete
experimental evaluation of porous plug nozzle suppressor, measure the
effects of finite amplitude wave distortion on far-field noise spectra
of supersonic jets, and complete detailed mapping of flow field of
coannular jets.
Accomplishments: Achievements of the basic jet noise research program
are incremental additions to the knowledge of this noise source and
occur on a more or less continuous basis. One example is the development
of the "flash-light" theory of jet noise sources. Another is the devel-
opment and application of the two-point correlation measurement technique,
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Jet Noise and Suppressors (Continued)
which has given new insights into the generation of jet noise. The
completion of a controlled source-in-motion experiment with a jet
mounted on top of a moving auto confirmed the theoretical expectation
that relative jet velocity is the 'major determiner of forward motion
effects on subsonic jet noise. The existence of both large-scale
coherent and small-scale random flow structures in jets has also been
experimentally validated. The experimental results have been accom-
panied by significant improvements in the capability for analytical and
numerical modeling of jet noise generation processes.
Sponsor: Lewis Research Center and Langley Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 572 651 657 492
Agency Manpower (Man-Years): 16 18 17 13
B-7
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Forward Velocity Effects on Jet Engine Exhaust Noise
This program is aimed at improving the data base and interpretation
of the effect of aircraft velocity on jet noise. Improved understanding
of forward velocity effects will result in more accurate predictions of
aircraft noise reaching the ground, and in the design of effective noise
suppressors.
Comparisons between flight-measured and static test jet noise
fields show that simulation of inflight conditions by static measure-
ments at a reduced jet velocity equal to the relative velocity experi-
enced in flight does not result in an adequate representation of the
actual conditions, even for the case of a simple round conical nozzle.
While the peak noise is predictable by this technique, the noise in the
forward quadrant is not. The effect of flight is not readily predict-
able even at the peak noise location for noise suppressing nozzles. The
net effect is that the noise in flight is generally higher than pre-
dicted when the aircraft noise signature is dominated by jet noise.
Need for Study; Research on flight effects on jet noise is essential
for two reasons. One is that flight effects must be predictable or the
certification of a jet noise dominated aircraft becomes an unacceptable
risk. The other reason is that the effects must be understood to design
noise suppressors which are effective in flight.
Approach: Research on flight effects consists of documentation of the
problem through high quality flight tests and tests in ground facilities
such as wind tunnels and free jets. Having documented the problems, the
next step is to isolate and understand the reason for the discrepancies
through diagnostic tests in ground facilities. These diagnostic tests
include signal processing to locate noise sources, laser velocimeter
measurements of the turbulent properties of the jet, and visualization
techniques. With the understanding gained from the diagnostic tests,
prediction procedures will be improved, and more effective inflight jet
noise suppressors can be developed.
It is expected that this research program will reduce the Effective
Perceived Noise Levels (EPNL) approximately 4dB below presently attain-
able levels for jet noise dominated aircraft. It may also lead to
simpler, more efficient noise suppressors.
Schedule; Establishment of the data base and certification of ground
based facilities will be completed in 1979. Diagnostic measurements and
their interpretation will be completed in 1982. Next, improved pre-
diction methods for flight effects will be developed. Finally, improved
jet noise suppressors will be available in 1985.
B-8
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Forward Velocity Effects on Jet Engines Exhaust Noise (Continued)
Accomplishments; Certification of the 40- by 80-foot wind Tunnel as a
jet noise research tool, including development of appropriate measure-
ment techniques, has been completed. A data base has been established
for a large number of suppressors including: round conical nozzles (both
full-scale engine and model tests), multi-element suppressor nozzles,
shrouded nozzles, and inverted flow nozzles.
Sponsor: Lewis Research Center and Langley Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 320 633 449 175
Agency Manpower (Man-Years): 9 20 13 5
B-9
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Fan/Compressor/Turbine Noise Reduction
The physical nature and relative strengths of rotor/stator and
rotor/inflow interactions are being studied to understand turbomachinery
noise source mechanisms. The program will define new noise reduction
concepts and evaluate designs embodying these concepts. Test conditions
will be controlled in such a way that results can be validly extrapolated
to actual community noise levels during aircraft flyovers.
Need for Study; With the introduction of high bypass turbofan engines,
the fan component is often the dominant noise source contributing to
community aircraft noise exposure during landing approach. Future
turbofan engines are projected to have still higher bypass ratios which
will further emphasize the importance of the fan. Some evidence also
exists that the turbine can contribute significantly to the approach
noise signature of some current high bypass turbofans. Attacking the
noise generation at the source through stage design features offers the
possibility of arriving at a quieter propulsion system having lower cost
and weight than could be obtained by using acoustic treatment alone.
Approach; The turbomachinery noise programs are pursued through a
mixture of in-house, contract and university grant research.
Experimental and analytical investigations are conducted to charac-
terize the interaction of flow fields with the rotor and stator blades
that generates and radiates noise. Fundamental studies include the
analysis of noise generation by rotor interaction with the inherent
disturbances present in the inflow, the measurement of unsteady surface
pressures on rotor and stator blades, measurement and modeling of rotor
blade wakes in terms of rotor design parameters, measurement of inlet
flow distortion and turbulence properties, and development of airfoil
lift response functions. Random signal analysis techniques are applied
to both near- and far-field noise measurements to define average behavior
of the fluid dynamic and acoustic fields and the magnitude of the random
fluctuations.
An experimental data base has been accumulated on a series of nine
full scale fans over a range of pressure ratios, tip speeds and fan
loadings. Full scale experiments investigated rotor/stator interaction
by varying rotor/stator spacing, and designing a fan stage to reduce
stator lift fluctuations due to rotor wakes. Full scale fan blades
instrumented with surface pressure transducers were used to characterize
the inlet flow field fluctuations due to distortion and turbulence.
Empirical knowledge and analytical models of generation mechanisms
are used to devise low noise fan stage designs. Twenty inch scale
models based on these designs are being used for experimental evaluation.
B-10
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Fan/Compressor/Turbine Noise Reduction (Continued)
Noise control concepts under study include rotor sweep and shock swallowing
or containment in the rotor blade passages for multiple pure tone reduc-
tion, stator sweep for reduced rotor/stator interactions, and high
specific inflow for overall inlet quieting. In addition, methods of
increasing wake dissipation by blade vortex generators and effects of
cowl boundary layer control are being investigated. The 20-inch fan
noise evaluations are being conducted in the Lewis anechoic chamber.
Methods of controlling the static noise test conditions are being
investigated so that tests in facilities such as the anechoic chamber
will produce fan noise signatures similar to those which would be mea-
sured in flight. Inlet flow control devices are being developed to
smooth inflow disturbances and reduce inlet turbulence intensities and
scales. Two such devices under investigation are a hemispherical honey-
comb screen and an annular suction ring around the outside of the inlet
cowl.
Schedule: Development of experimental procedures, an anechoic chamber
for testing 20-inch fans, and acquisition of full scale fan data were
completed in 1975. An interim fan noise prediction procedure was
developed from the full scale static fan data.
During 1976, refinement of the analytical tools and experimental
scale model data acquisition took place.
In 1977, the sensitivity of fan noise to inflow disturbances was
determined and the first honeycomb screen inflow control device was
tested in the anechoic chamber. A swept rotor was tested. Cutoff and
rotor/stator spacing effects were measured with inflow control. A high
specific inflow fan was constructed and full scale fan inflow analysis
completed.
During 1978, it is planned to complete the analysis of the swept
rotor data; test the high specific inflow fan, swallowed shock fan,
annular cowl suction concept; determine rotor wake characteristics with
loaded fan; and begin a second series of inflow control tests.
Accomplishments: A data base on fan noise was acquired in a series of
nine full scale fans covering the range of pressure ratios from 1.2 to
1.6 and tip speeds from 700 to 1550 ft/sec. These data formed the basis
of an empirical prediction procedure for fan noise which was adopted as
the initial input to the NASA Aircraft Noise Prediction Program (ANOPP).
Full scale fan experiments were conducted to study methods of
reducing rotor/stator interaction noise. These studies included spacing,
long chord stators and stage redesign to minimize stator lift fluctua-
tions . It was determined that second harmonic levels and broad-band
B-ll
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Fan/Compressor/Turbine Noise Reduction (Continued)
levels could be reduced and that fundamental tone levels were con-
trolled by inflow distortion and turbulence rather than rotor/stator
interaction.
Blade surface pressure data acquired on the full scale fan rotor
and stator blades were analyzed to characterize the inflow disturbances
which were controlling fan fundamental levels. Time series analyses
techniques such as amplitude probability density function analysis
were applied to blade pressure data to determine the relative amount
of periodic and random content in the pressure signals. For example,
it was determined that the amplitudes of rotor wakes striking a stator
blade have a strong random content at the blade passing frequency
indicating high rotor wake turbulence.
An anechoic chamber for testing 20 inch diameter fans became
operational in 1975. To date, fan tests have demonstrated scaling
correspondence with full scale data, and experiments have explored
inflow control with honeycomb/screen structures which have shown sub-
stantial reductions of inflow generated tone noise. Reductions in inlet
turbulence intensities by more than a factor of five were measured.
Effects of cutoff and rotor/stator spacing on inlet noise have also been
determined with inflow control. Model fans incorporating unique acous-
tic design concepts such as swept blading and high specific inflow have
been designed and built under contract. The first of these, the swept
rotor, is being tested.
The importance of inflow disturbances in an anechoic chamber facility
has also been explored, both in-house and under contract. The sensiti-
vity of fan noise to inlet vortices and large scale turbulence was shown
to be greatest at subsonic fan tip speeds, and the studies lead to
proposed control concepts involving cowl contouring and boundary layer
suction. Preparation for tests of these ideas is underway.
In the fundamentals area, contracts, grants and in-house efforts
have modeled rotor/distortion and rotor/turbulence noise; developed a
blade lift response model and applied it to rotor/stator interaction
analysis; measured rotor wake characteristics as a function of rotor
loading; and applied time series analysis techniques to noise and pres-
sure signals to characterize the random nature of the generation processes.
Sponsor: Lewis Research Center and Langley Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 507 715 700 731
Agency Manpower (Man-Years): 14 23 21 20
B-12
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Forward Velocity Effects on Fan Noise
Accurate (+^1 dB) static-to-flight noise predictions are a prime
objective of this program. A basic understanding of the flight effects
on fan noise and the development of experimental techniques using ground
facilities and wind tunnels are therefore required.
Need for Study; It has been found that noise signatures of fans tested
statically on the ground do not correspond to those found in flight.
Because of this, static noise tests have practically ceased in the
industry. An understanding of the flight effects and the ability to
predict them from static tests is therefore needed to accurately eval-
uate new fan noise reduction methods and materials by economical static
tests.
Approach: The general approach to solving these problems will be to
carefully evaluate the relative merits of static testing and wind tunnel
testing by using flight data. Three NASA Centers (Langley, Lewis and
Ames) will conduct this program. It will consist of a combination of
in-house and contract research activities. The in-house research will
consist of JT15D engine static tests outdoors, JT15D fan static tests in
the anechoic chamber, flow duct turbulence control experiments and inlet
radiation studies using a spinning mode synthesizer and flow duct, and
flight tests of an experimental airplane specially fitted with an engine
identical to the one used for ground tests. The contract activities
will include, but not be limited to, JT15D engine modifications and
instrumentation by the P&WA Company; OV-1B airplane modifications by the
Grumman Corporation; a research technology contract by the P&WA and
Boeing companies; grants on the study of the fundamentals of turbulence
and its control; a contract for an advanced noise source theory; and a
contract for advanced suppressor concepts.
The emphasis of this program is on developing reliable methods for
extrapolating fan noise data measured in a ground test facility to
flight. However, the opportunity is also being utilized to collect
ground static, wind tunnel, and flight data on the jet and core com-
ponent noise sources of a turbofan engine to enhance understanding of
forward speed effects on these other noise sources. The results of this
program will lead to more efficient noise reduction in engine inlets and
fan exhaust ducts since less conservatism will be required in noise
treatment. Several promising noise reduction concepts that failed to
show the expected results because of a lack of understanding of the
vagaries of static testing will now be retested and probably applied to
design problems. It is anticipated that the static and wind tunnel
testing techniques produced by this program will allow engine manu-
facturers to guarantee fan noise levels of their engines to much closer
tolerances than before. Finally, the results of this program will allow
B-13
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Forward Velocity Effects on Fan Noise (Continued)
a certain amount of "fine-tuning" of fan noise control by optimizing the
tradeoff between noise reduction and weight and performance penalties.
Schedule;
Completed Grumman feasibility study - (Langley) December 1977
Initiate JT15D static tests, in-house - (Lewis) January 1978
Complete initial 40'x 80' wind tunnel tests - (Ames) October 1978
Complete OV-lB modification by Grumman - (Langley) April 1979
Complete Phase I of JT15D static tests - (Lewis) April 1979
Initial flight tests October 1979
Accomplishments; The major accomplishments to date have been to iden-
tify the problems to be solved and the resolution of an approach. In
particular, a common engine, the JT15D, has been identified and pro-
cured. Modifications and instrumentation of these engines is under way
at the Pratt and Whitney Aircraft Company. A feasibility study com-
pleted in December 1977 determined that it was possible to attach the
JT15D engine under the wing of an OV-lB airplane for noise tests. A new
streamlined static test stand has been fabricated for the static engine
tests which are scheduled to begin in January 1978.
Sponsor: Langley Research Center and Lewis Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 351 205 366 1,487
Agency Manpower (Man-Years): 10 6 11 38
B-14
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Internal Noise Transmission Through Turbines and Nozzles
This work involves experiments and mathematical analysis to deter-
mine the characteristics of acoustic propagation of internally generated
engine noise to the far field. The research is focused on acoustic
transmission through the turbine and through the engine nozzles and
associated flow fields. The acoustic sources contributing to internal
noise include the combustor, turbines, and support/flow transfer struts.
It is expected that the results of this research will yield engi-
neering methods that can be used to compute the attenuation of upstream-
generated low frequency noise by the turbine. The nozzle/flow trans-
mission investigations will also lead to engineering prediction methods
which will permit calculations to be made of engine far-field noise due
to the engine core, given the acoustic power output of the core components.
Need for Study; Noise radiating from the exhaust core of a gas turbine
engine includes components transmitted by the internal components,
contributing to the far-field overall perceived noise level particularly
at approach. This work is essential to an understanding of the nature
of core noise generation and to the development of quantitative core
noise prediction methods.
Approach; The work is being done principally by contract. Transmission
of sound through turbines is being investigated by the General Electric
Company.
Transmission of sound through nozzles and their associated flow
fields is being investigated by Lockheed-Georgia. The contractors are
conducting both analytical and experimental investigations.
The experimental portion of the turbine transmission work encom-
passes measurements of the attenuation of low frequency sound by a high-
pressure single stage turbine, and low-pressure turbine operated both as
a single-stage and as a 3-stage machine. The results of the experi-
mental investigations are compared with the predictions from a rather
basic actuator-disc turbine model theory. Under a separate contract,
work is being undertaken to improve the actuator-disc analytical model
and to develop a new finite-chord model that implicitly incorporates
frequency dependence.
B-15
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Internal Noise Transmission Through Turbines and Nozzles (Continued)
The nozzle/flow transmission work involves experimental measurement
of acoustic radiation from artificial sound sources embedded in coaxial
nozzle/flow systems. A parallel mathematical analysis is being con-
ducted to guide the conduct of the experiments and to develop a suitable
model.
Other contracts with General Electric and with Lockheed-GA on
combustor noise tests of the CF6 engine and on free-jet forward velocity
simulation, respectively, will also materially contribute to this tech-
nology area. In addition, this research is being complemented by FAA-
sponsored work at General Electric on turbine noise generation and its
transmission through successive turbine stages.
Schedule: Contracts with General Electric are nearing completion.
Contract with Lockheed-Georgia commenced in August 1977.
Accomplishments; The final report by G. E. on attenuation of upstream-
generated low frequency noise by gas turbines (CR-135219) has been
issued. In the program, the influence of inlet temperature and turbine
speed on attenuation was evaluated; and the effects of turbine pressure
ratio, blade-row choking, and additional downstream blade rows were
determined. Preliminary identification of pertinent aeroacoustic corre-
lating parameters was made. Comparisons of the test data were made with
theoretical predictions to establish the limits of the actuator-disc
theory.
The G.E. draft report on a theory of low frequency noise trans-
mission through turbines is being reviewed. A new finite-chord analyt-
ical model has been developed which accounts for adjacent blade row
interactive effects, higher order spinning modes, blade passage shocks,
and duct area variations.
In the Lockheed-GA contract, the nozzle designs have been approved,
and fabrication is underway.
Sponsor: Lewis Research Center and Langley Research Center
Fiscal Year 1975 1976 1977 1978
Funding ($1000): 76 140 120
Agency Manpower (Man-Years): 343
B-16
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Duct Acoustic Treatment Projects
Acoustic treatment of aircraft engine nacelles has proven to be
very successful during the past 10 years. Refinement of this tech-
nology has the potential for significant additional noise reduction
as well as the possibility of achieving specified noise levels with
minimum weight and performance penalties. This requires that the
noise sources need to be accurately described, the mechanism of duct
propagation in the presence of airflow up to Mach 1 be fully under-
stood, and the performance of acoustic duct liner materials be under-
stood and improved.
The noise reduction lining treatment used in aircraft gas turbine
engine ducts usually consists of a honeycomb backing covered with a
perforated sheetmetal facesheet. The major mechanism of noise reduc-
tion is the conversion of acoustic energy into heat energy through
acoustic resonance phenomena in the honeycomb cavities. Another type
of acoustic treatment being reexamined for aircraft use is the bulk
absorber. This is the familiar material often found in insulation
applications. A major portion of the acoustic energy is converted
into heat energy during the process of propagation through the bulk
material.
High subsonic inlet flow is another noise reduction approach being
explored in conjunction with acoustic treatment. As the airflow
velocity approaches Mach 1 in a direction opposite to the noise prop-
agation, the noise is attenuated. The physical process that causes
this attenuation is not fully understood at present.
Need for Study; Continued reduction in all propulsion noise sources
is required in order to reduce the community noise of the next genera-
tion of commercial transports and to meet more stringent federal noise
regulations. In particular, further reductions in fan and compressor
noise must be achieved. Research indicates that appreciable gains in
engine noise reduction are possible through the use of more efficient
nacelle acoustic treatments and carefully designed high-speed inlets.
Data on liner and inlet performance taken under carefully controlled
aerodynamic and acoustic conditions are needed to illuminate the physi-
cal processes involved, to serve as a basis for planning flight demon-
strations of new concepts, and to provide preliminary information for
the design engineer.
Approach; The approach is multi-faceted and includes advanced theoreti-
cal work and extensive experimental work done both in-house and under
B-17
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Duct Acoustic Treatment Projects (Continued)
contract. The major portion of the in-house experimental research is
conducted with a spinning mode synthesizer (S.M.S.) apparatus in
which is produced a computer-controlled acoustic field in the presence
of airflow. This allows investigations of advanced acoustic treatment
concepts, noise attenuation as a function of high subsonic flow, and
inlet radiation as a function of geometry. In addition to the S.M.S.
apparatus, use is made of an advanced flow-impedance tube for the
precise evaluation of the acoustic properties of various candidate
materials. The theoretical approaches are closely coupled to the experi-
ments. They are currently concentrating on solutions for noise propa-
gation in ducts with high subsonic flow and changing cross-sectional
area and on solutions for noise radiation from inlets with different
geometries.
The eventual results of the duct acoustics program will be to
significantly reduce gas turbine engine noise propagation without
adversely affecting aircraft performance.
Schedule;
Completion of flow impedance experiments of
bulk absorbing materials, in-house October 1978
Completion of S.M.S. experiments of segmented
bulk absorbers - General Electric June 1978
Completion of radiation theory for simple
geometrically shaped inlets, in-house July 1978
Complete no-flow inlet radiation experiments,
in-house November 1978
Complete analytical study, high subsonic flow
using wave-envelope method - VPI&SU November 1978
Complete finite element theory for compressible
flow - Wyle Laboratories December 1978
Complete initial experiments to demonstrate
impedance control of acoustic material January 1979
Complete S.M.S. study of advanced hybrid inlet July 1979
Accomplishments; Two major duct acoustic facilities, the Spinning
Mode Synthesizer and Flow Duct (S.M.S.) and the Flow-Impedance Tube,
became operational in 1977.
A study of the acoustic properties of a bulk absorber with water
repellant properties was completed in-house. Other in-house accomplish-
ments include the development of a two-dimensional finite element
technique for calculation of normal modes in a duct in the presence
of non-uniform mixed boundary conditions for application to segmented
liner design, and a systematic study on the effect of measurement
errors on specifying acoustic impedance material.
B-18
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Duct Acoustic Treatment Projects (Continued)
A finite element theory for ducts with compressible mean flow
was developed under contract by Wyle Laboratories. An experimental
study completed by the Boeing Company demonstrated that inlet noise
directivity can be controlled by changes in inlet geometry. Sound and
high-speed flow interaction studies were completed by the University
of Tennessee, for application to hybrid inlet design.
Sponsor: Langley Research Center and Lewis Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 981 807 1,066 828
Agency Manpower (Man-Years): 26 25 32 22
B-'19
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Propeller Studies
This research area will develop and demonstrate noise reduction
technology for propeller driven general aviation aircraft that minimizes
performance penalties without degrading flight safety. The projects are
specifically aimed at developing capability for including noise con-
straints into propeller design. An element of this research is also
aimed at determining the noise characteristics, validating prediction
methods, and developing low-noise concepts for propellers designed for
cruise at transonic speeds (M ~.8).
Need for Study; The large numbers of propeller-driven general aviation
aircraft and their growing operations from small airports near suburban
residential areas are causing increasing community noise impacts. The
dominant noise source from all the turbine-powered vehicles and most of
the reciprocating-engined vehicles is the propeller. Propeller noise
technology has been neglected in recent years although a substantial
base had been established prior to the advent of the turbojet engine.
However, the early technology base did not include the effects of for-
ward speed on noise. Newer, better predictive methods and computer
technology are also now available. In addition, the revived interest in
the application of propellers to transonic cruise aircraft (M ~.8) for
fuel economy introduces a new and relatively unexplored range of opera-
ting parameters where propellers are known to be noisy. For such
vehicles to be economically viable, efficient propeller concepts must be
evolved that are quieter both in cruise for passenger comfort and in
terminal operations for community acceptability.
Approach: Theoretical and experimental studies will be undertaken
inhouse and under contract to refine and validate existing propeller
noise prediction methods. Flight and wind tunnel experiments will be
conducted with specially instrumented propellers and the results com-
pared with theory to relate noise radiation to fluctuating pressure
measurements on the blade surface. Exploratory wind tunnel experiments
will be conducted for novel concepts such as acoustically-designed
shrouded propulsors and performance designed propellers. A parametric
wind tunnel study of a family of quiet propellers in simulated flight
will expand the noise data base to include forward speed effects. The
noise signatures of typical general aviation aircraft will be documented
as required to identify the separate noise source contributions of the
propeller and power plant.
Parametric studies and several critical experiments in flow facil-
ities and flight will be conducted on propeller configurations specially
designed for transonic cruise to establish noise characteristics and
validity of the predictive methods.
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Propeller Studies (Continued)
Schedule: The general aviation propeller study is jointly funded with
EPA. The research in this area is of a continuing nature and the near
term plans (FY 78) are as follows:
Complete comparative wind tunnel noise/performance tests
on a Cessna 327 having a standard free propeller and
a quiet-fan shrouded propulsor
Initiate development of a general aviation propeller noise
data base including forward speed effects in the Langley
Quiet Flow Facility
Complete software development and initiate parametric
study of high speed propellers using Farassat's theory
Conduct Phase I of three phase joint EPA/NASA program
to demonstrate general aviation propeller noise/
performance technology
Obtain near field noise data on M -.8 propeller in
UARL facility
Accomplishments; A new general aeroacoustic theory for propellers
operating at all speeds has been developed (the Farassat theory).
Initial applications to general aviation propellers where data exists
have been very encouraging. A static test of propellers having four
different airfoils specifically designed to test this theory has been
completed wherein the propeller tip speed range from M= .4 to M = 1.1
was covered. A flight test of a general aviation aircraft, where both
near-field noise and oscillating surface pressure on the propeller blade
were measured, has been completed and documented.
Sponsor: Langley Research Center and Lewis Research Center
Fiscal Year: 1975 1976 1977 1978
General Aviation Propeller Projects
Agency
Funding ($1000) 130 120 350* 360*
Manpower (Man-Years) 3 4 10 10
Mach 0.8 Propeller Projects
Funding ($1000) - 66 154 171
Manpower (Man-Years) 254
A total of $150,000 of this funding is being applied by NASA to the
joint EPA/NASA small Propeller Technology program, described on
page E-3.
B-21
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY: ROTOR NOISE
Helicopter Rotor Noise Control
The helicopter has many sources of noise with the principal ones
associated with the main rotor, tail rotor, and their interactions.
The dominant noise source depends on the configuration and operating
conditions. Therefore, rotor noise control requires that a multitude
of configurations and operational variables be considered. This research
area is aimed at sorting, ranking, and understanding the various sources
of rotor noise, developing and validating methods for predicting the
noise, evolving noise control concepts and methods, and providing
engineering design methods.
Need for Study; To be economically viable, helicopters must be operated
in urban areas and from small landing areas. This requirement means
that their noise characteristics must be non-intrusive to achieve
community acceptability. The current demand for rotor noise control
technology is driven by pending national and international noise regu-
lations that recognize that making the helicopter a better neighbor
will increase opportunities for its utilization.
Approach: In-house and contract projects are addressing both analyti-
cal and experimental questions. Experiments are being designed and
conducted specifically to verify the applicability and limits of
recently developed rotor aeroacoustic theory (Farassat theory). These
critical experiments will be conducted with scale models in wind tunnels
and at full scale in flight. One of the most annoying rotor noise
sources is blade slap. Special attention is given to its understanding
and reduction. Laboratory and flight experiments are also conducted
to define poorly understood noise problems such as main rotor/tail
rotor interaction noise.
It is expected that vortex interaction blade slap, the most annoy-
ing rotor noise source, will be eliminated on future helicopters by
configuration changes. High speed blade slap, due to transonic rotor
tip speeds will continue to set a noise limit for cruise flight. It
is also expected that the emerging analytical tools, when validated,
will provide a new plateau of noise design capability to the rotor-
craft industry.
Schedule: The research in this area is of a continuing nature and short
range plans are as follows:
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Helicopter Rotor Noise Control (Continued)
Conduct Huey Cobra Noise Experiment in V/STOL FY 1978
Tunnel for comparison with flight
Report noise radiation patterns of Civil Helicopter FY 1978
Systematic noise tests with Rotor Tip Modifications FY 1978
in V/STOL Tunnel
Main Rotor/Tail Rotor Interaction Experiments in FY 1979
Quiet Flow Facility
Exploratory Acoustics Tests of Advanced Rotor Concepts FY 1979
Accomplishments: Wind tunnel tests have demonstrated that the tip air
mass injection scheme will successfully reduce blade slap due to vortex
interactions. An alternate passive concept for blade slap alleviation,
the OGEE tip modification, has been successfully demonstrated in flight
on a UH-lH. Initial tests on the main rotor/tail rotor interaction
noise project have been completed with indications of the geometrical
configurations that generated the minimum noise. Ground noise foot-
prints and directivity patterns for two different configurations have
been measured with the ROMAAR system at Wallops Flight Center. The
major theoretical achievement has been the development and partial
validation of the Farassat non-compact source theory for rotors.
Sponsor: Ames Research Center and Langley Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 178 1,300 1,141 1,272
Agency Manpower (Man-Years): 7 11 19 13
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - INTERIOR NOISE
General Cabin Noise Research
The objective of this research program is to provide design
guidelines for reduction of aircraft interior noise through attenuation
of airborne and structural transmission of noise and vibration. The
emphasis will be on the development of analytical procedures for
general aviation and high speed turboprop aircraft, with decreasing
emphasis on powered lift vehicles.
Need for Study: The interior noise levels of commercial transport
aircraft are, for the most part, acceptable in terms of passenger
comfort and aircrew efficiency. However, the interior noise levels
of general aviation propeller aircraft, helicopters, powered-lift
vehicles, and turboprop transport aircraft are considerably higher.
Such high levels can seriously compromise crew efficiency and passenger
comfort and, if experienced for sufficiently long periods of time,
can contribute to hearing damage. The current procedure for reducing
noise levels is to add soundproofing material which appears to provide
acceptable results for conventional commercial aircraft. However,
excessive weight and performance penalties are expected if the same
approaches are used to reduce the levels of the noisier aircraft to
acceptable levels. Since the noise spectra of these aircraft contain
more energy in the low-frequency range where soundproofing material is
inefficient, further research is needed to arrive at efficient solutions.
Approach: Research is being conducted in-house and through contracts
and grants. Characteristics of the source such as spectral content,
spatial distribution, and point-to-point correlations are determined
through wind tunnel and flight tests. Vehicles included in the program
are propeller-driven general aviation aircraft powered-lift vehicles
(specifically, the YC-14 upper-surface-blown and YC-15 externally-
blown flap systems); helicopters (with emphasis on noise from the main
gear box), and high speed turboprop aircraft utilizing supersonic tip
speed "propfans."
The major thrust of the program is the development of analytical
methods for predicting interior noise, and the application of these
methods to develop low-weight, low noise transmission sidewall concepts.
Detailed analytical models of the structural response to acoustic
inputs are being developed that include the influence and coupling of
the acoustic (cabin) space. The models range in complexity from
cavity-backed simple panels to stiffened panels and stiffened cylinders.
In all cases, the validity of the analytical model is being verified by
comparison with experiments.
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
General Cabin Noise Research (continued)
The effectiveness of various add-on noise reduction treatments is
also being examined. Treatments being studied include absorptive
materials, double walls, septum, damping tapes, constrained layer
damping, composites for stiffness control. The emphasis is on the
development of maximum noise attenuation per unit weight and cost.
Full-scale flight tests incorporating noise reduction concepts will
finally verify the analytical techniques and the passenger/crew
acceptability.
Schedule;
Propeller/propfan acoustic input measured FY 1978
Responses to acoustic input measured FY 1978
Transmission loss of stiffened cylinders measured FY 1979
Analytical procedures for transmission loss developed FY 1980
Mach 0.8 turboprop structure/treatment defined FY 1979
Mach 0.8 turboprop verified in flight FY 1982
Quiet General Aviation aircraft demonstrated FY 1980
Accomplishments; Progress to date suggests that the accurate predic-
tion of aircraft interior noise is feasible. A number of flight tests
to define interior noise environments of typical vehicles have been
completed and the data published. Included are a single and twin engine
general aviation vehicle, the CH-53 civil helicopter with and without
interior noise treatment, and the YC-14/YC-15 powered-lift vehicles.
Analytical results have been compared with experiment, demonstrating
the effects of curvature, pressure, cavity backing, and stiffening on
panel transmission loss.
Sponsor: Langley Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 141 94 331 262
Agency Manpower (Man-Years): 3 2 7 5
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - INTERIOR NOISE
Sound/Structure Interaction
Short takeoff and landing (STOL) aircraft proposed for future use
in the U.S. transportation system feature direct impingement of the
jet engine exhaust on the wing and flap system to redirect the high
velocity jet downward to obtain the high lift required for STOL
operation. The direct impingement subjects wing, flap, and fuselage
structures to higher acoustic loads than for non-STOL aircraft and
requires new technology to adequately design for prevention of acoustic
fatigue and for quiet crew and passenger cabins. This program combines
flight testing, scale model testing, and analytical scaling studies
to develop and validate methods for predicting acoustic loads on
current powered-lift aircraft as well as future STOL aircraft.
Need for Study; The successful utilization of powered-lift STOL
aircraft requires designs with acceptable acoustic fatigue lifetime
and passenger environments. The acoustic phenomena associated with
powered-lift engine/wing configurations require development of advanced
technologies for prediction of the acoustic loads and the resultant
structural response and fuselage noise transmission. The random and
configuration-dependent nature of the acoustic loads associated with
the jet exhaust and its impingement on the wing and flaps precludes
purely theoretical prediction methods and forces reliance on empirical
methods based on model tests and scaling to full-size aircraft.
Approach: Experimental programs have been conducted on full-scale
aircraft, large-scale models utilizing jet engines, and small-scale
laboratory models using air jets to simulate the engine exhaust.
Theoretical and empirical scaling studies have been conducted to develop
scaling laws. The full-scale aircraft studies were conducted with
the Air Force AMST aircraft; namely, the Boeing YC-14 aircraft which
features the upper-surface-blowing (USB) powered-lift concept and the
Douglas YC-15 aircraft which features the externally-blown-flap (EBF)
powered-lift concept. In a cooperative NASA/Air Force program,
acoustic loads; structural response of wing, flaps, and fuselage;
and interior noise were measured during flight and ground operations.
A preliminary ground test utilized a full-scale YC-14 engine-flap system
to measure acoustic loads and flap accelerations. Large-scale model
tests have included an approximately one-half scale EBF wing/flap
system with an 8,000 pound thrust turbofan engine and an approximately
one-quarter scale USB wing/flap system with a 2,000 pound thrust
turbofan engine. Laboratory tests utilized airjets of about 2 inches
diameter to simulate the engine exhaust, with both USB and EBF wing/
flap systems of about one-sixteenth scale.
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Sound/Structure Interaction (Continued)
Current emphasis is on analysis and interpretation of the results
from the various tests to establish scaling and prediction methods. Work
ongoing at Boeing and Douglas is focused on flight test results and is
expected to be completed in FY 78. Correlation of all results from
the various model tests with full-scale data and scaling theories is
also planned for completion in FY 78. The final output of this
project will be a published, high quality data base for acoustic loads
on powered lift, vehicles, validated scaling methods, and empirical
prediction methods.
Schedule:
Complete analyses of flight data:
Boeing YC-14 July 1978
Douglas YC-15 August 1978
Complete analyses of data from large-scale models March 1978
Complete scaling studies October 1978
Accomplishments; All testing has been completed. Data from most
model tests have been published. Flight tests on the Douglas YC-15
airplane were conducted in January-February 1976 and the flight tests
on the Boeing YC-14 were done in October-November 1976. Results from
the large-scale model and flight programs have been analyzed and are
being published to display the level and spectrum of the actual
acoustic loads for use of designers. A preliminary assessment was
released at an AIAA Meeting in July 1976. Comparisons of the results
from the models at various scales with scaling parameters have already
been made for development of prediction procedures. Progress reports
on scaling methods and their comparison were presented at conferences
in May 1976 and June 1977.
Sponsor: Langley Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 476 245 370 391
Agency Manpower (Man-Years): 4 4 2 9
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - AIRFRAME NOISE
General Airframe Noise
Airframe noise is the nonpropulsive noise of an aircraft in flight.
The generation of turbulence by flow separation, the impingement of
wakes on wings and flaps, and the passage of turbulence thru gaps in
high lift devices and across trailing edges are believed to be signi-
ficant sources of airframe noise. These mechanisms are present and most
effective during landing approach operations when leading and trailing
edge flaps and slats are deployed, landing gear are lowered, and various
cavities and cutouts in the airframe are open or partially exposed.
Need for Study: Airframe noise sets a lower limit to which aircraft
noise can be reduced by the elimination of propulsion system noise.
Measurements of commercial jet transport airframe noise during landing
approach indicates that this noise source is only about 10 EPNdB
below FAR-36 1969 certification requirements for approach operations.
Thus, to realize the full benefits from future quiet engines, airframe
noise must be reduced below its current level. Airframe noise increases
with landing speed, gross weight, and wing area and thus, is expected
to be most serious for very large, heavy, advanced transport aircraft.
Approach: Both theoretical and experimental investigations are being
conducted. Experimental studies employ models of individual aircraft
components and complete aircraft to identify the principal noise
generating mechanisms, locate the components most responsible for
airframe noise, and identify and test noise reduction concepts. The
current focus is on trailing edge and leading edge high lift devices,
landing gear and wheel wells. Considerable testing is carried out in
quiet open-jet anechoic flow facilities such as the Langley Aircraft
Noise Reduction Laboratory (ANRL). A testing technique using radio-
controlled geometrically and aerodynamically scaled models of commer-
cial and advanced design transports is also under development as a
means of studying scaling effects while avoiding the acoustic data
interpretation problems of testing in wind tunnels. Pull-scale flight
data from commercial aircraft are obtained and analyzed under contracts
with the airframe manufacturers.
Theoretical studies consist of the analysis and correlation of
measured data to obtain empirical prediction schemes and scaling laws
as well as computerized theories for calculating turbulent flow fields
and noise from the fundamental equations of fluid dynamics, unsteady
aerodynamics and acoustics.
Throughout, the focus of this research effort is on very large
transport aircraft.
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
General Airframe Noise (Continued)
Schedule;
Report results of SCAR tests FY 1978
Initiate definitive trailing-edge noise experiments FY 1978
Identify sources of interaction noise FY 1978
747 noise measurements using R/C model FY 1979
Test low-noise, high-lift devices FY 1979
Noise Tests of Spanloader FY 1979
Accomplishments: Airframe noise tests of a 2-foot span SCAR concept
have been completed in the four-foot diameter open-jet anechoic noise
facility in ANRL. A powered model of a 747 and a two-engine recoverable
lifter have been constructed and test flown in the radio controlled
model development activity. These models are being used to develop and
check out onboard instrumentation and flight procedures. Extensive
overall sound pressure level (OASPL), spectra and directivity measure-
ments have been made on cavity noise. The spectral data has been used
to identify the mechanism of cavity noise generation at low flow speeds,
and develop and verify prediction formulae for tones. The extensive
directivity data now undergoing analysis is the only such data available
on cavity noise. A contract has been awarded to United Technologies
Research Center (UTRC) to conduct an experimental study of airframe
component interaction noise. The purpose of the study is to pinpoint
the interactions which are principally responsible for landing approach
airframe noise and to collect definitive acoustic and flowfield data
to relate noise to specific physical processes. A preliminary study by
Bolt Beranek & Newman, Inc. (BBN) of the potential of panel vibra-
tions for generating high frequency (~1,000 Hz) airframe noise has
arrived at a negative conclusion. Predicted panel noise, based on
vibration spectra measured on a rectangular panel, is much too low to
account for observed levels. This conclusion leaves the source of
high frequency "airframe" noise unexplained.
An acoustic mirror technique for locating noise sources in a
turbulent flow has been applied to study noise generation by various
combinations of a model of a landing-gear-cavity flap arrangement.
The arrangement simulates the underside of a transport wing in landing
approach. Flap side edges and wake closure regions have been found
to be regions of high frequency noise production.
Sponsor: Langley Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 374 401 767 789
Agency Manpower (Man-Years): 4 9 8 20
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - AIRFRAME NOISE
Aerodynamic Noise
This research area is directed toward a better understanding of
turbulence—sound interactions with particular emphasis on noise
generation by unsteady fluid flows in the presence of surfaces. Much
of the activity is basic research which has direct input to a broad
spectrum of more applied research on aircraft noise problems.
The emphasis of the current research effort is to bring the best
existing experimental and theoretical tools of turbulent flow field
prediction and aerodynamic noise generation to bear on the problem of
trailing edge noise production. This is a technically important problem
of extensive interest since trailing edge noise is believed to be a
primary contribution to propulsive lift noise as well as landing approach
and cruise configuration airframe noise.
Need for Study: Aerodynamic or turbulence induced noise and vibration
are associated with all types of aircraft and all flight regimes. Some
specific examples are: jet noise, trailing-edge noise, propulsive
lift noise, core noise generated by exhaust flows over duct splitters
and struts, and aircraft interior noise arising from structurborne
sound and boundary layer-induced panel vibrations. Some fan, rotor, and
propeller noise is the result of blade-turbulence interactions—large
coherent eddies produce tones whereas small scale turbulence appears
responsible for broadband noise generation. Aerodynamically generated
noise can be objectionable within an aircraft interior and in the
surrounding airport community. High acoustically-induced vibration
levels can be detrimental to aircraft structures. Therefore, this
research is necessary to create the basic understanding of the mechanics
underlying the generation of noise by aerodynamic flows and eventually
lead to the reduction or elimination of many of the individual air-
craft noise sources for passenger and community acceptability.
Approach: A wide range of basic experimental and theoretical research
is required to solve aerodynamic noise problems. Primary emphasis
will be placed in three areas: (i) understanding noise producing
turbulent flow fields, (ii) developing aerodynamic noise prediction
theories, (iii) conducting definitive experimental studies.
Methods for predicting the mean and time-dependent properties of
turbulent flows around bodies will be developed and applied. These
methods include finite element, finite difference, stability analyses
and vortex model approaches to solving appropriate forms of the
Navier-Stokes equations. For the foreseeable future, empirical inputs
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Aerodynamic Noise (Continued)
and flow field simulations must be used in these studies to supplement
methods based on first principles. The applicability of existing
turbulence models for predicting aircraft generated flow fields and the
associated aerodynamic noise will be determined. The need to develop
new turbulence models—in particular models appropriate for three-
dimensional flows—will be identified.
Practical noise prediction methodologies will be formulated.
Approaches to be followed include the method of matched asymptotic
expansions, vortex models, direct evaluation of the Lighthill integral,
and the Bernoulli Enthalpy formulation of the aeroacoustic equations.
This latter formulation appears to provide a unified analytical basis
for investigating the generation, refraction, and scattering of sound
by flow as well as acoustically induced flow modification. These various
noise prediction methods will first be applied to shear layer and cavity
flows and to noise production by large scale structures. The more
successful and tractable methods will be brought to bear on trailing-
edge noise fields.
Carefully conducted and thorough experiments of trailing-edge
flow fields and noise will be carried out. Extensive measurements of
the flow and acoustic field will be made. This data will provide a
complete statistical characterization of the turbulence, be used to
validate turbulent flow field and noise prediction methodologies,
and make it possible to relate noise generation to the fluid dynamics.
Successful convergence of the theoretical and experimental studies will
then provide the background for identifying and testing noise reduction
concepts. These might involve turbulence modification or suppression
schemes such as flow additives, compliant or porous surfaces, and
fluid injection (trailing-edge blowing). In the case of noise
generated by aircraft components it is desirable, whenever possible,
to relate noise to gross aerodynamic parameters and performance, in
particular drag, since the tradeoffs between noise reduction and
mission capability must be evaluated.
Schedule;
Initiate definitive trailing edge flow and noise experiments 1978
Measurement of Large Scale Structures using vorticity probe 1978
Complete finite element prediction of trailing-edge flow 1978
field
Fabricate electronics (VORCOM) for real time application 1979
of vorticity probe
Compare trailing-edge flow field calculations and 1979
measurements
Apply Bernoulli Enthalpy formulation of aerodynamic 1979
noise theory
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Aerodynamic Noise (Continued)
Accomplishments; The Bernoulli Enthalpy formulation of the aerodynamic
noise equations has been applied to problems of noise generation and
sound scattering by vortices as well as the excitation and resonance of
pairs of turbulent eddies by sound. It is significant that the theory
provides a unified basis for such a wide variety of problems. Current
effort is to incorporate the effects of mean flow into the analysis and
investigate the effects of convection on sound generation and scattering.
A parabolic approximation to the Navier-Stokes equations and a
supplementary set of turbulence equations have been solved using finite
element methods to predict the mean and turbulent flow fields of a
USB configuration. Comparison of calculations with existing measure-
ments of wake turbulence were encouraging. Several improvements in
the prediction method are now being made-—allowance for curved surfaces,
a better turbulence model, inclusion of a surface pressure prediction
module, and a more accurate solution very close to the edge. The computer
program will be used to make extensive calculations for comparison with
upcoming trailing edge noise experiments.
Analytical studies of the noise generation by large-scale structures
in shear layers and of the excitation of a shear layer by incident
sound have been completed. The analyses use matched asymptotic expan-
sions and stability theory. The theory predicts the directivity of the
sound generated by large-scale instability waves in a shear layer and
estimates their sensitivity to a beam of externally imposed sound.
Measurements of the refraction of sound by the shear layers of
free jets have been made as part of a contract effort with UTRC. The
measurements confirm existing theories being used to predict shear
layer angle and amplitude corrections. These corrections must be
applied to noise data obtained from models placed in open-jet flow
facilities to simulate forward speed.
A hot wire probe for directly measuring vorticity in a flow has
been developed under a grant with Michigan State. A prototype has
been delivered to Langley researchers. Data reduction software is now
being written and proof-of-concept experiments are planned.
Experiments to identify the fluid dynamic processes involved in
the generation of trailing edge noise on an USB configuration have been
completed and the data analyzed. The interaction of large coherent
eddies in the upper mixing region of the jet with the trailing edge
and its wake was pinpointed as being of major importance for the
sound generation. A follow-on experiment to modify the large eddies
and thereby alter the noise is now being conducted. A phase averaged
method of predicting the evolution of large scale structures in a
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Aerodynamic Noise (Continued)
turbulent shear layer has been completed. The scheme predicts the
growth and eventual decay of these structures. The flow model is now
being used to evaluate the Lighthill integrand in order to predict the
noise from large-scale structures.
Sponsor: Langley Research Center, Ames Research Center,
and Jet Propulsion Laboratory
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 584 975 846 925
Agency Manpower (Man-Years): 6 23 34 19
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - AIRFRAME NOISE
Flow Interaction/Propulsive Lift Noise
The objective of this effort is to identify the noise sources
associated with jet/surface interaction noise and to examine means of
suppression, including the shielding of jet noise associated with the
engine-over-the-wing (OTW) concept. The established data base is
being extended on the near-field and far-field acoustics, surface
pressure fluctuations, and aerodynamics, for various jet/surface appli-
cations such as under-the-wing (UTW) and OTW powered lift, thrust
reversal, and thrust vectoring. Included are the effects of noise
directly generated by jet/surface interaction, jet noise modification
through the use of mixer nozzles, surface treatment, source modification
devices, and forward velocity effects. Prediction methods have been
developed and are being improved to facilitate the integration of this
technology into the design of practical, low-noise, jet powered-lift
aircraft.
Need for Study: In order to evaluate a goal of 95 EPNdB at a 152 meter
sideline distance for future Short Take-Off and Landing (STOL) air-
craft, the noise sources for STOL configurations needed identification.
It was determined that jet/flap interaction and thrust reversal are
dominant noise sources for powered-lift jet short- and reduced-takeoff-
and-landing (STOL and RTOL) aircraft. The QCSEE* and AMST** jet
powered-lift projects each include both UTW and OTW configurations.
The UTW configuration appears to be simpler and may have better cruise
performance. The OTW configuration remains of interest, for both
STOL and CTOL, because of the high-frequency exhaust noise shielding
benefits attainable. This benefit, however, must be balanced against
the increased low-frequency noise generated. Because of the low noise
levels required for commercial STOL aircraft, thrust reverser noise
is a serious concern. In addition, jet/surface noise such as that
produced by thrust reversers may become important for other aircraft
categories if noise regulations more stringent than present are
enacted.
Approach: Experimental and theoretical studies have been conducted
in-house, by contract, and by grant. The in-house work included
small scale (5 cm nozzle diameter) and large scale (TF-34 engine)
experimental studies. The experimental OTW and UTW studies included
the effects on noise of nozzle location, nozzle shape, wing size, flap
deflection, flap number, jet exhaust velocity, and forward speed.
* Quiet, Clean, Short-Haul Experimental Engine.
** Advanced, Medium STOL Transport.
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Flow Interaction/Propulsive Lift Noise (Continued)
Prediction methods have been developed in-house and under contract by
United Technologies.
Presently planned cross-correlation and coherence in-house studies
will determine the far-field contributions of the various noise sources
associated with STOL aircraft concepts. This information, together with
the large acoustic and aerodynamic data base that has been provided by
in-house and contract efforts, should lead to an improved, unified
method for prediction methodology. Trade-off studies can also be made
to assess the merits of design changes on both acoustics and aerodynamic
performance.
The parameters evolved in correlating the test data and the ana-
lytical studies to date should point the way toward reducing jet/flap
interaction noise for future STOL aircraft using powered lift concepts.
Schedule: An in-house effort was initiated in 1970 and is still in
progress. A study of impingement and scrubbing noise was conducted by
United Technologies in 1973 through 1977. A study of acoustic source
location for a jet-blown flap was conducted by the University of Ten-
nessee Space Institute in 1973 through 1977 under a NASA grant.
Accomplishments; Work under this program has already provided an early
assessment of OTW and UTW jet/flap interaction noise and thrust reverser
noise in support of powered-lift programs, and interim prediction
methods for externally blown flap noise and thrust reverser noise have
been developed.
Static scale model tests of QCSEE-OTW flyover and thrust reverser
noise and performance have been conducted and the validity of acoustic
scaling for geometrically similar models has been tested in-house. An
analytical model for UTW externally blown flap noise has been developed
and its validity demonstrated for models of various size and for the
TF34 engine. Other accomplishments are the development of suppression
mechanisms for UTW application; in-house test of a large-scale model
segment of an augmentor wing designed by Boeing under a NASA Ames
contract; verification that fundamental theory predicted the correct
noise levels, spectra, and directivity patterns for jet flow impingement
on struts; and the development of a predictive model for flow/surface
interaction noise both inside and outside the engine.
Sponsor: Lewis Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 366 995 1,089 1,101
Agency Manpower (Man-Years): 10 12 17 14
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - NOISE PREDICTION TECHNOLOGY
Noise Prediction Techniques
An integrated computer software system for aircraft noise predic-
tion (ANOPP) is being developed. It features state-of-the-art tech-
nology in both noise prediction and computer software. Prediction is
based upon semi-empirical methods which are used to compute one-third
octave spectra vs. time for individual aircraft noise sources such as
jet noise, turbine noise, or airframe noise. Noise from individual
sources is then summed, the effects of propagation through the atmo-
sphere and ground reflection are included, and the noise received at
arbitrarily selected observer positions is calculated. Perceived
noise level, effective perceived noise level, or other noise measure-
ment scales may be used for the computations.
Need for Study: The capability to accurately predict the noise of both
current and future technology aircraft is essential to the agency,
the industry, and the country in order to quantify the noise benefits
from proposed noise reduction technology programs, to identify the
research areas where present knowledge of noise generating mechanisms
is deficient, to support the formulation of reasonable noise standards
for future aircraft, and to predict the community noise impact of pro-
posed aircraft early in their design cycle.
Approach: ANOPP development rests upon three key concepts: (1) an
executive and data base software system architecture that provides
maximum problem solving flexibility and user-oriented featui.es, (2)
modular noise component prediction methodology that can easily be
modified, updated, or replaced by an engineer-user as the state of
the art in prediction technology advances, and (3) complete documen-
tation to allow independent use of ANOPP by organizations outside of
NASA.
Emphasis has been and will continue to be placed on prediction
methodology for jet powered CTOL aircraft. Noise prediction method-
ology required by V/STOL, helicopter, and propeller aircraft will be
added when possible. It is expected that by FY 80, ANOPP development
will be essentially complete and that future effort will consist of
adapting the system to new computer hardware and software and of up-
dating the various prediction modules as improved methods are developed
through NASA noise reduction and basic research programs.
Schedule: ANOPP is now operational. Executive and data base software
system development is complete and prediction modules for CTOL jet
aircraft noise have been programmed and installed. Documentation in-
cluding Theoretical, User's, Demonstration, and Programmer's manuals
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Noise Prediction Techniques (Continued)
should be completed in early FY 79. Updates of present prediction
modules and the addition of modules for rotor and propeller noise
are planned during FY 79. Validation of ANOPP predictions against
measured data have commenced and will continue through FY 79.
Accomplishments: ANOPP has been successfully demonstrated for use
in the preliminary design loop for advanced SST aircraft studies.
The Aircraft Noise Prediction Office and Langley Advanced Supersonic
Transport Office have defined and demonstrated an interface for ANOPP
in the design process. The two project offices, working in unison,
will complete in FY 78 a comprehensive inhouse study of probable noise
levels of future SST aircraft. The results of this study will be
used by the FAA in support of a U.S. position to be placed before an
ICAO rule making committee.
Sponsor: Langley Research Center and Lewis Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 228 172 410 283
Agency Manpower (Man-Years): 8486
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - ATMOSPHERIC PROPAGATION AND GROUND EFFECTS
Noise Propagation
This research is improving the ability to predict the effects of
the atmosphere and ground on noise generated by an aircraft as it is
radiated to an observer. Effects of particular concern under study
in the program are randomness in the atmosphere, extremes of temperature
and humidity, mechanisms of absorption of acoustic energy by the atmo-
sphere, and procedures for determining the impedance properties of
ground reflecting surfaces.
Need for Study; Knowledge of atmospheric propagation is adequate for
noise transmission over relatively short distances and for a restricted
range of known, stable atmospheric conditions. However, the ability
to accurately determine propagation effects must be improved for several
aircraft applications. The greatest need is for the ability to accurately
predict the transmission of aircraft noise at shallow angles and over
relatively long distances during terminal area operations. The state
of the art in this particular case causes deviations between prediction
and actual airport community noise by over 10 decibels. In addition,
unpredictable variations in community noise from flight to flight, or
during a single flyover, from the random character of the atmosphere,
vary by the same order of magnitude and are readily detectable by the
listener. Even for certification-type measurements, significant cost
and time savings could be realized if the presently approved temperature-
humidity-wind constraints could be relaxed through better information
about atmospheric propagation effects.
Approach: Airplane flight tests, towers with fixed noise sources and
atmospheric instruments, shock tube decay tests at high pressures, and
specially developed noise sources and microphone arrays are used in
these experiments. Acoustic and atmospheric data are being correlated
with analytical methods for predicting atmospheric sound propagation
that takes into account refraction, scattering, absorption, diffusion
and ground reflection mechanisms. Existing flight test data is used
wherever feasible to extract data on atmospheric effects.
The emphasis in this program is in establishing the effects of
the atmosphere, over a wide range of temperature, humidity, and tur-
bulence, on the propagation of noise into aircraft communities. The
results are expected to enable the relaxation of certification test
requirements and to increase the confidence with which airport community
noise can be predicted. The results are also expected to be applicable
to the propagation of noise from other sources such as highways and
railroads.
B-38
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
Noise Propagation (Continued)
Schedule;
Conduct Flight Experiment to Determine the Effect FY 1978
of Propagation Angle and Distance on Sideline Noise
Conduct Flight and Fixed Source Experiments at the FY 1978
Outdoor Anechoic Test Apparatus (DATA) for a Range
of Realistic Ground Impedances
Accomplishments: The NASA program provided the basic data that led
to an improved standard for acoustic absorption by the atmosphere. A
flyover experiment using a helicopter was conducted at Wallops Flight
Center to measure the sideline propagation to relative large distances
at shallow angles. Aircraft noise data collected in cooperation with
the FAA in operations at Fresno-Yuma have led to revisions in the pro-
cedures used for propagation corrections in certification testing.
Flyover data collected during REFAN project flight test have been
analyzed and are giving insights into how noise data may be corrected
over wide ranges of temperature and humidity.
Sponsor.- Langley Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 489 369 549 481
Agency Manpower (Man-Years): 12 12 14 16
B-39
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - OTHER
Acoustic Instrumentation and Measurement Techniques
The purpose of this effort is to provide the necessary support
for experimental research activities by developing instrumentation and
data analysis techniques.
A Remotely Operated Multiple Acoustic Array Range (ROMAAR) has
been developed and is in operation.
Sponsor: Langley Research Center and Ames Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 254 265 280 247
Agency Manpower (Man-Years): 2526
B-40
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NASA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - OTHER
Noise Shielding
A physical entity placed between a noise source and a receiver
can reduce the noise at the receiver by providing a physical barrier
that blocks the propagation of the sound waves. On an aircraft, this
can be a wing blocking the sound from an overhead engine.
Need for Study: Designing an aircraft to take advantage of shielding
can reduce the overall noise signature of the aircraft, therefore
it is a method that can be used for noise abatement.
Approach: The effectiveness of noise shielding has been demonstrated
both in laboratory tests and on full scale engine installations. Predic-
tion methods for realistic noise sources and configurations must now
be worked out. This requires development of a sophisticated computer
program and the experimental verification of that program.
Development of prediction techniques will permit noise configur-
ing an aircraft so that the overall noise signatures can be reduced.
While the predictive capability will be beneficial for all noise barrier
problems, the emphasis is on shielding by aircraft structures.
Schedule:
Develop computer program by 1981.
Experimental verification of program by 1983.
Accomplishments:
Many large and small scale shielding experiments have been com-
pleted.
A simplified computer program for predicting the shielding of
simple noise sources was developed, followed by the development of
an "exact" computer program for shielding predictions.
Sponsor: Ames Research Center and Lewis Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 67 11 37 46
Agency Manpower (Man-Years): 1 1 1 1
B-41
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY - CTOL (SUBSONIC)
Refan Program
The objective of the Refan program, which ended in 1975, was to
demonstrate the technical feasibility of substantially reducing the
noise levels of production JT8D engine powered aircraft, such as the
Boeing 727 and 737 series, and the Douglas DC-9 series. The program
consisted of the design, fabrication, and ground and flight testing of
the refan engines with modified nacelles.
Need for Study; One of the major problems confronting civil aviation
today is public exposure to noise generated by aircraft in the vicinity
of airports. The principal sources of airport noise are identified with
the large number of narrow-body aircraft representing about three-
fourths of the domestic commercial fleet. The narrow-body aircraft
fleet is comprised of the DC-8's and B707's powered by the JT3D turbofan
engine and the DC-9's, B727 and B737's powered by the JT8D turbofan
engine. The JT8D powered aircraft, which are newer and are still in
production, are estimated to number about 1600 by 1985 compared to about
400 JT3D powered aircraft. The reduction of the noise in the JT8D
powered aircraft, therefore, would represent a significant reduction in
overall noise exposure in communities across the nation.
Approach: A principal objective of the Refan program was to provide
engine and air-frame modifications that will make the aircraft signi-
ficantly quieter. Another objective was to retain a retrofit capability
at minimum cost. Accordingly, the changes were limited to modifications
of the low pressure spool and the nacelle, while the engine core was not
altered. The basic approach was to replace the existing low bypass
ratio two-stage fan with a larger higher bypass ratio single-stage fan.
The higher bypass ratio fan with its attendant lower fan pressure ratio
reduced fan jet discharge velocity and noise. The engine and nacelle
design featured a full-length fan duct which provided considerable
surface area for acoustic treatment. The tailpipe of the new nacelles
provided additional surface area for sound treatment.
Pratt and Whitney Aircraft performed the feasibility studies,
design and fabrication of refanned engines, component testing, endurance
testing for limited flight qualification, and ground testing to estab-
lish acoustical characteristics.
Feasibility studies and subsequently engineering and fabrication of
the refanned 727 nacelle for ground testing were performed by the Boeing
Company. The ground test nacelle was configured to simulate both the
center engine and the outboard engines. Component tests included eval-
uations of the modified center engine "S" duct. Ground acoustical tests
B-42
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
Re fan Program (Continued)
were conducted with the baseline configuration and the refanned engine
center and outboard configurations. Based on these ground test data,
refanned engine B727 fly-over noise predictions were made.
Similarily, McDonnell Douglas Company conducted feasibility studies
and subsequently designed and fabricated refanned nacelles for the DC-9
airplane and associated airplane pylon modifications. This was followed
by extensive flight tests of both the JT8D baseline configuration and
the refanned configuration.
Supporting contracts were let with United Air Lines and American
Airlines to provide valuable input regarding airline operational con-
straints, airline economics and retrofit costs.
In-house tests were performed by the Lewis Research Center on model
fans, with and without the Boeing center engine "S" duct and with and
without distortion screens. The Lewis Research Center also conducted
altitude performance tests on a full-scale refan JT8D-9 engine in the
Propulsion System Laboratory.
Schedule; Major program milestones have been as follows:
Pratt and Whitney
Complete Component Tests
Complete Engine Design
Sea Level Tests of Refanned Engines
November 1974
December 1974
April 1975
Boeing
Complete Component and Model Tests
Complete Nacelle Design
Complete Nacelle Manufacture
Complete 727 Ground Tests
April 1974
September 1974
February 1975
March 1975
McDonnell Douglas
Complete Nacelle Design
Complete Nacelle Manufacture
Complete Flight Tests
February 1974
December 1974
April 1975
B-43
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
Refan Program (Continued)
Accomplishments; Boeing fly-over noise predictions based on refan
engine and nacelle ground test data indicate that the refan engine
equipped 727-200 will be in full compliance with FAR Part 36 (1969).
Refan engine noise improvements compared to the baseline airplane ranged
from 7 EPNdB at approach to 8.5 EPNdB at takeoff. This means that the
95 EPNdB noise exposure contour area would be reduced by 67 percent and
the 90 EPNdB noise exposure contour area would be reduced by 74 percent.
The Douglas fly-over noise comparisons indicate the refanned DC-9
to be also in full compliance with FAR Part 36 (1969). Noise reductions
compared to the baseline airplane ranged from 5 EPNdB at approach to 10
EPNdB at takeoff. The 90 EPNdB noise exposure contour area would be
reduced by 61 percent.
The takeoff thrust of 16,600 pounds for the refanned engine was
demonstrated, compared to a rated thrust of 14,500 pounds for the base-
line engine. The durability, reliability, and operational suitability
of the refanned engines was demonstrated through extensive ground
testing and flight testing.
Retrofit programs involving retrofitting existing airplanes with
refanned engines have not emerged, primarily because there has been no
compelling regulation. However, Pratt and Whitney, Boeing, and Douglas
have pursued marketing activities aimed at the sale of new airplanes
with JT8D engines incorporating refan features. The Pratt and Whitney/
Douglas effort recently met with success and Douglas has announced the
introduction of the DC-9-Super-80, utilizing JT8D-209 refanned engines.
Douglas has announced 27 firm orders and 9 options, with first flight
planned for mid-1979 and first delivery planned for early 1980. Douglas
has announced that these airplanes will be 5 to 6 EPNdB quieter than
required by FAR part 36 (1969), and that they will meet the noise regu-
lations established by the ICAO Committee on Aircraft Noise (CAN-5) for
new aircraft produced in the 1980"s. The DC-9-Super-80 features a
20,000 pound increase in takeoff gross weight, an increase of about 32
passengers, and a reduction in fuel consumed per passenger mile of about
20 percent.
Sponsor: Lewis Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 1,000
Agency Manpower (Man-Years): 14
B-44
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY - CTOL (SUBSONIC)
Advanced Acoustic Composite Nacelle Plight Program
This program demonstrated the application of advanced interwoven
acoustic absorbent and composite structural materials to an engine
nacelle on a modern wide-body transport in airline operation.
Approach; Various design concepts for the integration of composite
materials with nacelle acoustic treatment were evaluated in terms of
initial cost, noise reduction, weight reduction, maintenance cost, and
feasibility of application to existing propulsion systems as well as to
advanced installations. In addition, ground tests and commercial
service flight tests of production composite/acoustic nacelles were
conducted to provide sufficient data on performance, maintenance re-
quirements, and maintenance costs to establish airline industry con-
fidence in the application of composites to engine nacelles.
Sponsor: Langley Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 500
Agency Manpower (Man-Years): 8
B-45
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY - CTOL (SUBSONIC)
New Propulsion Systems Studies
Studies are currently underway investigating the application of
advanced technologies to allow for the development of future small
transport and commuter aircraft with significantly reduced initial and
operating costs and improved operational capability, energy efficiency,
and environmental compatibility.
Need for Study: Historically, advanced technology has been applied to
the larger transport aircraft operated by the trunk and local service
airlines. As these aircraft have grown in size, service to the small
communities has become increasingly less economic for these airlines.
In some cases this service has been provided by commuter airlines.
However, the choice of aircraft available to the commuter airlines is
very limited and, for the most part, reflects older technology. There
is a need to closely examine the requirements for this class of aircraft
and identify areas where advanced technology can be cost-effectively
applied to provide significant improvements.
Approach: Design and system studies will determine the most promising
advanced technologies. The advantages of the selected technology will
then be verified by more detailed analysis or experimental testing.
All indications are that the application of advanced technology—
structure, propulsion, aerodynamics, and systems—can result in greatly
improved future small transport aircraft.
Schedule: The initial contracted design studies are underway and will
continue through 1978. Wind tunnel testing has begun on advanced air-
foils and will continue through 1979.
An expanded effort in this area is being considered for 1980 or
1981.
Accomplishments: Final oral review of first phase of a design contract
with Boeing was presented at NASA Ames on November 10, 1977.
A symposium on short-haul small community air service was held at
Ames on November 9-10, 1977.
Sponsor: Lewis Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 800 196 94 120
Agency Manpower (Man-Years): 11 .1 .5 .5
B-46
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY - CTOL (SUBSONIC)
Flight Operational Procedures
Two flight procedures for reducing the community impact of aircraft
landing operations were thoroughly tested. Operational avionics and
flight procedures were developed for the "two-segment" landing approach,
and the "delayed flap" approach.
Flight operational procedures have been proposed as an immediate
solution to the increasing community noise problem around airports. The
delayed flap approach reduces both noise impact and fuel consumption by
remaining at high airspeeds and low drag configurations until late in
the approach.
Need for Study; It is necessary to demonstrate the avionics for the
two-segment and delayed flap procedures under instrument flight condi-
tions during routine scheduled service. The actual noise reductions to
be realized, and the feasibility of using area navigation equipment also
need to be evaluated.
Approach; To develop the two-segment approach procedure, the avionics
were developed and flight evaluated using ILS co-located DME and baro-
metric altitude for vertical guidance in a Boeing 727. Similar flight
tests were also conducted in a commercial R-NAV system in a DC-8. Both
aircraft were operated in routine commercial service with two-segment
concept operational procedures to gain experience.
For the delayed flap procedure, flight tests were conducted on
NASA's Convair 990 aircraft with NASA and industry pilots. Piloted
simulations were conducted on a Boeing 727, and ATC simulations were
conducted with high density traffic mixes to evaluate compatibility with
conventional type approaches.
The results of these programs indicated that the procedures will
probably not be implemented by commercial carriers because of cost of
installing the new equipment in the airline fleet. Safety is another
important consideration. The two-segment approach increases the prob-
ability of wake vortex encounters by trailing aircraft, while the
delayed flap approach poses ATC compatibility problems.
Schedule; Two-segment approach procedures were studied between 1972 to
1975. Delayed flap procedures were evaluated from 1975 to 1977.
Accomplishments: Equipment and two segment approach were certified for
routine operations in commercial service and were successfully operated
for 6 months in a UAL DC-8 and a VAL 727. Significant reductions in
ground perceived noise under the approach path were achieved.
B-47
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
Flight Operational Procedures (Continued)
The 90 EPNdB noise contour area of a delayed flap approach was
measured to be 33% of that of current airline procedures in both
CV-990 flight tests and B-727 simulations.
Fuel savings per approach was measured to be 1% to 2% of typical
mission fuel loads in both CV-990 flight tests and B-727 simulations.
Delayed flap procedures were generally rated as having good pilot
acceptability.
High density traffic ATC simulations indicated a sharp drop off
of. fuel savings and actually increased overall fuel consumption at
traffic rates higher than 35 aircraft per hour.
Sponsor: Langley Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 1200 536 54 43
Agency Manpower (Man-Years): 17 1 .5 .5
B-48
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY - CTOL (SUPERSONIC)
New Propulsion Systems Studies
The objective of this program is to demonstrate the critical com-
ponent technology required for supersonic cruise engines affording high
propulsive efficiency together with reduced noise and emission levels.
The technology thus demonstrated will minimize the costs and risks of
follow-on programs and remove some of the critical technical barriers
which now inhibit the development of an advanced supersonic cruise
aircraft. Large-scale component testing under simulated engine con-
ditions will be supported by aero/acoustic nozzle model tests and rig
testing of critical components prior to installation in test engines.
Need for Study; One of the major challenges facing civil aviation in
the future will be to allow all the passengers to fly to their destina-
tions without overcrowding the available airspace. The solution to this
problem can be approached in two ways: making the airplanes larger, or
faster. The second alternative is being addressed in the Supersonic
Cruise Aircraft Research/Variable Cycle Engine (SCAR/VCE) programs. Not
only is the airspace problem addressed by flying faster at supersonic
speeds at higher altitudes, but the convenience to the user of the
service is greatly enhanced, especially when city pairs separated by
great distances are considered. For example, an advanced SST flying
from San Francisco to Tokyo could reduce the present 11-hour flight time
to about four hours.
The problems with existing first-generation SST's are poor economics
(small payload, limited range) and environmental considerations such as
noise and pollution. The NASA SCAR program, which was started in 1972
was intended to provide our airframe and aircraft propulsion industry
with the technology readiness to begin an advanced SST development
program should it ever be determined to be in the national interest to
do so.
Maximum propulsive efficiency at supersonic conditions dictates a
cycle with high specific thrust. Lower specific thrusts, however, are
optimum at subsonic conditions and also from the standpoint of alle-
viating the takeoff jet noise problem. These conflicting propulsion
system objectives are difficult, if not impossible, to meet with a fixed
engine cycle but are best reconciled with a Variable Cycle Engine (VCE).
Such an engine exhibits many of the characteristics of an advanced leaky
turbojet at supersonic conditions and those of a moderate bypass tur-
bofan at subsonic cruise and takeoff conditions. In both advanced VCE
concepts under consideration, an inverted flow coannular exhaust system
has been identified having the potential to significantly reduce takeoff
jet noise without unduly compromising weight or performance. High
turbine temperatures and advanced materials are required in both VCE
concepts to meet the stringent performance and weight objectives re-
quired for a viable second-generation SST.
B-49
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
New Propulsion Systems Studies (Continued)
Since the advanced VCE has been identified as the pacing item in
any future SST development program that may ensue, a VCE Component
Technology Program has been initiated by NASA to address the most crit-
ical VCE component technologies not being addressed by any other engine
programs.
Approach: Early studies on airplane and propulsion system concepts have
indicated that, indeed, with the proper development of identifiable
advanced technologies, the deficiencies of existing first-generation
SST's can be overcome. The payload-range characteristics can be signi-
ficantly enhanced, with resultant operating costs competitive on a seat-
mile basis with those of the current wide-body subsonic fleet. Jet
noise, too, can be reduced to be at or slightly below FAR 36 (1969)
limits. The emissions problems can also be alleviated with the appli-
cation of burner concepts derived from the NASA ECCP program.
The challenge presented to the engine designer was to provide an
advanced engine that would offer excellent supersonic cruise perfor-
mance, and yet provide good off-design subsonic cruise performance while
at the same time having the capability to provide high takeoff thrust at
noise levels significantly lower than the current first-generation SST
engines. In addition, these engines had to be light-weight and be
within a certain dimensional envelope so that they could be properly
integrated with the airframe for good overall airplane aerodynamic
performance.
Certain component technologies have been identified as critical to
the successful development of proposed VCE concepts. In order to pro-
vide the required development and testing necessary to assess the fea-
sibility and readiness of these most critical technologies a VCE Com-
ponent Test Program was initiated through a series of contracts to the
two engine companies, Pratt and Whitney Aircraft (P&WA) and the General
Electric Company (G.E.).
VSCE/F100 Component Test Program (P&WA): The Variable Stream Control
Engine (VSCE) is essentially a duct burning turbofan in which the flow
and exhaust velocity profile can be optimally tailored for a given
flight condition through variable geometry, rotational speed, and fuel
flow control. P&WA will simulate the VSCE cycle using an existing FlOO
high-technology engine. The unmodified engine is used to provide the
appropriate high-flow high-temperature air to a quiet coannular ejector
nozzle and a low-emission duct burner. A new boilerplate tailpipe will
be added to separate the bypass stream from that of the core flow. A
coannular ejector nozzle with a cylindrical shroud configured for take-
off conditions will be attached to the tailpipe, and a low-emission duct
burner will be located in the outer bypass duct to accelerate the bypass
B-50
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
New Propulsion Systems Studies (Continued)
flow to demonstrate the acoustic benefits of an inverted velocity pro-
file. The coannular nozzle and duct burner .configurations for this test
program will be based on current VCE supporting technology programs.
Design and long-lead material and hardware procurement have been
initiated for the duct burner and coannular nozzle. Fabrication,
assembly and testing are scheduled for the 1978-1979 time period.
Scale models of the product engine nozzle will be tested in the
Lewis 8- by 6-Foot Wind Tunnel to provide thrust performance at takeoff,
subsonic and supersonic cruise conditions.
The results of an analytical screening study to identify advanced
duct burner concepts was completed were used to select the three-stage
vorbix configuration for the FIDO component test engine. Experimental
evaluation of this duct burner in a two-dimensional segment rig is in
progress. Results of this experimental program will be applied to the
design of the low-emission duct burner for the VSCE/F100 component test
engine.
A low-emission duct burner and a low-noise coannular nozzle are
being procured for the Pratt and Whitney VSCE/F100 Component Test
engine. It is expected that the first large-scale verification of the
coannular jet noise benefit of an inverted velocity profile will be
accomplished in September 1978. This noise test will be followed by
measurements of advanced duct burner emissions in May 1979.
DBE/YJlOl Component Test Program (G.E.): The General Electric Component
Test VCE will validate some of the critical technologies peculiar to
their Double Bypass Engine (DBE) concept. The test engine will be built
around a military YJ101 low-bypass turbofan. It will be modified to
incorporate a split fan with an additional bypass duct emanating from
between the two fan sections. This second duct later is merged with the
inner bypass duct from the last fan stage before being discharged into
either the main flow downstream of the turbines in the high performance
mode, or supplied to the interior of a coannular plug nozzle to provide
the low-energy inner exhaust flow in the low-noise mode of operation.
Appropriate valving in the bypass ducting, and variable geometry fea-
tures in the inner nozzle and certain turbomachinery components are
required for this demonstration of mode-switching capability. An aero-
acoustic test of this exhaust concept used in conjunction with the
modified YJ101 will take place in September 1978. This test will pro-
vide the first large-scale demonstration of the significant jet noise
reductions found in small-scale model tests of similar coannular nozzles
with inverted velocity profiles.
B-51
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
New Propulsion Systems Studies (Continued)
A model nozzle program to investigate the static aeroacoustic
performance and the low-speed aerodynamic performance of coannular plug
nozzles has been completed. G.E. is testing model high-radius-ratio
coannular plug nozzles in a free jet noise test facility which provides
an acoustic test at simulated takeoff freestream velocities. An
acoustic prediction methodology for coannular plug nozzles will be
developed from the results of these tests and used to refine the design
of the component test engine exhaust nozzle.
In order to fully demonstrate all the advantages of the DBE system,
however, a new variable geometry front block fan designed for greater
airflow capability than that of the YJ101 fan is needed. A detailed
aerodynamic design and preliminary mechanical design of such a fan has
already been completed. A contract for the detailed mechanical design,
fabrication, assembly, and rig test of this fan will be awarded in the
summer of 1978. The rig testing of this fan would be completed in 1980.
A contract is presently underway with G.E. to define a core-driven-
second-block-fan testbed engine. A design, fabrication and test program
is planned to begin in the late summer of 1978. This would be the first
time for the test of a fan stage on the high-pressure spool of an
engine—a promising element of the recommended DBE product engine cycle
identified in the NASA-sponsored SCAR/VCE propulsion system studies.
The front block fan in this test would consist of the first two stages
of the existing YJ101 fan driven by the low-pressure turbine.
A bypass control valve and a coannular acoustic plug nozzle are
being procured for the G.E. DBE/J101 Component Test engine. It is
expected that the first large-scale verification of the coannular
acoustic model test data for high radius-ratio plug nozzles will be
accomplished in September 1978. It is also expected that a double
bypass engine with a J101 core-driven third stage fan will be assembled
and tested for aero/acoustic performance and component interactions and
controllability evaluation in calendar year 1980. Rig testing of the
first two stages (front block) of the double bypass engine's variable-
geometry fan is also expected to occur in 1980.
Schedule: Major program milestones are tabulated below.
Pratt and Whitney Aircraft
Complete Duct Burner Segment Rig Tests April 1978
Complete Nozzle Aero/Acoustic Model Tests. August 1978
Demonstrate Coannular Noise Benefit With
Large-Scale Hardware September 1978
Demonstrate Duct Burner Emissions Reduction
With Large-scale Hardware May 1979
B-52
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
New Propulsion Systems Studies (Continued)
General Electric Company
Complete Nozzle Aero/Acoustic Model Tests June 1978
Complete Forward Valve Test June 1978
Demonstrate Coannular Noise Benefit With
Large-Scale Hardware September 1978
Core Engine Test February 1980
Variable Flow Fan Rig Test April 1980
Double Bypass Engine Performance/Acoustic Test June 1980
Accomplishments; Coannular nozzle noise reduction benefit has been
verified via model tests at static conditions and with forward velocity
effects. Nozzle thrust coefficients at Mach numbers up to 0.45 have
been measured and it has been verified that performance was at an
acceptable level.
Preliminary design of a high-speed multistage variable-geometry
fan for G.E. Double Bypass Engine has been completed. The segment rig
test program of low-emission duct burner for Pratt & Whitney Variable
Stream Control Engine has been initiated. Design and procurement of
long-lead hardware for VSCE/F100 and DBE/J101 testbed engines have
been completed to provide large-scale coannular noise tests in
September 1978.
All technology thus verified and demonstrated will minimize the
costs and risks of follow-on programs and remove some of the critical
technical barriers which now inhibit the development of an advanced
supersonic cruise aircraft.
Sponsor: Lewis Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 300 1,137 2,457
Agency Manpower (Man-Years): 577
B-53
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY: CTOL (SUPERSONIC)
New Aircraft Studies
This program addresses three objectives. It will provide the data
necessary to enable rational decisions relative to the consideration of
future operations of civil supersonic aircraft in the United States. An
expanded technology base is expected to result that will provide data
necessary to assess the environmental impact of present and future
foreign supersonic cruise aircraft.
It will establish a supersonic propulsion technology base, in
parallel with other disciplinary technologies, that permits reduction in
noise in takeoff and landing to levels consistent with other heavy,
long-range aircraft such as the Boeing 747.
And finally, research will be conducted on low-sonic-boom aircraft
configurations. The development of capability for computer-aided
analysis and synthesis will be undertaken. The computer tools and
methodology will be applied to Supersonic Cruise Aircraft Research
(SCAR) configurations.
Sponsor: Langley Research Center and Lewis Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 362 272 272
Agency Manpower (Man-Years): 511
B-54
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY: STOL
Aircraft Operational Systems
The purpose of this project is to provide information to aid in
the choice of STOL terminal area guidance, navigation and control
systems and operational procedures to minimize noise and fuel use and
maximize operational safety.
Need for Study; The flight path requirements as a function of system
capability to contain the 90 EPNdB noise footprint within the airport
boundary need to be defined. Onboard avionic system concepts (hard-
ware and software) that will allow STOL aircraft to steep, curved and
decelerating approaches will be needed for safety.
The usability of TRSB MLS in terminal are RNAV for performing
such complex approaches also needs to be determined.
Approach; Avionic system concepts using TRSB MLS, VORTAC and barometric
altitude for lateral and vertical guidance in an Augmentor Wing Jet
STOL Research Aircraft (Modified DeHaviland C-8 Buffalo) and a DeHaviland
Twin-Otter are under development, with flight tests planned for 1978.
The data so obtained will be used in the development of avionics
systems for future powered lift and light wing-loading STOL air-
craft.
Certification criteria for STOL flight director and autoland
systems will be developed, and terminal area RNAV requirements will
be e stabl i shed.
Schedule; The current program phase is planned to be completed by 1979.
Accomplishments: Four autoland system concepts have been developed for
the Augmentor Wing aircraft utilizing various control configurations.
Flight tests to establish system performance will be initiated in
May 1978.
Two flight director system concepts have been developed for the
Augmentor Wing aircraft to facilitate flying complex flight paths and
reduce pilot work load. Flight tests have been completed which indicate
that curved flight paths within 1 mile radius of the airport can be
flown with reasonable workload in simulated IFR conditions.
Two autoland system concepts are being developed for the Twin-
Otter. Flight tests to establish system performance will be initiated
in February 1978.
B-55
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
Aircraft Operational Systems (Continued)
RNAV system concepts have.been developed and flown. Data is being
analyzed.
Sponsor: Ames Research Center and Langley Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 63 71 68
Agency Manpower (Man-Years): 147
B-56
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY: STOL
Quiet, Clean, Short-Haul Experimental Engine (QCSEE)
The overall objective of the QCSEE program is the development of
propulsion system technology suitable for powered-lift short-haul air-
craft for the 1980's time period. The program requires the design,
fabrication, and ground testing of two engines, an under-the-wing (UTW)
engine and an over-the-wing (OTW) engine by the General Electric Com-
pany. Following completion of the General Electric acoustic tests,
NASA-Lewis will perform aerodynamic and acoustic tests with an engine-
wing-flap system.
Need for Study; Public acceptance of the short-haul STOL type aircraft
requires a minimal environmental impact by operation of such aircraft
from small airports that are close to metropolitan centers. Primary
environmental concerns are low noise and low exhaust pollutants.
Further, economically viable short-haul aircraft require good propulsion
system performance.
Although directed toward short-haul commercial applications, it is
evident that QCSEE technology has a potentially broad range of appli-
cation. Low noise and low pollution are of interest for conventional
long-haul aircraft. Improved propulsion system performance is important
to energy conservation requirements. And finally, many of the QCSEE
engine features are applicable to propulsion systems for U.S. Navy
V/STOL type aircraft which are currently under study.
Approach; Two powered-lift, short-haul aircraft propulsion systems were
designed and fabricated. The engine location for the UTW system is
conventional. The OTW or over-the-wing concept offers a distinct
acoustic advantage. In this arrangement the wing serves as an acoustic
shield, and reduces the propagation of aft-end noise to the ground.
Consequently, for a given noise level, the OTW system can be designed
for a higher fan pressure ratio than the UTW system. This favors low
engine weight and drag for a given thrust level. However, the UTW
engine is compatible with a reverse thrust system achieved by reversing
the fan blade pitch to exhaust fan flow air forward from the engine
inlet. This type of thrust reverser represents a significant weight
advantage over the target type reverser system employed on the OTW
engine. QCSEE test results will help to determine which of these
powered-lift systems is best for future applications.
The very stringent noise goals of the QCSEE program include an
aircraft noise level of 95 EPNdB during takeoff and approach and a
reverse thrust maximum level of 100 PNdB, all measured on a 500 foot
sideline. In addition, a 95 EPNdB contour area of less than 0.5 square
miles is desired. To attain such goals a number of advanced acoustic
concepts were employed.
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
Quiet, Clean, Short-Haul Experimental Engine (QCSEE) (Continued)
The QCSEE acoustic designs incorporate low source noise features
such as low fan tip speed, low fan pressure ratio (for low jet/flap
noise and low fan exhaust noise), high bypass ratio, and large rotor to
outlet guide vane (OGV) spacing. Fan inlet noise suppression is ob-
tained by a near-sonic (0.79 throat Mach number) inlet with multiple-
thickness treated walls. Fan exhaust suppression is provided by
multiple-thickness treated exhaust walls, a 40 inch acoustically treated
splitter, acoustic treatment on the fan discharge passage walls between
the rotor and OGV's, and acoustic treatment on the pressure surface of
the OGV's. Core noise suppression is provided by using a "stacked
treatment" concept in which thick low-frequency combustor noise treat-
ment is located under and integral with thin high-frequency turbine
noise treatment panels.
The QCSEE acoustic designs and the predicted noise levels and
suppression estimates were supported by various engine and scale-model
tests. The model tests were conducted in the General Electric anechoic
chamber test facility and the Lewis 9- by 15-foot acoustic wind tunnel.
The QCSEE engines are being designed to meet the proposed EPA 1979
emission standards. A double annular dome combustor is being adapted to
the F101 combustor of the UTW engine in a series of combustor rig tests.
Both engines currently use a modified F101 core engine combustor.
To help attain the high installed thrust/weight ratios of 4.3 and
4.7 for the UTW and OTW engines respectively, some QCSEE engine parts
are fabricated from light weight composite materials. The UTW engine
has composite fan blades and will also be tested with a composite
nacelle. Both engines use a composite fan frame.
Other features of the engines include digital control systems and
main reduction gears. Also featured are fast thrust response times from
approach to takeoff thrust and from approach to reverse thrust.
Schedule: Major program milestones are:
General Electric Company
Initiate Contract January 1974
Complete UTW Engine Design January 1975
Complete OTW Engine Design July 1975
Complete OTW Engine Tests June 1977
Complete UTW Engine Tests March 1978
B-58
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NASA - DEMONSTRATION PROGRAMS-AND SYSTEMS STUDIES
Quiet, Clean, Short-Haul Experimental Engine (QCSEE) (Continued)
NASA - Lewis
Initiate Preparations for Engine Tests December 1975
Complete OTW Engine Tests June 1978
Complete UTW Engine Tests March 1979
Accomplishments: Aerodynamic and acoustic testing of the UTW and OTW
engines is nearing completion at General Electric. Preliminary noise
test results indicate the OTW system noise level at takeoff to be
96.5 EPNdB, about 1.5 EPNdB above the goal. The approach noise level
of 93.2 EPNdB is well below the 95 EPNdB goal. The reverse thrust
level of 107 PNdB maximum exceeds the noise goal by 7 PNdB. The
projected 95 EPNdB footprint area of 0.33 square miles meets the 0.5
square mile goal.
The significance of the OTW acoustic technology can be illustrated
by comparison of the QCSEE OTW engine with conventional engines. An
OTW-powered aircraft takeoff noise level, if extrapolated to the FAA
sideline condition, would be about 22 EPNdB below the FAA limit. It
would also be about 12 EPNdB lower than the DC-10 aircraft, which is
representative of the modern wide body jet aircraft.
Combustor rig test results indicate that the exhaust emission
goals will either be achieved or be very close to being achieved.
Installed forward thrust requirements were met by both engines,
(20,300 Ibs for the OTW, 17,400 Ibs for the UTW engine). The OTW
reverse thrust of 35% of takeoff met the design goal. The UTW value
of 25% fell below the goal. However, there is a possibility of
improvement in later tests employing different engine parameters.
Fan performance met or exceeded specifications for both engines.
The digital control performance was, in general, good. The main
reduction gears on both engines have performed without difficulty.
Sponsor: Lewis Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 5,000 1,500 488 90
Agency Manpower (Man-Years): 71 21 30 10
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY: STOL
Systems and Design Studies
The objective of this work is to help develop a sound technological
base for future decisions relating to the design, development, and
operations of STOL commercial air transportation systems. This will
be achieved through studies and experiments that examine the relation-
ships between aircraft technology, airline economics, and environmental
constraints.
Potential applications of advanced technologies such as prop
fans, powered lift, and simplified designs, to future commuter air-
craft will be identified and evaluated in terms of cost reduction,
operational capability, fuel efficiency, and environmental acceptability.
Sponsor: Langley Research Center and Lewis Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 50
Agency Manpower (Man-Years): 6
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY: STOL
Quiet, Propulsive Lift Technology
NASA's continuing search for a practical means to alleviate
aircraft noise impact on the airport community will be enhanced by a
versatile new research aircraft now being built for NASA by the Boeing
Commercial Airplane Company. The Quiet Short-Haul Research Aircraft
(QSRA), which is utilized to investigate the quiet propulsive lift
technology, will be the quietest four engine jet aircraft built to
date, with a 90 EPNdB noise footprint area of approximately 0.3 sq.
mi. QSRA technology applied to a 150,000 Ib. aircraft would yield
a footprint of less than one sq. mi., versus about 30 sq. mi. for
current civil transports of equivalent size. This technology could
permit future aircraft operations with no excessive noise levels
extending beyond the boundaries of hundreds of large and small air-
ports in the U.S., many of which are now threatened by restricted
operations due to noise.
Need for Study; STOL aircraft are viewed as a means for improving the
National Transportation System through delivering the passenger
closer to his house and relieving congestion at major airports. Since
the aircraft would be operated near small suburban communities, a
low noise aircraft is an absolute requirement. This requirement
is especially difficult to meet because STOL aircraft are relatively
high powered.
Approach: The QSRA employs the upper-surface-blowing propulsive-
lift concept in order to achieve good low-speed performance at noise
levels acceptable to the community. With the lift augmentation
provided by four engines mounted over the wing plus an advanced
flap and boundary layer control system, the QSRA will be able to
safely takeoff and land in field lengths ranging from 5000 ft. to
under 1500 ft., and to fly steep approach and climb angles or curved
flight paths with a turn radius of as little as 700 ft. The aircraft
will be used by NASA to investigate new flight procedures that can be
used in combination with advanced air traffic control concepts to
reduce airport community noise, relieve air traffic congestion, and
increase terminal-area flight safety.
Construction of the research aircraft is nearly complete. Flight
investigations will begin in July 1978. During the next several years,
flight experiments conducted in cooperation with the FAA and private
industry will establish design criteria and certification criteria
needed for future development of civil and military transports and
business aircraft utilizing QSRA technology.
The total cost of the program at completion is estimated at
$32 million.
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
Quiet, Propulsive Lift Technology (Continued)
Schedule: QSRA is expected to first fly in mid-1978. Flight tests
and noise evaluations are planned through 1979. Modifications will
be made in 1980, with renewed flight tests in 1981.
Accomplishments; Accomplishments to date are the development of the
upper surface blowing technology and the design of the aircraft.
Sponsor: Ames Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 2,000 544 85 95
Agency Manpower (Man-Years): 27 8 5 10
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY: ROTORCRAFT/VTOL
Aircraft Operational Systems
This project will be conducted to develop avionics and procedures
for quiet helicopter terminal area operations. The project will
proceed through stages of analysis and simulation into actual flight
tests. One facet of this project is concerned with alleviating airport
community noise for VTOL operations through the tailoring of airport
approach paths.
Need for Study: Reduction of both interior and exterior noise is of
key importance in advancing helicopter air transportation, particularly
in terminal area operations at high density metropolitan heliports.
By approaching airports above pattern altitude and using spiral descents
in airport areas adjacent to the CTOL active runways, ground noise
can be confined to within the airport boundaries.
Approach; Flight path trajectories and procedures that minimize noise
will be developed through stages of analysis and simulations prior to
actual flight tests.
Onboard digital avionics systems will generate noise abatement
flight paths in real time along with the required navigation and guidance
for providing automatic flight path tracking.
Noise measurements will be made and compared to noise generated
during conventional procedures.
ATC simulations will be conducted to evaluate operational
compatibility at city-center heliports and hub-airports. Techniques
for VTOL spiral descents and terminal approaches to VTOL landing pads
will be flight evaluated using peripheral MLS Azimuth coverage for
horizontal guidance and barometric/radio altitude and DME for vertical
guidance.
During the operating experiments phase, spiral descent techniques
with the VSTOLAND integrated research avionics system will be implemented
and flight tested in the UH-lH helicopter and in the XV-15 Tilt-Rotor
research aircraft.
Schedule; The testing and evaluation program is expected to commence
in 1978 and continue on to 1983.
Accomplishments: The VSTOLAND systems for both the UH-lH and the
XV-15 have been fabricated and delivered to Ames. The UH-lH system
has been installed and checked out in the helicopter. The XV-15 system
is being installed in the Ames S-19 Simulator for checkout.
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
Aircraft Operational Systems (Continued)
Sponsor: Ames Research Center
Investigator: Not Cited
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 80
Agency Manpower (Man-Years): 1
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY: ROTORCRAFT/VTOL
Rotor Systems Research Aircraft (RSRA)
The Rotor Systems Research Aircraft (RSRA) Program is a joint
project with the Army that will provide research on a wide variety of
promising new quiet rotor concepts.
An in-flight rotor test facility is being developed for the in-
vestigation of advanced rotor systems technology in the actual flight
environment including maneuvering flight. In addition, the facility
will provide a basis for the in-flight verification of advanced ana-
lytical methods and noise reduction studies.
Full-scale helicopter rotor blades are being constructed using a
soft tooling concept which will allow relatively easy modification of
basic parameters such as airfoil section, twist and tip shape. This
program is intended to improve noise and aerodynamic characteristics of
helicopter rotors.
Need for Study; Helicopter noise is a particular problem, both in civil
and military operations, because of its peculiar signature and long
duration. The impulsive noise from the advancing tip and from blade tip
vortex intersection is a primary problem.
Approach; The research rotor system will be constructed at full scale,
and performance and acoustic characteristics will be measured in the 40-
by 80-Foot Wind Tunnel. Modifications to the rotor will be guided by
generic research in airfoils for rotorcraft and research on rotor noise
sources.
The emphasis of this program is on reduction of helicopter noise by
aerodynamic refinement of the rotor.
Schedule; The rotor will be delivered in January 1980. Test of the
basic rotor is scheduled for April 1980, with rotor test with modified
airfoil sections in September 1981, and rotor tests with modified tip
sections in September 1982.
Accomplishments: Evaluation of acoustic signatures for several tip
shapes was completed in 1973. Evaluation of acoustic signatures for a
compliant rotor with several tip shapes was completed in 1977.
B-65
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
Rotor Systems Research Aircraft (RSRA) (Continued)
Sponsor: Ames Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 510 30 100
Agency Manpower (Man-Years): 721
B-66
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY: ROTORCRAFT/VTOL
Tilt Rotor Research Aircraft (TRRA)
An integrated flight vehicle is being developed to demonstrate the
technology readiness of the tilt-rotor concept for quiet civil opera-
tions. An objective is to establish a safe operating envelope and
initially assess the handling qualities of the XV-15 Tilt Rotor Research
Aircraft.
The Tilt Rotor concept uses large diameter (low disc loading) prop
rotors mounted on wing-tip nacelles, which operate in the horizontal
plane for hover and helicopter operations and are tilted forward to the
normal propeller position for airplane type flight.
Furthermore, the tilt rotor aircraft's extensive reduction of rotor
RPM for airplane mode results in a predicted noise level at below 65
PNdB for a 1000 ft. altitude fly-by at 200 knots—a noise level below
most urban ambient conditions.
Approach: One of the principal flight research objectives of this
program includes the evaluation of hover mode noise over a range of tip
speeds and disc loading (gross weight). Preliminary sound level data
recorded, at a 500 ft. distance during the initial flight of the XV-15,
confirm predictions that the hover noise generated by the tilt rotor's
highly twisted blades is lower than the noise produced by a conventional
(Bell Model 206L) helicopter of approximately one-third the tilt rotor's
gross weight, and about 6dB below the noise level of equivalent weight
helicopters. The broad conversion corridor, the rapid speed of con-
version, and the steep descent and climb capabilities of the tilt rotor
aircraft will be examined during the impending flight test program for
verification of what is predicted to be a significant reduction of the
90 and 95 EPNdB terminal area footprint areas compared to other V/STOL
and CTOL aircraft. The tilt rotor research program is jointly funded
with the Army. The noise portion of the program is funded by NASA.
Sponsor: Ames Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 200 80 30
Agency Manpower (ManYears): 351
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY: GENERAL AVIATION
Quiet, Clean General Aviation Turbofan (QCGAT)
The objective of the QCGAT Project is to demonstrate the appli-
cability of large turbofan engine technology to small turbofan engines
and to obtain significant reductions in noise and pollutant emissions
while reducing or maintaining fuel consumption levels. Engine modi-
fications using existing gas generator cores will be developed through
component tests and engine ground tests. Nacelles, which will be in-
tegrated with the modified engines, will be designed and fabricated.
Analyses will be made of the design, performance, emission and acoustic
benefits of the engine and nacelle systems installed in typical general
aviation aircraft.
Need for Study: The turbine powered general aviation aircraft fleet
size is increasing at a greater rate than the rest of general aviation
aircraft. Jet powered general aviation aircraft numbered approximately
1400 in 1974. Annual sales are expected to grow from a current figure
of around 200 in 1975 to over 400 within the next ten years.
The airlines serve approximately 500 airports across the nation.
General aviation serves these 500 airports plus over 12,000 additional
airports that are served exclusively by general aviation. These air-
ports are more apt to be located in small communities where background
noise and pollution are low. Therefore, the increasing use of small
aircraft has the potential to create a very widespread adverse community
reaction.
The small turbine engines used in general aviation and business
aircraft generally produce the same type of noise that is produced by
the larger commercial and military aircraft engines. Engine quieting
and emission reduction technology and, more recently, means for im-
proving fuel economy have been directed primarily at the larger engines
used in the commercial carriers. It is, therefore, important to deter-
mine the suitability of the large engine technology to small turbine
engines and develop new technology where required.
Although existing FAR 36 noise restrictions probably can be met by
new production aircraft, it is probable that this regulation will be
modified to require reduced noise levels for the next generation of
aircraft, possibly by as much as 10 PNdB at each of the measuring
stations.
Approach: This systems technology program will provide reference data
necessary for establishing feasible approaches and probable limits to
emissions and noise reduction of general aviation turbofan engines in
time to relieve the effects of the predicted increase in aircraft using
this type of engine.
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
Quiet, Clean General Aviation Turbofan (QCGAT) (Continued)
A principal objective of the QCGAT program is to demonstrate the
technology required to provide quiet turbofan engines for general avi-
ation. One of the ground rules for the program was that each contractor
use an existing core for the QCGAT engine. Therefore, the quieting
technology is primarily limited to modifications of the low pressure
spool and the nacelle, while the core engines are not altered. Noise
reduction features in the QCGAT engines include: no inlet guide vanes,
medium-to-high bypass ratio fan resulting in low jet velocities, single-
stage fan with low fan-tip speed and low pressure ratio, large rotor-
stator spacing, optimum number of vanes and blades, mixer nozzle, and
acoustic treatment.
An additional objective of the QCGAT program is to reduce engine
emissions to meet the 1979 EPA standards for the T class engines. This
is to be accomplished through design changes to the combustor liner and
injector nozzles. Component testing and results of the NASA Lewis
Research Center T Combustor Program will be utilized.
The program is being conducted in two phases. In the first phase,
which was completed in October 1975, six-month studies by three manu-
facturers of small turbine engines, AiResearch, AVCO-Lycoming and
General Electric, provided NASA with information required to prescribe
an effective experimental engine program. These studies included an
assessment of the applicability of existing large turbofan quieting and
emission control techniques, how this technology can be scaled, and its
applicability to small general aviation turbofan engines.
The second phase is an experimental program that consists of de-
sign, fabrication, assembly, ground tests, and delivery of experimental
engines and nacelles to NASA Lewis. Similar contracts were awarded to
Garrett-AiResearch and to AVCO-Lycoming. Lewis Research Center plans to
perform testing upon delivery of the two engines. This will include
altitude performance tests, emissions tests and acoustic tests.
Schedule: Major program milestones are given below:
Study Phase
Awarded Contracts April 1975
Completed Studies December 1975
B-69
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NASA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
Quiet, Clean General Aviation Turbofan (QCGAT) (Continued)
Experimental Phase
Awarded Contracts Nov. & Dec. 1976
Final Design Reviews September 1977
Begin Engine Testing July & Oct. 1978
Engine Deliveries Feb. & July 1979
Accomplishments; Both contractors have completed final engine design
and fabrication has started. Analyses based on these final engine
designs indicate that both engines will meet the QCGAT Program goals in
acoustics and emissions.
Sponsor: Lewis Research Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 808 1,100 1,327
Agency Manpower (Man-Years): 11 8 8
B-70
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APPENDIX C
DEPARTMENT OF DEFENSE
(AIR FORCE, ARMY AND NAVY)
AVIATION NOISE RT&D PROGRAM
This appendix describes DOD's aviation noise programs
in terms of research, technology and demonstration projects.
The activities of each of the three military departments
within DOD: Air Force, Army, and Navy, are grouped separately,
Funding for FY 76 includes the transition quarter (July
1, 1976 to September 30, 1976). Funding cited for FY 77 and
FY 78 includes estimates. Projects for FY 78 have not been
finalized.
c-i
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FUNDING SUMMARY
DEPARTMENT OF DEFENSE
(Air Force, Army and Navy)
Fiscal Year Funding ($1000)
CATEGORY 1975
RESEARCH AND TECHNOLOGY
PROPULSION NOISE 1,510
ROTOR NOISE
AIRFRAME NOISE 63
NOISE PREDICTION TECHNOLOGY 22
1976 1977 1978
874 433 319
14 695 610
208 76 32
410 703 658
TOTAL: All Projects 1,595 1,506 1,907 1,619
C-3
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FUNDING SUMMARY
DEPARTMENT OF THE AIR FORCE
Fiscal Year Funding ($1000)
CATEGORY 1975 1976 1977 1978
RESEARCH AND TECHNOLOGY PROGRAMS
PROPULSION NOISE 315 76 62 68
AIRFRAME NOISE 63 188 66 22
NOISE PREDICTION TECHNOLOGY 22 378 383 366
TOTAL: All Projects 400 642 511 456
C-4
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FUNDING SUMMARY
DEPARTMENT OF THE ARMY
Fiscal Year Funding ($1,000)
CATEGORY 1975 1976 1977 1978
RESEARCH AND TECHNOLOGY
PROPULSION NOISE - - 71 86
ROTOR NOISE - 14 695 610
NOISE PREDICTION TECHNOLOGY - 32 160 172
TOTAL: All Projects - 46 926 868
C-5
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FUNDING SUMMARY
DEPARTMENT OF THE NAVY
Fiscal Year Funding ($1000)
CATEGORY 1975 1976 1977 1978
RESEARCH AND TECHNOLOGY
PROPULSION NOISE 1,195 798 300 165
AIRFRAME NOISE - 20 10 10
NOISE PREDICTION TECHNOLOGY - - 160 120
TOTAL: All Projects 1,195 818 470 295
C-6
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Supersonic Jet Exhaust Noise Investigation (Density Model)
This project was undertaken to develop the technology to signifi-
cantly reduce supersonic aircraft propulsion system noise with minimum
associated performance and weight penalties. The specific technical
objectives of this project are to solve numerically the applicable
turbulence and acoustic theories that describe jet noise generation and
radiation for the subsonic and fully expanded supersonic flow regime,
and to measure the necessary turbulence and acoustic parameters in order
to verify the numerical prediction or to supply data to the turbulence/
noise theories, as necessary.
Sponsor: U.S. Air Force
Investigator: Lockheed Aircraft Corporation
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 120
C-7
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Supersonic Jet Exhaust Noise Investigation (Velocity Model)
This project was initiated to develop the technology to signifi-
cantly reduce supersonic aircraft propulsion system noise with minimum
associated performance and weight penalties. Emphasis was placed on
afterburning and non-afterburning supersonic jet exhaust systems with
operating conditions typical of supersonic transport (SST) and long-
range strategic (B-l) aircraft propulsion systems. The specific tech-
nical objective of the research project was to develop a comprehensive
mathematical model capable of providing aeroacoustic design data to be
used in the development of future supersonic jet exhaust noise sup-
pressors.
Sponsor: U.S. Air Force
Investigator: General Electric Company
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 155
C-8
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Sound Transmission Through Supersonic Jets
This study will investigate the manner in which sound is trans-
mitted from within a supersonic jet to the surroundings.
Need for Study: Under the Air Force function to improve aerospace
vehicles, a better understanding of the phenomena and mechanism of sound
transmission is required in order to design aircraft which are quieter
without incurring a performance penalty.
Approach; The primary quantity to be measured is the spatial distri-
bution of sound pressure, as a function of frequency, in the field
outside the jet due to a simple sound source within the jet. The major
effort of this project is experimental; however, consideration was given
to a theoretical description of the phenomena.
Schedule: The completion date is Oct. 1977.
Accomplishments; A continuous run facility has been constructed. It
consists of a room with highly absorbing walls, a convergent-divergent
nozzle, settling chamber and appropriate controls for the air supply.
Measurements of the sound field of the jet without a synthetic sound
source have been made using a half-inch exit diameter convergent nozzle
at speeds ranging from 500 to 900 ft per sec. Hot wire measurements of
the jet showed that the jet had a very flat velocity profile at the
nozzle exit. Comparisons of the overall sound pressure level as a
function of jet speed agree closely with the semi-empirical prediction
formulae of previous investigators. Analysis of the spectra confirmed
the satisfactory performance of the facility. This indicated that
despite the simplicity of the facility, the jet sound field behaves much
like those of more sophisticated facilities. Measurements have been
made of the sound field due to the combination of the jet and the
synthetic sound source, for a range of jet speeds, driving frequencies,
and measurement angular locations. It is seen that the sound pressure
level peaks sharply at the driving frequency of the loudspeaker and
reduces to the sound pressure level of the jet alone at frequencies away
from the driving frequencies. The theoretical directivity factors have
been chosen to pass through the 90 degree points and it was seen that
the Ffowcs-Williams directivity factor applied to the Lighthill noise
theory agreed with the data only qualitatively, whereas the directivity
factor predicted more recently by Goldstein and Howe agreed with the
data quite well.
C-9
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
Sound Transmission Through Supersonic Jets (Continued)
Sponsor: U.S. Air Force
Investigator: Case Western Reserve University
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 40 30 29
C-10
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Duct Acoustics Research
The objective of this research investigation is to understand the
dependence of sound levels withinvaircraft engine ducts upon such
factors as duct geometry, sound absorbing properties of the duct walls,
type of sound source, and flow within the duct. The research will lead
to new aeroacoustic models and solution techniques for general duct
acoustics problems.
Need for Study; This work will be a significant contribution to the Air
Force Aero Propulsion Laboratory's (AFAPL) efforts to reduce turbine
engine noise levels. Current engine noise levels are hazardous to
personnel and structures, detrimental to tactical operations, and
annoying to the general public. Eventually, there is a need to assess
engine performance/noise trades in the design of aircraft engines.
Approach; To handle variable area ducts with no flow, a method of
conformal mapping in conjunction with a finite difference method is
used. As an alternative approach for the same problem an integral
equation potential theory method is appropriate. For the more general
problem of variable area ducts containing fairly general flows, a
finite element method may be required. The acoustic equation for this
general problem must be derived, and an efficient numerical method must
be implemented using local computer facilities.
Schedule:
Initiate Research (In-House) December 1975
End Preliminary Phase February 1977
Estimated Completion June 1979
Accomplishments: In October 1975 issues of the AIAA Journal, the
method of conformal mapping in conjunction with finite differences was
presented in a paper authored by the principal investigator. In 1976, a
second paper by the principal investigator appeared in the Progress
in Astronautics and Aeronautics series. This second paper compared
uniform and multisectional duct lining to determine optimum attenuation
characteristics. In July 1976, at the AIAA 3rd Aero-Acoustics Con-
ference in Palo Alto, CA, a paper summarizing the integral equation
method as applied to duct acoustics was presented. This paper has
appeared in the AIAA Journal, Vol. 15, February 1977. The publication
of these papers concludes the preliminary phases of this work unit. The
final phase has now begun, namely to develop a method for solving the
general acoustics equation which take into account nonuniform duct
geometries and general flows within these nonuniform ducts. A least
C-ll
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
Duct Acoustics Research (Continued)
squares finite element approach is generating solutions of duct acous-
tics problems, and the computer programs are being tested for rectangu-
lar ducts without flow.
Sponsor: U.S. Air Force
Investigator: Air Force Flight Dynamics Laboratory
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 46 9 28
C-12
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Noise Suppression In Jet Inlets
This effort will develop an analytical technique that will allow
the accurate prediction of the far field noise levels of an engine inlet
and changes to this level due to inlet duct treatment or inlet geometry
without the costly cut and try full scale testing that is presently
required.
Need for Study: Under the Air Force function to improve aerospace
vehicles a better understanding of the coupling mechanisms of the noise
generated in the engine inlet ducting (fans and compressor noise) with
the far field radiated noise is required. Also methods of evaluating
the effects of various duct wall acoustic treatments and engine-inlet
configurations are needed.
Approach: An integral formulation of the Hemholtz equation will be
developed, discretized and solved numerically; this formulation will
couple the sound source with the radiated far field and will account for
changes in the far field due to inlet geometry and wall acoustic liner
treatments. Experimental data will be obtained of the radiated sound
field from several simple inlet configurations to evaluate the theo-
retical predictions.
Schedule: Estimated date of completion is March 1979.
Accomplishments: None to date.
Sponsor: U.S. Air Force
Investigator: Georgia Institute of Technology
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 24 40
C-13
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - AIRFRAME NOISE
Acoustics Research
The objective is to develop methods for the prediction and control
of exterior and internal noise of military aircraft. The known physical
and geometric parameters of sources will be correlated to the charac-
teristics of the noise and aeroacoustic fields. Accurate prediction of
spectra, acoustic power, and directivity, is the aim.
Emphasis of this effort is the correlation of physical and geo-
metric parameters of known noise sources in aircraft with characteris-
tics of the emitted noise and aeroacoustic field. Results of this
endeavor will provide aircraft designers with methods to predict noise
emanations and engineers with the information necessary to control
noise. Products will be design charts, computer programs, specifica-
tions, and acoustic and vibration criteria.
Need for Study; Various problems encountered in the development of AF
weapon systems are related to the noise generated by the propulsion
systems and pseudo-noise associated with flight thro'ugh the atmosphere.
These problems include degradation of the structural integrity, equip-
ment reliability, crew health and performance, and aircraft surviv-
ability. Additionally, aircraft generated noise may have a deleterious
effect on ground structures or the population.
Approach: Existing methods of noise source estimation will be used to
prepare design charts and write computer programs that will enable users
to commute easily the near-field aircraft source noise levels. Vibra-
tion and pseudo-noise level measurements on the X24B will be used to
develop boundary layer pressure oscillation prediction methods.
Weapons bay cavity pressure oscillation problem will be studied.
Suppression devices and slender cavity noise prediction methods will be
flight-test demonstrated for the Air Launched Ballistic Missile (ALBM).
YC-14 and YC-15 noise prediction efforts will include analyses of
internal noise and measurement of STOL flap loads. (It is possible that
the latter efforts may not be funded).
Another area of this effort will be the prediction of total radi-
ated airframe acoustic power.
Part of this program involved a cooperative effort with NASA.
Schedule:
Start of In-House Laboratory Effort - AFFDL April 1977
Estimated Completion March 1980
C-14
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
Acoustics Research (Continued)
Accomplishments; Planning for the effort is underway.
Sponsor: U.S. Air Force
Investigator: Air Force Flight Dynamics Laboratory
Fiscal Year: 1975 1976 1977 1978
Funding ($1000) : 86 42 22
C-15
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - AIRFRAME NOISE
Noise and Sonic Fatigue of High Lift Devices
Current Air Force interest in STOL aircraft includes designs using
externally blown flaps with over-the-wing and under-the-wing blowing.
Other concepts such as internally blown flaps, augmentor wing, and cold
thrust augmentation with hypermixing nozzles are also being investi-
gated. A prediction methodology was developed for the fluctuating
pressure characteristics of surfaces exposed to the jet, and the results
are reported in AFFDL-TR-77-40, "Noise and Sonic Fatigue of High Lift
Devices," July 1977. The data will be useful to STOL aircraft designers
in developing concepts and selecting configurations with higher struc-
tural durability, lower maintenance, and minimum noise generation.
Need for Study: Noise predictions for these concepts have indicated
potential problems associated with community noise, sonic fatigue, and
internal noise. The objective of this effort is to investigate selected
high lift or thrust augmentation systems as they pertain to noise
generation and to define the associated noise field as it relates to
performance and engine operating parameters.
Approach; Powered lift and thrust augmentation systems will be reviewed
and practical systems design parameters will be determined. Consider-
ation will be given to thrust, by-pass ratio, mass flow, exit velocity,
exit temperature, jet diameter, engine flap geometry, engine flap
spring, etc. The most promising configuration will be selected for
further investigations including both analytical and experimental
phases. Model studies will investigate the practical range of design
parameters and determine the ascoustic loading for near field noise and
infra-sound effects.
Schedule;
Start (McDonnell Douglas Astronautics Co.) - AFFDL March 1975
Completion - AFFDL July 1977
Accomplishments: An extensive experimental program, applicable to
externally blown flaps (EBF) of STOL vehicles, was conducted providing
detailed information on the surface loads produced during jet impinge-
ment. Test specimens used in the program were varied from a simple flat
plate to a complicated wing-flaps configuration, simulating under-the-
wing blown flaps (UBF) and over-the-wing blown flaps (OBF) configura-
tions. The test program considered five categories of parameters,
namely (1) jet Mach number, (2) temperature of the jet, (3) nozzle
configuration, (4) relative position between nozzle and specimen, and
(5) deflection angle at downstream edge of specimen. From the test
results, a method was developed for predicting the fluctuating pressure
characteristics. Considered in the program were (1) overall rms level,
C-16
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
Noise and Sonic Fatigue of High Lift Devices (Continued)
(2) frequency at the peak of the power spectrum, (3) halfpower frequency
of the power spectrum, (4) peak amplification or peakedness of the power
spectrum, (5) high frequency rolloff rate of the power spectrum, (6)
maximum magnitude of the narrow band correlation spectrum for separated
locations, (7) frequency at the maximum of the narrow band correlation
spectrum, and (8) narrow band convection speed. The results for each
test case have been tabulated on layouts of the specimen surfaces
showing them in their proper spatial relation to each other. The
results have also been plotted for ease in recognizing trends produced
from parametric variations.
Sponsor: U.S. Air Force
Investigator: McDonnell-Douglas Astronautics Company
Fiscal Year: 1975 1976 1977 1978
Funding ($1000) : 63 102 24
C-17
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - NOISE PREDICTION TECHNOLOGY
Validation of Aircraft Noise Exposure Predictive Procedures
A research project was undertaken to validate the major aircraft
noise exposure prediction algorithms contained in Noisemap, a predic-
tive procedure used to describe the noise environment around airbases.
Approach; All aircraft noise exposure maps previously prepared were
reviewed to recommend four air bases where noise exposure validation
measurements should be made. Noise measurements were conducted on and
about the bases to acquire the data necessary to validate and/or
modify the noise predictive algorithms in Noisemap for runup, traffic
pattern, takeoff, and landing operations. Noisemap conputations were
then made and compared with the measured values, and detailed error
analyses were performed to account for the differences between measured
and predicted values.
Schedule: The project was completed in PY 1976.
Sponsor: U.S. Air Force
Investigator: Bolt, Beranek and Newman, Inc.
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 82 23
C-18
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - NOISE PREDICTION TECHNOLOGY
Excess Sound Attenuation Model
The program will develop analytical models for predicting the
generation and propagation of noise produced by ground run-ups for
Air Force aircraft and will account for the excess and attenuation
caused by ground cover, topography, and obstacles.
The emphasis of this program is on determining the effects of
various air base noises on personnel, on establishing exposure criteria,
and evaluating/developing personal protective devices. It is antici-
pated that this work will result in guidelines, specifications, and
regulations to control noise exposure within acceptable limits.
Need for Study; The noise produced on base and in communities by Air
Force air base operations is a major environmental concern. The Air
Staff, MAJCOMS, and air bases assess the impact of such noise by
applying community noise predictive models and noise data. The accuracy
of these predictive models and data depend in large part on the accuracy
of the algorithms used to account for Excess Sound Attenuation (ESA)
caused by reflection/absorption of sound by the earth's surface/ground
cover (e.g., sand, grass, crops), scattering caused by wind turbulence,
obstacles (e.g., buildings, trees), and other factors. Although the ESA
model presently used is the best available, it has significant uncer-
tainties which cause corresponding uncertainties in the environmental
noise assessments.
Approach: The approach is to conduct air base noise measurements over a
one- to two-year period using six to ten all-weather acoustic measuring
stations. Data taken will define ESA over a range of 75 m to several
kilometers from the source for all times of day and night, all seasons,
various weather conditions, and for the flat farm land and urban/suburban
areas. Statistical analyses will provide the basis for new empirical
ESA models which better define such attenuation for specific classes of
conditions.
Schedule:
Complete data collection January 1979
Complete model and incorporate into NOISEMAP July 1980
Accomplishments: The test plan has been completed and approved. Data
is being collected from ground run-up noise over mowed grass on flat
land. The tests are being conducted at Wright-Patterson AFB, OH.
C-19
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
Excess Sound Attenuation Model (Continued)
Sponsor: U.S. Air Force
Investigator: Aerospace Medical Research Laboratory
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 108
C-20
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - NOISE PREDICTION TECHNOLOGY
Measurement, Prediction and Evaluation of Bioenvironmental Noise From
Air Force Systems and Operations
Technical support is provided to System Program Offices, commands,
bases, laboratories, and others on specific environmental noise pro-
blems .
Need for Study; Problems involving noise are commonplace and many
must be dealt with immediately. The expertise of the 6570th Aerospace
Medical Research Laboratory is required for environmental impact state-
ments, facility siting, real estate decisions, monitoring of air base
noise, sound propagation, run-up suppressors, and identifying hazardous
noise areas. Their expertise is not available in other organizations.
It is expected that this work will benefit not only the Air Force
but all parties concerned with environmental noise problems.
Approach; The appoach is to measure and evaluate the customer's speci-
fic noise problem by applying the instrumentation, measurement methods,
NOISE-BANK, OMEGA software, predictive methods and other tools developed
by AMRL. Travel/per diem costs will generally be paid by the customer.
Results will usually be documented in the form of letter reports or
memoranda.
Schedule; Work is accomplished as required and within existing prior-
ities of efforts and resources.
Accomplishments: Approximately 250 customers were provided with the
noise data and/or guidance necessary to evaluate the impact of the noise
produced by existing or planned Air Force systems and operations on crew
members and nearby community populations. The third and final measure-
ment of a Titan III launch was accomplished to obtain the noise data
required by Space and Missile Systems Operations (SAMSO) in writing an
Environmental Impact Statement for the Space Shuttle Program. Consul-
tation was provided to Air Force to assist them in making preliminary
environmental assessments of various KC-135A engine retrofits.
Sponsor: U.S. Air Force
Investigator: Aerospace Medical Research Laboratory
Fiscal Year: 1975 1976 1977 1978
Funding ($1000) : 268 246 366
.C-21
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - NOISE PREDICTION TECHNOLOGY
Computerized Procedure to Assess Turbine Engine Noise/Performance
Tradeoffs
A computer code was developed in-house with previous funding to
perform noise/performance trades. The current funding provides for
further work in analyzing noise propogation in ducts for installed noise
refinements and exercising tradeoffs. The program capabilities include:
uninstalled engine noise prediction applicable to current and future
aircraft gas turbine engines; prediction of installed engine noise
levels, including the effects of special noise reduction devices; and
assessment of propulsion performance and weight penalties as a function
of noise level reduction.
Need for Study; Current systems and proposed systems require data on
performance/noise trades to make decisions on buying engineering changes,
performing system studies, and performing source selections. Also, the
military is attempting to comply with FFA noise requirements wherever
possible.
Approach: The AF Aero Propulsion Laboratory has already developed the
capability for uninstalled predictions and installed predictions (pre-
viously developed in-house). Further work is being done under contract
to a local university. Evaluations/trade studies will be made on vari-
ous engine-airframe configurations and further refinements on installed
engine noise calculations will be made through improved duct propagation
models.
Schedule:
Complete duct noise propagation work -
Univ. of Dayton December 1978
Integrate duct propagation into installed
trade model - (AFAPL) and Univ. of Dayton December 1979
Final integration of all elements and final
reports - Univ. of Dayton December 1980
Accomplishments; System studies for F15, F-16, B-l, A-7, A-10, YC-14,
YC-15, and RPVs have been accomplished. The F101 engines were evaluated
for the B-l, reduced throttle take-offs were evaluated for the A-7 and
A-10, liner treatment was evaluated for the A-10, the YC-14 and YC-15
were "compared," as well as JT8D-209 vs CFM-56 engine, new engines for
the KC-135 were evaluated and compared with B-52 noise patterns, and
some RPV configurations were evaluated.
C-22
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U.S. AIR FORCE - RESEARCH AND TECHNOLOGY PROGRAMS
Computerized Procedure to Assess Turbine Engine Noise/Performance
Tradeoffs (Continued)
Sponsor: U.S. Air Force
Investigator: Air Force Aero-Propulsion Laboratory
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 20 28 6
C-23
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U.S. ARMY - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Propulsion System Noise
Methods for reducing the helicopter cabin noise generated by the
propulsion/transmission system of Army helicopters are being developed.
Need for Study; The noise and vibration caused by the propulsion/drive
train system of helicopter contributes to crew fatigue and obstructs
effective communication between crew members. The transmission system
is the major source of cabin noise. There is a need to develop new
transmission case designs to minimize contributions to cabin noise.
Approach: Areas where structural characteristics of transmission cases
develop resonances are determined through analysis and experimentation.
These resonances are transmitted to the airframe or generated noise
directly. Stiffening of the transmission case is being evaluated to
eliminate the resonances. New composite casing materials will also be
evaluated.
Schedule; The project was initiated in FY 1977.
Accomplishments: Tests have shown that substantial reduction in trans-
mission noise can be made by selective stiffening of existing cases and
proper design of new cases. Material research in composite metal matrix
patches and structures for helicopter gear boxes is underway.
Sponsor: U.S. Army
Investigator: Boeing Vertol Co. and Bell Helicopter Co.
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 71 86
C-24
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U.S. ARMY - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - ROTOR NOISE
Helicopter Rotor Noise
This program will develop the analytical methodology, and tech-
niques necessary to gain an understanding of the fundamental sources and
mechanism of generation of rotor noise. The program will examine rotor
configuration, materials, and interaction with ambient environment at
both subsonic and transonic mach numbers in hover and forward flight.
Need for Study: The suppression of the aural signature of Army heli-
copters is necessary for effective nap-of-the-earth mode of employment
of Army helicopters. The helicopter rotor is a primary element in this
signature, producing the characteristic "blade slap" impulsive noise
that can alert the enemy to approaching helicopters. This character-
istic noise also contributes to the environmental noise pollution
generated at military installations during training operations. The
noise must be controlled if community pressure to curtail or relocate
training operations is to be avoided.
Approach: Several complementary theoretical investigations and analy-
tical studies are being performed to develop improved analytical formu-
lations for identifying and quantifying the primary factors that cause
rotor noise. Analysis efforts are supported by scale-model and full
scale whirl and wind tunnel tests. An open jet test section of an
anechoic room will be utilized to determine the effects of blade number,
advance rotation, thrust and rotor disk tilt angle on rotational noise
and blade slap. Comparative studies of sources of broad band noise are
used to determine mechanisms leading to random blade loading and asso-
ciated boradband noise. Rotortip geometry (ogee tip) is evaluated for
reduction of implusive and blade-vortex noise. The use of materials
having vectored porosity to improve laminar flow over airfoils for noise
reduction is also being investigated. This is a joint program with NASA.
Accomplishments: Methodology has been developed for calculating high
frequency rotor noise due to random forces and a simplified mach number
scaling law has been developed for rotational and high frequency broad-
band noise based upon geometric parameters of the rotor. Full scale
flight tests have confirmed that forward flight propeller noise levels
are lower than those experienced under static conditions. The use of
electronic beam drilling techniques to produce vectored porosity in
wood-metal laminate samples has been demonstrated. The ogee tip rotor
geometry has been evaluated on the UH-lH.
C-25
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U.S. ARMY - RESEARCH AND TECHNOLOGY PROGRAMS
Helicopter Rotor Noise (Continued)
Sponsor: U.S. Army
Investigator: George Washington University, Polytechnic
Institute of New York, Massachusetts Institute
of Technology, and In-House
Fiscal Year: 1975 1976 1977 1978
Funding ($1000) : - 14 695 610
C-26
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U.S. ARMY - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - NOISE PREDICTION TECHNOLOGY
Helicopter Noise Propagation, Prediction and Mitigation
This program studies the effects of terrain geometry and ground
cover on helicopter noise propagation and develops methods for pre-
diction and mitigation of helicopter noise.
Need for Study; The need for detection and suppression of the aural
signature of helicopters in nap-of-the-earth operations, crew comfort
and the need for reducing the environmental impact of noise generated by
helicopter operations on military and civil communities requires a
better understanding of noise propagation. Methods for predicting and
mitigating helicopter noise also need development.
Approach; A method for modeling the effects of terrain features on
aural detection of helicopters is being developed. Tests will be
conducted to determine the influence of soil type and vegetation height
on theoretical helicopter noise levels.
Noise frequency signatures of various types of military helicopters
are recorded and human response to the frequency spectrum evaluated and
used as the basis for noise prediction. Finally methods and guidelines
for mitigation of noise from helicopter operations at military instal-
lations will be developed, based upon flight path constraints in areas
of community development.
Accomplishments; Preliminary theoretical model of terrain effects on
noise propagation, and a test set-up for investigation of soil and
vegetation absorption effects on noise have been developed. Guidelines
have been developed for mitigation of helicopter noise at military
installation by establishment of flight path constraints for helicopter
operations in areas of community housing. Frequency signatures of
various Army, Navy and Air Force helicopters have been recorded and
human response to helicopter noise has been incorporated into the heli-
copter prediction submodel.
Sponsor: U.S. Army
Investigator: CERL, Boeing, University of Mississippi
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): - 32 160 172
C-27
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U.S. NAVY - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Jet Engine Ground Run-up Noise Suppression
The objective of this program is to provide the Navy with the
capability to reduce noise levels from jet engine ground run-up opera-
tions. This must be accomplished in the most responsible and cost-
effective manner by developing the technical base for supporting alter-
nate systems/concepts and for optimizing current design developments.
Need for Study: One of the most pressing noise problems confronting
the Navy is that associated with post-maintenance jet engine ground
run-up operations both in and out of airframes, at Naval Air Rework
Facilities and Naval Air Stations. The fundmental issue is how best
to deal with the unabated high noise levels and concomitant effects
on Navy military and civilian personnel working in the immediate
vicinity of the run-up spots. These effects have included hearing loss,
physiological and psychological damage, and general reduction in morale.
These problems obviously affect the Navy's mission and the need is for
a unified advanced development program to deal with these problems.
Approach: Specific program objectives are to develop a materials and
fabrication technology base for increasing the life cycle of suppressor
designs to conduct model studies to optimize the acoustic design of
current and'alternate systems/concepts, to test promising system
solutions, to provide guidelines and safety requirements for operating
personnel, and to develop life cycle costs and benefit impacts for
each reasonable technical solution to the jet engine ground run-up
noise problem.
Schedule; Date
Start air-intake de-icing tests Apr 77
Metal liner fatigue test and design Sep 77
Record low frequency noise from hush-house, etc. Apr 78
Fabricate scale models of various acoustical
enclosures for aerothermodynamic and acoustic tests Jun 78
Cost/benefit analysis, phase II Jun 78
Response to compressor stall tests Jul 78
Laboratory tests of ground run-up noise Jul 78
Accomplishments: the primary concern of the U.S. Navy relative to
aviation noise during the relevant period was the suppression of jet
engine ground run-up noise. This has resulted in the development
of jet engine noise suppression equipment and an alternate, the
Brauburgh dry jet engine noise suppression system. An advanced
C-28
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U.S. NAVY - RESEARCH AND TECHNOLOGY PROGRAMS
Jet Engine Ground Run-up Noise Suppression (Continued)
development plan, considering the alternate systems, has been issued
and cost/benefit analyses have been initiated.
Sponsor: U.S. Navy
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 1195 798 300 165
C-29
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U.S. NAVY - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - AIRFRAME NOISE
Anechoic Flow Facility Airframe Noise Experiment
The U.S. Navy and the National Aeronautics and Space Administration
are conducting an interagency project to estimate the airframe radiated
noise of a scale-model Boeing 747 aircraft during landing. The Navy
is providing the test facility, support personnel, and instrumentation;
NASA will report the results.
The airframe noise experiments were conducted in September 1977.
The next phase of the program includes studies of airframe radiated
noise during aircraft landings.
Sponsor: U.S. Navy and National Aeronautics and Space
Administration/Langley Research Center
Investigator: David Taylor Naval Ship R&D Center
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 20 10 10
C-30
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U.S. NAVY - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - NOISE PREDICTION TECHNOLOGY
Naval Air Facilities Noise Prediction
Methodology and instruments for acquisition and prediction of
environmental noise data in the vicinity of air installations are being
developed. Corrections to the tri-service NOISEMAP model for ground
run-up and helicopter blade-slap noise are being determined.
Need for Study: Accurate prediction of environmental noise levels
around naval air installations is essential for future planning and
maintaining community acceptance of aviation activities.
Approach; Portable noise monitoring equipment with digital printout is
being evaluated. Data using this equipment will be compared with
conventional instruments.
Operations at NAS Miramar have been monitored for a period of
one year. This data will be analyzed in light of the local topography
and weather.
Ground map and helicopter blade slap corrections will be determined
in cooperation with U.S. Army helicopter studies.
Schedule;
Complete documentation of noise data systems May 77
Report on helicopter blade-slap Feb 78
Report on "average busy day" at NAS's Mar 78
Accomplishments: One year of operations data, noise data, and telephone
complaints at NAS Miramar has been compiled. Laboratory tests on 70
samples of helicopter noise with various degrees of blade-slap have
been completed.
Sponsor: U.S. Navy
Fiscal Year: 1975 1976 1977 1978
Funding ($1000): 160 120
C-31
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APPENDIX D
DEPARTMENT OF TRANSPORTATION
(FEDERAL AVIATION ADMINISTRATION)
AVIATION NOISE RT&D PROGRAM
This appendix describes DOT's aviation noise program in
terms of its research, technology and demonstration projects.
Aviation noise activities concerning DOT/FAA's regulatory and
rulemaking responsibilities are not included in this report.
Funding for FY 76 includes the transition quarter (July
1, 1976 to September 30, 1976). Funding cited for FY 77 and
FY 78 includes estimates. Projects for FY 78 have not been
finalized.
D-l
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FUNDING AND MANPOWER SUMMARY
DEPARTMENT OF TRANSPORTATION
(FEDERAL AVIATION ADMINISTRATION)
Fiscal Year Funding ($1,000)
(Agency Manpower in Man-Years)
CATEGORY 1975 1976 1977 1978
RESEARCH AND TECHNOLOGY
PROPULSION NOISE 700 917 770
NOISE PREDICTION TECHNOLOGY 95 86 -
ATMOSPHERIC PROPAGATION
AND GROUND EFFECTS *
SUBTOTAL: Research and
Technology 795 1,003 770
DEMONSTRATION PROGRAMS AND
SYSTEMS STUDIES
CTOL (Subsonic) 164 250 950 1,730
TOTAL: All Projects 959 1,253 1,720 1,730
(6) (5) (5) (4)
In-house project, with 1.5 man-year effort only.
D-3
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DOT/FAA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Jet Noise Research
This project examines promising noise suppression concepts to
determine the probable noise reduction benefits, the potential effects
on flight performance over flight speeds and jet velocity ranges of
practical interest.
Need for Study: An improved understanding and ability to predict noise
performance of turbojet aircraft is necessary to support aircraft noise
regulation.
Approach: This project includes both theoretical and experimental
research of high-velocity jet noise suppressors, including inflight
effects. The goal is the development of a fundamental understanding of
jet noise suppression, including the effects on inflight performance,
and thrust losses.
Schedule: This project began in FY 1973, under a $5 million research
contract, by the Office of the Secretary of Transportation. In FY 1976,
the project was transferred to the FAA for continued funding and com-
pletion. The project should be completed and reports available early in
FY 1979.
Accomplishments: Early analytical and ground testing have provided
insight into noise suppression performance, including the effects of
forward motion on those suppressors.
Sponsor: Federal Aviation Administration
Investigator: General Electric
Fiscal Year: 1975 197^ 1977 1978
Funding ($1,000): 782 720
D-4
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DOT/FAA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Core Engine Noise Control
This project develops information on source noise levels of air-
craft turbofan engines, examining in particular the internal noise
sources.
Need for Study: An improved understanding and knowledge of engine core
noise characteristics is necessary to support aircraft noise regula-
tions.
Approach: This project will identify, evaluate, and attempt controls
for the component noise sources (e.g.: combustion, turbine, jet inter-
action) inherent in the core or gas generator portion of a turbofan
engine. The effort includes both theoretical and experimental investi-
gations of these noise sources.
Schedule; The project is expected to be completed in late FY 1978.
Accomplishments; Accomplishments to date include a rank ordering of the
significant noise sources and a core engine noise prediction capability,
which includes prediction models for the major core engine noise com-
ponents.
Sponsor: Federal Aviation Administration
Fiscal Year: 1975 1976 1977 1978
Funding ($1,000): 700 135 50
D-5
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DOT/FAA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - NOISE PREDICTION TECHNOLOGY
Aircraft Source Noise Data Base
This project collects and maintains noise data for various types
of aircraft, such as STOL, VTOL, and conventional aircraft. Component
noise source data, such as airframe noise, is also being obtained.
Need for Study: These data are necessary to support aircraft noise
regulation.
Approach: This effort is conducted largely as an in-house FAA activity,
but some contract support is included. An aircraft noise measurement
and test range is being established for the measurement of flight noise
data under conditions which can be controlled and measured accurately.
These data are then used to improve source noise prediction capabilities
and noise certification test techniques.
Schedule: This is a continuing project, with periodic data reports as
appropriate.
Accomplishments: A series of helicopter noise measurements has been
completed in support of the drafting of VTOL noise certification re-
quirements. An airframe noise prediction model has also been developed.
Sponsor: Federal Aviation Administration
Fiscal Year: 1975 1976 1977 1978
Funding ($1,000): 95 86
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DOT/FAA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - ATMOSPHERIC PROPAGATION AND GROUND EFFECTS
Atmospheric Attenuation, Data Acquisition
This project is intended to provide reliable measurements of
attenuation effects on the propagation of aircraft noise. The data will
increase the accuracy of aircraft noise prediction for use in the FAA's
Integrated Noise Model.
Need for Study; Accurate noise predictions are essential in developing
land-use noise plans for airports, and in assessing alternative noise
impacts of proposed airport projects and noise abatement policies.
Approach: Noise measurements of selected aircraft will be taken under
controlled conditions of flight and meteorology, utilizing in-house FAA
capabilities. Measured data will then be compared with computed data to
determine the computational accuracy, and corrections applied as warranted,
Schedule; This is a continuing project, which began in FY 1978. Results
will be available beginning in FY 1979.
Accomplishments: The first series of flyover measurements, using a
business jet aircraft, have been completed.
Sponsor: Federal Aviation Administration
Investigator: In-house
Fiscal Year: 1975 1976 1977 1978
Funding: I'anyr
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DOT/FAA - DEMONSTRATION PROGRAMS AND SYSTEMS STUDIES
CATEGORY - CTOL (SUBSONIC)
Jet Noise Suppression
This project involves the application and demonstration of avail-
able technology for noise suppression devices, to demonstrate what is
technologically practicable, economically reasonable, and capable of
airworthiness certification.
Need for Study: Demonstration of practicable noise suppression devices
is necessary to support aircraft noise regulation.
Approach: Efforts involve studies and analyses, scale model experi-
ments, static engine testing, and flight demonstrations. The major
current effort involves application of mixer technology to the JT8D
turbofan engine. Is is hoped to demonstrate the noise benefits achiev-
able from the efficient mixing of core engine exhaust and fan bypass air
flow in a common exhaust nozzle.
Schedule: The results of static engine tests of JT8D mixer nozzles are
expected by late FY 1978. Flight test results are planned by mid FY
1979.
Accomplishments: A study of the noise suppression capabilities for
business jet aircraft has been completed. Studies and scale model tests
for the mixer nozzle in the JT8D have also been completed. Full-scale
static testing is about to begin.
Sponsor: Federal Aviation Administration
Investigator: Pratt & Whitney Aircraft
Fiscal Year: 1975 1976 1977
Funding ($1,000) 164 250 950
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APPENDIX E
ENVIRONMENTAL PROTECTION AGENCY
AVIATION NOISE RT&D PROGRAM
This appendix describes EPA's aviation noise research
and technology projects.
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FUNDING AND MANPOWER SUMMARY
ENVIRONMENTAL PROTECTION AGENCY
Fiscal Year Funding ($1000)
(Agency Manpower in Man-Years)
CATEGORY
RESEARCH AND TECHNOLOGY
PROPULSION NOISE
1975
1976
1977
1978
100
(-)*
TOTAL
100
(-)*
Less than 1 man-year
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EPA - RESEARCH AND TECHNOLOGY PROGRAMS
CATEGORY - PROPULSION NOISE
Small Propeller Technology
This project will support efforts towards lowering the noise levels
of propeller driven aircraft through the application of aeroacoustic
theory to the design of propellers. The project is designed to comple-
ment other NASA propeller studies reported on page B-20.
Need for Study: Current projections indicate that general aviation
aircraft noise impacts will increase significantly by the year 2000
unless small aircraft noise levels are lowered below current levels.
The dominant noise source from all turbine-powered vehicles and most of
the reciprocating-engined vehicles is the propeller. Updated design
methods and technology need to be developed and demonstrated from the
analytical tools that exist today but were not available before the jet
engine era.
Approach: NASA Langley Research Center, which posesses the necessary
qualified staff expertise in this area, will manage the jointly funded
project. The work will be performed under contract by the Massachusetts
Institute of Technology. It is divided into three phases, with each
phase dependent on the success of the previous one. The goal is to
lower the propeller noise levels three to five decibels below current
noise levels, while maintaining propeller efficiency.
Phase I, Background Studies and Design, will involve the develop-
ment of the analytical tools necessary for low noise propeller design.
Aeroacoustic theory will be integrated with other propeller design
criteria such as aerodynamic performance and mechanical characteristics
(shape, number of blades, diameter and rpm) to develop a complete design
calculation procedure.
During Phase II, scale models of quiet propeller designs will be
tested in a semi-anechoic wind tunnel at MIT. The anechoic character-
istics of the wind tunnel will permit the simulation of outdoor test
conditions with very low background noise levels. The noise produced by
the test propeller will be compared with the known noise characteristics
of current technology propellers.
Under Phase III, a full scale test propeller will be fabricated and
flight tested and actual noise level reduction will be demonstrated.
The full scale test data, along with the scale model data obtained in
Phase II, will permit the verification of scaling laws important in the
development of generalized design procedures. Finally, design charts
will be developed to facilitate future quiet propeller designs.
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EPA - RESEARCH AND TECHNOLOGY PROGRAMS
Small Propeller Technology (Continued)
Schedule: The program will start in January 1978, with completion of
all phases scheduled for December 1979.
Sponsor: The program will be funded jointly by EPA Office
of Noise Abatement and Control and NASA. NASA will
also be responsible for the management and technical
direction of the program.
Investigator: Massachusetts Institute of Technology
Fiscal Year: 1975 1976 1977 1978
Funding ($1,000): 100*
Agency Manpower:
(Man-Years) \
*EPA share of funding for FY 78. See Page B-20, Propeller Studies for
NASA funding share.
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APPENDIX F
BIBLIOGRAPHY
This appendix contains a list of the prinicpal NASA and
DOT/FAA aviation noise RT&D publications, as well as some
selected general interest publications. There are, in
addition, numerous other RT&D related technical memoranda,
contractor progress reports, and professional society and
journal presentations.
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BIBLIOGRAPHY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
AMES RESEARCH CENTER
1. Ahtye, Warren F.; and McCulley, Gerladine, "Evaluation of Simple Methods for the Prediction
of Noise Shielding by Airframe Components," NASA TP 1004, 1977.
2. Atencio, A., Jr., "The Effect of Forward Speed on J-85 Engine Noise from Suppressor Nozzles
as Measured in the Ames 40- by 80-Foot Wind Tunnel," NASA TN D-8428, February 1977.
3. Aoyagi, K.; Falarski, M.D.; and Koenig, D.G., "Wind Tunnel Investigation of a Large-Scale Upper
Surface Blown-Flap Model Having Four Engines," NASA TM-X-62,419, July 1975.
4. Falarski, M.D.; Aiken, T.N.; and Aoyagi, K., "Acoustic Characteristics of a Large-Scale Wind
Tunnel Model of a Jet Flap Aircraft," NASA TM-X-3263, July 1975.
5. Click, J.M.; Shevell, R.; and Bowles, J.r "Evaluation of Methods of Reducing Community Noise
Impact around San Jose Municipal Airport," NASA TM X-62-503, November 1975.
6. Lee, A., "A Computer Program for the Identification of Helicopter Impulsive Noise Sources,"
NASA CR-151997, 1977.
7. Lee, A., "High Speed Helicopter Noise Sources," NASA CR-151996, 1977.
8. Lee, A.; Biggers, J.C.; Orloff, K.L.; and Lemmer, O.J., "Laser Velocimeter Measurements of
Two-Bladed Helicopter Rotor Flow Field," NASA TM-73238, 1977.
9. Soderman, Paul T., "Comparison of Tilt-Rotor Noise Measured in the 40- by 80-Foot Wind Tunnel
and at Wright-Patterson Air Force Base," FSA Technical Memorandum No. 7, March 1975.
10. Soderman, Paul T., "Test-Section Noise of the Ames 7- by 10-Foot Wind Tunnel No. 1," NASA
TMX 73,134, May 1976.
11. Soderman, Paul T.; and Page, V. Robert, "Acoustic Performance of Two 1.83- Meter-Diameter Fans
Designed for a Wind Tunnel Drive System," NASA TP 1008, August 1977.
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LANGLEY RESEARCH CENTER
1. Abrahamson, "A Finite Element Algorithm for Sound Propagation in Axisymmetric Ducts Containing
Compressible Mean Flow," Wyle Laboratories, June 1977.
2. Abrahamson, A.L.; and Osinski, John, "Resonance Testing of Space Shuttle Thermoacoustic
Structural Specimens," NASA CR-145154, 1977.
3. Abrahamson, A.L.; Rasper, P.K.; and Pappa, R.S., "Acoustical Characteristics of the NASA-
Langley Full-Scale Wind Tunnel Test Section," NASA CR-123604, 1975.
4. Barton, D. Kearney, "Internal Noise Considerations for Powered-Lift STOL Aircraft," NASA TM
X-72675, 1975.
5. Bliss, Donald B.; and Hayden, Richard E., "Landing Gear and Cavity Noise Prediction," NASA
CR-2714, 1976.
6. Block, Patricia J.W., "Noise Response of Cavities of Varying Dimensions at Subsonic Speeds,"
NASA TN D-8351, 1976.
7. Block, Patricia J.; and Heller, Hanno, "Measurements of Farfield Sound Generation from a Flow-
Excited Cavity," NASA TM X-3292, 1975.
8. Borksy, Paul N., "A Comparison of Laboratory and Field Study of Annoyance and Acceptability of
Aircraft Noise Exposures," NASA Grant NSG-1164, Columbia University, February 1977.
9. Borsky, Paul N., "Special Analysis of Community Annoyance with Aircraft Noise Reported by
Residents in the Vicinity of JFK Airport—1972," NASA CR-132678, 1975.
10. Brooks, Thomas F., "An Experimental Evaluation of the Application of the Kirchhoff Formulation
for Sound Radiation from an Oscillating Airfoil," TP 1048, December 1977.
11. Catherines, John J.; and Jha, Sunil K., "Sources and Characteristics of Interior Noise in
General Aviation Aircraft," NASA TM X-72839, 1976.
12. Catherines, John J.; and Mayes, William H., "Interior Noise Levels of Two Propeller-Driven
Light Aircraft," NASA TM X-72716, 1975.
13. Catherines, John J.; Mixson, John S.; and School, Harland F., "Vibrations Measured in the
Passenger Cabins of Two Jet Transport Aircraft," NASA TN D-7923, 1975.
14. Cawthorn, Jimmy M.; and Mayes, William H., "Review of Subjective Measures of Human Response
to Aircraft Noise," NASA TM X-72807, 1976.
15. Clark, Lorenzo R., "Effects of Inlet Treatment Location and Treatment Cavity Depth on Com-
pressor Noise," NASA TM X-72698, 1975.
16. Clark, L.R.; and Yu, J.C., "Effects of Geometry and Jet Velocity on Noise Associated with an
Upper-Surface-Blowing Model," NASA TN D-8386, 1977.
17. Clevenson, Sherman A., "Subjective Response to Combined Noise and Vibration During Flight of a
Large Twin-Jet Airplane," NASA TM X-3406, 1976.
18. Connor, Andrew B.; Hilton, David A.; Copeland, W. Latham; and Clark, Lorenzo R. , "Noise
Characteristics of the 0.1 Airplane and Some Approaches to Noise Reduction," NASA TM X-72638,
1975.
19. Connor, Andrew B.; Hilton, David A.; and Dingeldein, Richard C., "Noise Reduction Studies for
the Cessna Model 337 (0-2) Airplane," NASA TM X-72641, 1975.
20. Connor, Andrew B.; Copeland, William L.; and Fulbright, Danny C., "Low Altitude Temperature and
Humidity Profile Data for Application to Aircraft Noise Propagation," NASA TN D-7975, 1975.
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21. Cooper, "The Acoustical and Electrical Performance o£ Direct Actuated Ceramic Microphone
Systems," TRACOR Sciences and Systems, December 1977.
22. Dempsey, Clevenson; and Leatherwood, "Development of Noise and Vibration Ride Comfort Criteria,
Journal of the Acoustical Society of America, 1977.
23. Dempsey, Coats, and Cawthorn, "Model of Aircraft Noise Adaptation," TMX74052, June 1977.
24. Dempsey, Thomas K.; Leatherwood, Jack D.; and Clevenson, Sherman A., "Noise and Vibration Ride
Comfort Criteria," NASA TM X-73975, 1976.
25. Dempsey, Thomas K.; Leatherwood, Jack D.; and Drezek, Arlene B., "Passenger Ride Quality
Within a Noise and Vibration Environment," NASA TM X-72841, 1976.
26. Dingeldein, Richard C. ; Connor, Andrew B.; and Hilton, David A., "Noise Reduction Studies of
Several Aircraft to Reduce the Aural Detection Distance," NASA TM X-72644, 1975.
27. Edge, Philip M., Jr.; and Cawthorn, Jimmy M., "Selected Methods for Quantification of
Community Exposure to Aircraft Noise," NASA TN D-7977, 1976.
28. Farassat and Brown, "A New Capability for Predicting Helicopter Rotor and Propeller Noise
Including the Effect of Forward Motion," TM X 74037, June 1977.
29. Farassat, F., "Theory of Noise Generation from Moving Bodies with an Application to Helicopter
Rotors," NASA TR-451, 1975.
30. Findley, Donald S.; Huckel, Vera; and Henderson, Herbert R., "Vibration Responses of Test
Structure No. 1 During the Edwards Air Force Base Phase of the National Sonic Boom Program,"
NASA TM X-72706, 1975.
31. Findley, Donald S.; Hickel, Vera; and Hubbard, Harvey H-, "Vibration Responses of Test
Structures No. 2 During the Edwards Air Force Base Phase of the National Sonic Boom Program,"
NASA TM X-72704, 1975.
32. Getline, G.L., "Low-Frequancy Noise Reduction of Lightweight Airframe Structures," NASA
CR-145104, i976.
33. Graham, E.W.; and Graham, B.B., "Theoretical Study of Refraction Effects on Noise Produced by
Turbulent Jets," NASA CR-2632, 1975.
34. Guinn, Wiley A.; Balena, Frank J.; and Soovere, Jaak, "Sonic Environment of Aircraft Structure
Immersed in a Supersonic Jet Flow Stream," NASA CR-144996, 1976.
35. Gunn, Walter J.; Shigehisa, Tsuyoshi; and Shepherd, William T, "Relative Effectiveness of
Several Simulated Jet Engine Noise Spectral Treatments in Reducing Annoyance in a TV-Viewing
Situation," NASA TM X-72828, 1976.
36. Gunn, Walter J.; Patterson, Harrold P.; Cornog, June; Klaus, Patricia; and Connor, William K.,
"A Model and Plan for a Longitudinal Study of Community Response to Aircraft Noise," NASA
TM X-72690, 1975.
37. Gunn, Walter J.; Shepherd, W.T.; and Fletcher, John L., "Effects of Three Activities on
Annoyance Responses to Recorded Flyovers," NASA TM X-72673, 1975.
38. Gupta, "Low Frequency Cabin Noise Reduction Based on the Intrinsic Structural Tuning Concept,"
Contractor Report, November 1977.
39. Hanson, Donald B., "Study of Noise Sources in a Subsonic Fan Using Measured Blade Pressures
and Acoustic Theory," NASA CR-2574, 1975.
40. Hardin, Jay C.; Fratello, David J.; Hayden, Richard E.; Kadman, Yoran; and Africk, Steven,
"Prediction of Airframe Noise," NASA TN D-7821, 1975.
41. Hardin, Jay C., "Airframe Self-Noise—Four Years of Research," NASA TM X-73908, 1976.
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42. Hayden, Richard E., "Exploratory Investigation of Aeroacoustic Optimization of the Variable
Impedance Edge Concept," NASA CR-145072, 1976.
43. Hayden, R.E.; Fox, H.L.; and Chanaud, R.C., "Some Factors Influencing Radiation of Sound from
Flow Interaction with Edges of Finite Surfaces," NASA CR-145073, 1976.
44. Hersh and Walker, "Effects of Grazing Flow on the Steady-State Flow Resistance and Acoustic
Impedance of Thin Porous-Faced Liners," Hersh Acoustics Engineering, July 1977.
45. Hilton and Bruton, "Near Noise Field Characteristics of NIKE Rocket Motors for Application to
Space Vehicle Payload Acoustic Qualification," TM X 12111, June 1977.
46. Hilton, David A.; and Henderson, Herbert R., "The Remotely Operated Multiple Array Acoustic
Range (ROMAAR) and its Application for the Measurement of Airplane Flyover Noise Footprints,"
presented at the 92nd Meeting of the Acoustical Society of America, NASA TM X-73986, November
1976.
47. Hilton, D.A.; Connor, A.B.; Copeland, W.L.; and Dibble, A.C., Jr.; "Noise Reduction Studies
for the OV-1 Airplane," NASA TM X-72639, 1975.
48. Hilton, David A.; Connor, Andrew B.; and Hubbard, Harvey H., "A Noise Study of the A-6 Airplane
and Techniques for Reducing Its Aural Detection Distance," NASA TM X-72643, 1975.
49. Hilton, David A.; Connor, Andrew B.; Hubbard, Harvey H.; and Dingeldein, Richard C-, "Noise
Reduction Studies for the U-10 Airplane," NASA TM X-72640, 1975.
50. Hilton, David A.; Henderson, Herbert R.; and Lawton, Ben W., "Ground Noise Measurements During
Static and Flyby Operations of the Cessna 02-T Turbine Powered Airplane," NASA TM X-72642,
1975.
51. Hosier, R.N., "A Comparison of Two Independent Measurements and Analyses of Jet Aircraft
Flyover Noise," NASA TN D-8379, May 1977.
52. Hosier, Robert N., "Some Comparisons of the Flyover Noise Characteristics of DC-9 Aircraft
Having Refanned and Hardwalled JT8D Engines with Special Reference to Measurement and Analysis
Procedures," NASA TM X-72804, 1976.
53. Hosier, Robert N.; and Hilton, David A., "Some Effects of the Atmosphere and Microphone
Placement on Aircraft Flyover Noise Measurements," NASA TM X-72791, 1975.
54. Hewlett, James T.; Clevenson, Sherman A.; Rupf, John A.; and Snyder, William J, "Interior
Noise Reduction in a Large Civil Helicopter," NASA TN D-8477, 1977.
55. Hewlett, James T.; and Morales, David A., "Prediction of Light Aircraft Interior Noise,"
NASA TM X-72838, 1976.
56. Hewlett, James T.; and Clevenson, Sherman A., "A Study of Helicopter Interior Noise Reduction,"
NASA TM X-72655, 1975.
57. Karamcheti, K.; Wooley, J.P.; and Guenther, J.L., "An Analytical Study of Noise Generation
by Subsonic Flows in the Presence of Rigid Surfaces," NASA CR-145027, 1976.
58. Jackson, Robert L.; Taylor, Allan H.; and Rucker, Carl E., "Sonic Environment Tests of an
Insulator/Ablator Material," NASA TM X-74022, 1977.
59. Kasper, P.K., "Determination of Rotor Harmonic Blade Loads from Acoustic Measurements," NASA
CR-2580, 1975.
60. Kasper, Peter K.; Paupa, Richard S-; Keefe, Laurence R.; and Sutherland, Louis C., "A Study
of Air-to-Ground Sound Propagation Using an Instrumented Meteorological Tower," NASA CR-2617,
1975.
61. Kentzer, Czeslaw P., "Nonclassical Acoustics," NASA CR-145071, 1976.
62. Klaus, Patsy A., "Emotionality in Response to Aircraft Noise: A Report of Developmental
Work," NASA CR-2600, 1975.
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63. Lane, Frank, "Broadband Noise Generated by Turbulent Inflow to Rotor or Stator Blades in an
Annular Flow," NASA CR-2503, 1975.
64. Langley Research Center, "Concorde Noise Induced Building Vibrations for Sully Plantation,
Chantilly, Virginia," NASA TM X-73919, June 1976.
65. Langley Research Center, "Concorde Noise Induced Building Vibrations for Sully Plantation,"
Report No. 2, Chantilly, Virginia, NASA TM X-73926, July 1976.
66. Langley Research Center, "Concorde Noise Induced Building Vibrations-Montgomery County,
Maryland," Report No. 3, TM X-73947, August 1976.
67. Lansing, D.L.; and Chestnutt, D., "Survey of Inlet Noise Reduction Concepts for Gas Turbine
Engines," TM X-72801, April 1976.
68. Lawton, Ben William, "The Noisiness of Low Frequency Bands of Noise," NASA TM X-72649, 1975.
69. Lawton, Ben William, "The Noisiness of Low-Frequency One-Third Octave Bands of Noise,"
NASA TN D-8037, 1975.
70. Lawton, Ben W., "Subjective Assessment of Simulated Helicopter Blade-Slap Noise," NASA TN
D-8359, 1976.
71. Leatherwood, Jack D.; and Dempsey, Thomas K., "Psychophysical Relationships Characterizing
Human Response to Whole-Body Sinusoidal Vertical Vibration," NASA TN D-8188, 1976.
72. Lester, Harold D.; and Posey, Joe W., "Optimal One-Section and Two-Section Circular Sound
Absorbing Duct Liners for Plane-Wave and Monopole Sources without Flow," NASA TN D-8348, 1976.
73. Lester, Harold C.; and Posey, Joe W., "Duct Liner Optimization for Turbomachinery Noise
Sources," NASA TM X-72789, 1975.
74. LeVere, T.E., "Arousal from Sleep: The Uniqueness of an Individual's Response to Noise,"
presented at 9th International Congress on Acoustics, NASA Grant 34-002-095, NC State Univer-
sity, July 1977.
75. Lukas, J.S.; Peeler, D.J.; and Davis J.E., "Effects on Sleep of Noise from Two Proposed STOL
Aircraft," NASA CR-132564, 1975.
76. Lumsdaine, Edward; Cherng, Jenn G. ; and Tag, Ismail, "Noise Suppression wj-th High Mach Number
Inlets," NASA CR-2708, 1976.
77. Maciulaitis, Algirdas; Seiner, John M.; and Norum, Thomas D., "Sound Scattering by Rigid
Oblate Spheroids with Implication to Pressure Gradient Microphones," NASA TN D-8140, 1976.
78. Maestrello and Bayliss, "Measurements and Analysis of Far-Field Scattering from a Prolate
Spheroid," TM 94098, October 1977.
79. Maestrello, Lucio, "Two-Point Correlations of Sound Pressure in the Far-Field of a Jet:
Space Experiment," NASA TM X-72835, 1976.
80. Magliozzi, B., "The Influence of Forward Flight on Propeller Noise," NASA CR-145105, 1976.
81. Mall, G.H., and Farassat, F., "A Computer Program for the Determination of the Acoustic
Pressure Signature of Helicopter Rotors Due to Blade Thickness," NASA TM X-3323, 1976.
82. Marsh, Alan H-, "Recommended Procedures for Measuring Aircraft Noise and Associated Parameters,
NASA CR-145187, 1977.
83. Mayes, Scholl, and Stephens, "Concorde Noise-Induced Vibrations—International Airport-Dulles,"
Final Report, October 1977.
84. McDaniel, Oliver Herbert, "Propagation of Sound at Moderate and High Intensities in Absorbent
and Hard-Walled Cylindrical Ducts," NASA CR-132650, 1975.
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85. McDonald, Vaicaitis, and Myers, "Noise Transmission Through Plates into an Enclosure,"
September 1977.
86. Metcalfe, Ralph A.; and Orszag, Steven A., "Numerical Simulation of Turbulent Jet Noise—
Part II," NASA CR-144978, 1976.
87. Metcalfe, Ralph W.; and Orszag, Steven A., "Numerical Simulation of Turbulent Jet Noise—
Part I," NASA CR-132693, 1975.
88. Mueller, Arnold W., "A Description and Some Measured Acoustic Characteristics of the Langley
220 Cubic Meter Reverberation Chamber," NASA TM X-72775, 1975.
89. Norum, Thomas D.; and Liu, Chen-Huei, "The Acoustic Monopole in Motion," NASA TM X-73985,
1976.
90. Norum and Seiner, "Shape Optimization of Pressure Gradient Microphones," TM 78632, December 1977.
91. Ogilvie, P.L.; Levy, A.; Austin, F.; and Ojalvo, I.U., "Programmer's Manual for Static and
Dynamic Reusable Surface Insulation Stresses (RESIST)," NASA CR-132607, 1975.
92. Ojalvo, Irving U.; and Ogilvie, Patricia L., "Modal Analysis and Dynamic Stresses for Acous-
tically Excited Shuttle Insulation Tiles," NASA CR-144958, 1976.
93. Padula, Sharon L.; and Liu, Chen-Huei, "Numerical Study of Sound Propagation in a Jet Flow,"
NASA TN D-8012, 1975.
94. Pao, S. Paul; and Maestrello, Lucio, "Evidence of the Beam Pattern Concept of Subsonic Jet
Noise Emission," NASA TN D-8104, 1976.
95. Paterson, Robert W.; and Amiet, Roy K., "Acoustics Radiation and Surface Pressure Character-
istics of an Airfoil Due to Incident Turbulence," NASA CR-2733, 1976.
96. Pearson, Richard G.; Hart, Franklin D.; and O'Brien, John F., "Individual Differences in
Human Annoyance Response to Noise," NASA CR-144921, 1975.
97. Pegg, Robert J.; Hosier, Robert N.; Balcerak, John C.; and Johnson, H. Kevin, "Design and
Preliminary Tests of a Blade Tip Air Mass Injection System for Vortex Modification and Possible
Noise Reduction on a Full-Scale Helicopter Motor," NASA TM X-3314, 1975.
98. Plett, E.G.; Ebdelhamid, S.N.; Harrje, D.T.; and Summerfield, M., "Combustion Contribution to
Noise in Jet Engines," NASA CR-2704, 1976.
99. Posey, J.W., "Comparison of Cross-Spectral and Signal Enchancement Methods for Mapping Steady-
State Acoustic Fields in Turbomachinery Ducts," NASA TM X-73916, 1976.
100. Powell, Clemans A., "Judgments of Relative Noisiness of a Supersonic Transport and Several
Commercial-Service Aircraft," NASA TN D-8434, June 1977.
101. Ramakirshnan, R., "Sound Radiation from a Turbulent Wall Jet with Compliance Boundary,"
Ph.D. Thesis, George Washington University, January 1977.
102. Ramakrishnan, Ramani; Randall, Donald; and Hosier, Robert N., "A Computer Program to Predict
Rotor Rotational Noise of a Stationary Rotor from Blade Loading Coefficients," NASA TM X-3281,
1976.
103. Raney, John P., "Research Needs in Aircraft Noise Prediction," NASA TM X-72787, 1975.
104. Reddy, N.N.; and Yu, J.C., "Radiated Noise from an Externally Blown Flap," NASA TN D-7908, 1975.
105. Revell, Prydz, and Hays, "Experimental Study of Airframe Noise vs. Drag Relationship for
Circular Cylinders, July 1977.
106. Ribner, Herbert S., "Theory of Two-Point Correlations of Jet Noise," NASA TN D-8330, 1976.
107. Savkar, S.D.; and Edelfelt, I.H., "Radiation of Cylindrical Duct Acoustic Modes with Flow
Mismatch," NASA CR-132613, 1975.
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108. Schloth, Arthur P., "Measurements of Mean Flow and Acoustic Power for a Subsonic Jet Impinging
Normal to a Large Rigid Surface," NASA TM X-72803, 1976.
109. Schoenster, James A.; Willis, Conrad M., "Temperature and Vibration Characteristics. Wind
Tunnel Investigation of Aerodynamic Performance, Steady and Vibratory Loads, Surface Temperatures,
and Acoustic Characteristics of a Large-scale Twin-Engine Upper-Surface Blown Jet-Flap Con-
figuration—Part III," NASA TN D-8235, November 1976.
110. Schoenster, James A.; and Pierce, Harold B., "Comparison of Vibrations of a Combination of
Solid-Rocket Launch Vehicle and Payload During a Ground Firing and Launching," NASA TN D-8074,
1975.
111. Shepherd, Kevin P., "The Subjective Evaluation of Noise from Light Aircraft," NASA CR-2773,
December 1976.
112. Shepherd, William T., Editor, Noise and Speech Interference—Proceedings of Minisymposium,
NASA TM X-72696, 1975.
113. Smith, Goldie C-; and Laneave, Jean (Compilers), "Publications in Acoustics and Noise
Control from the NASA Langley Research Center During 1940-1974," NASA TM X-72710, 1975.
114. Sternfeld, Bukowski and Doyle, "Evaluation of the Annoyance Due to Helicopter Rotor Noise,"
Vertol, September 1977.
115. Ventres, C.S.; Myles, M.M.; Ver, I.L., "Measurements of the Reflection Factor of Flat Ground
Surfaces," NASA CR-145138, 1977.
116. Watson, Willie R.; and Lansing, Donald L., "A Comparison of Matrix Methods for Calculating
Eigenvalues in Acoustically Lined Ducts," NASA TN D-8186, 1976.
117. Wiley, J.F.; and Scharton, T.D., "Acoustic Transmission Through a Fuselage Sidewall," NASA
CR-132602, 1975.
118. Woolley, J.P.; Karmacheti, K; and Guenther, J.L., "An Analytical Study of Noise Generation
by Subsonic Flows in the Presence of Rigid Surfaces," NASA CR-145027, October 1976.
119. Yates, "Application of the Bernoulli Enthalpy Concept to the Study of Vortex Noise and Jet
Impingement," Contractor report, September 1977.
120. Zorumski, W.E.; and Tester, B.J., "Prediction of the Acoustic Impedance of Duct Liners,"
NASA TM X-73951, September 1976.
121. Zorumski, William E.; and Lester, Harold C., "Un:fled Analysis of Ducted Turbomachinery
Noise," NASA TM X-72633, 1975.
122. Zuckerwar, Allan J; and Holmes, H.K., "A Unified Acquisition System for Acoustic Data,"
NASA TN D-8326, March 1977.
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NASA/LEWIS RESEARCH CENTER
1. Albers, James A.; Stockman, Norbert O.; and Hirn, John J., "Aerodynamic Analysis of Several
High Throat Mach Number Inlets for the Quiet Clean Short-Haul Experimental Engine," NASA TM
X-3183, January 1975.
2. Albers, James A.; and Breulin, Douglas C., "Theoretical Surface Velocity Distributions on
Acoustic Splitter Geometries for an Engine Inlet," NASA TM X-3114, October 1974.
3. Balombin, Joseph R.; and Stakolich, Edward G., "Effect of Rotor-to-Stator Spacing on Acoustic
Performance of a Full-Scale Fan (QF-5) for Turbofan Engines," NASA TM X-3103, September 1974.
4. Baumeister, K.J., "Finite-Difference Theory for Sound Propagation in a Lined Duct with Uniform
Flow Using the Wave Envelope Concept," NASA TP 1001, August 1977.
5. Baumesiter, K.J.; and Rice, E.J., "Flow Visualization in Long Neck Helmholtz Resonators with
Grazing Flow," NASA TM X-73400, July 1976.
6. Baumeister, K.J.: and Rice, E.J., "Visual Study of the Effect of Grazing Flow on the Oscillatory
Flow in a Resonator Orifice," NASA TM X-3288, September 1975.
7. Baumeister, K.J., "Generalized Wave Envelope Analysis of Sound Propagation in Ducts with Stepped
Noise Source Profiles and Variable Axial Impedance," NASA TM X-71674, March 1975.
8. Becker, R.S.; and Maus, J.R., "Acoustic Source Location in a Jet ilown Flap Configuration Using
a Cross-Correlation Technique," Final Report NCR 43-001-135, February 1977.
9. Bekofske, F.I,.; Scheer, R.E.; and Wang, J.C.F., "Effect of Inlet Distil bsnces on Fan Inlet-
Noise During a Static Test," NASA CR-13'5177, 1977.
10. Bliss, D.B.; Chandiramani, R.L.; and Peersol, A.G., "Data Analysis and Noise Prediction for
the QF-1B Experimental Fan Stage," NASA CR-135066, August 1976.
i]. Bloomer, Harry E.; and Schaefer, John W., "Aero-Acoustic Performance Comparison of Core Engine
Noise Suppressors on NASA Quiet Engine C," NASA TM X-73662, July 1977.
12. Bloomer, H.E.; and Schaefer, J.W., "Aerodynamic and Acoustic Performance of a Contracting Cowl
High Throat Mach Number Inlet Installed on NASA Quiet Engine C," NASA TM X-73424, July 1976.
13. Burns, Robert J.; McKinzie, Daniel J., Jr.; and Wagner, Jack M., "Effects of Perforated Flap
Surfaces and Screens on Acoustics of a Large Externally Blown Flap Model," NASA TM X-3335,
April 1976.
14. Cornell, W.G., "Experimental Quiet Engine Programs Summary Report," NASA CR-2519, March 1975.
15. Chun, K.S.; Herman, C.H.; and Cowna, S.J., "Effects of Motion on Jet Exhaust Noise from
Aircraft," NASA CR-2701, June 1976.
16. Dean, L.W., "Coupling of Helmholtz Resonators to Improve Acoustic Liners for Turbofan Engines
at Low Frequency," NASA CR-134912, May 1976.
17. Dean, P.O.; and Tester, G.J., "Duct Wall Impedance Control as an Advanced Concept for Acoustic
Suppression," NASA CR-134998, November 1975.
18. Dietrick, Donald A.; Heidmann, Marcus F.; and Abbott, John M., "Acoustic Signature of a Model
Fan in the NASA-Lewis Anechoic Wind Tunnel," NASA TM X-73560, January 1977.
19. Dittmar, James H.; Woodward, Richard P.; and Stakolich, Edgard G., "Noise of Fan Designed to
Reduce Stator Lift Fluctuations," NASA TM X-3538, May 1977.
20. Dittmar, J.H.; Scott, J.N.; Leonard, B.R.; and Stakolich, E.G., "Effects of Long-Chord
Acoustically Treated Stator Vanes on Fan Noise, Part I—Effect of Long Chord (Taped Stator),"
NASA TN D-8062, October 1975.
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21. Dittraar, J.H.; Scott, J.N.; Leonard, B.R.; and Stakolich, E., "Effects of Long-Chord Acoustically
Treated Stator Vanes on Fan Noise, Part II—Effect of Acoustical Treatment," NASA TN D-8250.
22. Dittmar, James H.; and Groeneweg, John P., "Effect of Treated Length on Performance of Full-
Scale Turbofan Inlet Noise Suppressors," NASA TN D-7826, December 1974.
23. Dorsch, R.; Clark, B.; and Reshotko, M., "Interim Prediction Method for Externally Blown Flap
Noise," NASA TM X-71768, August 1975.
24. Doyle, V.L.; and Matta, R.K., "Attenuation of Upstream-Generated Low Frequency Noise by Gas
Turbines," NASA CR-135219, August 1977.
25. Emmerling, J.J.; and Bekofske, K.L., "Experimental Clean Combustor Program—Noise Measurement
Addendum, Phase II—Final Report," NASA CR-135045, 1976.
26. Emmerling, J.J.; and Bekofske, K.L., "Experimental Clean Combustor Program—Noise Measurement
Addendum, Phase I, Final Report," NASA CR-134853, July 1975.
27. Erwin, J.R.; and Heldenbrand, R.W., "Advanced Acoustic and Aerodynamic 20-Inch Fan Program,"
NASA CR-135093, February 1977.
28. Fink, M.R., "Additional Studies of Externally Blown Flap Noise," NASA CR-135096, August 1976.
29. Fink, M.R., "Prediction of Externally Blown Flap Noise and Turbomachinery Strut Noise,"
NASA CR-134883, August 1975.
30. Fink, M.R., "Investigation of Scrubbing and Impingement Noise," NASA CR-134762, February 1975.
31. Glaser, Frederick W.; Woodward, Richard P.; and Lucas, James G., "Acoustic and Aerodynamic
Performance of a Variable-Pitch 1.83-Meter-(6-FT-) Diameter 1.20- Pressure-Ratio Fan Stage
(QF-9)," NASA TN X-3402, February 1977.
32. Glaser, F.W.; Wazyniak, J.A.; and Friedman, R., "Noise Data from Tests of a 1.83-Meter (6-Ft)
Diameter Variable-Pitch 1.2 Pressure-Ratio Fan (QF-9)," NASA TM X-3187, March 1975.
33. Goodykoontz, Jack H., "Acoustic Tests of Augmentor Wing Model," NASA TM X-3519, April 1977.
34. Goodykoontz, J.' von Glahn, U.; and Dorsch, R., "Forward Velocity Effects on Under-the-Wing
Externally Blown Flap Noise," NASA TM X-71656, March 1975.
35. Groesbeck, Donald E.; Huff, Ronald G.; and von Glahn, Uew H., "Comparison of Jet Mach Number
Decay Data with a Correlation and Jet Streaking Contours for a Large Variety of Nozzles,"
NASA TN D-8423, June 1977,
36. Heidelberg, L.J.; and Jones, W.L., "Full-Scale Upper-Surface-Blown Flap Noise," NASA TM X-71708,
May 1975.
37. Heidemann, M.F., "Interim Prediction Method for Fan and Compressor Source Noise," NASA TM
X-71763, June 1975.
38. Hersh, A.S.; and Walker, B., "Fluid Mechanical Model of the Helmholtz Resonator," NASA
CR-135123, December 1976.
39. Hersh, A.S.; and Liu, C.Y., "Sound Propagation in Choked Ducts," NASA CR-135123, December 1976.
40. Hersh, A.S.; and Rogers, T., "Fluid Mechanical Model of the Acoustic Impedance of Small
Orifices," NASA CR-2682, May 1976.
41. Hickcox, T.E.; Lawrence, R.L.; Syberg, L.; and Wiley, D.R., "Low-Speed and Angle-of-Attack
Effects on Sonic and Near-Sonic Inlets," NASA CR-134778, March 1975.
42. Huff, Ronald G.; and Groesbeck, Donald E., "Cold-Flow Acoustic Evaluation of a Small-Scale,
Divergent, Lobed Nozzle for Supersonic Jet Noise Suppression," NASA TM X-3210, March 1975.
43. Ingebo, Robert D.; and Norgren, Carl T., "Combustor Exhaust Emissions with Air-Atomizing
Splash-Groove Fuel Injectors Burning Jet A and Diesel Number 2 Fuels," NASA TM X-3255, June
1975.
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64. Rice, E.J., "A Theoretical Study of the Acoustic Impedance of Orifices in the Prescence of a
Steady Grazing Flow," NASA TM X-71903, April 1976.
65. Rice, E.J., "Spinning Mode Sound Propagation in Ducts with Acoustic Treatment," NASA TN
D-7913, May 1975.
66. Rice, E.J., "Spinning Mode Sound Propagation in Ducts with Acoustic Treatment and Sheared Flow,"
NASA TM X-71672, March 1975.
67. Roffe, Gerold and Fern, Antonia, "Prevaporization and Premixing to Obtain Low Oxides of
Nitrogen in Gas Turbine Combustors," NASA CR-2495, March 1975.
68. Saule, Arthur V., "Some Observations about the Components of Transonic Fan Noise from Narrow-
Band Spectra Analysis," NASA TN D-7788, October 1974.
69. Sawdy, D.T.,; Beckemeyer, R.J.; and Patterson, J.D., "Analytical and Experimental Studies of an
Optimum Multisegment Phased Liner Noise Suppression Concept," NASA CR-134960, May 1976.
70. Scott, James N., "A Far Field Analysis of the Propagation of Sound Waves from Various Point
Sources Through a Linear Shear Layer," NASA TM X-73686, May 1977.
71. Shields, F. Douglas; and Bass, H.E., "Atmospheric Absorption of High Frequency Noise and
Application to Fractional-Octave Bands," NASA CR-2760, June 1977.
72. Sofrin, T.G.; and Riloff, N., Jr., "Experimental Clean Combustor Program—Noise Study," NASA
CR-135106, PWA-5458, September 1976.
73. Sofrin, T.G.; and Ross, D.A., "Noise Addendum Experimental Clean Combustor Program, Phase I,
Final Report," NASA CR-134820, October 1975.
74. Soltau, J.D.; Orelup, M.J.; Beguhn, A.A.; Wiles, F.M.; and Anderson, M.J., "Detailed Design of
a Quiet High Flow Fan," NASA CR-135126, February 1977.
75. Stone, James R., "Interim Prediction Method for Jet Noise," NASA TM X-71618, November 1974.
76. Strahle, W.C.; Muthukrishnan, M.; Neale, D.H.; and Ramachandra, M.K., "An Investigation of
Combustion and Entropy Noise," NASA CR-135220, July 1977.
77. Strahle, W.C.; and Shivashankara, B.N., "Combustion Generated Noise in Gas Turbine Combustors,"
NASA CR-134843, August 1974.
78. von Glahn, U.; and Goodykoontz, J., "Installation and Airspeed Effects on Jet Shock-Associated
Noise," NASA TM X-71792, November 1975.
79. von Glahn, U.; and Groesbeck, D., "Geometry Effects on STOL Engine-over-the-Wind Acoustics with
5:1 Slot Nozzles," NASA TM X-71820, November 1975.
80. von Glahn, U.; and Groesbeck, D., "Acoustics of Attached and Partially Attached Flow for
Simplified OTW Configurations with 5:1 Slot Nozzle," NASA TM X-71807, November 1975.
81. von Glahn, U.; and Groesbeck, D., "Influence of Multitube Mixer Nozzle Geometry on CTOL-OTW
Jet Noise Shielding," NASA TM X-71681, April 1975.
82. Wazyniak, Joseph A.; Shaw, Loretta M.; and Essary, Jefferson D., "Characteristics of an Anechoic
Chamber for Fan Noise Testing," NASA TM X-73555, March 1977.
83. Woodward, Richard P.; Lucas, James G.; and Balombin, Joseph R., "Acoustic and Aerodynamic
Performance of a 1.5-Pressure-Ratio, 1.83-Meter (6-Ft) Diameter Fan Stage for Turbofan Engines
(QF-2)," NASA TM X-3521, April 1977.
84. Woodward, R.P.; and Lucas, J.G., "Acoustic and Aerodynamic Performance of a 1.83-Meter Diameter
1.25-Pressure-Ratio Fan (QF-8)," NASA TN D-8130, February 1976.
85. Woodward, Richard P.; and Lucas, James G., "Acoustic and Aerodynamic Performance of a 1.83-
Meter- (6-Ft) Diameter 1.2 Pressure-Ratio Fan (QF-6)," NASA TN D-7908, December 1974.
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44. Karchmer, A.; and Reshotko, M., "Core Noise Source Diagnostics on a Turbofan Engine Using
Correlation and Coherence Techniques," NASA TM X-73535, November 1976.
45. Kozlowski, Hilary; and Packman, Allan B., "Aerodynamic and Acoustic Tests of Duct-Burning
Turbofan Exhaust Nozzles," NASA CR-2628, December 1976.
46. Kupcis, E.A., "The Results of a Low Speed Wind Tunnel Test to Investigate the Effects of the
Refan JT8D Engine Target Thrust Reverser on the Stability and Control Characteristics of the
Boeing 727-200 Airplane," NASA CR-134699, July 1974.
47. Mani, Ramani, "Isolated Rotor Noise Due to Inlet Distortion or Turbulence," NASA CR-2479,
October 1974.
48. McKinzie, Daniel J., Jr., "Analytical Modeling of Under-the-Wing Externally Blown Flap Powered-
Lift Noise, Powered-Lift Aerodynamics and Acoustics," NASA SP-406, May 1976, pp. 263-282.
49. McKinzie, Daniel J., Jr.; Burns, Robert J.; and Wagner, Jack M., "Noise Reduction Tests of
Large-Scale-Model Externally Blown Flap Using Trailing-Edge Blowing and Partial Flap Slot
Covering," NASA TM X-3379, April 1976.
50. McKinzie, Daniel J., Jr.; and Burns, Robert J., "Analysis of Noise Produced by Jet Impingement
Near the Trailing Edge of a Flat and a Curved Plate," NASA TM X-3171, January 1975.
51. Miles, J.H.; Stevens, G.H.; and Leininger, G.G., "Analysis and Correction of Ground Reflection
Effects in Measured Narrowband Sound Spectra Using Cepstral Techniques," NASA TM X-71810,
November 1975.
52. Miles, J.H., "Analysis of Ground Reflection of Jet Noise Obtained with Various Microphone Arrays
over an Asphalt Surface," NASA TM X-71696, April 1975.
53. Miles, Jeffrey H., "Method of Representation of Acoustic Spectra and Reflection Corrections
Applied to Externally Blown Flap Noise," NASA TM X-3179, February 1975.
54. Miller, Brent A., "Experimentally Determined Aeroacoustic Performance and Control of Several
Sonic Inlets," AIAA and SAE llth Propulsion Conference, Anaheim, California, NASA TM X-71765,
September 29-October 1, 1975.
55. Miller, Brent A.; Dastoli, Benjamin J.; and Wesoky, Howard L., "Effect of Entry-Lip Design on
Aerodynamics and Acoustics of High-Throat-Mach-Number Inlets for the Quiet, Clean, Short-Haul
Experimental Engine," NASA TM X-3222, May 1975.
56. Winner, G.L.; and Rice, E.J., "Computer Method for Design of Acoustic Liner for Turbofan Engines,
NASA TM X-3317, October 1976.
57. Minner, G.L.; and Homyak, L., "Noise Reduction as Affected by the Extent and Distribution of
Acoustic Treatment in a Turbofan Engine Inlet," NASA TM X-71904, July 1976.
58. Motsinger, R.E.; Kraft, R.E., et al, "Optimization of Suppression for Two-Element Treatment
Liners for Turbomachinery Exhaust Ducts," NASA CR-134997, April 1976.
59. Olsen, W., "Noise Generated by Flow Impingement on Airfoils of Varied Chord, Cylinders, and
Other Flow Obstructions," AIAA Paper No. 76-504, NASA TM X-73464, July 1976.
60. Olsen, W.; and Karchmer, A., "Lip Noise Generated by Flow Separation from Nozzle Surfaces,"
NASA TM X-71859, January 1976.
61. Plumblee, Harry E., Jr. (editor), "Effects of Turbulent Velocity on Turbulent Jet Mixing Noise,"
NASA CR-2702, July 1976.
62. Reed, D.H., "Scale Model Testing of the Jet Noise Characteristics of the JT8D Refan Engine
Nozzle System," NASA CR-134618, March 1974.
63. Rice, E.J., "Acoustic Liner Optimum Impedance for Spinning Modes with Mode Cut-off Ratio as the
D'esign Criterion," NASA TM X-73411, July 1976.
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BIBLIOGRAPHY
DEPARTMENT OF TRANSPORTATION
FEDERAL AVIATION ADMINISTRATION
1. Bundgaard, Robert, et. al., "Test and Evaluation of a Real-Time Simulated Supersonic Boomless
Flight System," FAA-RD-75-131, I.
2. Goethert, B.H., et. al., "Investigation of Feasible Nozzle Configurations for Reduction in
Turbofan and Turbojet Aircraft-Vol. I. Summary and Multi-Nozzle Configurations; Vol. II, Slot
Nozzle Configurations," FAA-RD-75-162-I,II, Contract DOT-FA72WA-3053, July 1975.
3. Hershey, R.L. Kevala, R.J., Burns, S.L., "Analysis of the Effect of Concorde Aircraft Noise
on Historic Structures," FAA-RD-75-118, July 1975.
4. Kagliozzi, B., Metzger, F.B., Bausch, W., and King, R.J., "A Comprehensive Review of Heli-
copter Noise Literature," FAA-RD-75-79, June 1975
5. Mayer, J.E., Linscheid, L.L., and Veldman, H.F., "FAA JT8D Quiet Nacelle Retrofit Feasibility
Program, Volume II, Addendum A, Model and Full Scale Plug Nozzle Tests," FAA-RD-73-131,11,
Addendum A, Contract DOT FA71WA-2628, April 1975.
6. McCollough, 'JB', and Carpenter, L.K., "Airborne Meteorological Instrumentation System and
Data Reduction," FAA-RD-75-69, March 1975.
7. McCollough, 'JB1, and True, B.C., "Effect of Temperature and Humidity on Aircraft Noise Pro-
pagation," FAA-RD-75-100, September 1975.
8. Reddy, N.N., et. al., "V/STOL Aircraft Noise Prediction (Jet Propulsors) ," FAA-RD-75-125,
Contract DOT FA72WA-3099, June 1975.
9. Dunn, D.G., et. al., "Aircraft Configuration Noise Reduction, Volume I—Engineering Analysis,"
FAA-RD-76-76-I, Contract DOT FA74WA-3497, June 1976.
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User's Guide and Other Appendices," FAA-RD-76-76-II, Contract DOT FA74WA-3497, June 1976.
11. Dunn, D.G., et. al., "Aircraft Configuration Noise Reduction, Volume ill—Computer Program
Source Listing," FAA-RD-76-76-III, Contract DOT FA74WA-3497, June 1976.
12. Emmerling, J.J., "Core Engine Noise Control Program, Volume III, Supplement I—Prediction
Methods," FAA-RD-74-125,111-1, Contract DOT FA72WA-3023, March 1976.
13. Galloway, W.J., "Noise Reduction for Business Aircraft," FAA-RD-76-125, Contract DOT
PA75WA-3668, October 1976.
14. Magliozzi, B., "V/STOL Rotary Propulsion Systems Noise Prediction and Reduction, Volume I—
Identification of Sources, Noise Generating Mechanisms, Noise Reduction Mechanisms, and
Prediction Methodology," FAA-RD-76-49, I, Contract DOT FA74WA-3477, May 1976.
15. Magliozzi, B., "V/STOL Rotary Propulsion Systems Noise Prediction and Reduction, Volume II—
Graphical Prediction Methods," FAA-RD-76-49,II, Contract FA74WA-3477, May 1976.
16. Magliozzi, B., "V/STOL Rotary Propulsion Systems Noise Prediction and Reduction, Volume III—
Computer Program User's Manual," FAA-RD-76-49,III, Contract DOT-FA74WA-3477, May 1976.
17. Matta, R.K. and Mingler, P.R., "Core Engine Noise Control Program, Volume II—Supplement I—
Identification of Noise Generation and Suppression Mechanisms," FAA-RD-74-125,II-l, Con-
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18. Munoz, L.F., "727/JT8D Jet and Fan Noise Flight Effects Study," FAA-RD-76-110, Contract
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19. "Noise Produced by the Interaction of Acoustic Waves and Entropy Waves With High-Speed Nozzle
Flows," Report DOT-TST-76-103, NTIS PR 264/989/AS, May 1976.
20. "Analytical Studies of Some Acoustic Problems of Jet Engines," Report DOT-TST-76-104,
Interim Report, NTIS PB 264-918/AS, May 1976.
21. "Experimental Studies of the Noise Produced in a Supersonic Nozzle by Upstream Acoustic and
Thermal Disturbances," Report DOT-TST-76-105, NTIS PE 264-933/AS, June 1976.
22. "Analysis of Combustion Generated Noise," Report DOT-TET-77-25, NTIS pending, 1976.
23. "Dispersive Effects of Liners on Nonlinear Wave Propagation in Ducts," Report DOT-TST-77-37,
NTIS pending, 1976.
24. Clapper, W.S., et. al., "High Velocity Jet Noise Source Location and Reduction, Task 4—
Development/Evaluation of Techniques for 'Inflight1 Investigation," FAA-RD-76-79,IV, Con-
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25. Cooper, B.K., "Preliminary Design of an Aircraft Noise Measurement System for Certification
and Research, Task B Report," FAA-RD-75-217, Contract DOT-FATQWA-3900, January 1977.
26. Fink, M.R., "Airframe Noise Reduction Method," FAA-RD-77-29, Contract DOT-FA76WA-3821,
March 1977.
27. Goethert, B.H., et. al., "Investigation of Feasible Nozzle Configurations for Noise Reduction
in Turbofan and Turbojet Aircraft, Vol. Ill, Shrouded Slot Nozzles," FAA-RD-75-162,III, Con-
tract DOT-FA72WA-3053, March 1977.
28. Mathews, D.C., Rekos, N.F., and Nagel, R.T., "Low-Emissions Combustion Noise Investigation,"
FAA-RD-77-3, Contract DOT FA75WA-3663, February 1977.
29. Matta, R.K., Sandusky, G.T., and Doyle, V.L., "General Electric Core Engine Noise Investiga-
tion Low-Emission Engines," FAA-RD-77-4, Contract DOT FA75WA-3688, February 1977.
30. Perley, R., "Design and Demonstration of a System for Routine, Boomless, Supersonic Flights,"
FAA-RD-77-72, Contract DOT-FA-WA-3363, April 1977.
31. Savell, C.T. and Stringas, E.J., "High Velocity Jet Noise Source Location and Reduction, Task
1—Activation of Facilities and Validation of Source Location Techniques," FAA-RD-76-79,I,
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32. Savell, C.T., et. al., "High Velocity Jet Noise Source Location and Reduction, Task 1—
Supplement-Certification of the General Electric Jet Noise Anechoic Test Facility,"
FAA-RD-76-79, la. Contract DOT-OS-30034, February 1977.
33. True, H.C., Rickley, E.J., and Letty, R.M., "Helicopter Noise Measurements Data Report, Vol. I,
Helicopter Models: Hughes 300-C, Hughes 500-C, Bell 47-G, Bell 206-L," FAA-RD-77-57, I,
April, 1977.
34. True, H.C., et. al., "Helicopter Noise Measurements Data Report, Vol. II, Helicopter Models:
Bell 212 (UH-IN), Sikorsky S-61 (SH-3A), Sikorsky S-64 "Skycrane" (CH-54B), Boeing Vertol
"Chinook" (CH-47C)," FAA-RD-77-57-II, April 1977.
35. "Supersonic Jet Noise Reduction By Coaxial Cold/Heated Jet Flows," Contract DOT-OS-20094,
NTIS pending, March 1977.
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BIBLIOGRAPHY
GENERAL INTEREST
1. "FAR Part 36 Compliance Regulation, Final Environmental Impact Statement Pursuant to Section
102 (2) (c) , PL 91-90," Department of Transportation, Federal Aviation Administration,
Washington, D.C., November 1976.
2. "FAA Aviation Forecasts Fiscal Years 1978-1989," Department of Transportation, Federal Aviation
Administration, Washington, D.C., FAA-AVP-77-32, September 1977.
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Phased Compliance with Part 36 Noise Limits by Turbojets with Maximum Weights Greater than
75,000 pounds," 41 FR 56016, December 23, 1976.
4. "Federal Aviation Regulations Part 36, Noise Standards: Aircraft Type and Airworthiness Certif-
ication, Amendment 36-8: Noise Level Limits and Acoustical Change Requirements for Subsonic
Transport Category Large Airplanes and for Turbojet Powered Airplanes," 43 FR 8722, March 2, 1978.
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the Subcommittee on Aviation of the Committee on Public Works and Transportation, House of Repre-
sentatives," Committee on Public Works and Transportation, Ninety-Fourth Congress, First and Second
Sessions, 1976.
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