Aircraft noise abatement technology : report

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Title:
Aircraft noise abatement technology : report
Series Title:
Serial no. 94-W
Physical Description:
v, 22 p. : ill. ; 24 cm.
Language:
English
Creator:
United States -- Congress. -- House. -- Committee on Science and Technology. -- Subcommittee on Aviation and Transportation R. & D
Publisher:
U.S. Govt. Print. Off.
Place of Publication:
Washington
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Subjects / Keywords:
Airplanes -- Noise   ( lcsh )
Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

General Note:
At head of title: Committee print.
Statement of Responsibility:
prepared by the Subcommittee on Aviation and Transportation R. & D. of the Committee on Science and Technology, U.S. House of Representatives, Ninety-fourth Congress, second session ... February 1976.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 025790197
oclc - 02209125
lccn - 76601364
System ID:
AA00025941:00001

Full Text


[COMMITTEE PRINT]






AIRCRAFT NOISE ABATEMENT
TECHNOLOGY





REPORT
PREPARED BY THE

SUBCOMMITTEE ON
AVIATION AN TRANSPORTATION R. & D.
OF THE

COMMITTEE ON
SCIENCE AND TECHNOLOGY
U.S. HOUSE OF REPRESENTATIVES
NINETY-FOURTH CONGRESS
SECOND S ESSION
Serial W











SWASHINGTON : 197
%i --. 1



_- -2 M, AII



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COMMITTEE ON SCIENCE AND TECHNOLOGY
OLIN E. TEAGUE, Texas, Chairman
KEN HECHLER, West Virginia CHARLES A. MOSHER, Ohio
THOMAS N. DOWNING, Virginia ALPHONZO BELL, California
DON FUQUA, Florida JOHN JARMAN, Oklahoma
JAMES W. SYMINGTON, Missouri JOHN W. WYDLER, New York
WALTER FLOWERS, Alabama LARRY WINN, JR., Kansas
ROBERT A. ROE, New Jersey LOUIS FREY, JR., Florida
MIKE McCORMACK, Washington BARRY M. GOLDWATER, JR., California
GEORGE E. BROWN, J., California MARVIN L. ESCH, Michigan
DALE MILFORD, Texas JOHN B. CONLAN, Arizona
RAY THORNTON, Arkansas GARY A. MYERS, Pennsylvania
JAMES H. SCHEUER, New York DAVID F. EMERY, Maine
RICHARD L. OTTINGER, New York LARRY PRESSLER, South Dakota
HENRY A. WAXMAN, California
PHILIP H. HAYES, Indiana
TOM HARKIN, Iowa
JIM LLOYD, California
JEROME A. AMBRO, New York
CHRISTOPHER J. DODD, Connecticut
MICHAEL T. BLOUIN, Iowa
TIM L. HALL, Illinois
ROBERT (BOB) KRUEGER, Texas
MARILYN LLOYD, Tennessee
JAMES J. BLANCHARD, Michigan
TIMOTHY E. WIRTH, Colorado
JOHN L. SWIGERT, Jr., Executive Director
HAROLD A. GOULD, Deputy Director
PHILIP B. YEAGER. Counsel
FRANK R. HAMMILL, Jr., Counsel
JAMES E. WILSON. Technical Consultant
J. THOMAS RATCHFORD. Science Consultant
JOHN D. HOLMFELD, Science Consultant
'r+a, RALPH N. READ, Technical Consultant
ROBERT C. KETCHAM, Counsel
REGINA A. DAVIS, Clerk
S' MICHAEL A. SUPERATA, Minority Staff



SS-BCSBOMM.lfITEE ON AVIATION AND TRANSPORTATION R. & D.
DIALE MILFORD, Texas, Chairman

SROBERT A. OE, Neyw ersey JOHN W. WYDLER, New York
JAMES H. S*CEUEZ.NeW York BARRY M. GOLDWATER, Ja., California
'i BARKIN,'Iowa JOHN B. CONLAN, Arizona
JIM LLOYD,Calif ornla
TIM, L. IiALL, allnois-
RICIHAARD, .QTTIGER, New York


SUBcoMMITTrr STAFT
RALPH N. READ, Technical Consultant
ANTHONY C. TAYLOR, Technical Consultant
H. GERALD STAUB. Counsel
JOHN V. DUGAN, Jr., Science Consultant, Minority Staf
(I.)













LETTER OF TRANSMITTAL


HOUSE OF REPRESENTARIVES,
CoM,?nIr ON SCIENCE AN-D TECHNOLOGY,
HonVashi'u~gton, D.C., October 4, 1976.
Hon. OGN E. TEAouf,
Chairn. Committee on Science and Technology, House of Iepre-
sentatives, 1ashintgon, D.C.
DEAR MR. CHAIRMAN : As you instructed, the Subcommittee on Avi-
ation and Transportation R. & )D. conducted public hearings on Sep-
tember 29 and October 1 and 2. 1975, on Aircraft Noise Abatement.
I am forwarding a report entitled "Aircraft Noise abatement Tech-
nology." The report includes conclusions and recommendations in the
following major areas:
1. Advanced research and technology for noise abatement in future
aircraft.
2. Progress by FAA~ EPA and NASA toward achieving a coordi-
nated national aircraft noise abatement program.
3. R. & D. status of Aircraft Noise Abatement Technology (inc.
SAM and REFAN).
4. Possible aircraft noise abatement operating procedures with a
view to maximizing effectiveness of available technology (inc. two-
segment apporh and procedures after take-off).
It was of particular interest to the Subcommittee to understand the
status of R. & D. in noise abatement so that the near term implementa-
tion of noise reduction technology can be coordinated with the longer
term efforts. The concern of the Subcommittee in this context is to
speed up action by government and industry in reducing aircraft noise
by providing a comprehensive view of noise abatement technology for
present and future aircraft. The Subcommittee recognizes that the
ultimate implementation of this technology must take into account
a variety of interrelated factors including public health and welfare
as well as technological and economic capabilities.
The hearings show that substantial progress continues to be made in
various R. & D. programs. However, no progress has been made on
the key economic question: How would expensive retrofit prorams be
paid for?
A brief summary of the Subcommittee's recommendations are:
1. To encourage NASA to conduct and FAA to sponsor an increased
level of effort in basic research and other aspects of noise reduction
technology (e.g., aerynamic noise, core noise, etc.).
2. To encourae more rapid action by the Executive Department
in achieving a coordinated national aircraft noise abatement program
'throh FAA, EPA and NASA in the framework of a national trans-
portation policy.
;:::4








3. To urge the Secretary of Transportation to give early, full and
thorough consideration of the Sound Absorption Material (SAM)
retrofit option with particular attention to the economic cost-benefit
aspects. The cost and the resultant noise reduction benefits over the
short term must be weighed versus the long term reduction that could
be achieved by the expenditure of such a significant sum of money on
alternative options such as Refan or purchase of new, quieter aircraft.
4. To encourage NASA, FAA and the air transportation industry
to accelerate the resolution of problems and differences concerning op-
erational procedures which do not derogate safety and serve to reduce
noise, and to encourage appropriate implementation by FAA.
In carrying out these hearings I wish to extend my appreciation to
Mr. Lloyd and Mr. Wydler; both made significant contributions to the
dialogue with witnesses. Also, I wish to acknowledge the assistance
of committee staff members, Mr. Ralph N. Read, Mr. Tony Taylor,
Mr. H. Gerald Staub, Dr. John V. Dugan, Jr. and Mrs. Patricia
Schwartz.
Sincerely,
DALE MILFORD,
Chairman, Subcommittee on
Aviation and Trasportation R. & D.















CONTENTS

i""""""" ------
Page
Letter of transmittal --.-- -------------------_-. III
The witnesses ...------ ---..---------- v
Summary of conclusions and recommendations ...___ __ 1
I. Introduction --------------- -------------- 5
II. R&D status of noise abatement technology--- ------------------ 7
II. Interagency cooperation ----------------------- --- ----- 13
IV. Ttestimony summaries of end-users of technology-------------- 17
V. Testimony of certain citizens directly affected by aircraft noise ----21

WITNESSES

September, 1975
David Sheftel, Director, Systems Research and Development Service, FAA.
Roger Strelow, Assistant Administrator for Air and Waste Management, EPA ;
John S. Schettino, Aviation Control Requirement Group, EPA.
Harry Johnson, Director, Aeronautical Propulsion Division, NASA; Kenneth
E. Hodge, Director, Aeronautical Operating Systems Office, NASA.

October, 1975
Jack I. Hope, General Manager, CFM 56 Program Department, General Electric.
Grady McRae, Refan Program Manager, Pratt & Whitney Aircraft
A. L. McPike, Director, Industrial Association Activities, McDonnell Douglas
Corporation.
Clifton A. Moore, General Manager, Los Angeles International Airport and Vice
President, Airport Operators Council International (AOCI).
Caesar B. Patteini, Director of Aviation, Port Authority of New York and New
Jersey and Member of the Board, AOCI; accompanied by Lou Achitoff, Chief.
Aviation Technical Services, Port Authority of New York and New Jersey and
Member of the Board, AOCI; J. Donald Reilly, Executive Vice-President,
AOCI; and Milford Coor, Vice-President, Legal and Environmental Affairs,
AOCI.
Dick Mooney, Director of Aviation, Massachusetts Port Authority and Member
of the Board, AOCI.
Clifton von Kann, Senior Vice-President, Operations and Airports, Air Transport
Association.
William Becker, Assistant Vice-President, Air Transport Association.
John J. O'Donnell, President, Air Line Pilots Association, by R. N. Rockwell.
Chairman, Air Line Pilots Association; accompanied by R Lahr, Air Line
Pilots Association Noise Abatement Committee.
Ralph G. Caso, Chairman, National Organization to Insure a Sound-controlled
Environment (NOISE), by Joseph H. Driscoll, Jr., Director, NOISE; accom-
panied by Lloyd Hinton, Executive Director, NOISE.
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SU3C IRY OF CONCLUSIONS AND RECOM3ENDATIONS
As in 1974, the geral conclusions of the DOT concerning the 23-
airport study reviewed in the 1974 Aeronautics and Space Technology
Subcommittee report provided the framework for hearings on Noise
Abatement Technology with soe qualifications as indicated below:
1 Airport noise exposures are gradually declining and this
trend should continue into the next decade. The rate of this decline
has slowed, however, and whether these levels will decrease
through the early 1980's depends very much on the rate of attri-
tion of old aircraft (e.g. DC-8 and 707) as well as the level of
purchase of new environmentally acceptable aircraft by presently
capitally pressed airlines.
2. Implementation of operational procedures and aircraft modi-
fication programs (e.g. SAM Retrofit) will further decrease noise
exposure impacts around our airports. However, the near-term
decision whether to SAM Retrofit and/or Refan does not appear
conducive to straightforward cost/benefit analysis. In the light of
recent events it appears critical for the airport and airlines to
become recogned as "good neighbors."
3. Aircraft modifications together with advanced aircraft pur-
chases and optimized noise abatement operational procedures will
never eliminate aircraft noise. Land areas adjacent to airport
boundaries will continue to be exposed to aircraft noise levels
hgher than desirable ambient levels. Therefore, effective land use
plaing remains an imperative factor in dealing with residual
noise. [This conclusion is identical to that which appeared in last
ear's report.]
The Subommitte agrees that fundamental noise rsearch by NASA
and FAA must be expanded but holds to the view that there is adequate
information on present technology to go forward with certain noise
reduction measures. Data have been presented to the Subcommittee
which sug est that the reductions in noise which can be achieved will
be perceived by the airport neighbor and will perceptibly improve the
climate for air transportation growth.
The detailed Subcommittee recommendations together with relevant
conclusions from which they were drawn are:
1. To endorse increased emphasis on advanced research and tech-
nology on aircraft noise abatement as it evolves from the basic
research stage through component evaluation to full engine and air-
craft testn It is clear to the Subcommittee that continuing reduc-
n of aircraft noise toward the end of the century will involve the
successive lowering of floors for various noise contributions such as
engine core and arodynamic (airframe) sources. The Quiet Clean
Short-Haul Experimental Engine (QCSEE) engine program pres-
ently incorporates the best available noise reduction technology but
the Subcommittee recognizes that to produce "truly quiet" aircraft
(1)






2 2

by the turn of the century will most certainly require a better under-
standing of noise source processes and some significant reduction of
the challenging "airframe floor." Thus the climate for future research
and technology appears to be one where reductions will become more
difficult to achieve and it will be necessary for NASA and FAA to
address the priority of various areas very carefully. Certainly, in
view of the outcry about Concorde, the Subcommittee feels that a
major goal should be development of a much quieter supersonic en-
gine which will probably incorporate variable cycle concepts.
2. To endorse the framing of a national Noise Abatement Policy
for Aircraft in the context of the needs, economics and technological
capability of the national transportation community. The implemen-
tation of this policy will require the cooperation and coordination of
the cognizant federal agencies as well as the various components of
the private sector. To this end the Subcommittee will continue to
address the need for interagency cooperation in its oversight hear-
ings as well as to keep informed of the regulatory progress toward
the implementation of such technology. Noise abatement R&D "can-
not take place in a vacuum." The Subcommittee also notes that the
recent statement of a national transportation policy by the Secretary
of Transportation did include some mention of the environmental
compatibility of transportation systems. The Subcommittee also rec-
ognizes that there must be cooperation between the various legisla-
tive entities charged with responsibility in transportation (i.e. the
Committees on Science and Technology, Public Works and Inter-
state and Foreign Commerce).
3. To urge the Secretary of Transportation to give early, full and
thorough consideration of the Sound Absorption Material (SAM)
Retrofit option with particular attention to the economic cost-benefit
aspects. The cost and the resultant noise reduction benefits over the
short term must be weighed versus the long term reduction that could
be achieved by the expenditure of such a significant sum of money on
alternative options such as Refan or purchase of new quieter aircraft.
In this regard, the Subcommittee does not feel that the relative
merits of this approach can be simply evaluated on a classical cost/
benefits analysis or "dollar per dB" scale in view of the over 4 billion
dollars in damage suits pending against airports as well as instances
of stoppages in runway expansion at large airports and threatened
closings of smaller airports. Noise reduction technology has been con-
vincingly demonstrated and it is time to facilitate its implementation.
As regards the Refan program, it appears to the Subcommittee that
in the face of continuingly difficult financial conditions of the airlines
it does not seem realistic to set a timetable for Rulemaking to imple-
ment the Refan Retrofit. In fact, noise reduction technology, derived
from Refan and incorporated in the next generation of fuel conserva-
tive engines, may be a more likely route to further noise reduction. In
this era of escalating fuel costs, it seems unlikely that the airlines will
invest nearly a million and a half dollars per plane on a relatively
high fuel consumptive aircraft. It must be recognized, however, tt
the cost of incorporation of these new engines on existing narrow body
aircraft ranges from twie to 10 times as expensive as the Refan
Retrofit. Further, it should be noted that these new engines are de-






3

sianed to operate at optimum conditions only on the next gneration
of airraft. Thus the alternatives of Refan and new engie retrofits
will be weighed against the purchase of wide body aircraft or new
generation aircraft wherein the airframe is matched to the engines for
optimum performance.
It should be noted that Rulemaking is being considered to lower
FAR Part 36 levels for newly cerified aircraft. If implemented, this
will assure the incorporation of even quieter engines on the next gen-
eration of aircraft.
4. To have FAA bring the question of two-segment approach to a
timely resolution by a critical evaluation of the testimony submitted in
the Notice of Proposed Rule Making (NPRM) #75-35 hearings on
November 5. The Subcommittee has heard conflicting testimony very
similar to its predecessor Subcommittee on the two-segment approach
under ILS conditions. The Subcommittee concludes that the conflict
to be resolved is between NASA and FAA and the various pilots who
have flown the approach on one hand and the majority of the airline
pilots who strongly indicate that safety will be compromised severely
by its implementation on the other. In this regard, the Subcommittee
feels that the question of multiple two-segment approaches must be
studied and whether ground control personnel will suffer a severely
aggravated workload should be addressed. Also, the Subcommittee rec-
ognizes that ALPA objections to two-segment must be obtained in a
more quantified form in order to weigh these factors against the NASA
findings and FAA position.
5. To endorse the careful examination of the Northwest Airlines
"Quiet EPR" cut-back after take-off procedure by the other carriers in
cooperation with the FAA. The Subcommittee recognizes that the
other airlines contend the FAA "AC 91-49" procedure provides more
noise reducon than "Quiet EPR" and Northwest and ALPA have
countered thi. However, from the point of view of fuel management
and engine wear the Northwest procedure would seem to have some ad-
vantages and the Subcommittee encourages the various parties to ex-
plore these additional benefits. The Subcommittee recognizes the lack
of resolution of this matter since the 1974 Aeronautics and Space Tech-
nology Subcommittee Report but feels the present controversial cli-
mate precludes any rulemaking incentives by FAA on this matter.
evertheless, the adoption of a generalized "by-the-book" procedure
might contribute positively to the economic health of the airlines as
well as provide a more uniform and controllable traffic situation.










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I. INTRODUCTION
The Summary Section of this report is arranged in the following
manner. The written and spoken testimony by NASA and the engine
and aircraft manufacturers (Pratt-Whitney, General Electric, and
Donnell-Douglas) on the status of R&T in noise abatement has
been summarized in one cohesive section. This was done so as to recog-
nize th close NASA/industry partnership in noise abatement technol-
y while still delineating the R&T and R&D roles of NASA and
FAA. Also this allows for the regulatory aspects of noise abatement
to stand apart in such a way that the nature of the meaningful inter-
faces (among NASA, EPA and FAA) required for technology imple-
mentation become tter defined. Similarly the R&D status of opera-
tional procedures has been summarized in recognition of the close
NASA/FAA cooperation in this work. To complement this approach,
throughout the FAA summary an attempt has been made to point out
where R&D programs (cyclically related to regulatory priorities)
complement the NASA R&T effort. The EPA coordination activity in
nise abatement is similarly broken out, particularly to delineate the
interface with FAA. The AOCI, ALPA and ATA testimony repre-
sents the opinion of the end-users toward potentially implementable
teclology. Finally, the NOISE testimony represents a significant seg-
ment of the populace who suffer directly from aircraft noise. The
major Subcommittee conclusions regarding all testimony as well as
certain as t which were felt to deserve special attention have been
included in the Summary of Conclusions and Recommendations
section.
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II. R&D STATUS OF NOISE ABATEMENT TECHNOLOGY
A. SAM AND REFA_
The hearings in December 1973 and July 1974 and the subsequent
Subcommittee report, published in December 1974, dealt at length with,
the subjects of SAM and Refan technology. They presented detailed
data on fuel consumption, the cost and schedule of various options for
retrofit to the civil fleet, noise reduction, and human and community
responses.
Since that time the NASA-sponsored JT 8D Refan program has
been completed. It included a full scale flight demonstration of a
McDonnell-Douglas DC-9 aircraft, modified to incorporate two Pratt
& Whitney JT8D-109 refanned engines, and ground tests of a Boeing
727-200 propulsion system. In the DC-9 flight test program, noise
measurements were made by both McDonnell-Douglas and the Langley
Research Center during fly-over tests of both a refanned and an un-
modified DC-9 aircraft. Test results agree quite well with earlier pre-
dictions and show significant reductions below the unmodified aircraft.
Cost and schedulerequirements for a program of retrofitting SAM
and/or Refan technology to the existing civilian narrow-body jet air-
craft fleet are still within the general estimates presented at previous
hearings. This cost and schedule data is included in Table I.
With regard to fuel consumption, Refan engine altitude tests at
the Lewis Research Center, together with Pratt & Whitney data, sub-
stantiate fue consumption levels very similar to those presented last
year.
Pratt & Whitney has designed a derivative of the refanned JT-SD
that could be used in new production airplanes. The JT8D-200 series
engine will use the Refan concept, but will incorporate several ad-
ditionl component improvements that will derease cruise fuel
consumption.
B. NEW ENGINES
GE did not testify during the last noise abatement hearings thus
they included a history of their research and technology effort, de-
scribed their facility capability and indicated present areas of em-
phasis. Both of the major jet engine manufacturers, General Electric
and Pratt & Whitney, are developing advanced, high bypass ratio
enines for potential use on short and medium range aircraft. The
E version is the CFM-56, Pratt & Whitney's, the JT10D. The
engines achieve substantial reductions in noise because of their lower
jet velocities.
The bypass ratio of a turbofan engine is the ratio of the air flow
"bypassing" the core to the core air flow alone. In Figre 1
presented by G, theve effect of bypass ratio on take-onoise
is hown. Current narrow-body jet engines such as the JT8D (DC-9,
(7)





8
727, 737) have a bypass ratio of approximately 1. The refanned JT8D
has a ratio of about 2 and the high bypass engines such as the CFM-56
and JT10D have ratios of approximately 6. Figure 1 also shows that
for the high bypass engines, the noise improvement to be gained from
take-off thrust reduction is less than that for the low bypass ratio
engines.

Effect of Bypass Ratio on Takeoff
Noise 3.5 N.M. from Brake Release

NOISE LEVEL

TAKEOFF GROSS WEIGHT
CONSTANT IN THE
150-250 KIb. RANGE


SNFULL POWER
5 EPNdB /


CUTBACK
POWER


0 1 2 3 4 5 6 7
BYPASS RATIO
FIGURE 1
The high bypass ratio engines also have greater fuel efficiency than
the low bypass turbofans and are designed for lower exhaust emissions.
Although bypass ratio is a very important noise control feature of
the modern high bypass ratio engine, there are others. The large
single stage fan which provides lower pressure ratio, the axial spac-
inlg between rotating fan blades and downstream stationary outlet
guide vanes are also important. Proper selection of this latter design
parameter reduces the fan noise radiated both forward and aft. The
number of outlet guide vanes, as well as fan blades, is important to
reducing fan noise. Acoustic treatment of the airflow passages is a
cont in ing area for potential improvement.
Dring the past year therae ave been investigations by McDonnell-
)ouglas of the feasibility of modifying the DC-8 and DC-9 aircraft
to ic'orporate a high-bypass-ratio engine. While the study was don
for tlhe General Electric/SNECMA CFM-56 engine, the analysis is
generally correct for the Pratt and Whitney JT10D engine or any
ot0 Ie erlngi having the same characteristics.
A slulmary of the performance changes that would result from
the incorporation of the CFM-56 engine on the several models of the






9

DC-8 Series 60 aircraft is shown in Table II provided by McDonnell-
Douglas. On a 2600-nautical-mile mission there would be a reduction
of 15 to 21 percent in the fuel burned with the new and more efficient
high-bypass-ratio engine. Noise reductions of from 11 to 15 EPNdB
at the Part 36 locations are indicated and these reductions would not
decrease farther from the airport as is the case with the SAM sup-
pressors. There would be increases in the range of the aircraft of
from 10 to 20 percent and decreases in the takeoff field length re-
quired of from 600 to 1400 feet. Payload on a 4000-nautical-mile mis-
sion could be increased by from 17,000 to 22.,00 pounds and there
would be increases in initial cruise altitude of from 1600 to 3350 feet.
The DC-8 aircraft is no longer in production. Accordingly, the
only possible application of high bypass ratio technology is through a
program of retrofitting with new engines. McDonnell-Douglas esti-
mates that the cost of such a program, using the CFM-56 engine,
would be $8.2 million per aircraft, in 1975 dollars. At this cost it
would require perhaps 20 years for fuel savings alone to pay for the
modification. However, it should be noted that increased revenues due
to enhanced payload capacity would be very significant and the in-
creased range and shorter takeoff requirements would allow for greater
flexibility in operation of these aircraft.
For the DC-9. which is still in production, the noise improvements
as estimated by McDonnell-Douglas are also substantial. At the FAR
part 36 measuring points, the reductions in effective perceived noise
level (EPNDB) are: sideline, 11: take off, 18; takeoff with cutback,
10; and approach, 10.

C. LONGER RANGE RESEARCH
NASA reDrted on some of the long range fundamental research
and technolo* investigations directed at the development of practical
technology for future applications. Since the hearings of last year.
NASA has completed some airframe aerodynamic noise tests on a
model of the Boein- 747 mounted in an anechoic test chamber. Aero-
dynamic noise measurements are lso being taken on a half-span model
of the Boeing 747 aircraft mounted in the Ames 40 x 80 wind tunnel
to determine, on large scale, the relative contributions of the wing.
landing gear and high lift system. These and other tests indicate that
airframe- enerated noise may be only about ten decibels below the
present FAR part 36 requirements for new aircraft. Design techniques
are being explored to reduce this component of aircraft noise.
Research in the use of sound absorbing material is directed toward
increasing the acoustic absorption efficiency of sound suppression
linear materials and configurations, and finding ways to improve the
aerodynamic and acoustical characteristics of air passages to suppres
noise naturally.
Less obvious is how to improve the basic aerodynamic, thermo-
dnamic and mechanical design of engine internal colponents so that
they inherently generate less noise, requiring less aorption or sp-
presion. Still other portions of the aNASA effort re aimed at investi-
gating the fundamentals of the jet noise that is produced outside the
i by rapid mixing of the high velocity streams with the sur-
roundmin air.








In the area of exhaust jet noise, NASA has recently started research
on mixer nozzles for turbofan engines to mix the fan jet exhaust
air more efficiently with the primary jet exhaust gases. This program
shows promise of about five decibels of jet noise reduction relative
to current design techniques together with improved fuel economy.
The noise generated within the engine combustor may form another
"noise floor" if fan and jet noise are controlled. This noise is loosely
called "core noise." Recent test results obtained from scale model rigs
show that core noise reductions of five decibels or more may be possible
using advanced sound suppression design techniques.
High internal flow velocities and improved sound suppression ma-
terial design concepts show great promise for increased inlet noise
suppression. Some results of tests conducted in June, 1975 on a 20-
inch inlet model configuration demonstrate noise reductions of about
13 decibels over a conventional inlet.
The Quiet Clean Short-Haul Experimental Engine (QCSEE) Pro-
gram is in its second year. Detailed designs for both the under-the-
wing and the over-the-wing propulsion systems have been completed.
The noise goal of this program is the equivalent of 95 EPNdB at
500-feet distance for a 4-engine, 150,000 lb. aircraft.
The QCSEE engine incorporates every feasible advanced noise sup-
pression concept including the high throat Mach number inlet de-
scribed previously; advanced acoustic treatment in the inlet, exhaust
duct and engine internal passages; low pressure ratio variable pitch
fan with efficient acoustic design of fan outlet guide vanes; a fan duct
splitter suppressor; and turbine and core noise suppressors.

D. OPERATIONAL PROCEDURES
Two segment approach
One method of abating aviation noise is through modifying opera-
tional procedures. The FAA has identified two operational procedures
which might be utilized to lessen noise impact and which have had a
requirement for R&D support.
One of these is the two-segment approach. Through this method, on
aircraft would descend at a steeper than normal glide slope (approxi-
mately 6) for the first portion of the approach, and then resume
normal glide slope (3) for the latter portion of the approach. By
flying at a steeper angle at the outset, aircraft noise would be a greater
distance above land than with a normal approach and would therefore
have a reduced impact. Noise footprint area reductions from 54 to
;7 percent were predicted by NASA for various aircraft within their
90 EPNdB noise contours, and DC-8 test results have borne out this
prediction. However, the Air Line Pilots Association (ALPA) has
(questioned these results because of the controlled conditions surround-
ing tlle testing. Representative contributions of modified procedures
to SAM Retrofit and "untreated" aircraft are summarized in
Table III.
As another aspect of this testing, NASA contends that two-segmet
approaches using modified RNAV equipment are compatible withthe
air traffic control environment when properly coordinated with the
approach controllers. Once again, ALPA questions this conclusion by
stating that the two-segent approach is not flyable by all semens of








aviation under current traffic conditions and weather minima. During
last year's hearings there was some discussion of this issue and NASA
was requested to perform additional research.
As prt of additional studies, NASA conducted a simulation test
for the FAA to understand the wake vortex problem, and is continuing
its research in wake vortex alleviation techniques.
In addition, NASA investigated alternative approach techniques
such as a 40 glide slope, and a low drag approach with gear nd lap
extension delayed until 21, miles from touchdown. Iata from these
tests have not been completely analyzed but preliminary indications
are that each technique produced less noise than the conventional
approach.
It is known that other, more sophisticated procedures have even
greater potential for noise abatement. For example, a decelerating ap-
proach on a 3 glide slope can yield noise abatement approximating
that of a two segment approach. However, more research is required to
deterine if this is suitable for airline use.
For the present, NASA contends that the two-segment approach
R&D has met all its technical objectives.
The FAA isued an Advance Notice of Proposed Rule Making on the
two-segment approach in March, 1975, followed by issuance of NPRM
75-35 in August, 1975 and hearings on Nov. 5. 1975.
There was considerable discussion of the relative merits of FAA AC
91-49 cutback-after-take-off procedure versus the Northwest Airline's
"Quiet EPR" procedure which consists essentially of a power climb
until flaps are retracted.
icrowave landing system
The Microwave Landing System (MLS) is an advanced electronic
landing aid designed to replace the Instrument Landing System
(ILS).
With MLS, the pilot could exploit the full range of operational
capabilities of his aircraft and select segmented or curved paths.
A curved approach, utilizing the advanced technology of MLS,
would enable an aircraft to fly a tighter route into an airport, result-
ing in less land area being overflown. This procedure has been flown
successfully in simulators but further test and evaluation are needed
to prove the concept.





















































































































































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III. INTERAGENCY COOPERATLION
Although the testimony of primary interest was the status of Noise
Abatement Technology, this Subcommittee, as its predecessor, recog-
nizes the critical need for a continuing examination of the technology
implementation interface between NASA and FAA as well as the coor-
dination role of EPA between both sister agencies.
FAA R. & D. and regulatory aspects
FAA updated their R. & D. program on noise abatement and indi-
cated the directions of its long-range R. & D. They reviewed their
cooperative efforts with DOD, NASA and EPA and cited the major
contribution of these efforts to formulation of FAA R. & D. programs.
FAA reviewed the status of their aircraft noise R. & D. program in
terms of its three main elements:
Control of Aircraft Noise Sources-FAA feels that fan and com-
pressor noise technology is in hand with the exposed "Jet Noise Floor"
revealed as an area of prime importance even for new quieter high
BPR engines. The DOT/USAF program on jet noise suppression is a
continuing effort and the Subcommittee understands that it is strongly
complementary to the NASA-industry program on mixer nozzles and
other suppression techniques.
The other important noise floor due to the "engine core" tends to
offset gains from reduced jet velocity. The first part of core noise con-
trol dealt with engine components (e.g. fan, turbine, compressor, etc.
and their floinduced interactions). FAA has expanded cooperation
with NASA and industry programs in isolating combustion and tur-
bine contributions to core engine noise.
FAA is also investigating airframe effects on noise directionality
utilizing a program developed through NASA-Ames which is being
used at NASA-Langley in the Aircraft Noise Prediction Office for
aerodynamic configuration noise modeling. It has become clear to the
Subcommittee that experimental data such as that gathered at NASA-
Flight Research Center is providing a data base for this major
program.
FAA briefly mentioned their more modest efforts in general aviation
and V/STOL and helicopter noise source programs:
Noise Path between the aircraft and the observer on the ground-An
ongoing major effort involving FAA, NASA. NCAR, and the Army
and Marine Corps was reviewed. The contribution of abnormal meteor-
ological conditions to noise measurements has been quantified and
frequency requirements identified.
Human Reaction to Aircraft Noise- umuan evaluation and response
sarch is clearly not as developed as the other two FAA program
eleents although it is an essential factor in developing adequate noise
measurement units for certification. The FAA program consists of
laboratory tests aimed finally at determiningi the true value of quanti-
(13)






14

fled noise exposure measure. Special studies underway in V/STOL
noise and "blade-slap" are directed at determining noise standards for
aircraft with unconventional characteristics. These programs seem to
clearly complement the NASA-Langley program in psychoacoustic
response. The aircraft industry does not have any significant role in
this area as contrasted with their major role in reducing engine noise
at the source.
EPA Coordination
The Environmental Protection Agency reviewed results of recent
analytical studies and possible benefits associated with specific po-
tential regulatory actions. The update of the DOT 23-airport study
indicates the energy crisis and economic recession have reduced the
noise reduction benefits previously predicted for the baseline fleet.
These predicted benefits were based on the introduction of a significant
number of relatively quiet wide-body aircraft into the fleet. It was
also noted that the potential SAM benefits have slipped in time by at
least one year.
Fleet noise level
EPA recently completed a parametric study of aircraft noise levels
assuming that all fleet aircraft had noise levels at FAR 36, minus 5,
10, 15 and 20 db's. One result indicated if all aircraft generated noise
levels at 5 db below FAR 36, then SAM benefits would be maintained
during the period 1978-1987. The FAA has received EPA recom-
mendations on an NPRM on Fleet Noise Level. It was pointed out that
40% of the 1972 impacted population would still be exposed to NEF
levels of 30 or higher clearly indicating the need for additional noise
research and development efforts.
National goals
The Noise Exposure Forecast description as a relative noise indi-
cator was mentioned. EPA reviewed the activities of the 1974-Aircraft
Noise Research Panel and indicated plans to reconvene the panel in
order to determine specific goals to meet long-range national noise
abatement objectives.
FAA interaction
EPA reviewed the status of its interaction with FAA on regu-
latorv actions. The recommended Notices of Preferred Rulemaking
(NPRM's) are listed in Table IV. FAA has conducted public hear-
ings on all eight proposals and is preparing its response for the public
record. The Fleet Noise Level Proposal is unique in that it is effec-
tively an airline reporting requirement which permits monitoring of
noise reduction in the operating fleet.
Supersonic civil aircraft
EPA clarified its recommendation on supersonic civil aircraft in the
sense it is separable from the FAA's Environmental Impact Statement
on Concorde. The EPA proposal applies to 3 categories (I) current
SST types, (II) future production types and (III) future types with
category III aircraft required to meet FAR 36 requirments in effect
for subsonic aircraft at time of application for certification. Categry
II aircraft would be required to meet current (1969) FAR 36 requre-







15

ments. Category I, the Concorde aircraft, had no reglaion prposed,
but EPA did identify a set of alterative actions to be discussed dur-
ing pubc hearings.
EPA does prefer case-by-case consideration of limited SST opera-
tion with the final decision left to the airport operator.1
Other actions
EPA summarized agency actions in addition to the previously cited
proposed regulations:
FAR 36 modifications-EPA position is that proposed rule acknowl-
edges current production technology and must be supported to prevent
further noise escalation. EPA intends to recommend further reduced
levels based on an extrapolation of today's research and technology.
Short Haul Aircraft-EPA is ready to review FAA's draft NPRM
on helicopters in order to determine if further action is required. The
EPA position on powered lift and STOL aircraft is that the noise
technology base is inadequate to develop a regulation at this time.
Airport Regulation-EPA's eight airport pilot program aimed at
gathering data to elicit proposed action plans from airport operators to
FAA in order to supplement noise reduction from regulatory impact.
1 Since these hearings took place EPA has issued NPRM to prohibit the operation of
any civil subsonic or supersonic transport without flight time before Dec. 31, 1974, unless
the airplane complies with FAR Part 36 for subsonic transport planes.















*4
















IV. TESTIMONY SUMMARIES OF END-USERS OF TECHIOLOGY

A. SUMMARY OF TESTIMONY OF AIRPORT OPERATORS COUNCIL
INTERNATIONAL (AOCI)
Mr. Moore of AOCI indicated that NASA and FAA should empha-
size research in air-frame, jet and core engine noise. He repeated their
formulation of a continued program of revising FAR Part 36 stand-
ards downward. AOCI indicated dissatisfaction with lack of Executive
actions to combat aircraft noise, specifically addressing the lack of
specific regulations on a revised retrofit schedule which is more opti-
mistic than Pratt-Whitney has outlined.
Recent airport damage suit results and other evidence of commu-
nity opposition were documented. The FAA statement on the slowing
of airport expansion was cited and the nature of potential limitations
on airport operation was discussed. Mr. Moore closed by repeating
support for implementation of the two-segment approach and SAM
Retrofit and later Refan and urged the Subcommittee to work to expe-
dite the adoption of tlhse policies.
Mr. Pattarini of AOCI focused on the need for a national solution
to the problem of aircraft noise to avoid a proliferation of local rules.
The Port Authority of New York and New Jersey handles a passenger
volume of 40 million at these airports where noise is a serious problem
because of densely populated surrounding areas. Mr. Pattarini indi-
cated that the- have been many pleas for noise relief via SAM retro-
fit. He reiterteed a plea for action on implementation of any noise re-
duction techniques.
Mr. Pattarini stated that 50% of the air-line movements at JFK
involve retrofit candidates with only 20% wide-body types. The JTSD
powered aircraft constitutes 95% of LaGuardia traffic and wide bodies
only account for 8% at Newark International.
Mr. Pattarini cited the increasing number of damage suits amount-
ing to 4 billion dollars in pending claims and growing legislative sup-
port for restrictions on airport operations. The economic penalties of
airport constraints were also pointed out.
Mr. Pattarini concluded by suggesting that small increases in fines
or aviation trust fund monies could be used to pay for retrofit.
Mr. Mooney of the Massachusetts Port Authority made a statement
which was not submitted in writing. The following is a summary of
that statement:
r. Mooney began by stating that the situation is orsening for
airport operators in the absen of federal ation. The Masshusetts
Port Authority has established its own retro-fitting regulations with
a near-term deadline which will ensure an adversar relationship be-
tween the Port Authority and the airlines because ihe noise problem
S teing slved. Two m r runway extensions at Logan rport
e ee stpebeause the commity h not been convince that
they are worthwhile. Mr. Mooney suggested that any retrofit option
(17)






18

be financed by a user charge since the airports are revenue-financed
operations. The alternative of passing the cuts on to the airlines, Mr.
Mooney felt, would result in operational restrictions. He indicated
that the airlines have cooperated in working on operational proce-
dures for noise abatement. He urged the Retrofit regulation be acted
upon in DOT and mentioned a variety of alternatives the Congress
might adopt for financing including surcharge and surplus funds. Mr.
Mooney closed by predicting the spread of severe constraints on the
airlines, which is imminent in Boston, to other communities. He prom-
ised that the airport operators will cooperate in implementing any
meaningful program to make the airport a "good neighbor."
B. ATA TESTIMONY
ATA substantially repeated the testimony given to the predecessor
Subcommittee in 1974. They reviewed the history of the operational
procedure for cut-back after take-off which has come into accepted
use. The ILS history of two-segment approach research was also
summarized. While admitting there has been some success in develop-
ing the procedure, ALPA restated reservations about two-segment
as presently envisioned. They cited icing and wake vortex as major
limitations to the adoption of two-segment. The widely used reduced
flap approach was mentioned as comparable in noise reduction.
In the category of advanced technology, ATA indicated that MLS
will permit precision guidance to become part of the flight control
system. In this context, it should be noted that FAA has just finished
a cost/benefits analysis of the relatively expensive MLS.
ATA pointed to the incorporation of increasing numbers of wide
bodies in the fleet as the ideal route to noise relief. The turndown of
growth in the airline industry since 1970 has, of course, significantly
lowered the originally projected rate of growth of the wide-body
fleet.
ATA reviewed the promise of SAM technology. They cited the
role of externally generated jet noise in the JT8D power plant as a
major limitation on take-off because of the low bypass ratio. The re-
sults of the more ambitious REFAN program were reviewed. Finally,
ATA presented estimates of increased fuel consumption costs due
to SAM retrofit as 1,460,000 barrels per year which translates to
roughly $515 million per year additional costs to the airlines.
ATA closed by mentioning the need for a systems approach to
restricting airport operations and noted the problem of restricting
land use so as not to aggravate the extremely serious situation for air
carriers.
The ATA conclusions are:
Research and development, both government and private, has
produced major progress in noise abatement technology. Finan-
cial considerations are the pacing item in adopting this new
technology.
The airlines will continue to explore operational procedures
and accompanying instrumentation to further abate noise With-
out compromising safety.
For theforeseeable future, fuel economy must be considered
along with noise abatement as a top priority R&D bjtive.







19

C. ALPA TESThMONY

ALPA focused on development of fundamentally quieter engines
and the value of cost/benefits analyses. ALPA repeated their reserva-
tions concerning the two-segment approach, presumably under ILS
conditions. They also called for review of critical factors in develop-
ing an environmentally compatible air transportation system. ALPA
closed by stating its encouragement for NASA's program in advanced
aircraft technology and reminding the Subcommittee of the over-
riding concern of the pilot community for safe operations.
The ALPA response to FAA ANPRM 74-12 on two-segment ap-
proach was included as an appendix. The Subcommittee at this time
does not feel that there is much merit in commenting on the ALPA
objections point-by-point. It is clear that although the many pilots
who have flown two-segment approaches have responded favorably,
the consensus of the pilot community is strong opposition to the
adoption of this procedure.






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V. TESTIMONY OF CEPRTAIX CITIZENS DIRECTLY AFC1C D BY
AI RcArr NOISE

A. NATIONAL ORGANIZATIONS TO ISSUE A SOUND-CONTROLLED
ENVIRONMENT (N.O.I.S.E.)

NOISE pointed to a contradiction in Mr. Butterfield's testimony on
the ATA/FAA recommended cutback-after-takeoff procedure con-
tained in A.C. 91-49. They reiterated their support of SAM and Re-
fan and emphasized the absence of real evidence that something is
being done about airport noise. NOISE cited the public turnout at
the FAA hearing on Concorde as an indicator of citizen concern. They
concentrated on modification of operational procedures to reduce noise
with associated benefits in fuel conservation and flight safety (i.e. a
suggestion to adopt substantially the Northwest procedures).
\NOISE further suggested a surcharge as an equitable means to pay
for Retrofit. The testimony closed with considerable critical discussion
of the possible Concorde landing in the U.S. under critical fuel condi-
tions. NOISE objected strongly to the FAA approval of a 250 bank
maneuver of the Concorde after take-off which they contend is done to
avoid the noise monitoring device at JFK. They further requested the
Congress to find out the extent of U.S. commitments to allow Concorde
landings. NOISE submitted some very specific recommendations on
an Aviation Performance, Engineering and Applications Program as
an appendix.
TABLE I.-RETROFIT UNIT COSTS AND SCHEDULE

Lead times
Cost Schedule (months)

SAM:
DC-8 (long duct pod)---....----...... .------... --.---..---. $650,000
707--------... ---- --........---..................... 800,000
DC-9--------...... -- ------------------------........ 140, 000 1977-82 18-36
727.......-------................----------------------------------................................... 152, 000
737----------------------.............................. 183, 000
REFAN:
DC-9---------------................-.....------.....------.............------------.......-....... 1,300, 000 1977-81 18
727------------------------------------- ---------------- 1,900, 000 1

I Figure presented at 1975 hearings of Aviation and Transportation R. & D. Subcommittee.
2 Figure presented at 1974 hearings of Aeronautics and Space Technology Subcommittee.
TABLE II.-DC-8 SERIES 60-PERFORMANCE SUMMARY-CFM-56 ENGINES

DC-8-61 DC-8-62 DC-8-63 DC-8-63F

uel burned (2,600 nmi) (percent) ------.....-------. -21 -16 -15 -15
Noise reduction (EPNdB):
Sideline---.............. .... ------12 -12 -11 -11
Takeoff.......---...............-..--.... -12 -13 -12 -12
Approach --------.......--....--- ------....... -13 -14 -15 -14
Range increase (percent)..----------......-----..--..-----------.. 28 19 19 18
l Takeoff (feet) ...-.---------.--------.. -1,400 -600 -900 -900
increase (4,00 nmi) (pounds).............22,600 17,500 17,500 17,500
nitial cruise atitude (feet)........................... +3,350 +2,100 +1,600 +1,600

117,500 nmi.
(21)
4sl







22

TABLE II A.-CONTRIBUTIONS OF MODIFIED PROCEDURES TO SAM RETROFIT NOISE LEVELS (FAA DATA-
WITHOUT MODIFIED OPERATIONAL PROCEDURE

Take-off Sideline Approach
noise noise noise

DC-9:
Baseline.-..--........----..--...- .....------..-- ....- -.. 105.5 102.0 108.0
SAM-..................................................................... 102.0 99. 3
SAM reduction -------......------------------.................. .------- O 9.7
727:
Baseline--.------.......... ...--------...... --------...---... 108.0 100.0 108.0
SAM .......... -...................-------.--------...-. 107.0 99.9 100.0
SAM reduction-...---.------......... ..-- ------. ..------.. 1.0 .1 8.0

1 Reference, 1974 report "Aircraft Noise Abatement" by Subcommittee on Aeronautics and Space Technology.

B. FAA DATA: WITH MODIFIED OPERATIONAL PROCEDURES

Takeoff Sideline Approach
noise noise noise

DC-9:
Baseline-...---...---------- ------.......... ........... 97.0 102.0 ().
Procedure reduction--...------..... --------- ---. -----8.5 0 ..............
SAM........-- .........----.-- .....-- ... ......-- ..----- 94.3 102.0 ---...........
SAM reduction.-----.. .......-- ..-----------.------------- 2.7 0 9.7
Total reduction-----........ .----------------......---.--- 11.2 0 2 9.7
727: **
Baseline -------.......--- ...----------... --------------100.0 100.0 106.8
Procedure reduction.. ------------------------------------. 8. 0 ..... .------.. 1.2
SAM ..---.. ----------------------........... ...... ----97.5 99.9 100.4
SAM reduction. ---------------------------------- 2.5 .1 6.4
Total reduction ---------......... -----------------------.. 10.5 .1 7.&

1 Not applicable-reduced flap procedure not performed.
2 SAM reduction from table II-A only since modification of procedures is not applicable.
S50* flap,

TABLE IV.-EPA RECOMMENDED NOTICES OF PROPOSED RULEMAKING (NPRM) TO THE FAA

FAA's NPRM No. Submitted I

1. Small prop driven aircraft .......------------......-. ------------74-39..--..---- December 1974.
2. Minimum altitude-.. ------.............----------------------. 74-40........------ Do.
3. Retrofit .---------....-----------........---------------- 75-5--......------- January 1975.
4.Fleet noise level --------.............. .--------........ ---.. ----. 75-6- .-------. Do.
5. Supersonic civic aircraft....----... --------.---------. 75-15-----......... February 1975.
6. Minimum flaps approach---....--............---- ------.---------- 75-35-1-..----- August 1975.
7. Visual flight rules 2-segment approach--.........................------------ 75-35-11...------. Do,
8. Instrument flight rules 2-segment approach---..............------------- 75-35-111...----.... Do.

I FAA has conducted public hearings on each NPRM.

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