army helicopters...20 ui-60a-'varlatlon of sel + 10 los (4l100 kinots) with speed at 500 ft 30...

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Sconstruction United States Army ngi.Corps of Engineers engine. Sering the a-n research TECHNICAL REPORT N-131 (• June 19'82 reeabor hy Integrated Installation Noise Contour System tl6 laboratory OPERATIONAL NOISE DATA FOR UH-GOA AND CH-47C ARMY HELICOPTERS by P. D. Schomer Aaron Averbuch - J iRichard Raspet . AUG 3 1 1982 A C--- UU. Approved fur public rele isc: distribution tiliiniItd. '' "... ...- iiil j

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Page 1: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

Sconstruction United States Armyngi.Corps of Engineers

engine. Sering the a-nresearch TECHNICAL REPORT N-131

(• June 19'82reeabor hy Integrated Installation Noise Contour System

tl6 laboratory

OPERATIONAL NOISE DATA FOR UH-GOA AND CH-47CARMY HELICOPTERS

byP. D. Schomer

Aaron Averbuch- J iRichard Raspet

. AUG 3 1 1982

A

C--- UU.

Approved fur public rele isc: distribution tiliiniItd.

'' "... ...- iiil j

Page 2: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

The contents of this report are not to be used for advertising, publication, ofpromotional purposes. Citation of trade names does not constitute anofficia! indorsement or approval of the use of such commercial products.The findings of this report are not to be construed as an official Departmentof the Army position, unless so designated by other authorized documents.

,I

DESTRO Y THIS REPOR T WHEN IT IS NO I. ONGER NEEDED

DO NOT RETURN IT TO THE ORIGIN,4 TOR

Page 3: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

SECURITY CLASSIFICATION OF THIS PAGE (hWan• 1 f

READ INMSTRUtOMeREPORT DOCUMENTATtON PAGE BEFORE C0ULKTM' F -OUMI. REPORT NUMBER G. GOVT ACCESSION NO: 1. RIECIPI NT-S CATALOG NUMBER

CERL-TR-N-131 @4 -D 8 - '7/,44. TITLE (and Subtf.le) s. TYPE Of REPORT a PERIOD COVERED

OPERATIONAL NOISE DATA FOR UH-60A AND CH-47CARMY HELICOPTERS FINAL

6. PERFORMING OOG. REPORT NUMBER

7. AUTHORI() 9. CONTRACT OR GRANT NUMBER.)P. D. SchomerAron AverbuchRichard Raspet

9. PERFORMING ORGANIZATION NAME AND ADOR,,5 10. PROGRAM ELEME T, PRCJRCT, TASKU.s. AM AREA& WORK UNI NUMUR

CONSTRUCTION ENGINEERING RESEARCH LABORATORY 4A762720A896-A-011 '1P.O. BOX 4005, CHAMPAIGN, IL 61820

II. CONTROLLING OFFICE NAME AND ADDRESS I. REPORT DATE IiJune 1982

1S. NUMBER OF PAGES

4214. MONITORING AGENCY NAME ADOORSS(AI dif.rm•nt hem Coewoff And 01.f.•) Is. SECURITY CLASS. (of this rep•e)

Unclassified

ISa. DECI, ASSI FICATION DOWkNS AOINGSCMEDULE

1S. DISTRIBUTION STATEMENT (ol A#nUe Report) -

Approved for public release; distribution unlimited.

17. DISTRIBUTION STATEMENT (of the abstract entered In Block 20, At different free, Report)

Copies are obtainable from the National Technical Information Service

Springfield, VA 22151

It. KEY WORDS (Contiaue an revere, side It neoessay and Adentify by block nummber)

Helicoptersf noise (sound)

aircraft noisesound exposure level

AS AESThACT' Mmkm -m Pvwwebb W~vee r m od. fd- I.11f by Wleak nuvmer)."The objectives of this study were to develop sound exposure level (SEL) versus distance

curves for the UH-60A a'd CH-47C Army helicopters, to investigate the varisAtion ofSEL with aircraft speed, and to confirm the validity of the measurement procedures bycomparing data obtained for UH-IH helicopters at Forts Campbell and Rucker.

Sound levels produced by the helicopters were measured for heavily and lightly loaded C,aircraft which were hovering and traveling at variouL speeds and distances.

WO~13 RoinmvoW I~ Nov asis fiomii~sruUNCLASSIFIED

9li0M CLASSIFICATION OF THIS PWAet f Doto Uisewcd)

Page 4: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

MU IAMSI=I• iiwouli, LASPCATON OP THIS PAGOVIII 09" 81101"

BLOCK 20. (Continued)

• --- The data show that a heavily loaded UH-60A is about 2 dB louder than a lightly loadedone. Landing noise with the UH-60A and CH-47 is substantially peater than for level

flyover. The variation of SEL with speed is rather modest, except for aircraft at very low

or very high speeds. The results for the UH--I H at Forts Campbell and Rucker did not

compare as favorably as expected. Various factors, inzluding main'enance procedures and

the surface of the test area, may have contributed to the discrepancies.,//!

UNCLASSIFIEDgmRCUMgIv CLASSIFICATION OF THIS [email protected] Doft fter*~4

-'

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FOREWORD

Th1 study was performed for the Directorate of Military Programs, Office of the Chiefof Engineers (OCE) under Project 4A762720A8%, "Environmental Quality Technology";Technical Area A, "Installation Environmental Mimiaement Strategies"; Work Unit 01i,"Integrated Installation Noise Contour System." The OCE Techtical Monitor was GordonValeco, DAEN.ME-I,-,

This Investigation was performed by' the Environmental Division (EN), U.S. ArmyConstruction Engineering Research Laboratory (EN). Dr. R. K. Jain is Chief of EN.

COL L J. Circeo is Commander and Director of CERL, and Dr. L R. Shaffer isTechnical Director.

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Page 6: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

CONTENTS

PaopDD FORM 1473IFOREWORD 3LIST OF TABLES AND FIGURES 5

INTRODUCTION.............................................. 9BackgroundObjectiveApproachiMods of Technology Transfer

2 COLLECTION OF DATA ........................................ 10 K

Helicopter OperationsMicrophone Placement '

Measurement InstrumentationGround Tracking SystemCalibration

3 DATA REDUCTION AND ANALYSIS.............................. 11Raw DateReduction of Dynamic Operation DataDate Analysis

4 RESULTS AND DISCUSSION.................................... 13Sound Exposure Level Versus DistanceHover Data

K Variation of Sound Exposure Level With SpeedComparison of Fort Campbell and Fort Rucker Results

for the UH-1H Aircraft

5 CONCLUSIONS AND RECOMMENDATIONS......................... 16

TABLES AND FIGURES 16

ME7 RIC CONVERSIONS 32

APPF- -i~lX A: Pilot's Log 33APPENDIX B: Hover Cate 38APPENDIX C: Data '.or Figures S Through 22 41

DISTRIBUTION

4

Page 7: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

TABLES

Number popg

I Dynamic Operations Performed at Fort Rucker 16

2 Helicopter Types and Loading Conditions Measured at Fort Rucker 16

3 Dynamic Operations Performed at Fort Campbellby CH-47C and UH-IH 17

4 Average (Energy) Me~sured Data 17

5 Hover Directivity Versus Position 18

6 Energy Average A-Weighted Hover Sound Levels 18 I

7 Difference, in Decibels, Between Composite SpeedVariation Functions 18

8 Comparison of Fort Campbell and Fort Rucker UH- I H Data 19

BI UH-IH HoverData 38

B2 UH-60A Hover Data-Unloaded 38

B3 UH-60A Hover Data-Loaded 38

B4 CH-47C Hover Data 38

B5 Energy Averages of Fort Campbell Single-Rotor Aircraft by DegreesWith Respect to the Aircraft (0" Is Front of Aircraft); Table B IThrough B3 Data 39

B6 Difference From Average; Table B5 Data 39

B7 Weighted Average of Single-Rotor Aircraft Directivity Change 39

B8 Energy Averages of Fort Campbell Dual-Rotor Aircraft by DegreesWith Respect to the Aircraft (00 Is Front of Aircraft); Table B4 Data 39

B9 Difference From Average; Table B8 Data 39

BIO Weighted Averakge of Dual-Rotor Aircraft Directivity Change 40

CI Variation of SlL With Distance at 100 Knots (Figures 8 and 9) 41

C2 Variation ofSELLWith Speed at 500 ft (Figures 10 through 13) 41

C3 Variation of L.q With Speed at 500 ft (Figures 14 through 17) 41

S

Page 8: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

TABLES (cont'd)

Numbr Paop

N'4 Variation of SEL + 0 Ilog (v/100 Knots) With Speedat 500 ft (Figures 18 Through 21) 42

CS Difference of Leq With Speed Versus SEL + 10 log (v/100 Knots)With Speed at S00 ft (Figure 22) 42

FIGURES 11I Flight Path for Level Flyovers 20)

2 Flight Path for Landing 20 ti3 Microphone/Cameia Layout at Fort Campbell 21

4 Hover Microphones at Fort Campbell 21

5 Sideline Microphones at Fort Cimpbell 22

6 Directivity Effects-300 ft AGL 23

7 Dlrectivity Effects- 1000 ft AGL 23

8 UH-60A-Variation of SEL With Distance, Level Flyover 24

9 CH-47C-Variation of SEL With Distance, Level Flyover 24

10 CH-47C-Variation of SEL With 1 weed at 500 ft 25

I I UH- I H-Variation of SEL With Speed at 500 ft 25

12 UH-60A-Variation of SEL With Speed at 500 ft 26 ij13 Composite Cturves of Variation of SEL With Distance at 500 ft 26

14 CH-47C-Variation of Lq With Speed at 500 ft 27

15 UH- I H-Varlation of Lqq With Speed at 500 ft 27

16 UH-60A-Variation of Lq With Speed at 500 ft 28

17 Composite Curves of Variation of i., With Speed at 500 ft 28

18 CH-47C-Variation of SEL + 10 log (v/ 100 Knots)With Speed at 500 ft 29

19 UH- IH-Variation of SEL + 10 log (v/100 Knots)With Speed at 500 ft 29

6

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Page 9: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

FIGURES (Nontd)

20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots)With Speed at 500 ft 30

21 Composite Curves of Variation of SEL + 10 to&(vt100 Knots) With Speed at 500 ft 30

22 Difference of L. Versus Speed and SEL + 10 log(vl100 Knots) at SO0 ft 31

23 UH-lI H-Varlatlon of SEL With Distance at 80 Knots(Levt Flyovers) 31

24 UH- IH-Variatlon of SEL With Distanca at 80 Knots

(Landinp) 32

A) Instruction Sheet for a Level Flyover-Operation 14 34

A2 Pilot's Entries for Leve! Flyover 34

AZ Instruction Sheet for Landing-Operation IS 35

A4 Pilot's Entries for Landing 35

AS Instruction Sheet for Hovers-Operations 16 and 17 36

A6 Pilot's Entries for Hovers 36 kA7 Instruction Sheet for Takeoff-Operation 18 37

SA8 Pilot's Entries for Takeoff 37

F77 _ _ *

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OPERATIONAL NOISE DATA FOR UN-BOA propogation front s, irce to receiver, and (3) data defln-AND CH-A7C ARMY HELICOPTERS ing the human and community rcsponse tu the received

noise.

1 INTRODUCTION degree, these sets of dat6 for rotary-wing aircraft andfor blast noise predictiun. In particular, CERL Tech-nical Report N-38 defines the noise emission charac-4

feekgm und teri~tics for rotary-wing aircraft operating in the ArmyIn recent years. residential development has occu.-red fleet during the late 1970s," Since then, the new UH-

nucr military and civilian airfields-areas subject to high 60A and CH-47C helicopters have be~en introduced,ntoise levels from aircraft and airfield operations. To their emissions data are required by the Army for ICUZcontrol this development, the U.S. Army has instituted and for environmental assessment.the Installation Compatible Use Noise Zone Program(ICUZ).' Like the Department of Defense's (DOD) Objective 7Constcrucion Criteria Mlanual and Air Installation Comn- The objectives of this study were: (1) to developpastible Use Zone program (AICUZ), the ICUZ program sound exposure level (SEL) versus distance curves fordefines land uses compatible with various noise levels the new Army aircraft, (2) to investigate the variationand establishes a policy for achievinig such uses.' Each of SEL with aircraft speets, and (3) to confirm thedocument describes three noise zones which restrict validity of the measurement procedures.

land use in varying degrees to ensure compatibility 1with military operations. The ICUZ program stresses ApproachArmy-unique noise sources such as blasts (e.g., artillery, To accomplish these objectives, the basic approacharmor, demolition) and rotary-wing aircraft. was to use as much as possible the microphone types

and layout, recording method, and analysis proceduresNoise zone maps for the ICUZ program are developed employed in April 1974 at Fort Rucker.' Chapter 21

by the Army Environmental Hygiene Agency (AEHA) details the collection of data and specifically highlightsusing U.S. Army Construction Engineering Research changes from the 1974 procedrs Chpe4 ecieLaboratory's (CERL's) integrated noise :ontour system the data analysis. I(INCS). This system can produce. joint noise ?.one mapsfor blast noise and fixed- and rotary-wing aircraft opera- To help confirm the validity of the measurementtions. Noise zone maps are produced using the CERL- orocedures. data were also gathered on the UH- IH atdeveloped BNOISE-3 .2 computerized prediction pro- Fort Campbell for comparison with the 1974 measure-cedure, helicopter noise zone maps are developed using ments for this aircraft at Fort Rucker. Similar resultsa CERL.,modifitcd Air Force NOISEMAP Computer from the two studies would &how that the measurementPrediction Program. 3 Each of these computerized pre- procedures wer'n independent of site, or that the opera-diction procedures relies on three separate data sources: tional/pilot technique or other factors had not changed(1) source emissions data, (2) data detailing sound in the 6 years between the two measurement periods.

Chapter 4 discusses this comparison and presents thebasic results.

""Installation Compatible Noise Use Zones" (Departmentof the Army, Office 4-. the Adjutent General, 20 May 1981). Mod* of Technolog Transfer

2Construction Cfter. Marn"a. DOD 4270.1-M (Depart- Data developed for helicopter SEL versus distance1'ment of Defense. 1972); Air Inuatlaations CompatNbe Us or soeed will be entered in the 1NCS input data baseTows,. DOD Instruction 4165-57 (Department or Defense,1973). and wiii be immediately availatble for use by AEHA and

3LiIScoln L Lattla, Violetta 1. Paniowska, and David L other DOD installations.Efflaztd. Bluut Noise P'edktlon Volume /P: BNOISE 3.2Computer horavin Description and Progrm Listing. Technical 'B. Homsans, L little, and P. Schomer, Rotary Wing Air-Report N-981ADA099335 (U.S& Army Construction En~gineer- craft Operational Noise Date. Technical Report N-38/ADAing Research Laboratory (CERLj, 1981); R. D. Iloronjeff. 051999 (CERL, 1978).R. R. Kandukuri. and N. H. Reddiniglus. Community NoiseE'xposure Resailting Pomt Aircraft Operation: Computer Pro- S11 IHomnsn, L. ULtk'. aind P. Se. -imvr. NoarY Wing Air.Sram Description. Air ForvA Report AMRL TR-73-1091/ craft Operational Noise lhiia. Tchnchkal Rcr'~rt N-38/AI)1%ADA004b2I (1974). 051999 (CERL., 1978).

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Page 11: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

2 COLLECTION OF DATA was flown at 300 ft AGL, Figure I illustrates the levelflyover flight path. Operation 15, a normal landing(Figure 2), began at 300 f AGL on a ground track of

Hellciptat Opeatlkes 280 degrees. The aircraft landed 800 ft west of the eastAt Fort Rucker, one set of data was based on the end of the microphone array (Figure 3).

dynamic operations listed Ln Table I. Forty helicopterstook part in that study; each aitc aft flew the series of Static operations consisted of in-ground and out-of.operations twice: once with tht pilot and once with ground effect hovers. These measurements were per.the co-pilot. Table 2 lists the aircraft types and 'ondi- formed largely over a grassy surfaced area (Figure 4).tions employed, The Fort Rucker study indicated that In ground effect hovers were performed with the air-level flyover data and landing data adequately charac- craft at a stabilized position between 0 and 5 ft above

t terized the noise emissions of all othtr dynamic opera- the ground. The aircraft maintained the stabilized posi-tions. Therefore, die study at Fort Campbell concen- tion by always facing into the wind. Out-of-groundtrated only on level flyovers and landings. hovers were performed at an altitude o1" I rotor

diameter.At Fort Rucker, cargo and utility aircraft were flown

lightly loaded and fuhy loaded. At Fort Campbell, this The pilots recorded in logs information about eachcondition vail.ad with aircraft type. The UH-IH and operation flown. Typical entries from a pilot's log areCH-47C were flown lightly loaded only. Table 3 lists shown in Appendix A.the operations performed by these helicopters. Theaircraft began by flying level flyovers with headings ofeither 100 de;rees or 280 degrees at 300 ft above Microphone Placement wsground level (AGL). In the middle of the test, they per- A basic array of six microphones was used at FortsRucker and Campbell (Figure 3). (Four additional side-formed two hover operations, and then resumed levelflyovers, but this time at an altitude of 1000 ft AGL. fiue ai s ofhelopte d at ten-Two aircraft of each type were used, each with a dif- future analysis of helicopter sound exposure level atten-

ferent pilot. The aircraft performed the 300-ft-AGL uation with distance [Figure 5].)

operations, the landing, the two hovers, and as many of Hover measurements were performed at point H onthe 1000-ft-AGL operations as they could before re- Figure 4. The hover measurement positions f( rmed aturning to base for fuel. The operations and procedures 400-ft-radius curve around the hover position. Measure-(as well as the measurement equipment described below) ments were made at eight equally spaced points on thewere designled to investigAte the change in SEL with hover circle. Three points were part of the six-micro-speed and distance, and to establish noise emissions hone array.anhfie points were pal manne s ta-data for the CH.-47C and the UH-60A. phone array, and five points were special manned sta-

tions used only during the hover operation.

The tests with the UH-60A were different in thatthe aircraft was flown both lightly loaded and more Measumnent Instramnentatlonfully loaded. To load the UH-60A, its sling was used As at Fort Rucker, the main acoustic instrumentationto carry a full 500-gal water buffalo. Two UH-60A at Fort Campbell consisted of six B&K 4149 W-in.

aircraft performed only operations 1 through 17 from quartz-coated microphones. Newer B&K 4921 outdoor

Table 3-once lightly loaded and once heavily loaded, microphone systems with silk windscreens were used inThe UH-60A aircraft were not flown at 1000 ft AGL. place of the older B&K 141 field amplifiers used at

Fort Rucker. The six microphones were wired to anThe level flyovers tit Fort Campbell were flown sim- equipment van. As at Fort Rucker, each microphone

ilarly to those at Fort Rucker The pilots were instruct- signal was received, amplified by a Neff 119 DC ampli-ed to maintain straight, level, steady flight for at least fier, split, and recorded on a 14-channel FM tape1.5 nautical miles before and after each dynamic opera- recorder. At Fort Campbell, Ampex PR 2200 recorderstion. All teardrop turns, other ancillary maneuvers, and were used in place of the older FR 1300 recorders.preparations for the actual dynamic operation were Rather than split the signal at 707 Hr as was done atperformed beyond 1.5 nautical miles. Flying this dis- Fort Rucker (a procedure which gained no more thantance allowed the pilot to stabilize the aircraft and pro- 6 dB in dynamic range of the high frequencies), it wasvided enough time for 10 •B down-sound-level points decided to split the recording into a high gain and lowto be recorded on magnetic tape when the operation gain channel to increase the dynamic range.

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Page 12: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

Time synchronization was handled by a Systron microphone systems was used to set a known level onDIXincr M350 time code generator which occupied one the tape. The electrostatic actuators were tested withtape recorder channel. The remaining data channel on B&K 4220, 124-dB pistonphones before and after thethe Ampex recorder was used for wind speed and wind enti measurement program. (Calibration of the elec-direction information. trostatic actuator with the B&K 4220 allows one to

The recordings for hover measurements were made establish an absolute K factor for ea,-h actuator)simultaneously by using three of the six permanentmicrophones and five identical portable systems manned The instrumentation for the hover ue~ation measure-by five individuals, Each of the portable systems con- ments was calibrated using B&K 4220 pistonphones.

sisted of a B&K 4145 l-in. condenser microphone The calibration tone was recorded on the Nagrarecorders.

powered by a B&K 2209 sound level meter. These sys-tems recorded from the AC output of the sound levelmeter onto a Nagra DJ full-track portable scientifictape recorder which was set to run at 7-% ips. In a 3 DATA REDUCTION AND ANALYSISdeparture from the Fort Rucker procedures, no record-ings at Fort Campbell were made at the 1.5 ips speed.

Ground Tracking System Raw DataThe tracking system used at Fort Campbell was very Each reel of tape from the 14-track Ampex PR-

similar to that at Fort Rucker. Two cameras and a the- 2200 tape recorder contained 12 channels of acousticalodolite (Figure 3) marked the position of an aircraft data; one channel of time code information; one chan-flying over the middle of the microphone Mrray. Camera nel onto which wind speed, wind direction, and signalsI was placed 500 ft south of microphone array, and from the cameras and theodolite were recorded; andcamera 2 was placed at the east end of the runway next one edge track onto which voice information was placed. Vto microphone 4. Stator poles in front of the camerapositions were marked with uniform graduations. By The 12 channels of acoustical data originated fromexamining photographs from both cameras, one could the six microphones in the dynamic operations array. Hascertain position information in three dimensions at Each microphone signal was split: one part recordedthe moment the pictures for the 300-ft-AGL test were linearly on one channel ond the other sent through ataken. For the !000-ft-AGL operations, only camera 2 14 to 24 dB amplifier arid recorded on another channel.was used. Two additional stator poles were used to de- The object was to increase the recorded dynamic range.termine the lateral deviation of the aircraft (north orsouth) from the desired flight line. Pictures were taken Time code information was supplieo by a Systronremotely by an operator who could see when the air- Donner model 8350 time code generator. Day of thecraft were precisely over the east-west middle of the year, hours, minutes, and seconds were record.d onmeasurement array. The helicopters' altimeters guaran- one channel of the Ampex recorder in digital zormat.teed that the aircraft were close enough to 100U ftAGL for this study. The remaining data channel contained the outputs

of t o voltage-controlled oscillators. These units wereA bus system connected the cameras with the van set up to form a discrete frequency band for each. The

and the theodolite. When a picture was taken from voltage-controlled oscillators were driven by an R. M.either camera, both cameras were fired and wind direc- Young wind speed and direction measurement appara-tion information on the Ampex 14 track tape recorder tus. Thus, this tape channel could be read by a spectrumwas interrupted momentarily. A push button activator analyzer, and wind speed and direction componentsat the theodolite interrupted wind speed information determined. The edge track contained a vocal runnin-on the Ampex recorder and sounded a bell at the test diary of events.control center. Photographs were taken when the air-craft was over the center of the microphone array. Each helicopter run was photographed when theexcept during landings. In this case, photographs were aircraft passed over the center ofthe landing lane. Fortaken when the aircraft reached the east end of the 300.ft-AGL runs. two cameras. 90 degrees apart.landing lane. focused on a point above the center of the runwayCalibration where it was anticipated that the helicopter would fly.

At the beginning of each reel of 14-track tape, the In the foreground of each photograph was a stator rod1000-Hz electrostatic actuator built into the 4921 marked with unifomil divisions. Wiien the helicopter

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iipassed over the appropriate spot, an operator triggered ground of each photograph allowed calculation ofone of' the cameras. A wire bus system triggered the altitude and lateral variation over the center of theother camera, and at the same time momentarily it, landing lane because the camera angle, distance to theterrupted the wind direction signal, as described in stator rod, and distance between graduations on theChapter 2. Each photograph carried information about stator rod were known. Corrections were made for aber-latitude and side-to-side variation. The time at which rations in the lens.the photographs were- shot was noted on the analogrecoidlrg. Negatives of each helicopter were projected on the

screen of a microfiche reader; measurements wereIn addition, a written record was kept by the the- taken in relation to the stator rod, and data were en-

odolite operator. Since the theodolite was fixed in place coded into the minicomputer for further calculation and

for each run, the operator could record the relative analysis. Given tb' information supplied by the two

altitude of the helicopter in the f.eld of view when the pictures, algorithms were written that located the

cameras were fired (and u Sonalert near the theodolite helicopter in three dimensions a, the tine both camerassounded). The theodolite was onl1 used to check were fired. The slant distance to each of the six micro-results from the cameras. phones in the array was calculated based on the position

of the helicopter in space and its forward speed.

Reduction of Dynamic Operation DataThe problem of different types of noise being pres-A Noa 100 iniompter amped he pecrum ent is inherent in any analysis procedure. However,

analyzer every 0.5 sec, summed the spectra into one-third octaves, and stored the co:,tents on disks. Since noise from different sources only becomes significant

each microphone signal was split while recording (one when it approaches the signal level. In this study, threehigh-gain and one low-gain channel), four passes were methods were used to determine the combined noiseperformed for each of the six microphones. (The level.spectrum analyzer requires a high. and low-frequency For the first reading-ambient noise-a recordingpass to properly constitute one-third octave bands overthe total range.) was made immediately after the helicopter left the area

following a set of passes. This reading reflected ambientsounds (such as wind, vehicles, birds, and other en-The procedure for the analysis system was as follows. vironiental sounds) that occurred during the tests.

When a helicopter was first detected, the tape and anal-ysis equipment were started. The first two passes were Electrical noise-the noise of the system that ismade i'n the high-gain channel for high and low fre- constant at different gain settings-was measured by

quencies. Some overloading of the spectrum analyzer attaci ing a dummy microphone to the input amplifierwas expected, and these portions were flagged by the at one of the stations and measuring the resultant levelminicomputer. For record-keeping purposes, the mini- on playback from tape.computer was used interactively; that is, informationwas requested from the operator before and after each The third noise reading-tape noise-was taken bypass. shorting the input to one channel and recording. On

playback, the level was measured.After the helicopter being analyzed was no longer

detectable, analysis stopped, the tape was rewound, These three readings were summed to calculate aand gain to the analyzer was lowered in preparation for composite noise level (CNL) by one-third octaves fora second set of passes. For these two low-gain passes, each gain setting used. The correct CNL was comparedthe analysis was started at the sawne time on tape by to the resultant one-third octave spectra for each 0.5using the time code channel to insure synchronization sec, and those 0.5-sec intervals were flagged if theirbetween the passes. The two sets of passes were meshed levels came within 3 dB of the CNL value. For all noiseby incorporating data from the second low-gain pass readings taken, gain settings throughout the system werewhenever the high-gain pass was overloaded. The results held the same as they were when the helicopter dLtawere fitted together to form the ,,Ji spectrum per 0.5 were recorded.sec for each microphone.

Data AnalysisReduction of data from the two cameras was hart- In addition to the reduction of dynamic operation

died differently. The graduated stator rod in the fore- data into one-third octave spectra for each 0.5 sec of

12

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recording, the SEL of each flyover was directly mea- eliminate the tone corrections. Additionally, it was

sured in the field using the CERL-developed True Inte- found that the concept of tone correction did not applygrating Noise Monitor and SEL Meter. The 0.5-sec to helicopters since the primary noise source over mostspectra and the overall fiel l-measured SEL were corn- of a flyby Is the rotor rather than. the engines.bined to produce A-weighted SEL versus distancerelations. Analysis of the hover data was quite simple. It should

be recalled that a 30-sec recording was made at 45-These relations were developed in four steps. First, degree increments around the hovering helicopter at a

the A-weighted SEL for the microphone flyover was distance of 400 ft from the center of the aircraft. Anal-entered. Essentially, this calculation involved forming ysis consisted of direct measurement of the equivalentthe integrai of the A-weighted pressure squared received A-weighted levels (Leq) for each recording. This Lqby the microphone. The CERL monitor performed this measurement was performed using the CERL Trueoperation automatically. Second, the 0.5-sec time Integrating Noise Monitor and SEL Meter (whichinterval having the maximum A-weighted value was de- employs a true integrating detector).termined, and the entire one-third octave spectrum forthat 0.5-sec interval was recorded. Third, from the posi-tional information on the photographs, the closest A4v RESULTS AND DISCUS-SIONapproach of aircraft to microphone for each individualflyover recording at each microphone was determinedand synchronized to the magnetic tape recording. This chapter explains the results of the operationalFinally, the maximum spectrum and distance of closest measurements performed at Fort Campbell on the UH-approach were used to convert the raw field-measured 60A, CH-47C, and UH-IH. SEL versus distance dataSEL (A-weighted) to an equivalent SEL for a day with are discussed, variations in SEL with aircraft speed area standard temperature of 59*F and relative humidity examined, and Fort Campbell data are compared withof 70 percent. the earlier results at Fort Rucker.

During this final step, A-weighted SEL versus dis- In analyzing the data, it was found that for dynamictance relations were established. The data used were operations microphone 5 consistently measured higherthe SEL at the microphone corrected to the standard than the other five primary microphones. This system-day conditions, the distance of closest approach from atic bias was about 5 dB or more. After intensiveaircraft to microphone, and the maximum one-third investigation, equipment malfunction or data analysisoctave spectra during the 0.5 sec having the maximum errors were eliminated as possible sources for the sys-A-weighted reading. Distance causes three factors to tematic variation.vary: air absorption (the one-third octave spectrum wasused to determine the effect of air absorption), the 1/ Site-specific terrain features offered a potentialr2 amplitude change of a point acoustical source, and explanation for the higher measurements at this posi-the apparent durational chaiage of a source moving in a tion. Microphone 5 was placed near the bottom of astraight line at constant speed. Appendix A of CERL wash (drainage depression) and thus may have experi-Technical Report N-38 contains a detailed description enced effects of sound focusing. In other words, micro-of this analysis procedure, which is structured similarly phone 5 may have been near the center of a groundto the Air Force procedure that was written in part to surface having a somewhat parabolic shape. If so, whendescribe the reduction of fixed-wing aircraft data.6 The a helicopter flew over, the ground surface would haveprimary difference between the Air Force and Army acted as a reflector focusing the helicopter sound neardata reductions is that the Air Force used tone correc- the microphone.tions and effective perceived noise level (EPNdB) aswell as A-weighted levels. The Joint Services (in con- However, the hover data, which include microphonejunction with DOD) subsequently agreed to eliminate 5, do not show the microphone to be any louder. ThisEPNdB and replace it with A-weighted levels, and to may have resulted from the height of the aircraft. If

f- the terrain did reflect noise, the source had to be high6 D. E. Bishop and W. J. Galloway, Community Noise Ex. enough to radiate into the reflector, which should have|; focused less on landings than on level flyovers. Exam-

posure Resulting From Aircraft Operations: Acquisition andAnalysis of Aircraft Noise and Performance Data, Report ination of the data reveals exactly this trend. Micro-AMRL-TR-73-107 (Bolt, Beranek, and Newman, 1975). phone 5 was high by 5 dB or more on level flyovers

13

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(when the aircraft was 300 to 1000 ft AGL), and by the data for microphones 2, 3, and 6, and a multiplierabout 3 dB on landings (when it was perhaps 50 to of I to the data for microphones I and 4.100 ft AGL). On hovers, microphone 5 was not higherthan the others. Sound Expoure Level Versus Distance

Figure 8 illustrates the developed SEL versus distanceThe data show that the helicopter is a very direc- for level flyovers at a speO of 100 knots (300 ft AGL)

tional source which can be loosely thought of as a for the UH-60A. Figure 8 also contains the SEL versusdipole with respect to sideline microphi, nes. The spac- distance curve developed for the UH-60A landings. (Foring of the dipole appears to be approximately the rotor the heavily loaded "landing,' the UH-60A actuallydiameter. Figures 6 and 7 illustrate the dire..tivity efTects brought the sting-loaded w iter buffalo in to the lan'ingof an ideal dipole for level flyovers at 300 ft AGL and point and hovered with the buffalo resting on 1e41000 ft AGL. The reader must note that Figures 6 and ground.) As with the 1974 Fort Rucker data, the heav-7 apply only when the aircraft is at the point of closest ily loaded aircraft is about 2 dB louder than the lightlyapproach to the microphone. The radiation directivity loaded aircraft, and the landing creates substantiallypattern of the helicopter in three dimensions can be more noise than a level flyov'er.

more nearly thought of as a portion of a donut (radia-

tion is also reduced from the trailing portion of the Figure 9 illustrates the SEL versus distance datadonut). developed for the CH-47C for level flyovers at a speed

of 100 knots. Two curves are for data gathered at 300Because of this directivity, a helicopter passing ft and 1000 ft AGL; the third is for data on CH-47C 4

directly overhead sounds the loudest when it forms an landing noise, which is substantially greater than forangle of perhaps 45 degrees between the observer and level flyover.the helicopter, and has not yet reached the observer. HBy the time the helicopter passes over and is leaving Hover Datothe area, it is already much quieter because of the direc- Table 4 lists the in. and out-of-ground effect hovertivity effects. Similar helicopter forward motion effects data (L.) taken at the eight measurement positions forare observed at the sideline microphones, but these are the various aircraft Raw data are in Appendix B.also very sensitive to helicopter altitude, as is shown inFigures 6 and 7. CERL Technical Report N-38 included generalized

hover contour, and a table of parameters to be usedThe data indicate that the complicated partial donut for individ--al aircraft. The data gathered at Fort Camp-

directivity pattern of the helicopter produces the follow- bell have been combined with the original data froming effects. The microphones directly underneath the Fort Rucker to form a revised set of generalized boveraircraft (microphones I and 4) consistently measure contours and individual aircraft parameters. Table 5lower levels than the sideline microphones. At 300 ft lists the amounts by which these genernlizaid hover con-AGL, the 200-ft sideline microphones measure higher tours depart from a purely omnidirectional source.levels than do the 400-ft sideline microphones. However, Table 6 contains the energy average hover emissionbecause of the directiviiy pattern (Figure 7) when the value produced by each aircraft, if treated as an omni-aircraft is at 1000 ft AGL, the 400-ft sideline micro- directional source. Together, these tables yield a gener-phones measure as great or greater le-els than do the alized hover emissions pattern scaled to each aircraft.200-ft microphones underneath the aircraft. To form these composites, the 400-ft data for Fort

Campbell were converted to 200 ft for the UH-60ATo develop average sound exposure level versus dis- and UH-IH, and to 300 ft for the CH-47C using a

tance or speed relations, the data for microphone 5 were factor of 7 dB attenuation for doubling of distance.

eliminated because they were consistently high. In addi- (The discrepancy between the measured UH-IH datation, the data from the other five microphones were at Forts Campbell and Rucker is discussed on p. 15.)not simply averaged. More complicated calculationswere done because microphones 1 and 4 could system- Variation of Sound Exposure Level With Speedatically bias the data by 0.1 or 0.2 dB. Since these Figure 10 illustrates the measured variation of SELmicrophones always measured lower than the sideline with speed for the CH-47C at a slant distance of 500microphones because of the directivity of the source, ft. The data are shown separately for the 300-ft andthe data were combined by applying a 4/3 multiplier to l000-ft-AGL flyovers. Figure I I presents the same type

14

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of data for the UH-IH. Figure 12 illustrates the varia- than at Fort Rucker. However, the Leq values for thetion of sound exposure level with speed for the UH- out-of-ground effect hover are similar.60A-again at a slant distance of 500 ft. In this case,the data are presented for heavily and lightly loaded The UH-IH aircraft measured at Forts Rucker andaircraft rather than for 300-ft. and 1000-ft.AGL Campbell are essentially the same. There have been noflyovers. The data in Figures 10 through I1A are largely modifications to blades, transmissions, or engines. The i

independent of aircraft altitude, slant distance, or load. only known change is the installation of dynamic bladeThus, composite curves can be constructed. Figure 13 balancing hardware during 1974. For level flyovers, aillustrates the composite variation of SEL with distance dynamically balanced IIH-!11 arcraft !xhibits bladefor the three aircraft studied. Figure 13 is a generalized slap in the speed range of 65 to 80 knuts. Withoutcurve, normalized to 0 dB at a speed of 100 knots. dynamic balancing, this range may b'. slightly wider

because the region of tip/wake vortex interaction in-Direct measurement of SEL versus aircraft speed creases. Thus, the 80-knot data from Fort Rucker

is one way to determine the speed relation. Another could well be 3 to 4 dB louder than the same measure-approach is to measure the variation of the %-sec ments at Fort Campbell. A similar effect may occurmaximum Leq with speed. The variation should be for landings.

equal to that of the %-sec maximum minus 10 log (air-craft speed). Figures 14, 15, and 16 present data for Why are the out-of-ground effect data similar whilethe %-sec maximum Leq of the aircraft operations and Fort Rucker's in-ground effect data are higher thanslant distances shown in Figures 10, 11, and 12. Again, Fort Campbell's? Here, blade/vortex interaction is notthe data and curves are largely independent of aircraft a factor. However, the answer may lie in the measure-height or I )ad. Figure 17 illustrates the composite ment surface. The hover area used at Fort Rucker wascurves for the three aircraft; these curves were developed the installation's helicopter parking, and hence wasusing maximum Leq plus the theoretical variation of almost entirely paved; the area at Fort Campbell wasflyover duration with speed. grass. Theoretical computer analysis' shows the hard

surface increases measured in-ground effect readings (atTo compare the variation with speed of SEL and 200 ft) by about 4 dB, but only increases out-of-grourd

maximum Wsec Leq, the quantity 10 log (velocity/ effect readings by about l-4 dB. Thus, the measure-100) was added to the curves of Figures 12, 14, and 15 ment surface may contribute to the differences in hoverto form Figures 18, 19, 20, and 21. The data in Figure levels.21 were then compared with those in Figure 17 by plot-ting the difference (Figure 22). Table 7 lists the data in Other reasons for the difference in levels might in-Figures 17, 21, and 22. The differences are small, show- elude changes in flight procedures, environmental fac-ing that the variation of SEL with speed can be approx- tors affecting the measurement, nr errors in measure-imated by the variation of Laq with speed minus 10 ment. At both installations, Army pilots flew the same [Ilog (velocity) plus a constant. The tables in Appendix type of aircraft 300 ft AGL at a speed of 80 knots, main-C list the data from Figures 8 through 22. taining constant altitude. In both cases, the pilots per-

formed in-ground and out-of-ground effect hovers. InComparison of Fort Campbell and Fort Rucker both cases, measurements were made during warmResults for the UH-1H Aircraft weather, and the flyovers were performed in a grass-

Figure 23 presents the SEL versus distance carve covered area with some trees nearby. (However, atdeveloped for level flyovers (lightly loaded) at 80 knots Fort Campbell, the forests surrounding the clear areaand 300 ft AGL. The values at Fort Campbell are 3 to were much thicker than at Fort Rucker.) In both cases,4 dB lower than those at Fort Rucker. Figure 24 pro- independently operated and calibrated measurementvides a similar comparison for landings. Again the values systems were used. The two systems at Fort Rockerare 3 to 4 dB lower at Fort Campbell than at Fort produced internally consistent measurements, as didRucker. Table 8 presents the maximum %-sec Leq the two at Fort Campbell. While environmental factorsfor several microphones at Forts Rucker and Campbell. may have affected the total integrated exposure level,These differ by 4 dB or more. The table also compares _ _

the 200-ft corrected average (energy) hover Leq for in- 7'This analysis is based on R. J. Donato, "Propagation of aground and out-of-ground effects at the two forts. Spherical Wave Near a Plane Boundary With a Complex Impe-Table 8 also shows that the Laq values for the In-ground dance," Journal of the Acoustical Society of America, Voleffect hover are about 3 to 4 dB lower at Fort Campbell 60, No. 1 (July 1976), pp 34-39.

15 A

-j ý=

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it seems unlikely that they could have affected the max. variation of SEL with speed data will be incorporatedimum Wsec Lq, or the hover data measured at dis- in CERL's INCS systenm and, thus, will be availabletances of 200 to 400 ft. Also, the two independent when (1) aircraft speeds differ slgnlfli•antly from themeasurement systems used at each installation tend to typical speeds, (2) the situation warrants this precision,,rule out lhe possibility of measlrernent error. Thus, and (3) the aircraft operational data are accurate enoughthe only known plausible explanations for the large to reliably indicate aircraft position, altitude, andvariations recorded are the dynamic blade-balancing speed as a function of time..procedure and the "hard" hover surface area at FortRucker. The measurements at Fort Rucker showed great j,

Internal consistency. Four aircraft of the same typemeasured during the same testing period at the samesite and with the same equipment yielded similar re-

5 CONCLUSIONS AND suits. The measurements at Fort Campbell also showedRECOMMENDATIONS great internal consistency--except for microphone 5.

However, the bias of microphone 5, and the discrep-ancy between the data gathered at Forts Campbell and

SEL versus distance curves for the UH-60A and Rucker, indicate problems that will have to be solvedCH-47C were developed. For the UH-60A, the data before the gathering of helicopter noise emissions data .Ishow that a heavily loaded aircraft is %bout 2 dB louder can be standardized. Better methods need to be devel-than a lightly loaded one. Landing noise with the UH- oped to control site terrain and environmental factors, J60A and CH-47C is substantially greater than for and to account for the effects of variations in main-level flyover. tenance procedures and pilot techniques. To begin

understanding such discrepancies, it will be useful toThe variation of SEL with speed is rather modest, replicate the measurements from Forts Campbell and

except for aircraft at very low or very high speeds. The Rucker with the UH-lH aircraft.

tTable I Table 2

Dynmoic Operations Performed at Fort Rucker Helicopter Types and Loading ConditionsMeasured at Fort Rucker

leginnins Giound Track (GT)Oetron (da ) Helicopter Loading

Modal Condition1. Level 3602. Level O80 OH-58 Normal3. NOE* 360 AH-IG Normal4. NOE !80 UH-IM Normal5. Ascent 360 UH-1 Ii Maximum ur Nojrmal6. Descent 180 UHt-1I0 Maximum or Normal7. Desmant 360 CH-47B Maximum or Normal8. AiaOlt 180 CH-54 Maximum or Normal9. Left turn 315 TH-55 Normal

10. Right turn 4511. Riht turn 22512. Left turn 13513. Landing 18014. Takeoff 180

*Nap of the earth (NOE) operations ere not used in theanalysis because of the inability to predict abrraft position.

16

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Ai

Table 3Dynamic Operatiom P•rformed at Fort Campbell

by CH-47C and UH- I H

Opemtkm* Altitude (ft) Speed (knots) GT (degrees)

I LF 300 80 2802 LF 300 80 1003 LF 300 40 2804 LF 300 40 tOo5 LF 300 100 2806 LF 300 100 1007 LF 300 60 2808 LF 300 60 1009 LF 300 120 280

t 0 LF 300 120 10011 LF 300 80 28012 LF 300 80 10013 LF 300 100 28014 LF 300 100 10015 Landing - 28016 IGE Hovey

17 OGE Hover18 Takeoff - 28019 LF 1000 80 10020 LF 1000 80 28021 LF 1000 100 10022 LF 1000 100 28023 "F 1000 120 10024 LF 1000 120 28025 LF 1000 60 10026 L.' 1000 60 28027 LF 1000 100 10028 LI 1000 100 28029 LI- 1000 80 10030 LF 1000 80 280

*LF' level flyover; IGE , in-1ound effect; OGE , out-of-pround effect.

Table 4Average (Energy) Meamufr Data (dB)

Position (dogem)*

Aircraft Hover 0 45 90 135 180 225 270 315 Averap

UH-IH IGE 74.1 80.6 75.8 75.1 75.5 75.3 77.9 74.2 76.7(Unloadnd)** OGE 78.8 81.5 84.4 86.0 85.0 85.5 80.5 78.7 83.4UH-60-A IGE 77.1 75.5 76.9 76.3 77.2 78.0 74.8 77.5 76.8(Unloaded)"* OGE 80.4 79.5 86.4 81.6 83.4 81.4 81.9 79.9 81.9

UH-60-A OGE 81.0 80.6 86.1 88.2 85.5 82.0 78.0 81.6 84.0(Loaded)**

CH-47C IGE 84.3 86.5 86.9 83.2 80.3 75.8 75.5 80.7 83.3(Unloaded)t OGE 84.7 88.1 88.3 87.3 81.9 81.6 82.2 84.19 85.6

*Front of aircraft Is 0o.**From Table B5.t From Table B8.

17

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Table S Table 6Hover Directivity Versus Position (dB) Enery Ave'age A-Weihted Hover Sound Levels (d0)

( Is Front of Aircraft) (To Be Used With Table5)

- SIe Rotor Dual Roo Aircraft Surface Distance (test) IGE OGE(Ovewd Averwue, (OvwM Averqep,

Position Table 87) Tabl elO) AH-IG Hard 200 88.3 87.8O04-58 Hard 200 81.4 83.7

0 -2.7 +0.2 UHAB-I Hard 200 85.9 90.145 -1.6 +2.8 UMiAWH* Hard 200 P8.4 91 890 --0.6 +2.5 UH-Ile* Sort 400 76.7 83.4

135 +1.4 0 UH-IM Hard 200 86.2 89.9

180 +1.1 -2.1 UH--60A Soft 400 81.7 83.1225 +2.2 -3.0 CH-47A/B* Hard 300 9',2 91.8

270 -0.4 -3.3 CH-47COO Soft 400 83.3 85.6S•350 --2.4 -- 1.1 T14-55 Hard 200 84.8

*Dual load.S*"*Light load.

Table 7Difference, in Decibels, Between Composite Speed Variation Functions

(Lqg vs Speed as Compared to the Function SEL Plus 10 log [Yvl001 vs Speed)*

Figure 21 Composite,Figure 17 Composite, SEL + O log (v/100 knots) Difference,

Speed (knots) L"l vs Speed** na Spftdoe* Filn 22tCSed.o7) UH-IH UH-E6A CH.47C UH-IH U-60A CH-47C UH-IH U--OA

40 3.6 0.4 -4.3 3.7 -3.7 -4.7 0.0 4,1 0,460 2.2 --4.0 -- 2.6 2.8 -4.0 •-2.8 --0.6 0.0 0.2

80 0.9 -- 2.3 --1.6 0.7 -- 2.3 -- 1.5 0.2 0.0 -0.1100 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

120 0.2 4.9 2.1 1.3 6.1 2.3 -1.1 -1.2 -0.2140 1.8 3.7 3.9 4.0 -2.1 -0.3

"Data for 300-ft and 1000-ft AGL are combined."From Table C3.

"*'*From Table C4.

t From Table C5.

iL

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Table 8

Compalron of Fort Campbell ad Fort Rucker UH-IH Data

Purt Rucker Fort Campbul Diffeennce

1U1f hover--200 ft 88.4 85.7 +2.7(W'ort Campbell corrected +7 dBfor distance and +2 dB forlight load)

OGE hover- 200 ft 91.8 91.4 +0.4(Port Campbell corrected +6 dBfoe distance and + 2 dE for

light load)

Max. 3'*.eC LeqMikes W&4 91.7 85.2 +6.5Mike 2&5 8&2 84.0 +4.2Mike 3 84.9 80.7 +4.2

*The 6 dB difforence (high reading at Fort Rucker) may be caused by the very loud noise duringthe few seconds Just before the aircraft went overhead. This may result from retreati blade/vortexinteraction. Since it wae a short-lived effect, it does not influence the SEL greaty,

kL

19

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tATIA MILES

Figur I. Flight Path for level flyovers.

GROUND TRACK a280 DEGREES

2000

-l~ 2 . ,.tp th fr ,. --g

20A

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i b CAME[RA I

_ _ _ _ . - - - - ..•_ _

IN TiUK[T VAN

xI

LAMMIN POINT./

;'3

THEOD)OLITE F

Filmg 3. Microphone/camera layout at Fort Campbell.

kill M 12 4xIl INSTRUMEP(T VAN

N, M13I

21"

I \ 'j

M N 4 K%.%IM.. Th0..IEes

I* - , -i, IS

L.i..,....OER OI.

Page 23: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

II ii

!: I

. ii

xM 3 INSTRUMENT20O' M 21cO0' VAN . •."'

XM2

-l low"' M4

XMSXms

FIpw S. SideWe r&-cphones at Fort Campbell.

22

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RADIUS

M5 M6m 1 2 M3GROUNDM4

ALTITUDE IS 300' AFL -MI AND M4 ARE IN A SHADOW,Ws, M3, M5 AND MG ARE AT EQUAL POINTS ON THEPATTERN.

Figure 6. Directivity effects-- 300 ft AGL.

M5 M6 M I M2 M3 GONM4 GON

ALTITUDE IS I000' AFL -MI AND M4 ARE IN A SHADOW.M3 AND M5 ARE ~qLOJE TO THE PATTERN THANARE M2 AND MS.

Fkure7. Directivity effects- 1000 ft AGL.

23

m A am

Page 25: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

uoý-, %NO~A

4X

ILA

Page 26: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

tic

tio

Illo

6 -0'0'

QOOFT W

40.-

10 40 m0 a0 to 60o 10 0 Ito 130 140 160 too 10 Igo

SPEED (KNOTS)

Figure 10. CH-471C-mrtialion of SEL with speed at 500 ft (300- and I1000-ft flyovers),

Ito -

Ito-

70-

so- 0300F

14 I I I I I ,/ . I I ._ I- I i i _

310 40 60 00 ?0 so 0 ODO tic O It0 140 0 N 00 I NO DO

SPEED (KNOTS)

Figu•e 11. UH-1.H-variation of SEL with speed at 500 ft (300- and 1000-ft flyovers).

25

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iIto

60-

-Jw

Go-S- • ULOAflED

SUNLOADED

40-

S o I I 1 I I I I I I I I0to 0 40 50 so 7O so 90 00 11o Ito 1,0 140 o 150too To ISO

SPEED (KNOTS)

Figure 12. UH-60A-variation of SEL with speed at 500 ft (loaded and unloaded flyovers).|0 U U U ' '' U U U U I ' U a

I0

4-

-4

-- ,- S CH4-47C

A UH-1Ha UH-6OA

-h i I _ I I I ,,I I I I i I I , I--30 10 40 50 P0 70 60 SO 800 110 lEo ,10 ,40 10 10 TO BoO

SPEED (KNOTS)

Figiu 13. Composite curves of variation of SEL with distance at 500 ft (normalized to 0 dB at 100 knots).

26

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lac• I I r 1 1 I II I I I I I I I

ISO

S9 0--

-Ilow

(0

410

so- 10 00 FT

A 3000FT

40

3J ,. . -. -. I . I I I. ! I I I . I I I I I _ I

3O s0 40 so eo TO s0 90 10D IO Ito i30 140 150 Ito ?10 soo

SPEED (KNOTS)

Figue 14. CH-47C-variation of Liq with speed at 500 ft (300- and 1000-ft flyovers). A

lie , I ' I I I I I I= I I ' I I '

i~ii

120I

Ito-

100O F

70

so 0 O o rO so s1o I lO 110 0 iso 140 1so o0 ir0 iso

SPEED {KNOTS)Fliure IS. UH-lH-I-variation of L.4 with speed at 500 ft (300- and 1000-ft flyovers).

too-'

"go-2 J. .1 mo-"

w- 1'

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Io

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44 o i

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a LOADED

40

i I i i I I I I ... I I , l i I I

S30 40 80 s0 To so so 100 It0 Ito 1o0 140 150 160 So too

SPEED (KNOTS)

Figure 16. UH-60A-variation of Le with speed at 500 ft (loaded and unloaded flyovers).

|O I I I s s 4 n

to

4-

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-11- 8 UH- WA

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SPEED (KNOTS)

Figme 17. Composite curves of variation of Lq with speed at 500 ft (normalized to 0 dB at 100 knots).

28

Page 30: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

ISO

too-

100

,so

gJ

a 300FTSO £ IQOO FT

40-

I0 IO 40 1 i I IO I0 I: I0 O 11 4 io lO 1'0 I

SPEED (KNOTS)

Figure 18. CH-47C-variation of SEL + 10 log (v/100 knots) with speed at 500 ft (300- and 1000-ft flyovers).

ItoIi

010T

to --

................... .............

so-

70

SOs 300 FTa 1000 F T

40-

30 40 50 s0 T0O W 0 m10 0 Ito It 110 140 150 ISO 170 ISOI SPEED (KNOTS)Figure 19. UH-1H-variation of SEL + 10 log (v/100 knots) with speed zt 500 ft (300- and 1000-ft flyovers).

29

Page 31: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

ISO

too-Jso

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so

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SPEED (KNOTS)MO 10 r IgFigue 2 .U~-60 ...v 1~5 j00 f S L +10 log (V/I100 knots) With Speed at 500 ft (loaded and unloaded flyuvers).

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40 4 0 70 s o 00It o 13 is o Igo 4~Flove 2 1. ~ SPEED (KNOYrS)110 70 wFlut2.Composite curves of VariatiOn Of SEL + 10 log (v/lao knots) With speed at 500) ft.

30

Page 32: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

41

0-

-4

0 CH- 47CA UH-IH-S- a UUH-60A

-S

30 40 50 so 70 S0 90 100 110 IUo I3O 140 i1O IS 170 wo

SPEED (KNOTS)

Figure 22. Difference of Le. versus speed and SEL + 10 log (v/100 knots) at 500 ft.

1340

130 L-1,.

I•

•K 0 300 FT (CAMPBELL)£ LEVEL (RUCKER)F

to ~~moo ooSLANT RANGE DISTANCE, FEET i

Figur 23. UB I H-variation of SEL with distntce at 80 knots (level flyovers).

310

J-..

Page 33: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

ItoU0-

so300 3FT LANDING ICAMPKUEL

101000 1114= IM000

SLANT RANGE DISTANCE, FEET

FigureM2. UH-IH--variation of SEL with distance at 80 knots (landings). I

METIMC CON~'VERSIONS

I ft = 0.3 mtIin. = 25.4 mmI Si = 4.5SLI knot = 30.85 rn/sec-F-32 ý

1.8

32

Page 34: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

APPENDIX A:PILOT'S LOG

This appendix contains typical pilot's log pages forlevel flyover, landings, hovers, and takeoffs-operations14, 15, 16, 17, and 18. (For a list of operations, seeTable 3 )

33

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Page 36: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

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Page 37: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

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Page 38: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

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Page 39: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

APPENDIX B:HOVER DATA

Table 51UI- I H Hoe Data (dB)

Set (d~eso) Type I 11 3 12 13 14 5 is 2 6 4

1 100 IGE 73.2 69.6 302 71.4 70.2 - 73.9 71.5 85.6 75.4 62.61 100 OGE 17.3 37.4 81.3 77.0 76.2 - 86.4 37.1 91.6 38.7 71.12 so IGE 77.7 72.6 7S.9 76.1 30.6 77.1 77.3 77,0 79.3 30.9 71.72 SO OGE 31.9 79.S 79.9 30.4 31.3 30.5 34.5 30.1 33.9 32.3 75.0

Table B2UH-60A Hover Datar-Unloaded (dB)

Set (dopeeOTy"e I 11 3 12 13 14 5 15 2 6 4

3 95 IGE 78. - 70.7 75.0 77.4 747 77.8 74.3 81.2 81.1 70.73 95 OGE 32.9 - 79.4 80.3 32.5 77.8 86.8 32.7 83.1 88.3 75.44 230 IGE 76.7 76.2 75.7 77.6 76.0 78.0 76.3 79.1 81.1 80.9 72.24 230 OGE 76.3 80.7 78.3 30.1 83.8 81.4 83.5 79.4 81.6 81.2 74.0

Table B3UH.-60A Hover Data-Loaded (dB)

S" (depme) Type 1 11 3 12 13 14 S 15 2 6 4

3 95 IGE 84.9 -. - 80.7 80.8 81.3 8U.9 88.7 - 90.3 75.73 95 OGE 88.3 - - 81.9 81.2 79.0 87.5 92.1 - 93.0 74.4 I4 230 IGE 83.5 81.6 78.4 82.6 81.2 80.2 33.2 79.1 86.0 81.5 76.84 230 OGE 33.2 82.3 77.5 80.8 30.3 81.4 85.5 82.4 85.8 85.3 75.9

Table B401-47C Hover Data (0l)

Set (dopse*Type I 11 3 12 13 14 S 1s 2 6 4

5 100 JOE 83.0 74.3 76.0 81.0 84.0 88.2 86.7 83.4 81.6 77.1 84.35 100 OGE 81.7 77.6 82.9 84.8 85.8 87.8 89.2 88.6 83.6 78.8 92.16 100 IGE 72.1 76.9 74.3 80.3 34.6 83.5 37.0 78.7 78.8 79.3 75.16 100 OGE 32.0 33.7 31.3 84.9 83.3 88. 87.1 85.4 85.4 87.4 73.0

38

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Table BSEnergy Averages of Fort Campbell Single-Rotor Aircraft by Degees

With Respect to the Aircraft (00 Is Front of Aircrft) Table B|I Though B3 Data

Averae 180 22S 270 315 0 45 90 13s

UN-IHIGE 76.1 7S.5 75.3 77.9 74.2 74.1 30.6 75.8 75.1OGY1 83A4 85.0 85.5 80.5 78.7 78.8 81.5 84.4 86.0UH-60AIGE 76,8 77.2 78&0 74.8 77.5 77.1 77.5 76.9 76.3OGE 81.9 83.4 81A4 81.9 79,9 80.4 79.5 84.4 81.6Loaded 84.0 85.5 82.0 78.0 81.6 81.0 80.6 86.1 88.2

Table 86

Difference From Average; Table BS Data

Aveaqe 180 225 270 315 0 45 90 13S 4UH-IHIGE 0.0 -1.2 -1.4 +1.2 -2.5 -2.6 +3.9 --0.9 --1.GOGE 0.0 +1.6 +2.1 -2.9 -4.1 -4.6 -1,9 +1.0 +2.6UH-60AIGE 0.0 +0.4 +1.2 -2.0 +0M7 +0.3 -1.3 +0.1 -0.5OGE 0.0 +1.S -0.5 0.0 -2.0 -1.5 -2.4 +2.5 -0.3Loaded 0.0 +1.5 -2.0 -f.0 -2.4 -3.0 -3.4 +2.1 +4.2

Table 87Weighted Average of Single-Rotor Aircraft Directivity Change

Number ofAircraft Aerag 180 225 270 315 0 45 90 135

Fort Racker Dut-* 63 0.0 +0.9 +0.2 - 1.3 -1.8 -2,0 ---0.1 +1.1 +1.5Vort ( impbell Mta"t;* 12 0.0 +1.1 +2.S -02 -25 28 1.9 1.0 +1.4

Overall Avoraw 75 0.0 +1,3 -2.2 -0.4 - 2.4 2,7 -1.6 -0.6 1,4*Frobm p 39 of CERL Technical Report N-38.

"•From Table B6.

Table B8Energy Averges of Fort Campbell Dual-Rotor Aircraft by Degrees

With Respect to the Aircraft (0W is Front of Airecrft), Table 34 Data

Avstage 180 225 270 315 0 45 90 135

CCH-47C IGE 83.3 80.3 75.8 75.S 80.7 84.3 86.5 86.9 83,2- CH-47C OGE 85.6 81.9 81.6 82.2 84.9 84.7 88.1 18.3 87.3

Table B9

Difference From Average; Table B8 Data

Averap 180 225 270 31S 0 45 90 135

CH--47C IGE 0.0 -3.0 -7.5 -7.8 --2.6 +1.0 +3.2 +3.6 -- 1('H-47C OGE 0.0 -3.7 --4.0 -3.4 -0.7 -0.9 +23S +2.7 +1.7

39

f!4

-j"j

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Table 310Weighted Average of Dtial-Rotor Aircraft DbectlitY ChMne

Number ofAircraft Avenge ISO 225 270 315 0 45 90 135

Fort Rucker Data*.....0.-3.3 -5.4 -5.1.-1.5 +0.2 . ...... +..2.+0.9

Fort CampbelliData"* 4 0.0 -1.1 -1.4 -2.0 -0.8 +0.1 +2.6 +1.6 -1.1

Overall Average 8 0.0 -2.1 -3.0 -3.3 -1.1 +0.2 +2.8 +2.5 0.0

*From CERL Technical Report N-38.**From Table B9.

40

Weisted ver8, o Dul-Roor ircrft irec~viy Chrt8

Number of .

Aircraf A-rq ..8 . .-2 . 27 1 45V

Page 42: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

APPENDIX C:DATA FOR FIGURES 8 THROUGH 22

Table C1Variation of SEL With Distance at 100 Knots (Figures 8 and 9)

I00 200 300 Soo IK 2K 3K 5K 10K 20K 30K 50K A

UH-60AUnloaded 95.9 92.8 90.9 88.4 84.9 80.8 78.1 74.2 67.7 59.6 53.8 45.6Loaded 94.5 91.5 89.5 87.1 83.5 79.6 76.9 73.1 66.8 58.8 53.2 45.2Unloaded Landing 100.3 97.2 95.3 92.8 89.1 84.9 82.1 77.9 71.0 62.3 56.5 48.4Loaded Landing 106.2 103.0 101.1 98.6 94.8 90.4 87.4 82.9 75.2 65.5 59.1 50.9

CH-47C300 ft 94.9 91.8 90.0 87.6 84.2 80.4 78.0 74.6 69.4 63.0 58.5 51.81000 ft 93.9 90.8 89.0 86.6 83.1 79.4 76.9 73.6 68.5 62.3 58.0 51.3300 ft Landing 106.9 103.8 102.0 99.6 96.2 92.4 89.9 86.3 80.5 73.2 68.1 60.8

Table C2Variation of SEL With Speed at 500 ft (Figures 10 Through 13)

40 60 80 100 120 140

CH-47C300 ft. 94.8 92.1 89.8 87.6 88.1 90.91000 ft. 87.5 86.6 86.8 87.4

IiTH-IH300 ft. 91.5 88.9 89.6 90.9 96.31000 ft. 87.4 87.5 88.8 Q4.1

UH-60AUnloaded 87.1 87.2 87.7 88.4 89.3 90.3Loaded 87.1 87.1 86.8 87.1

Composite (Normalizedto 100 Knots)CH-47C 7.7 5.0 9.0 0.4 2.4UH-1H 1.5 -1.8 -1.3 0.0 5.3UH-60A -0.7 -0.6 -0.5 0.0 1.5 2.!.

Table C3Variation of Le. With Speed at S00 ft (Figures 14 Through 17)

40 60 80 100 120 140

CH-47C300 ft. 84.1 82.7 82.1 79.4 79.6 84.21000 ft. 80.6 81.3 81.6 78.9

UH-1IH300 ft. 83.1 78.7 80.3 83.1 87.61000 ft. 78.7 80.4 82.2 87.5

UH-60AUnloa&ded 76.5 78.7 79.6 81.3 83.0 84.6Loa~ied 76.6 77.9 78.9 80.4

Composite (Normalizedto 100 Knots)CH-47C 3.6 2.2 0.9 0.0 0.2 1.8UH-1H 0.4 -4.0 -2.3 0.0 4.9"UH-60A -4.3 --2.6 -1.6 0.0 2.1 3.7

41

I _ _ _ _A--

Page 43: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

i•iTable C4

Variation of SEL 4. 10 log (v/i00 knots) With Speed at 500 ft (Figures 18 Through 21)

40 60 80 100 120 140

CH-47C

300 ft. 90.8 89.9 88.8 87.6 88.9 92.41000 ft. 86.5 86.6 87.6 88.9

UH-IH300 ft. 86.3 86.7 88.6 90.9 97.11000 ft. 85.2 86.5 88.8 94.9

UH-60AUnloaded 83.1 85.0 86.7 88.4 90.1 91.8Loaded 83.1 84.9 85.8 87.1

Composite (Nonnalizedto 100 Knots)CH-47C 3.7 2.8 0.7 0.0 1.3 3.9UII-IH -3.7 -4.0 -2.3 0.0 6.1UH-60A -4.7 -2.8 -1.5 0.0 2.3 4.0

Table CSDifference of Le. With Speed Versus SEL + 10 log (v/100 knots)

With Speed at 500 ft (Figure 22)

40 60 80 100 120 140 1

CH-47C -0.1 -0.6 0.2 0.0 -- l.1 -2.1UH-IH 4.1 0.0 0.0 0.0 -1.2UH-60A 0.4 0.2 -.0.1 0.0 -0.2 -0.3

424

I.

S f4

.242

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CERL DISTRIBUTION

Chief of Engineera Nth UIA, Kara oH4BrUM - Ch, inatl. DIv.ATTN: Tach Manitor ATTN S.EAFE (8) *201 ATTN% FaoilIties EngineerATIEN: & AEW-A8I-L (2) ATTIt SAFE-Y 96359 Arlington tVot1 teation (21 02`12ATTN: DAEN-CCP ATTN a SAFE-D WUSD4 Vint MiLL Foerm Station 2001ATT:t DAE--Cu ATth, SAFE-4M EROSATTN: GAIE- ATTN. SAF"-E 5371 NOATTNiE DAEM-CS-fl ATTI: LAFE-P 5535S ATTE: Facilities TiSineerATTN: DADE*- ATT:s EAFE-T t2`21 Caoeron Station 22314ATTNt DAE.-W Fort Lealey J. MoNair 30319Ai•i: DADIE-EP Rocky Mt. Aroenal, BRWM-IS O00DA Fort M4yer 2221ATThN DADE-P-4ATTN: DADE-RPE Ares Engineer, AUDC-Ares Office "MIICATriS DA•M-Efl Arnold Air Forte Station, Th 373s8 AlVNEt MISC-SA 20315ATi: DADE- -A ANtE: FaciLities EngineerATTN: DADE-RU Western Area Office, CE OakLand Army Sases 4•2ATTN: DAEN-iWC Venderbarg AFe, CA 53437 Bayonne NOT 07002ATTN? DADE-RON Sonny Point NOT 28451ATTN: DAEN 415th Engineer omaend 9030623ATTIS: DADE-ZC ATTNi: Facilities ýngftaor HARACOOM, ATTN: D"A-F 071!60ATTN: DAEE-ZCEATTNt DAEN-:CI USA Japan (USARJ) TARCDE, Fa•. Div. 48090ATTi: DAtEN-ZCH Ch, FE Div. AJEN-FE 96343

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A-,46

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FNA Teem Distribution

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US Army Engineer District AITN: ORDAR-BLT USA Logistics Management Center 23h01

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ATTN: Chief NAOEN-D TRADOC Ottawa, Ontario, Canada KIA %U2

Iunttngton 25721 Ft. Monroe, VA 23651FATN: Chief 0RHEO 109f Wil1mington 28401 Ft. Clayton, Canal Zone 34004 2

t ATTN: Chief. SAWEN-D ATTN- DFAE t

Savannah 31402 2-11z-82

ATTN, Chief, SASAS-L Ft. Detrick, NO 21701Mobi le 35628

SATTN: Chief, SAMEN-D Ft. Leavenworth, KS 66027

Louisville 40201 ATTN: ATZLCA-SAATTN: Chief, Engr Div

St. Paul 55101 Ft. McPherson, GA 30330 (2) I;ATTN: Chief, E0-D

Chicago 60604 Ft. Monroe, VA 23651 (6)

ATTN: Chaef, NCCPE-PESfrock Island 61201 Ft. Rucker, AL 36360 (2)

ATTN: Chief, Engr DivSt. Louis 63101 Aberdeen Proving Ground, MD 21005ATTN: Chief. ED-O ATTN: DRDAR-BLL

Omaha 58102 ATTN: STEAP-*T-EATrN: Chief. Engr Div

Now Orleans 70160 Human Engineering Lab. 21005 (2)ATTN: Chief, LMNED-OG

Little Rock 72203 USA-WES 39181ATTN: Chief, Engr Div

Tulsa 74102 Army Environmental Hygiene Agency 21005ATTN: Chief, Engr Div

Ft. Worth 76102 (2) Naval Air Station 92135ATTN: Chief, SWFED-O ATTN: Code 661

San Francisco 94105ATTN: Chief, Engr Div NAVFAC 22332 (2)

Sacramento 95814ATTN: Chief, SPKEO-D Naval Air Systems Command 20360

Far East 96301ATTN: Chief, Engr Div US Naval Oceanographic Office 39522

Seattle Q8124ATTN: Chief, EN-OB-ST Naval Surface Weapons Center 22485

Walla Walla 99362 ATTN: N-43ATTN: Chief, Engr Div

Alaska 99501 Naval Undersea Ceoiter, Code 401 92152 (2)

ATTN: Chief, NPASA-R ao)linq AFS, DC 20332

US Amy Engineer Division AF/LEEEUNew England 02154

ATTN: Chief, NEDEU-T Patrick AFB, FL 329?5North Atlantic 10007 ATTN: XRQ

ATTN: Chief, NADEN-TMiddle East (Rear) 22601 Tyndall AFB. FL 32403

ATTN: Chief. MEDED-T AFESC/TSTSouth Atlantic 30303

ATTN: Chief, SADEN-TS•. right-Patterson AFB, OH 454J3 (3)

Huntsville 35807ATTN: Chief, HNDEU-CS Building Research Advisory Board 20418

ATTN: Chief, HNOEO-SROhio River 45201 Transportation Research Board 20418

ATThk; Chief, Engr tiv

Missouri River 68101 Dept of Housing and Urban Development 20410ATTN. Chit", 14RDED-T

Suuthwe-atern 75202 Dept of Transportation Library 20590ATTNW. Chief, SWOED-T

South Pacif,.; 94111 Illinois EPA 62706 (2)ATTN: Chief, SPOED-TG

Pacific Octan 96858 Federal Aviation Administration 20591ATTN: Chief, Engr Div

North Pacific 97209 Federal Highway Administration 22201Region 15

•,1

Page 46: ARMY HELICOPTERS...20 UI-60A-'Varlatlon of SEL + 10 los (4l100 Kinots) With Speed at 500 ft 30 21 Composite Curves of Variation of SEL + 10 to& (vt100 Knots) With Speed at 500 ft 30

Schomer, Paul D.Operational noise data for UH-60A and CH-47C Army helicopters. - Champaign,

IL - Construction Engineering Research Laboratory ; Springfield. VA availablefrom NTIS, 1982.

42 p. (Technical report / Construction Engineering Research LaboratoryN-131)

1. Helicopters -- noise. I. Title. II. Series Technical report(Construction Engineering Research Laboratory (U.S.)) N-131.

73

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