£ LEVELUSAAEFA PROJECT NO. 77"25

PRELIMINARY AIRWORTHINESS EVALUATIONAH-1S HELICOPTER WITH OGEE

TIP SHAPE ROTOR BLADESFINAL REPORT

GARY L. BENDER LARRY HIGGINSPROJECT OFFICER MAJ, INF

US ARMYRALPH WORATSCHEK PROJECT PILOTPROJECT ENGINEER

JOHN S. TULLOCHDAVID OTTOMEYER CW4, USAPROJECT ENGINEER PROJECT PILOT

HENRY ARNAIZPROJECT ENGINEER

DTICMAY 1980 ELECTEV

SEP 2 I8

Approved for public release; distribution unlimited. A

UNITED STATES ARMY AVIATION ENGINEERING FLIGHT ACTIVITYEDWARDS AIR FORCE BASE, CALIFORNIA 93523

80 926025'C -

DISCLAIMER NOTICE

The findings of this report are not to be construed asmanofficiul Department ofthe Army position unian .o designaed by other amthoritsed documenit.

DISPOSITION INSTRUCTIONS

Destroy this report when it is no longer needed. Do not return it to the originator.

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Tie toe of trade names in this report does not constitute an official endorsementor approval of the use of1 the commercial hardware and software.

SECUnrIY CLASSIFICATION OF THIS PAGE (Man.. Da Knlared)

REPORT DOCMENTATION PAGE BEFORE COPEIGFORMt. REPORT NUMBER .GOVT ACCESSION NO. 3. RECIPIENT'S CATALOG NUMBER

USAAEFA Report No. 77-25 h- I AyP U 1 6I4.T~~It !QU_--.- -.. PERIOD COVERED

XRELIIN R IRWOTH S VALUATION LNLR2al LICO ER WTH 0 E PSHAPE

O) 'A ENDER _ALPHORATSCHE)HE~NRY NAIZ 102LR-A0GN~IPI9 c~I~c p.E AD ADR1S6. PRO6OXUELEMENT. PROJECT, TASK

AREA &WORK UNIT NUMBERS

US ARMY AVIATION ENGINEERING FLIGHT ACTIVITYEDWARDS AFB, CA 93523 ET9Y08O-E-G " l

II. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE

US ARMY AVIATION ENGINEERING FLIGH-T ACTIVITY MAY 1980EDWARDS AFB, CA 935231.NUBROPAE14. MONITORING AGENCY NAME-& A0ORESS(itd"ffenut ham Controlling Oflc) IS. SECURITY CLASS. (of this report)

IT UNCLASSIFIEDSC4HEDULE

1 DSTRIBUTION STATEMENT (of Chia Report)

Approved for public release; distribution unlimited.

17. DISTRIBUTION STATEMENT (of the abstract mitered h Block ". It difaIfereeho Report)

IS. SUPPLEMENTARY NOTES

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AH- I S Helicopter Level Flight Performance

K747 Rotor Blades OGEE Tip Shape Rotor Blades

20. ABSTVRACT (Centhoan revere. shle If neeseemy sd 14601y by Weeck uer

'The United States Army Aviation Engineering Flight Activity conducted a Preliminary Airworthiness* Evaluation of the AH- IS helicopter with OGEE tip-shape main rotor blades to determine if any* improvement in performance Or handling qualities resulted from replacing the K747 blades. Addi-

tionally, the acoustics signature of the OGEE blades were measured by the US Army Research andTechnology Laboratories (Aeromechanics Lab). Tests were conducted at Edwards Air Force Base(elevation 2302 feet) and Coyote Flats (elevation 9980 feet), California from 1 November 1979

* through 8 April 1980. Forty-five test flights were flown for a total of 36.6 productive hours (63.2total hours). Both hover and level flight performance were degraded by installation of OGEE tip-shape

WO , 3 m-nToW or I WOV *IlS OSLETIE

SECUhRVT CLASSIICATION OF THIS PAGE (Wen Dae t ntered)

IINCI Aq IFFlSECURIOTV CLASSIFVOCATION OF TH13 PAOC(b. DOOM$ lsm0

main rotor blades. Low-speed handling qualities were unaffected by the OGEE blades. Other handlingqualities tests were not accomplished. Results of acoustics tests will be reported by the laboratoriesunder a separate cov'er.

UNCLASSIFIED89CURITY CLASSIFICAI ON OF THIS5 PAOE(Whm.. Daita 5untit.(

DEPARTMENT OF THE ARMYif 3 NO, US ARMY AVIATION EESUARCN AND DEVELOPMENT COMMA0

4300 GOODFELLOW BOULEVARD. ST LOUIS, MO 63131

DRDAV-DI 14 JULION

SUBJECT: Directorate for Development and Qualification Position on theFinal Report of USAAEFA Project No. 77-25, PreliminaryAirworthiness Evaluation, Al-1S Helicopter with 0gee Tip Rotor Blades

SEE DISTRIBUTION

1. The purpose of this letter Is to establish the Directorate for Developmentand Qualification position on the subject report. The evaluation wasconducted as a research and development effort to evaluate performance,handling qualities, and acoustics characteristics of an AH-iS helicopterconfigured with Kamnan [747 rotor blades modified with an 05cc tip shape.

2. This Directorate agrees with the report findings and conclusions.Based on the test results, the AH-IS with the modified [aman [747 rotorblades exhibited degraded performance and handling qualities characteristics.

FOR THE COMMANDER:

CHARLES C. JR.Director of Developmentand Qualification

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TABLE OF CONTENTS

INTRODUCTION

Background .. . . . . . . . . . . . . . . . . . . . . . .ITest Objectives ........................................... 1IDescription........................................... ITest Scope.............................................. 2Test Methodology ......................................... 2

RESULTS AND DISCUSSIONS

General................................................ 4Performance............................................ 4

Hover Performance..................................... 4Level Flight Performance ................................ 4

Handling Qualities ......................................... 5Low-speed Flight Characteristics ........................... 5

CONCLUSIONS............................................. 6

RECOMMENDATIONS ........................................ 7

APPENDIXES

A. References........................................... 8B. Aircraft Description .... :.......... ...................... 9C. Instrumentation....................................... 14D. Test Techniques and Data Analysis Methods ................... 16E. Test Data............................................ 20

d DISTRIBUTION

INTRODUCTION

BACKGROUND

1. The U.S. Army and the National Aeronautics and Space Administration(NASA) are engaged in an effort to develop rotor blades which will improve theacoustic signature, vibratory loads, and performance of helicopters. Various rotor tipplanforms have been investigated for that purpose. To evaluate the potentialimprovements on an AH-I helicopter, two Kaman K747 main rotor blades have beenfabricated with an OGEE tip shape. Kaman Aerospace Corporation conducted initialtesting of OGEE tip rotor blades to obtain flight loads measurements prior togovernment testing. The U.S. Army Aviation Research and Development Command(AVRADCOM) requested that the U.S. Army Aviation Engineering Flight Activity(USAAEFA) conduct a preliminary airworthiness evaluation (PAE) of an AH-IShelicopter with OGEE tip main rotor blades (Ref 1, App A). A test plan (Ref 2) wasprepared by USAAEFA and approved by AVRADCOM (Ref 3).

TEST OBJECTIVES

2. The objectives of the test were as follows:

a. To compare the hover and level flight performance of the OGEE tip rotorblades to the performance of the K747 rotor blades.

b. To gather sufficient data to allow the US Army Research and TechnologyLaboratories (Aeromechanics Lab) to compare the acoustics signature of the K747and the OGEE tip blades.

c. Compare the handling qualities of the AH-l S with OGEE blades to thehandling qualities with K747 blades.

DESCRIPTION

3. The production AH-I S is a tandem seat, two-place helicopter with a two-bladed main rotor and a two-bladed Model 212 tractor tail rotor. The helicopter ispowered by a Lycoming T53-L-703 turboshaft engine derated from 1800 shafthorsepower (SHP) at sea-level, standard-day conditions to 1290 SHP for 30 minutesand 1134 SHP for continuous operation of the main transmission. Distinctive fea-tures of the helicopter include the narrow fuselage, stub wings with four stores sta-tions and a flat-plate canopy. A more complete description of the AH-IS ispresented in the operator's manual (Ref 4). Items affecting aerodynamic drag are

Idocumented in Appendix B.

I 4. The Kaman K747 rotor blade incorporates an advanced design airfoil, a taperedtip planform, composite material construction, and a multicell ballistically tolerantspar. The blades are designed to be individually interchangeable and when used as aset, may be used to replace the standard AH-I main rotor blades (B540). A completedescription of the K747 blade is contained in Reference 5.

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5. The OGEE tip rotor blade is a Kaman K747 blade with the tip modified to theOGEE shape. In order to quickly and economically make this modification, theK747' tip weights were left out of the OGEE configuration. This resulted in a lowinertia rotor by comparison to either K747 or B540 blades, rotor/engine fuel controlmatching which was not optimized, and rotor and aircraft dynamic stability whichwas not representative of a possible future production configuration of OGEEblades. Therefore, most handling qualities tests in Reference 2 were deleted by theReference 6 message.

TEST SCOPE

6. This PAE was conducted at Coyote Flats, California (elevation 9980 feet) andEdwards Air Force Base, California (elevation 2302 feet) from 1 November 1979through 8 April 1980. Forty-five tests flights were flown for a total of 36.6productive test hours (63.2 total flight hours). Flight restrictions contained in theoperator's manual (Ref 4, App A) and the airworthiness release (Ref 7) wereobserved during the tests. Tests were conducted primarily with the OGEE bladesinstalled. Some comparison flights were made with the K747 blades installed.Additional flights were made in support of the Aeromachanics Lab to gatheracoustics data. Results of those acoustics measurements will by reported by theAeromechanics Lab under a separate cover. Test conditions are shown in Table 1.

'fable I. Test Conditions t

Avg Avg AvY Avg AvgType of Test Gross Long Density Rotor Thrust Rotor

Weight CG Altitude OAT Speed Coefficient Blades(Ib) (FS) (170 C) (RPM)

7300 10000 -3.5 to 8.0 300 0.003720[lover perfornmance2 to 196.0 to to OGEE

8060 400 -2.0 325 0.006750

8280 195.1 6000 10.0 321 0.004959

8680 193.6 6580 6.5 319 0.005358Level Flight Performance " - OGEE

8860 194.0 10320 1.0 315 0.006299

8700 194.2 8980 -1.5 314 0.005969 K747

Low-speed Ilight 8480 195.0 10520 2.5 324 N/A OGEE

Notes: I All tests were flown in clean wing coutiguration.2 Ilover performance tests were flown out-of-ground effect using the tethertechnique while varying main rotor speed.

3 Level flight performance tests were flown at a constant referred mainrotor speed of 324 RPM.4 Average thrust coefficient. Thrust coefficient varied with fuel burn off during flight.

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TEST METHODOLOGY

7. The flight test techniques and data reduction procedures used during this evalu-ation are described in Appendix D or the appropriate Results and Discussionssection of this report. Data were obtained from instrumentation displayed on thepilot and copilot/engineer panels and recorded on magnetic tape. The on-board dataacquisition system is further described in Appendix C.

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RESULTS AND DISCUSSIONS

GENERAL

8. A PAE of the AH- IS helicopter was conducted to determine any differences inperformance or handling qualities caused by the OGEE main rotor blades. Bothhover and level flight performance was degraded by installation of the OGEE blades.Except for low-speed characteristics (which were unchanged) the handling qualitieswere not evaluated.

PERFORMANCE

Hover Performance

9. Out-of-ground effect (OGE) hover performance testing was accomplished withOGEE blades at 9980-foot and 2302-foot elevations using the tethered hovermethod. With K747 blades, limited hover testing was conducted at the 2302-footelevation site to verify the performance data presented in Reference 8, Appendix A.This data fell within the scatter of the data presented in Reference 8. Results of thehover performance testing is presented in Figures I and 2, Appendix E.

10. Figure 1 presents the hover capability of the AH-IS on a standard day andon a 35C day with K747 and OGEE blades. It is apparent that the hover perfor-mance is degraded by OGEE shaped blade tips. At a pressure altitude of 4000 feetwith an air temperature of 35C, the AH-IS with the OGEE blades can hover at9056 pounds, gross weight. This represents a reduction of 315 pounds (3.5%) whencompared to the K747 performance. At 10,000 feet on a standard day, the degrada-tion is 528 pounds (5.5%).

Level Flight Performance

I1. Level flight performance testing was conducted with both K747 and OGEEblades, using the test methods described in Appendix D. Figures 3 through 9,Appendix E, present the level flight performance data.

12. A nondimensional summary of the level flight performance with OGEE bladesis presented in Figures 3 through 5. Figures 6 through 8 present the test data fromwhich the summary was derived. Figure 9 presents data gathered with the K747blades and for comparative purposes, two curves are shown. One curve (derived fromRef 8, App A) is representative of the K747 data gathered during the program.The other is derived from Figures 3 through 5, Appendix E and represents AH-ISlevel flight performance with OGEE blades installed. At these conditions, an 8-knotreduction in maximum level flight speed resulted from the OGEE tip installation.

13. It should be noted that data gathered during this program with K747 bladesindicate an increase in airframe drag when compared to results from Reference 8,Appendix A. The drag change was approximately 2.5 square feet of equivalentflat plate area. A portion of the drag could be attributed to the main rotor mastextension installed to accommodate instrumentation slip rings and to the associatedstrain gages and wiring on the hub for the OGEE test program. The rest of thedrag change could be explained by a change in aircraft pitch attitude. During thesetests the aircraft flew in a more nose down pitch attitude than it did at similar

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conditions during Reference 8 tests. The aircraft tail boom was replaced betweenthe tests of Reference 8 and the current tests. Although the elevator was riggedproperly for both tests, other differences in the tail booms may have resulted in thechange in aircraft flight attitude.

HANDLING QUALITIES

Low-speed Flight Characteristics

14. The low-speed flight characteristics of the AH-IS with OGEE blades installedwere evaluated at the conditions listed in Table 1. Testing was performed to 30knots true airspeed (KTAS) rearward, 35 KTAS forward, 35 KTAS in left sidewardflight and 12 KTAS in right sideward flight. A ground pace vehicle was used as aspeed reference. Surface wind conditions were 5 knots or less. Tests were flown inground effect at a 10-foot skid height. The low-speed flight data are presented inFigures 10 and 11, Appendix E.

15. Longitudinal and lateral control margins were adequate at all test conditions.Directional control margin was less than 10% in right sideward flight. Inadequatedirectional control margin at high gross weights and high density altitudes, a pre-viously documented shortcoming of the AH-IS series aircraft, still exists. Theproblem is slightly worse with OGE blades because of the increased power requiredto hover (and therefore increased anti-torque tail rotor thrust requirements).

16. A directional control trim shift of more than 2 inches occurs between 10 and20 KTAS in left sideward flight. This trim shift will make hovering in gusty leftcrosswinds difficult. This trim shift is a characteristic of AH-I aircraft and is notcaused by the OGEE main rotor blades.

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CONCLUSIONS

1 7. Both hover and level flight performance of the Al- I S are degraded by install-ation of OGEE main rotor blades (paras 9 and 11).

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RECOMMENDATIOMS

18. None.

APPENDIX A. REFERENCES

I. Letter, U.S. Army Aviation Research and Development Command(AVRADCOM), DRDAV-EQI, 8 June 1979, subject: Preliminary AirworthinessEvaluation of the All-I Advanced (OGEE) Tip Shape Rotor Blades.

2. Test Plan, U.S. Army Aviation Engineering Flight Activity (USAAEFA), Project77-25, Preliminary Airworthiness Evaluation of the AH-l Advanced (OGEE) TipShape Rotor Blades, July 1979.

3. Letter, AVRADCOM, DRDAV-DI, 21 August 1979, subject: Advance TestPlan, Preliminary Airworthiness Evaluation of the All-I Advanced (OGEE) TipShape Rotor Blades. USAAEFA Project 77-25.4. Technical Manual, TM 55-1520-236-10, Operator's Manual. Army ModelAH-IS

Helicopter, 17 November 1976.

5. Technical Data Package for Main Rotor Blade Assembly K747-033-1 TDPR1397.

6. Message, AVRADCOM, DRDAV-DI, 131930Z March 1980, subject: Test Plan,Preliminary Airworthiness Evaluation of the AH-IS Advanced (OGEE) Tip ShapeRotor Blades, USAAEFA Project 77-25.

7. Letter, AVRAD('OM, D.DAV-DI, 17 October 1979, (with revisions19 October, 4 December 1979, and 27 March 1980), subject: Airworthiness Releasefor Airworthiness Evaluation (PAE) of the AH-I Advanced OGEE Tip Shape RotorBlades, USAAEFA Project No. 77-25.

8. Final Report, USAAEFA, Project No. 77-38, Production Validation Test-Go i'ernment, Kaman K 747 imprev ed Main Rotor Blade, to be published.

9. Final Report, US Army Aviation Test Activity (USAAVNTA) Project No. 66-06,Engineering Flight Test AIl-IG Helicopter (Hueycobra). Phase D, Part 2.Performance. April 1970.

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APPENDIX 3. AIRCRAFT DESCRIPTION

GENERAL

I. The test helicopter, S/N 76-22573, was a production AH-I S.The AH-I S mainrotor mast and hub assembly had been replaced with a mast and hub assembly froman AH-IG. The AH-iG hub was instrumented for structural loads measurements atseveral locations, and the mast incorporated wiring and slip rings to transmit loadsinformation from the rotor and hub to the data systems.

MAIN ROTOR BLADES

2. The tests were conducted with two sets of main rotor blades, the K747 bladesand K747 blades modified with OGEE-shaped tips. The K747 blade tip weights wereremoved to facilitate installation of the OGEE tips. The OGEE blades therefore, hadmuch lower rotational inertia than the K747 blades.

3. The blades utilize a multicell filament wound fiberglass spar, a nomex honey-comb core afterbody, and a Kevlar trailing edge spline, all enclosed by fiberglassskin. At the inboard end, cheekplates carry blade loads to an aluminum adapterwhich is attached to the hub with a pin.

4. The K747 blade airfoil shape is based on a family of airfoils developed byBoeing Vertol. To incorporate the OGEE-shaped tip, the outer 15% of the K747blade was replaced by the OGEE tip (Fig 1). The airfoil shape varies from bladetip to root as follows:

r/R (Blade Radius Station) Airfoil Design

From tip to 0.85 (K747) 8% thick Boeing Vertol VR-8From 0.85 to 0.67 Linear Transition to 12% thick

Boeing Vertol VR-7From 0.67 to 0.25 12% thick Boeing Vertol VR-7From 0.25 to 0.18 Gradual buildup to 25% thick

by cheekplates

ENGINE AND TRANSMISSION/TAIL ROTOR DRIVE

5. The T53-L-703 turboshaft engine is installed in the AK-IS helicopter. Thisi [ engine employs a two-stage, axial-flow free power turbine; a separate two-stage,axial-flow turbine driving a five-stage axial and one-stage centrifugal compressor:variable inlet guide vanes; and an external annular combustor. A 3.2105:1 reductiongear box located in the air inlet housing reduces power turbine speed to a nominaloutput shaft speed of 6600 RPM at 100 percent N2. The engine reduction gear boxis limited to 1]75 foot pounds (ft-lb) torque for 30 minutes and to I110 ft lbtorque for continuous operation. A T7 interstage turbine temperature sensor harnessmeasures interstage turbine temperatures and displays this information in the

Scockpit as turbine gas temperature on the cockpit instruments.

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6. The main transmission has a 1290 SHP limit for 30 minutes and a 1134 SHPlimit for continuous operation at a rotor speed of 324 RPM (100 percent N ) Theaircraft is further limited to 88% torque above 100 knots indicated airspeed NkiAS).The tail rotor drive system has a 260 SHP transient limit for 4 seconds and a 187SHP limit for continuous operation. The engine used during this test had serialnumber LE 13145Z.

PRINCIPAL DIMENSIONS

7. The principal dimensions and general data concerning the Al-IS helicopters

are as follows:

Overall Dimensions

Length, rotor turning 53 ft, I in (K747)53 ft, 1.35 in (OGEE)

Height, tail rotor vertical 13 ft, 9.0 inLength, rotors removed 44 ft, 7 in

Main Rotor K747 OG'EE

Diameter 44 ft 44 ft, 0.7 inDisc area 1520.5 ft2 1524.6 ft'Number of blades 2 2Blade chord See Figure 1 See Figure IBlade twist -0.556 deg/ft -0.556 deg/ftAirfoil See paragraph 2 See paragraph 2

Tail Rotor

Diameter 8 ft, 6 inDisc area 56.75 ft2

Solidity 0.1436Number of blades 2Blade chord, constant 11.5 inBlade twist 0.0 deg/ftAirfoil NACA 0018 at the blade

root changing linearly to aspecial cambered section at

8.27 percent of the tip

Fuselage

Length: 44 ft, 7 in

Height:

To tip of tail fine 10 ft, 8 in* Ground to top of mast 12 ft, 3 in

Ground to top of transmissionfairing 10ft, 2in

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Width:

Fuselage only 3 ftWing span 10 ft, 9 inSkid gear tread 7 ft

Elevator:

Span 6 ft, 11 inAirfoil Inverted Clark Y

Vertical Fin:

Area 18.5 ft2Airfoil Special camberedHeight 5 ft, 6 in

Wing:

Span 10 ft, 9 inIncidence 17 degAirfoil (root) NACA 0030Airfoil (tip) NACA 0024

8. A flight control rigging check performed in accordance with proceduresoutlined in TM 55-1520-234-20 demon trated that the cyclic collective pitch, anddirectional controls, and the elevator were within presecribed limits. The swashplateangles measured with respect to aircraft axes and tail rotor blade pitch angles areas follows:

SWASHPLATE ANGLES

Control Position Lateral Angle Longitudinal Angle

Neutral 1.5 deg L down 1.0 deg nose up

Full Forward 5.0 deg R down 10.0 deg nose down

Full AFT 5.0 deg R down 12.5 deg nose up

Full Right 7.0 deg R down 4.5 deg nose up

Full Left 7.5 deg L down 3.5 deg nose down

TAIL ROTOR BLADE PITCH ANGLES

V Pedal Position Blade Angle

Full Left 19.9 degFull Right -11.0 deg

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Weight and Balance

9. The aircraft weight, longitudinal center-of-gravity (cg) location and lateral cglocation were determined prior to testing and checked periodically throughoutthe tests. A fuel cell calibration was also performed prior to testing. Al weighingswere accomplished with instrumentation installed without external stores or chinturret weapons installed.

10. The fuel loading for each test flight was determined prior to engine start andfollowing engine shutdown by using a calibrated external sight gage to determinefuel volume and by measuring the fuel specific gravity. Fuel used in flight wasrecorded by a sensitive fuel-used system and verified with the pre- and postflightsight gage readings.

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APPENDIX C. INSTRUMENTATION

I. The test instrumentation system was installed, calibrated, and maintained byUSAAEFA. Data were obtained from calibrated instrumentation and recorded onmagnetic tape and/or displayed in the cockpit. The digital instrumentation systemconsisted of various transducers, signal conditioning units, a 10-bit PCM encoder,with a sample rate of 200 samples per second, and a magnetic tape recorder. Thedata were also telemetered to a ground station for monitoring/test control. Timecorrelation was accomplished with pilot/engineer event switches, and on-boardrecorded and displayed Inter Range Instrumentation Group (IRIG) B time. Add-itionally, during the acoustics measurement flights, a "beep" tone was transmittedonce per main rotor revolution from the All-IS to the YO-3A over an FM radiofrequency. The tone was generated when one main rotor blade was at the 82.75degree azimuth position (measured from the nose in the direction opposite to rotorrotation).

2. Cockpit displayed parameters and special equipment are listed below:

Pilot Station

Pressure altitude (boom)Pressure altitude (ship)Airspeed (boom)Airspeed (ship)Main rotor speedEngine torqueEngine turbine gas temperatureEngine gas producer speedAngle of sideslipEvent switchTether cable angles (longitudinal and lateral)

Copilot/Engineer Station

Airspeed (boom)Altitude (boom)Main rotor speedEngine torqueEngine gas producer speedTotal air temperatureFuel usedCable tensionTime code displayEvent switchData system controls

3. Parameters recorded on magnetic tape were as follows:

PCM Parameters

Time codeEventFlight number

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Run numberMain rotor speedFuel temperatureFuel usedEngine fuel flow rateEngine gas producer speedEngine power turbine speedAirspeed (boom)

Altitude (boom)Total air temperatureAngle of attackAngle of sideslipTether cable tensionTether cable angle (longitudinal and lateral)Engine torqueEngine exhaust gas temperatureControl positions

Longitudinal cyclicLateral cyclicPedalCollective

Aircraft attitudesPitchRoll

Aircraft angular velocitiesPitchRollYaw

Center-of-gravity accelerationsVerticalLateralLongitudinal

Main rotor hub flapwise bending momentAt station 5 (both blades)At station 8 (both blades)At station I I (one blade)At station 20 (one blade)At station 37 (one blade)

At station 68 (one blade)Main rotor pitch link axial loadMain rotor drag brace axial load (both blades)Main rotor shaft torqueMain rotor blade angle

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APPENDIX D. TEST TECHNIQUESAND DATA ANALYSIS METHODS

GENERAL

I.Helicopter performance test data were generalized by use of nondimensionalcoefficients. The purpose of this generalization was to accurately predict perfor-mance at aircraft gross weight/ambient air condition combinations not specificallytested. The following coefficients were used:

a. Coefficient of power (Cp):

C SHP x550

P pA (92R)' (1)

b. Coefficient of thrust (CT):

-T GWCT pA(92R)2 (2)

c. Advance ratio (p):

1.6878 x V T

RZR (3)

d. Advancing tip mach number (M T I P

lTP .6878VT + S2R

a (4)

Where:

SHIP =Engine output shaft horsepower

550 =Conversion factor (ft-lb/sec/SHP)

p =Air density (slUgs/ft3 )

A =Main rotor disc area (ft2 )

E2 M Nain rotor angular velocity (rad/gvc)

R =Main rotor radius

Gw= (vross weight (i1))

1 .6X-78 Conversion factor (ft/sec/ki)

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VT = True airspeed (kt)

a = Speed of sound (ft/sec)

2. Engine output SHP was determined from the engine torque pressure. Torquepressure as a function of the power output of the engine was obtained from theengine manufacturer's test cell calibration. Horsepower was determined by thefollowing equation:

NxGRxTqSHP=

q

63025 (5)

Where:

N = Main rotor speed (RPM)

GR = Engine to main rotor gear ratio = 20.38362

Tq Engine output shaft torque (in-lb)

63025 = Conversion factor (in-lb rev/min/SHP)

3. Shaft horsepower available and specification fuel flow were obtained fromLycoming Model Specification T53-L-703 (LTCJK-4G) Mo. 104-43 by usingcomputer program file number LS19.04.32.00 dated I May 1974 and the inletcharacteristics described in Reference 9, Appendix A.

HOVER PERFORMANCE

4. The tethered method of hover performance testing was used. This methodrequired that the aircraft be at a very light gross weight, that it be tied to the groundby a 100-foot cable, and that a load cell be used to measure cable tension. Duringthe test, the cable was kept taut and vertical at all times. To get a maximum varia-tion of CT (equation 2), rotor speed and cable tension were varied during the test.The technique used to vary cable tension was to set various torque settings fromminimum required to hover out-of-ground effect (OGE) to the maximum allowedat the test conditions. Cable angle was displayed to the pilot in the cockpit in orderto maintain the aircraft directly over the ground tie-down point.

* 5. The data were plotted as Cp versus C using equations I and 2. The grossweight in equation 2 was determined by adding cable tension to the engine startgross weight, and then subtracting the weight of the fuel burned prior to each datapoint. The data points obtained with the OGEE tip-shape blades were then fittedwith a curve using a multiple linear regression program. The equation of the resultingline is:

Cp = 0.000126 + 0.495915 CT3/ 2 +1203.1898 CT3 (6)

This equation is valid only for the range of C actually tested and should not beused to extrapolate to higher or lower values of

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LEVEL FLIGHT PERFORMANCE

6. Each level flight performance flight was designed to obtain one curve of Cversus u at a constant value of C The flight technique was to stabilize at zersideslip at incremental airspeeds from approximately 40 KIAS to the maximumattainable. Torque, altitude, airspeed, and rotor speed were held constant at eachairspeed for at least I minute prior to recording data. Altitude was increased bet-ween data points as a function of fuel burnoff in order to maintain a constantratio of gross weight to air pressure ratio (GW/6). Also, rotor speed (N) was variedas a function of ambient air temperature in order to maintain a constant ratioof rotor speed to square root of the air temperature ratio (N/v/O). By rearrangingequation 2 as follows:

CT _ GW/6

p0 A ( - 2("60/ (7)

it can be seen that C will also be constant if GW/S and N/,/t" are constant. Duringthese tests, the targel GW/S was different for each flight in a given aircraft con-figuration, but the tarjet N/\/(T was 324 RPM for all flights. The reason for main-taining constant N/\/O was to minimize the difference in compressibility effectsbetween flights.

7. Airspeed and altitude were obtained from a boom-mounted pitot-static probe.Corrections for position error determined during Reference 8 testing were applied.

8. For the OGEF blade data, the Ce versus y curves were cross plotted as Cversus C with lines of constant p. From these curves (Figs 3 through 5, App 6level flighit performance at any combination of gross weight, rotor speed, pressurealtitude, and air temperature can be detennined

,9. Measured (test) level flight power for both sets of rotor blades was correctedto the average dimensional (standard) conditions by assuming that the testdimensionless parameters. CP , CT , and p, are independent of atmosphericconditions. Consequently. thet standard dimensionless parameters C , T ' and1j, are identical to C, , CT , and p,, respectively. From the definition oriequition Itile following relation~hip chn be derived:

PS UsSliP s = SfIP t x (8)

Pt(8)

Where:

* t = 'est day (measured)

s = Standard day (corrected)

For K747 blade data, a curve of Cp versus IA was obtained from Reference 8at the appropriate value of CT. The data was then corrected for a drag increase of

18

-WIi -Ml

2.5 square feet. A similar correction for VT could be derived from the definition vfp (equation 3). This correction was insignificant and therefore not made.

10. Specific range was calculated using measured values of VT and fuel flow asfollows:

VTNAMPP = Wf

Where:NAMPP = Specific range (nautical air miles per pound of fuel)

Wf Fuel flow (lb/hr)

i

19

JL~~ --Z2-

APPENDIX E. TEST DATA

INDEX

FigureFigure Number

Summary Hover PerformanceINondimensional Hover Performance 2Nondirnensional Level Flight Performance 3 through 5Level Flight Performance 6 through 9

Low-Speedligh t Characteristics10adI

20

:-7- V-

........ .... - - ------ - - --- ----- .... .. .

.. .. ......---- ---------

... . ....... - ---- ----------- -----------

.................. ..... .. ------ ----- . ....... ..... ......

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

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

...... .... -

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

..........

-- --- ------

.... ......

--- .... ...........

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

..... ......

- --- ------- .

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

7- 7

... .......

.... ....... ---- --

... ..... . .

--------- ------

21

jh

- t7-

A.4 -Nr T~ 7j .< .-h .j-... 4ANAI NO

v~~~~~~i _, 4 7 hJL~4EL~

r I MI

07)~.4 Q- t. --A4 I Mhhi-RIM;r~~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ......... .- .. 1 . " Ft lf N 7Hy :

.2 ...... ...

7t-. -- K i---~ 4 ~ -~.~ - 1 '

1*-*- -

AW 77 i

t4 _

-- - - -.... .

4

_

Im1s! ES1

.7-7.

w/A - 4- --.-20-

32

T - --- -- 7!

.. P R r. '1)A iCIE T. ' /

1" /

-~~ ..- ~. v . ... ...

I, ....

I...........

v~- -I . I, 1

7. 7. =

- 4 -

-. 4:

T~ ----' --

-- - - - -----

..... .. .. .....II -7!

7'.%i~K I

.77t =_ _ _ .. . .. . . . . . ..7:7-7 L-~~ ........T

-72: _WL7iW7-AJ*77WLL=-T . ....

.....

7=:w:TT: I= tl

-:_:j; .: 7=7777. 77777

:7 ..... .::il

---- -- ---------- .. ... .. ..q- ... .... ....

t .... ......... ...

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

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

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

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

17

71

T-1 .... .... 77

:7: ---- ---- 7;... ..... . . ---- ---

CIL J-w

7HA 7--

---- - -- ... V

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

.. ........0.. ... ..... ........ . . - :: .-- 7:'

7

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

-- 4441- Ta

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

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

=771! no ..........-Lo

w rV........ ....

:w-, q.

nr. -o"T

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

.7i 4-1...... .... ....... ..... . 7 j

7 =7..... ...... .... .....

....... .. ..

7: ..... .:.:!7:

27

in- 7:::

------- ......

F

j7

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

t-71

A'AlT: :7...... ......... ..

.... ........ .......----------

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

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

.......... . .. .... ..... .... - w M -0

:1 7, :::mawlIP6 . ...........

Fl, :IfO--: 0:.

-T7.

H-, i i.... .... . - 4 -4 .... . . ....... ......... TT-T

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

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

-got; . ........ .. .. .. .

1: 7

: 7 .. .... ....

-mo

77.": -777,--t7-37-n- .-

AM , ::-:o.m

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

..... ........ .... ...... .... ........a 142 n::;.

:.:.T 7. i.

28

.~~~- . .~ . ....

7 a-

mI7-

.. -_.. ...... ..... .. . ------

!W :~:{: 1

.... . ... ...

-r ~ **... . .. . .. . .. . .. . .. .

VA-

4"H:

7"7

I j-7 .. 1FIGS ZA1177/_

+- -A ilm .

EM II

~2P __ _ _ __ _ _ _ _ _ _ _ _

-7UiZ T iI-

I 2~i

7 -:!:i

V.c A6-: ------__ __ _ _ __ _ _ _ __ _ _ __ _ _ __ _ _

* __ _ _ _

-j7

3 1 4:

C* 30

% SEW=

GROS#. - . OTOft __

7-7I~~~ - 'A~SPEED

-- A-* M-JV_1'-A I~E~ .t fI..

-F 7JT ~-W =60I~E

I--

iTH.

a _9L. LL.

) 77 a-7..0 1 . .. __ 10- 2..~ 30. 40________ - .JORARD

-...... . _ Tft MoIt (K )

31-

DISTRIBUTION

Assistant Secretary of the Army (R&D) I

Deputy Chief of Staff for Logistics (DALO-SMM) I

Deputy Chief of Staff for Operations (DAMO-RQ)

Deputy Chief of Staff for Personnel (DAPE-HRS) 1

Deputy Chief of Staff for Research Development and

Acquisition (DAMA-PPM-T, DAMA-RA, DAMA-WSA) 3

Comptroller of the Army (DACA-EA) I

US Army Materiel Development and Readiness

Command (DRCDE-DH, DRCQA-E, DRCRE-i, DRCDE-RT) 4

US Army Training and Doctrine Command (ATJG-U, ATCD-T,

ATCD-ET, ATCD-B) 4

US Army Aviation Research and Development Command

(DRDAV-DI, DRDAV-EE, DRDAV-EG) 10

US Army Test and Evaluation Command (DRSTS-CT,

DRSTS-AD) 2

US Army Troop Support and Aviation Materiel Readiness

Command (DRSTS-Q)

US Army Logistics Evaluation Agency (DALO-LEI)

US Army Materiel Systems Analysis Agency (DRXSY-R) 1

US Army Operational Test and Evaluation Agency (CSTE-POD)

US Army Armor Center (ATZK.CD-TE) I

US Army Aviation Center (ATZQ-D-T, ATZQ-TSM-A, ATZQ-TSM-S) 3

US Army Combined Arms Center (ATZLCA-DM)

US Army Infantry Center (ATSH-TSM-BH) I

US Army Systems Center (IGAR-TA, IGAR-Library) 2

slowI

DISTRIBUTION CONT.

LIS Army Research and Technology Laboratories/

Applied Technology Laboratory (DAVDL-ATL-D,

DAVDL-Library) 2

US Army Research and Tcchnology Laboratories!

Acromechanics Laboratory (DAVDL-AL-D)I

US Anny Research and Technology Laboratories/

Propulsion Laboratory (DAVDL-PL-D)I

US Army Troop SuIpport and Aviation

Materiel Readiness Command (DRCPM-CO-T)

Defense Technical Informiation Center (DDR) 12