82
HELICOPTER EQUIPPED MIT (U) ARMY AVIATION ENGINEERING U CL~i EJ)FLIGHT ACTIVITY EDNARDS AFS CA G L BENDER ET AL NLSIIO OCT 86 USAAEFA-86-02 F/G 1/3 1 i Eh 1 hhhh
HELICOPTER EQUIPPED MIT (U) ARMY AVIATION ENGINEERINGU CL~i EJ)FLIGHT ACTIVITY EDNARDS AFS CA G L BENDER ET AL
NLSIIO OCT 86 USAAEFA-86-02 F/G 1/3 1 i
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11111 1.0 5LO
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MICROCOPY RESOLUTION TEST CHARTNATIONAL BUREAU OF STANDARDS-1963-A
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USAAEFA PROJECT NO. 86-02 v
-
LI° US ARMY
AVIATION
SYSTEMS COMMAND
ENGINE/AIRFRAME RESPONSE EVALUATION OFTHE HH-60A HELICOPTER EQUIPPED WITH THE
T700-GE-701 TRANSIENT DROOP IMPROVEMENTELECTRONIC CONTROL UNIT
U. GARY L. BENDER JAMES M. ADKINSS, PROJECT OFFICER CW4, AVA P
A rROY A. LOCKWOOD
E PROJECT PLOT DTICF QELECT EF SEP 0 3 1987[1A OCTOBER 1986
FINAL REPORT
APPROVED FOR PUBLIC RELEASE, DISTRIBUTION UNLIMITED.
US ARMY AVIATION ENGINEERING FLIGHT ACTIVITYEDWARDS AIR FORCE BASE, CALIFORNIA 93523- 5000
87 9 1 29
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4. PERFORMING ORGANIZATION REPORT NUMBER(S) S. MONITORING ORGANIZATION REPORT NUMBER(S)
AEFA PROJECT NO. 86-02
6a. NAME OF PERFORMING ORGANIZATION 6b. OFFICE SYMBOL 7a. NAME OF MONITORING ORGANIZATION
U.S. ARMY AVIATION ENGINEERING (If applicable)
FLIGHT ACTIVITY _
6c. ADDRESS (City, State, and ZIP Code) 7b. ADDRESS (City, State, and ZIP Code)
EDWARDS AIR FORCE BASE, CALIFORNIA 93523-5000
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PROGRAM PROJECT TASK WORK UNIT4300 GOODFELLOW BLVD. ELEMENT NO. NO. NO ACCESSION NO
ST. LOUIS, MO 63120-1998 l1-6-01008-1-01
11. TITLE (Include Security Classification)Engine/Airframe Response Evaluation of the HH-60A Helicopter Equipped with the T700-GE-701Transient Droop Improvement Electronic Control Unit. Unclassified
12. PERSONAL AUTHOR(S)Gary L. Bender, James A. Adkins, Roy A. Lockwood
13a. TYPE OF REPORT 13b. TIME COVERED 114. DATE OF REPORT (Year, Month, Day) 15- PAGE COUNT
FINAL FROM09 /06 & TO5/08/87 October 1986 82
16. SUPPLEMENTARY NOTATION
17. COSATI CODES 18. SUBJECT TERMS (Continue on reverse if necessary and identify by block number)
FIELD GROUP SUB-GROUP Engine/Airframe Response, Engine Governor Configuration,ump Takeoff, Power Recovery from Autorotation, Quickstops,H-60A Helicopter, T700-GE-401 Engines, T700-GE-700 Enine
iI
19. ABSTRACT (Continue on reverse if necesry and identify by block number)
Engine/airframe response testing was conducted at Edwards AFB, California (elevation 2302feet) between 9 June and 25 August 1986. Five flights totaling 11.1 hours were conducted onthe HH-60A helicopter and one flight was conducted in the UH-60A helicopter. Four differentengine/engine governor configurations were tested. Engine/airframe response tests includedjump takeoff, nap-of-the-earth quickstops, power recovery from autorotation, and nap-of-tbe-
earth ridgeline crossing maneuvers. --,The engine/drive train response was stable for alltests performed. The best configuration for magnitude of main rotor speed droop, rotor
speed/power turbine speed droop recovery characteristics, and power turbine speed governingcharacteristics was the HH-60A with the T700-GE-401 engines equipped with the -401 trais|entdroop improvement engine control unit. The HH-60A with the T700-GE-401 engine equipped withthe -701 transient droop improvement engine control unit (with and without the collectivepotentiometer input) exhibited larger rotor speed droop, noticeable drive train oscillationduring droop recovery, and less desirable power turbine speed governing characteristics.
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Block No. 19rThe undesirable engine/airframe characteristics of the HH-60A with the -701 transient
droop improvement engine control unit is a shortcoming. The UH-60A with the T700-GE-700"'engine demonstrated the largest main rotor speed droop but residual drive train oscilla-tions were small, droop recovery characteristics were more predictable and power turbinespeed governing was noticeably more stable than demonstrated by the T700-GE-401 enginesequipped with the -701 transient droop improvement -engine control unit. The undesirableengine/airframe response (large main rotor speed droop) of the UH-60A with the T700-GE-700engines is a previously identified shortcoming. Future designs for the UH-60 enginecontrol units should include all the transient droop improvements of the -401 transientdroop impro vement engine control unit. Additionally, future designs of engine controlunits should have dynamics tailored to the particular helicopter in which the enginesare to be installed.
TABLE OF CONTENTS
Page
INTRODUCTION
Background ............................................... ITest objective ........................................... 1Description ...............................................Test Scope ............................................... 2Test Methodology ......................................... 2
RESULTS AND DISCUSSION
General .................................................. 3Engine/Airframe Response .................... o............4
General .............................................. 4Configuration One .................................... 4Configuration Two .................................... 6Configuration Three .................................. 7Configuration Four ................................... 8
Engine/Drive Train Stability ............................ 9
CONCLUSIONS
General .................................................. 10Shortcomings ........ o......o..............o................10
RECOMMENDATIONS ........................ o....................11
APPENDIXES
A. References. ....... o.............................o........12B. Description ........ o.....................................13C. Instrumentation .......... ... ............................ 21D. Test Datao...............................................23
DISTRIBUTION (Accesion For
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By . .........
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INTRODUCTION
BACKGROUND
1. The US Army has expressed a desire to install T700-CE-701engines in the UH-60A helicopter to provide added performancemargin. To provide commonality with the AH-64A, the UH-60Aengines would be equipped with the T700-GE-701 transient droopimproved electronic control units (-701 TDI ECU) and hydromechani-cal units (HMU). However, there is concern that with this enginechange the engine/drive train response of the UH-60A may be
degraded. As the -701 engine has yet to be installed in an ArmyUH-60A, the best available test article is the US Air ForceHH-60A, which is equipped with T700-GE-401 engines. The US ArmyAviation Systems Command requested (ref 1, app A) the US ArmyAviation Engineering Flight Activity (USAAEFA) to conduct anevaluation of the US Air Force HH-60A helicopter equipped withthe T700-GE-401 engines modified with the -701 TDI ECU and HMU.Additionally, USAAEFA evaluated the HH-60A with -401 TDI ECU anda US Army UII-60A with the T700-GE-700 engine with the standard-700 ECU and HMU.
TEST OBJECTIVE
2. The objective of the test was to evaluate the engine/drivetrain stability and transient rotor speed droop characteristicsof the HI-60A helicopter equipped with the T700-GE-401 enginesmodified with the installation of the -701 TDI ECU and HMU.
DESCRIPTION
3. The HH-60A helicopter is an Air Force version of the US ArmyUH-60A. The HII-60A and UH-60A are described in references 2 and3, respectively. The rotor and drive train systems are the sameon both aircraft and therefore, the results of this testing onthe HH-60A should be valid for the UH-60A also. The HH-60A andthe AH-64A helicopter use the same HMU. The -701 TDI ECU incor-porates a three-Hertz notch filter, a collective position signal,and modified torque and power turbine speed values for power tur-bine governor gain switching. The HH-60A TDI ECU incorporates acollective position signal and a rotor speed signal to improverotor speed droop characteristics. The dynamics of the two ECUsare different to accommodate the different rotor/drive traindynamics of the AH-64A and HH-60A aircraft. The UH-60A ECU doesnot incorporate a collective signal nor a rotor speed signal. Afurther description of the HMU and ECU can be found in appendix B.
T
TEST SCOPE
4. This evaluation was conducted at Edwards AFB, California,between 9 June and 25 August, 1986. Five flights were conductedon the HH-60A for a total of 11.1 hours. Because the Army test
pilots were not qualified in the Air Force HH-60A, and becausethe aircraft was under the operational control of the Air Force,an Air Force instructor pilot was in the left seat for all HH-60Aflights. The HH-60A aircraft was flown at an engine start grossweight and longitudinal center of gravity (cg) of 20,375 poundsand fuselage station (FS) 352.5, respectively. Tests were con-
ducted at field elevation (2302 feet), 6000 and 10,000 feet,pressure altitude. A one hour flight was flown in the UH-60A.
The UH-60A tests were flown by an Army crew at field elevationand 6000 feet, pressure altitude. Takeoff gross weight was17580 pounds at a longitudinal cg of FS 354.6.
TEST METHODOLOGY
5. The engine/drive train stability and engine/airframe response
were evaluated using collective steps and pulses, jump takeoffs,NOE quickstops, and recoveries from autorotation. Test techniquesare described in the results and discussion section of thisreport. Data were obtained from calibrated test instrumentationand recorded on magnetic tape. A detailed listing of the testinstrumentation is contained in appendix C.
2
RESULTS AND DISCUSSION
GENERAL
6. Three configurations of the US Air Force HH-60A helicopterequipped with the T700-GE-401 engines were evaluated to determineengine/drive train stability and transient main rotor speed (NR)droop characteristics. The following configurations are described
in the order in which they were evaluated. The first configurationwas obtained by modifying the engines with the installation ofthe -701 TDI ECU and HMU. The second configuration was identicalto the first configuration except for the addition of a collectivecontrol potentiometer signal to the ECU. For the third configura-tion, the engines were equipped with the -401 TDI ECU which incor-porates a collective control potentiometer signal and NR signalto the ECU. The -701 TDI HMU was used for all HH-60 testing.
Additionally, the US Army UH-60A with the T700-GE-700 engine wasevaluated for comparison and will be referred to as the fourthconfiguration. The low rotor speed warning horn and light isdesigned to illuminate when NR drops below 94% for all configura-tions. The undesirable engine/airframe response of configura-
tions one, two and four during power application from a lowtorque condition and during nap-of-the-earth (NOE) quickstopmaneuvers is a shortcoming.
7. Engine airframe response tests included jump takeoffs, NOEquickstops, power recoveries from autorotation, and NOE ridgeline
crossing maneuvers. The engine/drive train was stable for allconfigurations tested (i.e., all oscillations were damped). Thebest configuration for magnitude of NR droop, rotor speed/powerturbine speed (NR/Np) droop recovery characteristics, and Npgoverning was the T700-GE-401 engines with -401 TDI ECU (third
configuration). The first and second configurations (T700-GE-401engines with the -701 TDI ECU and HMU) exhibited larger NR droopfor the same collective input time (fig. A), noticeable drive
train oscillation during NR/NP droop recovery, and less desirableNp governing characteristics. Following the flight tests of
configuration one, the engine load demand spindles were foundmisrigged. The load demand spindles were rerigged prior toconfiguration two testing, but no significant improvement inengine response was apparent. The UH-60A with T700-GE-700 enginesdemonstrated the largest NR droop but residual drive trainoscillations were reduced from configurations one and two. NR/Npdroop recovery characteristics were more predictable, and Npgoverning was noticeably more stable than configurations one and
two.
3
FIGURE AH-650A ROTOR SPEED DROOP
SYM CONFIGILRATIONA NO. 1,* ItI-60A WITH -701 TDI ECU, NO COLL.ECTIVE SIGNAL+I NO. 2.. H--8- WITH -701 TDI ECU, WITH COLLECIVE SIGNALE] NO. 3, HH-f-80A WITH -40f TDI ECUJX NO. 4. U-80A WITH -700 ECU
NOTE: DATA OBTAIN~ED DUJRING COLLECTIVE PULLS TO 95%INTERMEDIATE RATED POWlFER FROM AUTOROTATION.
96 +U
o 8S 4 f_70-IL.
0 2 4 68 10 112 14COLLECTIVE IN'.PUT TIME
C SECOIS
4
ENGINE/AIRFRAME RESPONSE
General
8. Jump takeoffs were performed from the ground with the initialcollective control position at full down. Collective controlwas increased to 95% intermediate rated power (IRP) at severalrates (input times varied incrementally from 1 to 5 seconds).NOE quickstops were performed at 50 ft above ground level (AGL)
with entry speeds of 60, 80, 100 and 120 knots indicated airspeed(KIAS). The maneuvers were terminated at a stable hover. Powerrecovery from autorotation was performed from stable 80 KIASdescent (power levers at fly) with collective positioned tomaintain 1 to 15% split between NR and Np. Collective controlwas increased to 95% IRP in 2 to 12 seconds during recovery.
Ridgeline crossing maneuvers were performed at 100 ft AGL frominitial airspeeds of 60, 80, 100 and 120 KIAS using simultaneouscyclic and collective control inputs. No significant NR droopwas observed in the four configurations tested while performing
ridgeline crossing maneuvers.
Configuration One
9. Configuration one featured T700-GE-401 engines modified withthe -701 TDI ECU and HMU. Engine/airframe response of thisconfiguration was evaluated with the maneuvers described inparagraph 8. Time history data are presented in figures 1Athrough 5E, appendix D. A maximum of 3% NR droop was observedduring jump takeoffs, but 5 to 10% torque splits and torque
reversals between number one and number two engines occurredduring collective control increases. These torque splits and
torque reversals persisted for as much as 8 seconds after thecollective control movement was stopped (fig. IB). Power recoveryfrom autorotations resulted in larger NR droops and increasedengine and airframe oscillations. A 7 second collective controlincrease to 95% IRP with less than 5% NR/Np split resulted ina 5.5% NR droop, activating the low rotor rpm warning horn andlight, followed by a 4.5% NR overshoot prior to reaching 95%IRP. Residual oscillations persisted for 3 seconds after collec-tive control movement stopped (fig. 2, app D). An extremelyslow (11 second) collective control increase with 10% NR/Npsplit resulted in a 5% NR droop and 3.5% NR overshoot prior toreaching 95% IRP (fig. 3A). Residual oscillations persisted for5 seconds after the initial NR overshoot. More aggressivecollective control increase (2 seconds to 95% IRP) resulted in
NR droop to 90%, but the NR recovery was improved over theslower collective control increase in that NR/Np overshoot andresidual oscillations were reduced (fig. 4A). The recovery is
5
inconsistent with the previous examples (figs. 2A through 2Cand 3A through 3C) since the pilot will expect a more aggressivecollective control increase and larger NR droop to result indegraded recovery characteristics. These oscillations duringrecovery occur after the TDI circuit (described in fig. 3, app B)is disabled (i.e., engine torque is above 50 ft-lb). The dataindicates that recovery characteristics are improved when collec-tive control input terminates not more than 0.5 seconds afterthe maximum NR droop occurs.
10. Poor Np governing, large NR droop, and persistent residualengine/airframe oscillations were observed during quickstopmaneuvers. During the deceleration to a quickstop, Np and NRremained joined up to 104% (fig. 5A, app D). A clean NR/Np splitdid not occur until 5 seconds after collective reduction wasinitiated. During collective control increase, NR drooped to92% activating the low NR warning horn and light. NR/Npovershot to 106% during the final portion of the maneuver while
the aircraft was slowing to a stop. Poor Np governing, torquesplits and reversals, unpredictable and inconsistent NR/Np drooprecovery (para 9) and residual engine/airframe oscillations willmake it difficult to safely perform NOE maneuvers such as quick-
stops and recovery from low power descents with reduced visualcues (e.g., flying at night using pilot night vision systems).The pilot will be required to direct his attention inside the
cockpit to compensate for the rapidly changing aural and visualcues (cockpit torque and NR/NP indicators) resulting from engine,rotor, and airframe oscillations. This will reduce the NOE
maneuvering capability of the aircraft. The undesirable engine/airframe response with the -701 TDI ECU (without collectivepotentiometer signal) during power application from a low torquecondition and during NOE quickstop maneuvers is a shortcoming.
Configuration Two
II. Configuration two was identical to configuration one exceptfor the addition of a collective control potentiometer signal to
the ECU. Engine/airframe response of this configuration wasevaluated with the maneuvers described in paragraph 8. Timehistory data are presented in figures 6A through IOE, appendix D.No NR droop was observed during jurr takeoffs, but a torquesplit between number one and number two engines of more than 15%persisted for over 4 seconds after collective control movementstopped (fig. 6B). A 3 second collective control increase to 95%IRP during power recovery from autorvtation with an 11% NR/Npsplit resulted in NR droop to 91% whiciL ,_.i.ted the low NR
warning horn and light (figs. 7A through 7C). One NR/Np overshootto 102.5% was observed during recovery. A 6 sscond collectivecontrol increase with a 2% NR/Np split resulted in a smaller
6
NR droop to 95% (figs. 8A through 8C). An unintentional reductionin rate of collective control increase during the last two seconds
resulted in degraded recovery characteristics in that NR/Np over-shot to 103.5% and several residual engine/airframe oscillationsocurred. Addition of the collective control potentiometer signalimproved the magnitude of NR droop for a given rate of collectivecontrol input but this configuration demonstrated the same trendsas configuration one in torque splits and unpredictable NR/Nprecovery characteristics. The addition of the collective poten-
tiometer signal to the ECU had no effect on the torque and NR/Nposcillations since they occurred when the TDI circuitry wasdisabled (i.e., above 50 ft-lb engine torque).
12. Poor Np governing, large NR droop, and persistent residualengine/airframe oscillations were observed during quickstopmaneuvers. During deceleration to a quickstop, NR and Np remainedjoined up to 104% (fig. 9A, app D). After the NR/NP split, Npcontinued to increase to 105% followed by NR droop to
95.5%. No NR/Np split occurred during a quickstop with minimumcollective control position of 25% and NR drooped to 98%(figs. IOA through 10E). An 8 to 10% torque split and smallpersistent engine/airframe oscillations were apparent to thepilot as the aircraft came to a stop. Configuration two withthe collective potentiometer signal showed some improvement inmagnitude of NR droop, but demonstrated trends similar to con-figuration one in torque splits and unpredictable NR/Np drooprecovery characteristics. Poor Np governing, torque splits,unpredictable NR/Np droop recovery characteristics (para 11),and residual engine/airframe oscillations will make it difficult
to safely perform NOE maneuvers such as quickstops and recoveryfrom low power descent with reduced visual cues (e.g, flyingat night using pilot night vision systems). The pilot will berequired to direct his attention inside the cockpit to compensatefor rapidly changing aural and visual cues (cockpit torque andNR/NP indicators) resulting from engine, rotor, and airframeoscillations. This will reduce NOE maneuvering capability of the
aircraft. The undesirable engine/ airframe response with the-701 TDI ECU (with collective potentiometer signal) during powerapplication from a low torque condition and during NOE quickstopmaneuvers is a shortcoming.
Configuration Three
13. Configuration three featured the -401 TDI ECU, described inappendix B which incorporated a collective control potentiometersignal and NR signal to the ECU. This configuration was evaluatedwith the maneuvers described in paragraph 8. Time history dataare presented in figures IIA through 12E, appendix D. During jump
7
takeoffs, NR droop was minimum and the torque splits observed onthe previous two configurations did not occur. During recoveryfrom autorotation, an aggressive 1.5 second collective controlincrease to 95% IRP with a 10% NR/Np split resulted in NR droopto 87.5% with only one overshoot to 102% during recovery(figs. 11A through 11C). There was no degradation in NR/Nprecovery characteristics with slower collective control increasesor smaller NR/Np splits at the initiation of the collectivecontrol increase. During an aggressive quickstop maneuver, NRdrooped to 91.5% with one overshoot to 102% during recovery(figs. 12A through 12E). NR droop and NR/Np recovery character-istics were predictable with changes in maneuver aggressiveness.During all maneuvers, configuration three demonstrated noticeablyless NR droop, good Np governing, good NR/Np droop recovery char-acteristics, and minimum residual engine/airframe oscillations.The reduced magnitude of NR droop can be attributed to theaddition of an NR signal to the TDI circuit in the ECU. Futuredesigns of UH-60A engine control units should include all thetransient droop improvements of the -401 TDI ECU. The betterrecovery characteristics of the -401 TDI ECU (reduced oscilla-
tions) occur when the TDI circuit is disabled. Therefore, thebetter recovery characteristics must be attributed to the differ-
ent Np governor dynamics shown in figure 5, appendix B. Thedynamics of the -701 TDI ECU were developed for the AH-64A heli-
copter. In future designs, the dynamics of the engine Np governorshould be tailored to the helicopter in which the engine is tobe installed. The engine/airframe response characteristics ofthe HH-60A with the -401 TDI ECU are satisfactory.
Configuration Four
14. Configuration four was the UH-60A equipped with the T700-GE-
700 engines. Engine/airframe response of this configuration wasevaluated with the maneuvers described in paragraph 8. Timehistory data are presented in figures 13 through 16, appendix D.A Jump takeoff performed with a 1.5 second collective controlincrease to 95% IRP resulted in NR droop to 96.5% and one overshootto 102.5% during NR/Np recovery 'ig. 13). A torque split betweennumber one and number two engines persisted for 6 seconds aftercollective movement stopped. Autorotation with a 4.0 second'ollective control increase to 95% 11 resulted in NR droop to88% and one overshoot to 102% during NR/NP recovery (fig. 14).The torque split during NR/Np recovery was similar to thatdescribed for jump takeoffs. For a given rate of collectivecontrol input, the magnitude of Np droop was larger in thisconfiguration than the other three confiurntlons, but the NR/Npdroop recovery was more predictabie than to:u iguratlons one and
two. The dynamics in the UH-60A Np goveiior are the same as the
-401 TDI ECU and NR/Np recovery characteristics are good in bothconfigurations.
15. During quickstop maneuvers, good Np governing and good NR/Npdroop recovery characteristics were observed. During an aggressivequickstop maneuver NR drooped to 85% with one overshoot to 101.5%during NR/NP recovery (fig. 15, app D). A moderately aggressivequickstop resulted in NR droop to 94%, activating the low NRwarning horn and light, with one overshoot to 102% (fig. 16).For a given rate of collective control increase, the magnitudeof NR droop was larger in this configuration than the otherconfiguration tested. During all the maneuvers, the NR/Np drooprecovery characteristics were predictable and fewer residualengine/airframe oscillations were apparent to the pilot. Torquesplits occurred during all maneuvers but were less noticeable tothe pilot because the return to matched torque and steady statetorque conditions occurred more smoothly in this configurationthan configurations one and two. Large NR droop resulting inactivation of the low NR warning system and moderate residualengine/airframe oscillations will limit aggressive combat man-euvering tactics. The undesirable engine/airframe response(large NR droop) in the UH-60A with T700-GE-700 engines duringpower application from a low torque condition and during NOEquickstop maneuvers is a previously identified shortcoming.
ENGINE/DRIVE TRAIN STABILITY
16. Tests of engine/drive train stability were conducted inconfiguration one. Ground tests consisted of pulling up oncollective to get the aircraft light on the wheels, rapidlydropping the collective control 10%, holding for 5 seconds, thenrapidly pulling the collective up 10% and holding for 5 seconds.The collective was also cycled +5% at 2 to 3 Hertz and then heldsteady for 5 seconds. The collective oscillations were repeatedat a 300-foot hover. The engine/drive train response was welldamped. No residual oscillations were noted. The engine/drivetrain stability of the HH-60A with the -701 TDI ECU is satis-factory.
9
CONCLUSIONS
GENERAL
17. The dynamics of the -701 TDI ECU Np governor (AH-64A config-uration) degrade the power turbine speed governing of the HH-60Awhen compared to either the -401 TDI ECU (HH-60A configuration)or the UH-60A with the T700-GE-700 engines (paras 13 and 14).
18. The HH-60A with the -401 TDI ECU exhibited the least transientNR droop and the best NR/Np recovery characteristics and issatisfactory (para 7).
19. The TDI circuits in the -401 TDI ECU decrease the magnitudeof transient rotor speed droop (para 13).
20. The engine/drive train response is stable with the -701 TDIECU in the HH-60A.
21. The UH-60A with T700-GE-700 engines exhibited large transientNR droop but NR/Np recovery characteristics were comparableto the HH-60A with the -401 TDI ECU (para 7).
22. The HH-60A with the -701 TDI ECU (with and without collectivepotentiometer input) exhibited the least desirable Np governingcharacteristics (large NR droop and poor NR/Np recovery) (para 7).
SHORTCOMINGS
23. The following shortcomings were found:
a. The undesirable engine/airframe response of the IIH-60Awith -701 TDI ECU (with and without collective potentiometerinput) during power application from a low torque condition andduring NOE quickstop maneuvers is a shortcoming (paras 10 and 12).
b. The undesirable engine/airframe response (large NR droop)of the UH-60A with the T700-GE-700 engines during power applica-tion from a low torque conditiji, and during NOE quitckstop man-euvers is a previously identified shortcoming (para 15).
10
RECOMMENDATIONS
24. Future designs for UH-60 engine control units should includeall the transient droop improvements of the -401 TDI ECU
(para 13).
25. Future designs of engine control units should have dynamics
tailored to the particular helicopter in which the engines are tobe installed (para 13).
11
APPENDIX A. REFERENCES
1. Letter, AVSCOM, AMSAV-8, 29 January 1986, subject: HH-60AHelicopter Equipped with the T700-GE-701 Transient Droop Improve-ment Electronics Control Unit. (Test Request)
2. Technical Order, TO IH-60(H)A-l, Preliminary Flight Manual,HH-60A Helicopter, Headquarters Department of the Air Force, 16August 1985.
3. Technical Manual, TM 55-1520-237-10, Operator's Manual, UH-60AHelicopter, Headquarters Department of the Army, 21 May 1979 withchange 37 dated 17 July 1986.
12
APPENDIX B. DESCRIPTION
GENERAL
1. Only one type hydromechanical unit (HMU) was used on theHH-60A during these tests. The HJ on the UH-60A was different.The h'H-60A tests were done with -401 transient droop improvement(TDI) electronic control units (ECU) and with -701 TDI ECU (withand without a collective position signal input). The UH-60A
tests were done using a third type of ECU, which is standard onthe T700-GE-700 engines on the UH-60A.
Hydromechanical Units
2. The acceleration fuel schedules for T700-GE-700 and T700-GE-701 engines are shown in figure 1. The T700-GE-701 HMU used is
known as the TDI HMU because the acceleration fuel schedule wasraised above approximately 61% gas producer speed from the pre-vious T700-GE-701 HMU version.
Electrical Control Units
3. Figure 2 presents a schematic of the -700 ECU power turbinespeed governor. The governor switches from high to low gain atlow engine torque when the power turbine speed (Np) is close to100%. This is to prevent the engine from spooling down rapidlyso that it can respond to power demands more quickly. It switchesback to high gain if engine torque rises above 20 foot-pounds orNp is above 104% or below 99%.
4. Figure 3 presents a schematic of the -701 TDI ECU Np governor
and the cicuitry added to improve the transient rotor speeddroop characteristics. The TDI circuitry accepts a collectivecontrol position input which it differentiates. It then increases
fuel flow as a function of positive collective control rate ofmovement. This ECU was also tested with the collective signal
disabled. The TDI circuitry is disabled if the engine torqueis above 50 ft-lb or Np is above 107%. The Np governor gain isswitched from low to high if the engine torque is above 50 ft-lbor the Np is above 107% or below 99% (a change from the -700 Np
governor).
5. Figure 4 presents a schematic of the -401 TDI ECU Np governorand TDI circuitry. The TDI circuitry increases fuel flow as a
function of collective rate of movement and rotor speed decayrate. Differences between the -701 and -401 TDI ECU are high-lighted in dashed circles. Table 1 presents the differencesamong the ECU in Np governor gain switching conditions and input
signals.
13
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Gain Switch Conditions Input Signals
Engine Power TurbineType Torque Speed Collective Rotor
Configuration ECU (ft-lb) (%) Position Speed
One -701 50 107 No No
Two -701 50 107 Yes No
Three -401 50 112 Yes Yes
Four -700 20 104 No No
19
'B" ' ; ',X*,,pi-I
6. Figure 5 shows the difference in dynamics between the -700/-401 TDI ECU and the -701 TDI ECU. The notch filter in the -7019CU was added to prevent an instability on the AH-64A.
20
APPENDIX C. INSTRUMENTATION
1. Airborne data acquisition systems were installed on both air-craft. The systems included transducers, wiring, signal condi-tioning, pulse code modulation (PCM) encoder, magnetic taperecorder, and cockpit displays and controls. A boom was mountedon each aircraft, extending forward of the nose in the waterline plane. The booms incorporated pitot-static tubes, andangle-of-attack and angle-of-sideslip sensors.
2. Instrumentation and related special equipment required for thetest are presented in the following list.
Pilot Station Displays
Pressure altitude (boom system)Airspeed (boom system)Vertical rate of climb (ship system)Main rotor speed (high resolution)Engine torque (both engines)Engine measured gas temperature (both engines)Engine power turbine speed (both engines)Engine gas generator speed (both engines)Engine load demand spindle position (both engines)Angle of sideslipControl positions
LongitudinalLateralDirectionalCollective
Radar altitudeEvent switchCG Normal accelerationPrimary attitude indicatorTurn needle and ball
Copilot Station Displays
Pressure altitude (ship system)Airspeed (ship system)Main rotor speedEngine Torque (both engines)Engine measured gas temperature (both engines)Engine gas generator speed (both engines)Fuel used (both engines)Total air temperatureTime code displayEvent switchData system controls
21
Parameters Recorded on Magnetic Tape
Time codeEvent (pilot and copilot)Main rotor speedFuel used (both engines)Engine torque (both engines)Engine measured gas temperature (both engines)Engine gas generator speed (both engines)Engine power turbine speed (both engines)Engine fuel flow (both engines)Airspeed (boom system)
Airspeed (ship system)Pressure altitude (boom system)Pressure altitude (ship system)Total air temperatureControl positions
Longitudinal
LateralDirectionalCollective
Aircraft attitudesPitchRollYaw
Aircraft angular velocitiesPitchRollYaw
Radar altitudeCC normal acceleration
22
!%
APPENDIX D. TEST DATA
INDEX
Figure Figure Number
Jump Takeoff (Configuration One) IA through IC
Recovery from Autorotation (Configuration One) 2A through 4C
Quickstop (Configuration One) 5A through 5E
,Jump Takeoff (Configuration Two) 6A through 6C
Recovery from Autorotation (Configuration Two) 7A through 8C
Quickstop (Configuration Two) 9A through IOE
Recovery from Autorotation (Configuration Three) 11A through 11C
Quickstop (Configuration Three) 12A through 12E
Jump Takeoff (Configuration Four) 13
Recovery from Autorotation (Configuration Four) 14
Quickstop (Configuration Four) 15 and 16
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DISTRIBUTION
1HQDA (DALO-AV, DALO-FDQ, DAMO-H1RS, DAMA-PPM-T, 6
DAMA-RA, DAMA-WSA)
US Army Materiel Command (AMCDE-SA, AMCDE-P, AMCQA-SA, 4
AMCQA-ST)
US Army Training and Doctrine Command (ATCD-T, ATCD-B) 2
US Army Aviation Systems Command (AMSAV-8, AMSAV-ED, 15
AMSAV-Q, AMSAV-MC, AMSAV-ME, AMSAV-L, AMSAV-N,
AMSAV-GTD)
US Army Test and Evaluation Command (AMSTE-TE-V, 2
AMSTE-TE-O)
., US Army Logistics Evaluation Agency (DALO-LEI) 1
US Army Materiel Systems Analysis Agency (AMXSY-RV, AMXSY-MP) 8
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US Army Armor School (ATSB-CD-TE) 1
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ATZQ-TSM-S, ATZQ-TSM-LH)
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NASA/Ames Research Center (SAVRT-R, SAVRT-M (Library)
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Aviation Applied Technology Dir,,, !'ndi t , . TY-DRD
SAVRT-TY-TSC (Tech Library)
DISTRIBUTION
HQDA (DALO-AV, DALO-FDQ, DAMO-HRS, DAMA-PPM-T, 6
DAMA-RA, DAMA-WSA)
US Army Materiel Command (AMCDE-SA, AMCDE-P, AMCQA-SA, 4
AMCQA-ST)
US Army Training and Doctrine Command (ATCD-T, ATCD-B) 2
US Army Aviation Systems Command (AMSAV-8, AMSAV-ED, 15
AMSAV-Q, AMSAV-MC, AMSAV-ME, AMSAV-L, AMSAV-N,
AMSAV-GTD)
US Army Test and Evaluation Command (AMSTE-TE-V, 2
AMSTE-TE-O)
US Army Logistics Evaluation Agency (DALO-LEI) I
US Army Materiel Systems Analysis Agency (AMXSY-RV, AMXSY-MP) 8
US Army Operational Test and Evaluation Agency (CSTE-AVSD-E) 2
US Army Armor School (ATSB-CD-TE) 1
US Army Aviation Center (ATZQ-D-T, ATZQ-CDC-C, ATZQ-TSM-A, 5
ATZQ-TSM-S, ATZQ-TSM-LH)
US Army Combined Arms Center (ATZL-TIE) i
US Army Safety Center (PESC-SPA, PESC-SE) 2
US Army Cost and Economic Analysis Center (CACC-AM) 1
US Army Aviation Research and Technology Activity (AVSCOM) 3
NASA/Ames Research Center (SAVRT-R, SAVRT-M (Library)
US Army Aviation Research and Technology Activity (AVSCOM) 2
Aviation Applied Technology Directorate (SAVRT-TY-DRD
SAVRT-TY-TSC (Tech Library)
9'. .. I *,%* ~ ~
US Army Aviation Research and Technology Activity (AVSCOM) 1
Aeroflightdynamics Directorate (SAVRT-AF-D)
US Army Aviation Research and Technology Activity (AVSCOM) 1
Propulsion Directorate (SAVRT-PNr-D)
Defense Technical Information Center (FDAC) 2
US Military Academy, Department of Mechanics I
(Aero Group Director).
ASD/AFXT, ASD/ENF 2
US Army Aviation Development Test Activity (STEBG-CT) 2
Assistant Technical Director for Projects, Code: CT-24
(Mr. Joseph Dunn) 2
6520 Test Group (ENML) 1
Commander, Naval Air Systems Command (AIR 5115B, AIR 5301) 3
Defense Intelligence Agency (DIA-DT-2D) I
US Army Aviation Systems Command (AMSAV-EAA) 2
US Army Aviation Systems Command (AMSAV-ECU) 2
US Army Aviation Systems Command (AMSAV-EP) 2
US Army Aviation Systems Command (AMCPM-BH-T) 4
Commander, US Army Test and Evaluation Command (AMSTE-CT-A
AMSTE-TO, AMSTE-EV) 3
'Commander, US Air Force Aeronautical Systems Division
(ASD/AFX, ASD/YZA) 2
Commander, US Air Force Flight Test Center
(Test W/TEVH) 1
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