,..

,i'·

NASA Technical Memorandum 84908NASA-TM-8490819830013932

Airstart Performance of a DigitalElectronic Engine Control Systemin an F-15 Airplane

Stephen J. Licata and Frank W. Burcham, Jr.

April 1983

LIBRARY COpyi,PR ? 0 1983

NI\SI\National Aeronautics andSpace Administration

LANGLEY RESEARCH CENTERLIBRARY, NASA

H,o.~,'?TON. VIRGINIA

https://ntrs.nasa.gov/search.jsp?R=19830013932 2018-05-10T01:53:47+00:00Z

., r·. -;t-'.\ \ \ ~::;i" \.

Airstart pet~formance of a digit~l

F- t 5 .3 t r t:113r\2A/LICATA; S. j.; 8/BURCHAM~ 1= ~,l In

\. lj·i. ~ :...JG••

Natl0nal Aeronautics andSp2ce Admlntstratl0n~ Hugh L~ DrYden FlightR:~searct\ Cf::\\te~~~ t..Ci).;a(dSi Cal1f. A\lAIL.t\lTIS SAP: HC Af)3/"t'ilF PttJl/*F-15 AIRCRAFT/*NUMERICAL CONTROL/*STARTING/*TURBOFAN ENGINES/*TUR80JETCidC' T r,\c !.....r~rdTDn!L\\i1.,A i ""i\.- "J"j,',i" r....\j\-~/ p, I R.SPEED / FL I(;'HT AL.TITljOE/' FtJEL C()r\iTR()L~/ FJJEL FLO!).]AtJtt-ior

_ Th.e .:i.trst.3rt t:Jerftjrrfi.3rlce {)f ·tt-'~e··F"lC;()--erlglrte eC{tlt~=it:le(i u-Ittr·, a---dt';1,-t-al--~---­

el~e(:t{"orlt·~: eri91rH? cC·fitrc:l (OEEC) :3"}··lstern UJ.3.S e\laltlate{j tr"t .3f, F-t5 atr~:!'.3r'ie.tf'1E: C!EEC s~···~:tern tr-~c:Ot'''POt'ates ~:1(ise{1-1o(H~ ~3;lr:;t~3.rt lC::;1i~: f~Jr lrQPr~) ...}ec!c2pabtlttv. Srooldomn and let fuel starter-assisted atrstarts were madeQ'Jer a. rarr;je ;~)f att"'speerls 2riCl alttt~.l(ies~ All jet ftJel :;t.3rter-.3ss1stedatrstarts were successful~ mtth 2trstart ttme VarYlng from 35 to 60 sec.All spooldown atrstarts at 3trspeeds of 200 Knots and higher wereStl(:,:essfIJll ~31t·':;tax·t tlfaes c"at1ged frcirn 4!:, se~: .3t 25S~ ~-~..rv:)ts to ""l~35 sec; .3.t208 knots. The effects of altitude on atrstart success and ttme weresma 1. The flight results agreed C oselv wtth previous altitude factlitvtes results. The DEEC sYstem prov ded successful atrstarts at airspeeds

AtJTH:

tJTTL:

(:ORP:

t;'ll t\lS:ABA:......~DC"\U~--i·

•

NASA Technical Memorandum 84908

Airstart Performance of a DigitalElectronic Engine Control Systemin an F·15 AirplaneStephen J. Licata and Frank W. Burcham, Jr.NASA Ames Research Center, DrydenFlight Research Facility, Edwards, California 93523

NI\S/\National Aeronautics andSpace Administration

Ames Research CenterDryden Flight Research FacilityEdwards, California 93523

INTRODUCTION

The ability to achieve rapid and reliable airs tarts is crucial to the safe oper­ation of modern jet aircraft. The NASA Dryden Flight Research Facility is currentlytesting an engine equipped with a prototype digital electronic engine control (DEEC)in an F-15 airplane. Advantages of the digital control over engine control systemsnow in use are: more inputs and outputs of engine parameters into the control system,computing capability that is both faster and more accurate than possible at present,ann extensive self-test features and fault accommodation (refs. 1 and 2). One of thesignificant features of the DEEC is an improved airstart capability. The DEEC incor­porates closed-loop airs tart logic. The airstart logic has been tested in an alti­tude facility at the Arnold Engineering and Development Center (ref. 3). This reportpresents the flight evaluation of the DEEC airstart capability and a comparison tothe results of altitucte facility tests.

SYMBOLS AND ABBREVIATIONS

secondary engine control

compressor inlet variable vanes

digital electronic engine control

fan turbine inlet temperature, °C

pressure altitude, m

jet fuel starter

Mach number

engine fan speed

engine core speed, percent (100 percent is 14,000 rpm)

main burner pressure

power lever angle, deg

engine inlet static pressure

mixed turbine discharge pressure

rear compressor variable vanes

engine inlet temperature

engine fuel flow, kgfhr

DESCRIPTION OF APPARATUS

The F-15 aircraft (fig. 1) is a single seat, high performance, all-weather airsuperiority fighter capable of Mach 2.5. It is a twin-engine airplane with a high­mounted sweptback wing, twin vertical stabilizers, and large horizontal stabilizers.The F-15 has been modified to be a general test bed. The specific modification forthe DEBC flight test program was the replacement of the left engine with a specialF100 engine equipped with a DEEC system.

The F100 engine (figs. 2 and 3) is a twin spool, low bypass ratio augmented tur­bofan. It has a three-stage fan driven by a two-stage low pressure turbine. The 10­stage high-pressure compressor is driven by a 2-stage high-pressure turbine. A com­pressor bleed is used only during starting. The variable camber inlet guide vanesand rear compressor vanes allow for higher performance over the operating flightenvelope. Variable augmented thrust is provided by a mixed flow, five-segment after­burner. The mixed flow is exhausted through a variable area convergent-divergentnozzle. For these tests, engine serial number P680063 was used. It had been updatedto an F100(3) production engine configuration prior to the DEEC installation.

The DEBC is a full-authority digital electronic control system with a simpleintegral hydromechanical secondary engine control. DEEC replaces the functions ofthe supervisory electronic engine control and hydromechanical unified fuel control onthe standard F100 engine. The DEEC system, shown in figure 4, receives inputs from(a) the airframe through throttle position (PLA) and Mach number (M)i (b) the enginethrough pressure sensors PB, P6TM, and PS2, temperature sensors TT2 and FTIT, rotorspeed sensors N1 and N2; and (c) the control system through feedback resolvers thatindicate variable vane (RCVV, CIVV) positions, metering valve positions (fuel flowfor primary and augmented thrust modes), and exhaust nozzle positions. This infor­mation is used by the DEEC controller to (a) schedule the compressor bleeds and posi­tion the variable vanes through actuators in an open-loop system; (b) control primaryand augmented fuel flow in a closed-loop system; and (c) control nozzle in a closed­loop system.

The DEBC computer is a l6-bit, l.2-~sec cycle time microcomputer with lO.5K ofavailable memory. The entire electronic unit is fuel cooled.

The DBEC secondary engine control (SEC) is a purely hydromechanical engine fuelcontrol. It is integrated within the gas generator fuel metering hardware of theDEEC. In the event of a critical DEEC failure, or at the pilot's option, the SECsystem can be engaged. The SEC inputs are PLA, TT2, PS2, and RCVV position. Basedon these paraneters, the SEC system controls the engine fuel flow, the RCVV position,and the compressor start bleed.

The jet fuel starter (JFS) is a small auxiliary gas turbine power unit which canbe coupled to the F10a engine. The JFS is used to accelerate the high compressor forengine starting on the ground or in flight.

Pressures, temperatures, rotor speeds, fuel flow, and positions of variablegeometry are measured at various stations in the F10a engine. Engine parametersimportant to this report are PLA, N2, FTIT, and WF. All parameters are input into apulse code modulation (PCM) system during the test flights. The digital PCM data arerecorded on an onboard tape recorder and also telemetered to the ground for real-timedisplay in the control room.

2

DEEC AIRSTART LOGIC

In the event of an engine shutdown or flameout, the DEEC monitors several para­~eters to insure a successful airstart. A simplified block diagram of DEEC airs tartlogic is given in figure 5. An open-loop fuel scheduling routine is used until thehurner "light" (fuel mixture ignition) is indicated by a rise in the FTI'r signal.Once the burner light has been detected by the DEEC, fuel flow and compressor bleedcontrol switches to the closed-loop logic shown in the figure. This logic attemptsto maintain a desired N2 rate by varying fuel flow. The desired N2 rate is a func­tion of PT2, TT2, and M. If the fuel flow is too high the compressor will stall,resulting in a "hot start." If the fuel flow is too low, the energy available willnot be sufficient to overcome the losses in the engine and the accessory power drain,resulting in a "hung start." The DEEC airstart logic maintains the optimal N2 ratesubject to a bias if FTIT exceeds a limit of approximately 760 0 C. The minimum fuelflow set by a stop in the fuel metering valve is approximately 115 kg/hr. Thecompressor bleeds are held open until 56 percent N2 is attained. At airspeeds belowapproximately 200 knots, the DEEC airstart logic is designed to light the burner andmaintain N2, but not to accelerate the engine to idle.

The jet fuel starter may also be used to assist in airstarts. For JFS-assistedairstarts, the DEEC uses a higher scheduled N2 rate and a lower FTIT limit. Compres­sor bleeds are held open until 56 percent N2 is achieved.

TEST PROCEDURE

This report is concerned with the ability of the DEEC-equipped F100 engine toperform airstarts with and without a JFS assist. The three types of airstarts exa­mined are 40-percent spooldown, 25-percent spooldown, and JFS assist.

The spooldown airs tart is achieved in a four-step procedure: engine shutdown,pressurization, light, and acceleration of the engine to idle speed. The engineshutdowns were mostly performed from the intermediate power setting. The enginespool (compressor rotor) is then allowed to wind down (spooldown) to a predeterminedpercentage of maximum core speed. For the evaluation of DEEC airstart capability,values of 40-percent N2 and 25-percent N2 were used. The pressurization step isaccomplished when the pilot returns the throttle to the idle power setting to beginthe start cycle. This pressurizes the fuel system, and fuel begins to flow to thecombustor. Approximately 10 sec later, the fuel reaches the combustor nozzles and isignited (light). The fuel flow is modulated by the DEEC to maintain the scheduledN2 rate until the scheduled idle speed is reached and the airstart sequence iscompleted.

The JFS-assisted airs tart is accomplished by coupling the jet fuel starter tothe high compressor rotor through a gearbox. The JFS may be engaged at any N2 speedfrom 0 to 30 percent. It accelerates the core rotor to approximately 30 percent.The pressurization step may be initiated at a core speed of 12 percent or greater.The JFS disengages at 50-percent N2.

Of the 53 primary DEEC airs tarts attempted during the test flights, 21 were40-percent spooldown, 24 were 25-percent spooldown, and 8 were JFS assisted.Airstart time is calculated from the pressurization step to idle in the above proce­dure. For all airstarts the normal F-15 power requirements for the engine andaccessories were present.

3

During the airstart tests, the pilot used the right engine of the F-15 aircraftto maintain the desired airspeed and altitude. Airspeed was held within 4 knots andaltitude within 30 m of the desired test conditions. Test day temperatures varied asmuch as ±10 0 C from standard day temperatures. More details of the test procedure canhe found in reference 2.

RESULTS AND DISCUSSION

Spooldown Airstarts

Figure 6 is a time history of a DEEC airstart at an airspeed of 250 knots and analtitude of 9100 m, which also illustrates the use of closed-loop airstart logic. Theengine was shut down at t = 10 sec. Immediately after shutdown there was a corre­sponding drop in core speed (N2), fan turbine inlet temperature (FTIT), and fuel flowto the engine (WF). The pilot initiated the ignition sequence by moving the throttleup over the idle detent to the idle power setting at t = 22 sec as the core rpmreached 40 percent. At this point the fuel flow began at the minimum value of115 kg/hr. At t = 31 sec, the fuel mixture was ignited (light) as noted by theincrease in FTIT. The DEEC closed-loop logic modulated the fuel flow to achieve thedesired rate of acceleration of the engine core. N2 increased uniformly tot = 45 sec, sec, then increased more rapidly. Idle speed was reached at t = 77 sec.FTIT varied between 450 and 520 0 C during the airstart. The time required for the airstart, defined as the difference between idle and pressurization times, was 55 sec.

Figure 7 shows another airstart at the same flight conditions of 250 knots,9100 m, hut for a 25-percent spooldown. Shutdown occurred at t = 7 sec. The enginespooled down to 25 percent at t = 39 sec, and the light occurred at t = 47 sec. Theengine spooled up at a nearly constant rate, reaching idle at t = 111 sec. The FTITstayed below 500 0 C during the airstart. The airs tart time was 72 sec, as compared to55 sec for the 40-percent spooldown airstart.

Airstarts at lower airspeeds took longer due to the reduced energy of the inletflow, lower burner pressures, and lower stall margin. Figure 8 shows a 40-percentspooldown airstart at an airspeed of 200 knots and an altitude of 9250 m. Shutdowntime was t = 12 sec, pressurization at t = 23 sec, light at 32 sec, and idle att = 108 sec. Airstart time was 86 sec. The FTIT reached 600 0 C at t = 38 sec, withfuel flow on the minimum flow stop.

The 25-percent spooldown airstart at VC = 200 knots is shown in figure 9, at analtitude of 7600 m. Shutdown occurred at t = 3 sec, pressurization at t = 28 sec,light at t = 34 sec. The fuel flow was on the minimum stop from pressurization tot = 70 sec, and FTIT again reached 600 0 C. The airstart was completed at t = 139 secfor a time of 111 sec.

The effects of altitude were evaluated by performing airstarts at VC = 250 knotsand 200 knots at several altitudes. Examples of spooldown airstarts at VC = 200 knotsand an altitude of 4600 m are shown in figures 10 and 11. A 40-percent spooldown air­start is shown in figure 10. Shutdown occurred at t = 9 sec, pressurization att = 15 sec, and light at t = 23 sec. Following the light, the N2 continued todecrease for 10 sec as fuel flow was increased. At t = 40 sec, a positive N2 ratewas achieved and fllel flow was cut back as FTIT reached 600 0 C. In the time betweent = 50 and 70 sec, oscillations in N2, FTIT, and WF occurred indicating that the

4

gains in the closed-loop control logic were slightly too high. The airstart contin­ued and idle was reached at t = 104 sec, for an airstart time T = 89 sec, slightlylonger than the 86-sec time from figure 8 at the higher altitude but similarairspeed.

The 25-percent spooldown airs tart at VC = 200 knots at an altitude of 4600 m isshown in figure 11. Shutdown occurred at t = 16 sec, pressurization at t = 33 sec,and the burner light occurred at t = 42 sec. The airstart proceeded normally,although some oscillations are noted between t = 70 and 90 sec. The frequency ofthese oscillations was similar to that seen in figure 10, but the amplitude was muchsmaller. The airstart was completed at t = 130 sec for an airstart time, T, of97 sec, somewhat faster than the 111 sec of figure 9.

JFS-Assisted ~irstarts

For more rapid airstarts at altitudes helow 6100 m, the jet fuel starter wasused for assisted airstarts. Figure 12 shows a time history of a JFS-assisb!d air­start at VC = 255 knots at an altitude of 6100 m. Shutdown occurred at t = 11 sec,and the JFS was engaged at t = 33 sec at an N2 of 25 percent. The N2 increased as aresult of the JFS assist and stabilized at N2 = 32 percent. The pressurization wasdelayed for this test until stable JFS motoring speed was observed at t = 68 sec.~fter the light at t = 79 sec, N2 increased rapidly and idle was achieved att = 106 sec for an airstart time of 38 sec.

A more typical JFS-assisted airstart in which the pressurization occurred imme­diately after JFS engagement is shown in figure 13 at VC = 345 knots at an altitudeof 5200 m. Shutdown occurred at t = 13 sec. At this relatively high airspeed the N2spooldown was slow, and N2 was decreasing slowly through 21 percent when the JFS wasengaged at t = 59 sec, followed imMediately by pressurization. Light occurred at73 sec and idle was reached at t = 96 sec for an airstart time of 37 sec.

A JFS-assisted airstart at a lower speed of VC = 210 knots at an altitude of6100 m is shown in figure 14. Shutdown occurred at t = 14 sec, JFS engage att = 34 sec, pressurization at t = 36 sec, and light at t = 46 sec. The N2 rate wasreduced to nearly zero at t = 65 sec prior to JFS disengage. Following the JFSdisengage the N2 rate increased. The airs tart was completed at t = 83 sec, for anairstart time of 47 sec.

1\11 JFS-assisted airstarts attempted were successful from VCover a wide range of altitudes.

Summary of Airstart Times

200 to 400 knots

Airstart times, T, for the DEEC airs tarts are shown in figure 15 for the 40­percent spooldown airstarts, in figure 16 for the 25-percent spooldown airstarts, andin figure 17 for JFS-assisted airstarts. Airstart times for the 40-percent spooldownairstarts (figure 15) ,."ere approximately 50 sec at VC = 250 knots, 85 sec atVC = 200 knots, and up to 192 sec at VC = 175 knots. For the 25-percent spooldownairstarts, times were approximately 65 sec at VC = 250 knots, and from 97 to 135 secat airspeeds of 205 to 210 knots. It is clear that 25-percent spooldown airs tarts atVC = 200 knots are only marginally successful due to the long start times. Effects ofaltitude on airstart time are somewhat inconsistent, particularly at VC = 200 knots.For VC = 250 knots, the airstart times are plotted as a function of altitude infigure 18. No strong trends are evident, but there seems to he some trend towardslightly faster airstarts at intermediate altitudes of 6000 to 8000 m.

5

Unsuccessful Airstarts

At airspeeds below 200 knots, most of the spooldown airstarts were unsuccessful.This is not surprising since at these low airspeeds, the DEEC logic is only designedto light the burner and maintain rpm until the pilot can increase airspeed. Theunsllccessful airstarts were mostly hung starts, in which the N2 either decreased ordid not increase. A typical example of a hung start is shown in figure 19, a25-percent spooldown airstart attempt at VC = 180 knots at an altitude of 7600 m.Following the light, N2 increased very slowly to 28 percent and then stabilized. Thefuel flow remained on the minimum flow stop, and FTIT initially exceeded 600 0 C andthen slowly decreased.

Only one hot start occurred in the airstart tests; it is shown in figure 20. Itwas a 40-percent spooldown airstart attempt at VC = 160 knots at 7600 m. Followingthe burner light at t = 35 sec, N2 continued to decrease, while FTIT increasedrapidly, even with the fuel flow at the minimum value. When the FTIT reached themaximum allowable value of 800 0 C, the pilot shut down the engine.

Summary of Spooldown Airstart Success

Figure 21 summarizes the successful and unsuccessful spooldown airstarts. Allairstarts at airspeeds of 200 knots and above were successful. At VC = 175 knots,all 25-percent spooldowns were unsuccessful, and 40-percent spooldowns above 8000 mwere unsuccessful. All spooldown airs tarts at VC = 150 knots were unsuccessful. Thepilot's handbook airstart limit for the F100 engine with the standard control systemis also shown in figure 21. The DEEC provides airstart capability at least 50 knotslower than the handbook limit.

Comparison of Flight to Altitude Facility Test Results

TheDEEC airstart results from the flight tests are compared to the altitudefacility test results of reference 3. The lowest airspeed at which spooldownairstarts were successful is shown in figure 22. For 40-percent spooldown airs tarts(figure 22{a» and 25-percent spooldowns (figure 22{b» very good agreement is shownbetween the flight and altitude test results. This very good agreement is probablydue to the closed-loop features in the DEEC which tend to compensate for any smalldifferences between the flight and facility conditions.

CONCLUDING REMARKS

A series of airstarts·were conducted with the DEEC-equipped F100 engine in anF-15 airplane. The airstart envelope and time required for airstarts were defined.The success of an airstart is most heavily dependent on airspeed. Spooldownairstarts at 200 knots and higher were all successful. Spooldown airstart timesranged from 45 sec at 250 knots to 135 sec at 200 knots. JFS-assisted airstarts wereconducted over a wide range of airspeeds, and airstart times varied from35 to 60 sec. The effect of altitude on airstarts was small. The airstart flighttest results agreed closely with previous altitude facility data.

6

REFERENCES

1. Barrett, w. J.~ Rembold, J. P.~ Burcham, F. W., Jr.~ and Myers, L. P.: FlightTest of a Full Authority Digital Electronic Engine Control System in an F-15Airplane. AIAA Paper 81-1501, July 1981.

2. Burcham, F. W., Jr.~ Myers, L. P.; Nugent, J.; Lasagna, P. L; and Webb, L. D.:Recent Propulsion System Flight Tests at the NASA Dryden Flight ResearchCenter. AIAA Paper 81-2438, November 1981.

•

3. Ewen, J. S.; and Walter, W. A.:Engine Altitude Test Report •

F100 Engine Model Derivative Program InitialPratt & Whitney Aircraft FR-14785, July 1981.

7

8

Fi gure 1.

Static pressurenoseboom probe (PS2)

Figure 2.

Photograph of the F-15 airplane

Photograph of the DEEC test engine

-----

Fan turbine

~r:J~=>==--=4'Q~~.----=-.~r-Compressorstart bleed

Rear compressor variablevanes (RCVV)

High-pressurecompressor

High -press ureturbine (

Mixed fIO.W (Variable areaaugmentor nozzle (AJ)

.q1iLJu~ _. u ••• _.-::'~~ £a=c=: _, .. ~"ntl'1nftn --ill tV' \ fl~·· ,; .t Ii if \

Compressor inletvariable vanes(CIVV)

Figure 3. Cutaway view of the FIOO DEEC engine

1.0

......o

DEECSEC

-tpB- ----- ----rm-· 1N2 (Duall tTT2 Nl t PS2 PB HIT : PT6MI

Electric TT2 PS2I

Nl PB FTIT I PT6Malternator sensor sensor sensor sensor sensor i sensor

1Electric (Dual) (Dual) (Dual), power PLA TT2

DEEC I I r - PS2I I I Segment Segment Nozzle

Output _t ____ _,_ t_ 1, 2, 4 3, 5 controlInput

Digital : Hydromechanical I

Control r - -"1 secondary engine ~ - - l Core fu el , Duct fuelVariable toto digital software actuation 1- r _ ~It..!:o.!. __ J metering I metering ~

valve I valveconversion variable I Iconversion I I Fuel distribution

I ~ and regu lationI I Engi ne fuel, : metering

startCIVV I I valve

bleed RCVV

t+ t t Segment

Actuator I Actuator ~ ~ Actuator l sequenceActuator I Actuator I,. Actuator ,. Actuator ,. ,. actuator ,. ~

,

Position t Position Position Position Pos ition Position Positiontransducer Start transducer transducer transducer transducer transducer transducer

bleed(Duallsolenoid (Ouall

tI t t t

Figure 4. Block diagram of the DEEC control system

PS2

'"

JFSENGAGED

?

COMPRESSORSTART BLEEDI

~N2

N21L""1 N°2dt"

BLEEDCOMMAND

FTIT

WFI '1"'------..

p::2~II ~:q .6bN\ltM \1 WF -

N·2 ~N2 FTITSCHEDULES TO FUEL FLOW BIAS

Figure 5. DEEC airstart logic

..

80

/- IDLE

I

VC=250 knots,

6020

SHUTDmIN( PRESSURIZATION

I r LIGHT, I

I

I

40t, sec

DEEC 40-percent spool down airstart.HP = 9100 m

o

o

a

40

80

500

500

1000

Figure 6.

PLA,deg

FTIT,

WF,kg/hr

60

N2,

percent 40

20

0

80

'2

~JF ,

kg/hr

500

o

r SHUTDOWN~-PRESSURIZATIONI -LIGHT

FTIT,

1000

500

OL-.......l-._-l -+L~--...L.---..L----.L.------J

40

a

80

..

80

60

N2,40percent

20

PLA,

deg

a

Figure 7.

20 40 60 80t, sec

DEEC 25-percent spool down airstart.HP = 9100 m

100 120

VC = 250 knots,

13

WF,

kg/hr

(-SHUTDOl~N

--PRESSURIZATION

500 r--~ LIGHT

o

1000

500

o

80 ---....

N2,

rJercent

PLA,

deg

60

40

20

o

80

40

14

o

Figure 8.

20 40 60 80t, sec

- DEEC 40-percent spool down airstart.HP = 9250 m.

100 120

VC = 200 knots,

I IDLE

500

WF,kg/hr

0

1000

500

o

80

60

N2,percent 40

20

o

80

PLA,deg 40

1401201004020o 60 80t, sec

Figure 9. DEEC 25-percent spool down airstart. VC = 200 knots,HP = 7600 m

15

WF,kgjhr

500

o

rSHUTDOHN

r PRESSURIZATION

I LIGHT

IDLE l

12010080604020

0L-_.-J~-1-__-L. J.-__~ ......I-+-_-----l

o

20

40

60

80

80

500

1000

o

PLA,deg 40

N2,

percent

t, sec

Figure 10. DEEC 40-percent spooldown airstart. VC =200 knots,HP = 4600 m

16

/- SHUTDOWN

HF,

kg/hr

500 ...--.-,

.rO

- PRESSURIZATION

,- LIGHT/

1

IDLE '.I

I

Ol-_---IL.-L__....L.....J...;. .L..-__--L .....L ....&...-_~___I

1401201008020 60t, sec

Figure 11. DEEC 25-percent spooldown airstart. VC = 200knots,HP = 4600 m

o

()L......_--+-.....L_--l---l4-__....L...__---Jl-.__--'-__---JL...---+_-'

4()

500

1000

PLA,

deq

FTIT,

80

60

N2,

percent 40

20

a

80

17

r SHUTDOHN JFS DISENGAGH1ENTlJFS ENGAGEt1ENT

LIGHT~

PRESSURIZATION") I

o

500

WF,

kg/hr

•1000

FTIT ,500

o

80

60

N2,40percent

20

o

80

PLA,

deg 40

o 20 40 60t, sec

80 10n 120

Figure 12. DEEC JFS-assisted airstart. VC = 255 knots,HP = 6100 m

18

500

~JF ,

kgjhr

o

r-- SHUTDOWN

---.....

PRESSURIZATIONJFS ENGAGEMENT

~---JFS DISENG~GEMENT

" r- IDLErLI GHT

1

, ....' ------

o

500

1000

FTIT,

80

60 -I

N2, I40

percent

20

..

o

80

PLA,

deq 40

100 120a 20

Figure 13.

40 60 80t, sec

DEEC JFS-assisted airstart. VC =HP = 5200 m

345 knots,

19

WF,kg/hr

FTIT,

500

o

1000

500

SHUTDOWN- JFS ENGAGH1ENT

rPRESSURIZATION

IDLE

LIGHT

..

0

80

60

N2,

percent 40

20

o

80

PLA,

deg40

o 20 40 60t, sec

80 100

20

Figure 14. DEEC JFS-assisted airstart. VC = 210 knots,HP = 6100 m

120

192to

o

110HP,m

a 3,000-5,000

0 5,000-7,000100 0 7,000-9,000

6- 9,000-11,000

~ 11,000-13,000

90 06-

080 6-

T,

sec70

6-0

60~ 6-

1&.6-a

50 66-

40

175 200 225 250 275 300

VC, knots

Figure 15. Effect of airspeed on airstart time for40-percent spool down airstart

21

22

140

o

130

120

HP,m .,110 <>

0 3,000-5,000

D 5,000-7,000

100 <> 7,000-9,000

0 b. 9,000-11,000

~ 11 ,000-13,000

90

T,~

b.sec

80

0 ~70 0

Db.~

60 D <>

50

40o 0

30'--__---L. ..L-__----I ......L- .l-.__-'- ------I

175 200 225 250VC, knots

Figure 16. Effect of airspeed on airstart time for 25-percent spool down

60

(.

HP, m

() 3,000-5,000

[J 5,000-6,000

..

NeN

050~ 0

[J()T,

40L 0sec[J [J

0000

I30

2~~5 260 215 2do 2~5 360 3~5 35D 375 400

VC, knots

Figure 17. Effect of airspeed on airstart time for JFS-assisted airstarts

N~

() 40-percent spool down

o 25-percent spool down

80

70

T,

sec

60

50

40

o o

()

30J -' ~ ~ ; 8' ~ 1h 1{ 12 x 103

HP, m

Figure 18. Effect of altitude on airstart time for spool down airstarts.VC ~ 250 knots

'.' I. "

r- SHUTDmm

I PRESSURIZATION

500 ,LIGHTI~F ,

kg/hr

a I I I I I 1I

1000

500

a

N2,

percent

80

60

40

20

a

80

PLA,deg 40 -

aI

20I

40 60t, sec

I80

I100

I120

Figure 19. Unsuccessful DEEC 25-oercent spool down airstart.VC = 180 knots, HP = 7600 m

25

l

6040t, sec

20o

40

80

o

PLA,deg

500

WF,kq/hr

0

1000_I

FTIT ,

°c 500

0

80

60

N2,

percent 40

20

Figure 20. Unsuccessful DEEC 40-percent spool downairstart. VC = 160 knots, HP = 7600 m

26

r . ~

Handbook limit, standardFlOO engine

VC, knots300

~ - 40-percent spool down

~ - 25-percent spool down

Open symbol denotes successful airstart

Solid symbol denotes unsuccessful airstart

225 250175 200;

/1 .• e e

./ / /• e 8. R' , , T

II.~ e/ / /.~e

//6

2

10

8

4

12 X 103

HP,m

I I I ~ I Io .2 .4 M.6 .8 1.0

Figure 21. Summary of DEEC spool downairstart test success

N

"

N00

Open symbols denote data from altitude facility (ref. 3)Solid symbols denote flight data

VC, knots

o ' ! ! I

12,000

10,000

8,000

HP,

m 6,000

4,000

2,000

250

.2 .4 M.6 .8 .2

(a) 40-percent spool down

Figure 22. Comparison of lowest airspeed for successful

tests and altitude facility tests

.4 t1.6 .8

(b) 25-percent spool down

DEEC airstarts between flight

... ... I..,. "

c:

1. Report No. I2. Government Accession No. 3. Recipient's Catalog No.

NASA TM-84908

4. Title and Subtitle 5. Report Date

AIRSTART PERFORMANCE OF A DIGITAL ELECTRONIC ENGINE April 1983

CONTROL SYSTEM IN AN F-15 AIRPLANE 6. Performing Organization Code

7. Author(s) 8. Performing Organization Report No.

Stephen J. Licata and Frank W. Burcham, Jr.

10. Work Unit No.

9. Performing Organization Name and Address

Ames Research Center 11. Contract or Grant No.Dryden Flight Research FacilityEdwards, California 93523

13. Type of Report and Period Covered

12. Sponsoring Agency Name and Address Technical Memorandum

National Aeronautics and Space Administration 14. Sponsoring Agency CodeWashington, D.C. 20546 • RTOP 533-02-21

15. Supplementary Notes

16. Abstract

The airstart performance of the Fl00 engine equipped with a digital electronicengine control (DEEC) system was evaluated in an F-15 airplane. The DEEC systemincorporates closed-loop airstart logic for improved capability. Spooldown andjet fuel starter-assisted airstarts were made over a range of airspeeds and alti-tudes. All jet fuel starter-assisted airstarts were successful, with airstarttimes varying from 35 to 60 sec. All spooldown airs tarts at airspeeds of200 knots and higher were successful, airstart times ranged from 45 sec at250 knots to 135 sec at 200 knots. The effects of altitude on airstart successand time were small. The flight results agreed closely with previous altitudefacility test results. The DEEC system provided successful airs tarts at air- .speeds at least 50 knots lower than the standard Fl00 engine control system.

17. Key Words (Suggested by Author!s)) 18. Distribution Statement

Engine control Unclassified-UnlimitedAirstartsDigital engine controlFl00 engine STAR category 07F-15 airplane

19. Security Oasslf. (of this report) 20. Security Classif. (of this pagel 21. No. of Pages 22. Price'

Unclassified Unclassified 31 A03

~For sale by the National Technical Information Service, Springfield, Virginia 22161.

)

}

\

•

•