Performance Improvements of an F-15 Airplane With an

NASA Technical Memorandum 100431

- Performance Improvements of an F-15 Airplane With an Integrated Engine-Flight Control System Lawrence P. Myers and Kevin R. Walsh

(NASA-TH-lao431) PERPORHANCE IMPROVELTEN TS N88-21159 OF AN P-15 AIEPLANE R I T H A N I B T E G R A T E U ENGINE-PLIGHT CONTROL SYSTEH (NASA) 12 p

CSLL 2 1 k Unclas ti3/07 0 137313

May 1988 '*

I c

Ndional Aeronautics and Space Administration

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NASA Technical Memorandum 100431

Performance Improvements of an F-15 Airplane With an Integrated Engine-Flight Control System Lawrence P. Myers and Kevin R. Walsh Ames Research Center, Dryden Flight Research Facility, Edwards, California

v 1988

4

National Aeronautics and Space Administration Ames Research Center Dryden Flight Research Facility Edwards, California 93523 - 5000

PERFORMANCE IMPROVEMENTS OF AN F-15 AIRPLANE WITH AN INTEGRATED ENGINE-FLIGHT CONTROL SYSTEM

Lawrence P. Myers and Kevin R. Walsh

NASA Ames Research Center Dryden F1 i ght Research Faci 1 i t y

Edwards, C a l i f o r n i a

Abs t rac t

An in teg ra ted f l i g h t and p ropu ls ion c o n t r o l system has been developed and f l i g h t demonstrated on the NASA Ames-Dryden F-15 research a i r c r a f t . The h i g h l y i n teg ra ted d i g i t a l c o n t r o l (HIDEC) system provides a d d i t i o n a l engine t h r u s t by increas- i n g engine pressure r a t i o (EPR) a t in termediate and a f te rbu rn ing power. The amount o f EPR u p t r i m i s modulated based on a i r p l ane maneuver requi re - ments, f l i g h t cond i t i ons , and engine in format ion.

Engine t h r u s t was increased as much as 10.5 percent a t subsonic f l i g h t cond i t i ons by uptrimming EPH. The a d d i t i o n a l t h r u s t s i g n i f i - c a n t l y improved a i r c r a f t performance. Rate o f c l imb was increased 14 percent a t 40,000 ft and t h e t ime t o c l imb from 10,000 t o 40,000 f t was reduced 13 percent. A 14 and 24 percent increase i n acce le ra t i on was obtained a t in termediate and maximum power, respec t i ve l y .

The HIDEC l o g i c performed f a u l t free. No en- g ine anomalies were encountered f o r EPR increases up t o 12 percent and f o r angles o f a t tack and s i d e s l i p of 32' and 1l0, respect ive ly .

ADECS

AJ

alpha

beta

CAS

D

DEEC

DEFCS

DFCC

DFPR

EMD

EPR

EPRP

EPRS

EPRUS

Nomenclature

advanced engine c o n t r o l system

exhaust nozzle area, f t 2

angle o f a t tack, deg

s i d e s l i p angle, deg

c o n t r o l augmentation system

i n l e t d i s t o r t i o n

d i g i t a l e l e c t r o n i c engine c o n t r o l

d i g i t a l e l e c t r o n i c f l i g h t c o n t r o l

d i g i t a l f l i g h t c o n t r o l computer

change in fan pressure r a t i o

engine model d e r i v a t i v e

engine pressure r a t i o , PT6/PT2

engine pressure r a t i o f o r optimum performance

engine pressure r a t i o f o r maximum s ta - b i l i t y (minimum i n l e t d i s t o r t i o n )

engine pressure r a t i o a t d i s t o r t i o n o the r than minimum

system

EPRU

FNP

F PR

FPHS

FPRUS

FTIT

H I DEC

I N S

KEPR

N 1

N1C2

PLA

Ps

PS2

PT2

PT6

TSFC

TT2

UART

WA

WACC

a

B

A

EPR u p t r i m command implemented by DEEC

ne t p ropu ls i ve force, l b

fan pressure r a t i o , PT2.5/PT2

fan pressure r a t i o f o r maximum s t a b i l -

f an pressure r a t i o a t d i s t o r t i o n o the r

fan t u r b i n e i n l e t temperature, OF

h i g h l y i n t e g r a t e d d i g i t a l c o n t r o l

i n e r t i a l nav iga t i on system

cockp i t m u l t i p l i e r on EPR command sent

f a n speed, rpm

co r rec ted fan speed, rpm

power l e v e r angle, deg

s p e c i f i c excess power, f t / s e c

s t a t i c pressure a t fan i n l e t , p s i a

t o t a l pressure a t f a n i n l e t , p s i a

t o t a l pressure a t t u rb ine , p s i a

t h r u s t s p e c i f i c f u e l consumption

t o t a l temperature a t f a n i n l e t , O F

uni versa1 asynchronous rece i vet-

i t y (minimum i n l e t d i s t o r t i o n )

than minimum

t o engine OEEC

t r a n s m i t t e r

co r rec ted engine a i r f l o w , lb /sec

co r rec ted fan a i r f l o w , lb /sec

angle o f a t tack , deg

angle o f s i d e s l i p , deg

incremental change

I n t r o d u c t i o n

Subs tan t i a l performance gains can be obtained by i n t e g r a t i n g t h e f l i g h t and p ropu ls ion c o n t r o l systems.1 By us ing t h e h igh throughput and l a r g e memory o f cu r ren t onboard computers, along w i t h high-speed communication data buses, i t w i l l be poss ib le t o implement a wide range o f i n teg ra ted f l i g h t and p ropu ls ion c o n t r o l modes onboard fu tu re a i r c r a f t . Such modes w i l l increase t o t a l veh ic le

ef fect iveness wi thout s i g n i f i c a n t weight o r cost penal t ies. Independent op t im iza t i on o f each con- t r o l system i S usua l l y compromised by worst case assumptions of o the r systems. To i n v e s t i g a t e t h e problem associated w i t h i n t e g r a t i o n and t o quan- t i f y t h e performance bene f i t s , NASA Ames Research Center's Dryden F l i g h t Research F a c i l i t y i s con- duc t i ng a program c a l l e d h i g h l y i n t e g r a t e d e lec - t r o n i c c o n t r o l (HIDEC). One f e a t u r e i n t h e HIDEC program i s t h e advanced engine c o n t r o l system ( A D E C S ) . ~

engine s t a l l margin i s l a r g e enough t o accommodate t h e worst case combination o f engine and a i r p l a n e induced disturbances. I n t h e ADECS, t h e s t a l l margin i s modulated i n rea l t ime based on t h e cu r ren t engine and a i r c r a f t requirements and f l i g h t condi t ions. This permi ts t h e unneeded s t a l l margin t o be t raded f o r increased engine performance by i nc reas ing t h r u s t , reducing f u e l f low, o r lower ing operat ing temperatures. The exchange between unneeded engine s t a l l margin and increased engine performance i s implemented by uptr imming the engine pressure r a t i o (EPR). The performance b e n e f i t s obtained by reducing engine s t a l l margin were p red ic ted and presented by Burcham and others.3

I n a conventional engine c o n t r o l system, t h e

A f l i g h t eva lua t i on o f t he ADECS f e a t u r e was conducted a t t h e Ames-Dryden F l i g h t Research F a c i l i t y on an F-15 a i rp lane. An eva lua t i on o f the performance o f t h e F-15 a i r c r a f t w i t h one engine equipped w i t h a HIDEC system was presented by Myers and W a l ~ h . ~

Th is paper presents r e s u l t s o f t h e eva lua t i on w i t h two H I D E C engines, t h e ADECS system desc r ip - t i o n , f l i g h t t e s t procedures, engine t h r u s t gains, and a i r c r a f t performance improvements.

System Desc r ip t i on

A i rp lane

The NASA F-15 a i r p l a n e i s being used f o r t he HIDEC program. The F-15 i s a high-performance a i r s u p e r i o r i t y f i g h t e r w i t h e x c e l l e n t t ranson ic maneuverabi l i ty and has a maximum Mach number c a p a b i l i t y o f 2.5. burn ing turbofan engines.

Engine

It i s powered by two a f t e r -

The FlOO engine model d e r i v a t i v e (EMD) en- g i n e ~ ~ are an upgraded vers ion o f t he F100-PW-100 engine t h a t c u r r e n t l y powers t h e product ion F-15 airplanes. These two engines were b u i l t by P r a t t and Whitney (West Palm Beach, F l o r i d a ) and have a company des ignat ion o f PW 1128. The enyines i n - corporate a redesigned fan, rev i sed compressor and combustor, s i n g l e c r y s t a l t u r b i n e blades and vanes, a 16-segment augmentor w i t h l i g h t - o f f detector , and a d i g i t a l e l e c t r o n i c engine c o n t r o l (DEEC).

The DEEC, as discussed by Burcham and others,6 i s a key p a r t o f the HIDEC system. It i s a f u l l - a u t h o r i t y d i g i t a l c o n t r o l w i t h an i n t e g r a l hydro-

mechanical backup con t ro l . It c o n t r o l s t h e gas generator and t h e augmentor f u e l f lows, compressor bleeds, v a r i a b l e i n l e t guide vanes, v a r i a b l e Sta- t o r s , and t h e v a r i a b l e exhaust nozzle. l o g i c prov ides closed loop c o n t r o l o f co r rec ted fan a i r f l o w (WACC) and engine pressure r a t i o (EPR). pe ra tu re (FT IT ) . HIDEC program t o accept i npu ts from t h e a i rp lane .

The DEEC

It a lso l i m i t s f a n t u r b i n e i n l e t tem- It has been modi f ied f o r t h e

H I D E C System

The equipment and features used f o r t h e HIDEC program7 are shown i n Figs. 1 and 2. The two main features o f t h e HIDEC program were t h e DEEC engine c o n t r o l l e r and t h e d i g i t a l e l e c t r o n i c f l i g h t con- t r o l system (DEFCS). The DEFCS i s a d i g i t a l i m - plementation o f t he analog c o n t r o l augmentation system (CAS) and has t h e same f l i g h t c o n t r o l au- t h o r i t y as t h e analog CAS. The DEFCS communicates w i t h the DEEC through a d i g i t a l i n t e r f a c e and bus c o n t r o l u n i t . The p i l o t makes inpu ts t o the H I D E C system us ing t h e cockp i t c o n t r o l and d i s p l a y un i t s . The ADECS u p t r i m c o n t r o l law sof tware i s i n the d i g i t a l f l i g h t c o n t r o l computer (DFCC) which i s p a r t o f t he DEFCS.

F-15 i s shown i n Fig. 2. The var ious d i g i t a l systems on the a i r p l a n e use th ree separate data buses t o communicate w i t h each o the r through a d i g i t a l i n t e r f a c e and bus c o n t r o l l e r . Th is u n i t permi ts t h e HIDEC system t o communicate w i t h t h e F-15 HOU9 data bus, t h e un ive rsa l asynchronous re- c e i v e r t r a n s m i t t e r (UART) data bus from t h e DEEC, and t h e MIL-STU-1553A f l i g h t c o n t r o l data bus. The normal t h r o t t l e i npu ts from t h e cockp i t t o t h e DEEC c o n t r o l l e r and t h e backup engine con- t r o l a re maintained.

An ADECS b lock diagram i s shown i n Fig. 3. The a i r p l a n e data i s used t o est imate t h e angles o f a t tack (a) and s i d e s l i p ( 6 ) . This in format ion, along w i t h t h e co r rec ted engine a i r f l o w (WA), a l lows the c a l c u l a t i o n o f i n l e t d i s t o r t i o n (D) and t h e amount o f incremental change i n engine pressure r a t i o f o r maximum s t a b i l i t y u p t r i m (AEPKS). Another c a l c u l a t i o n uses engine param- e t e r s t o determine the amount o f engine pressure r a t i o f o r optimum performance (AEPRP). The lower va lue o f t he two EPR u p t r i m commands, w i t h a p i l o t se lec tab le EPR m u l t i p l i e r (KEPR), i s then sent t o t h e DEEC which implements t h e u p t r i m on t h e engine. The DEEC a l s o conta ins an upper l i m i t of a l l owab le u p t r i m f o r safety .

The amount o f EPK u p t r i m a l l owab le depends on t h e a v a i l a b l e excess s t a l l margin o f t h e engine. The F-l5/FlUO EMD engine combination has substan- t i a l excess s t a l l margin a t moderate i n l e t d i s t o r - t i o n l eve l s . The s t a l l margin allowance f o r normal enyine opera t i on i s shown i n Fig. 4 and con- s i s t s o f t h e f o l l o w i n g : engine t o engine a l low- ances f o r t h e manufacturing to le rance i n b u i l d i n g t h e engine, engine c o n t r o l t o le rance allowance, Reynolds number ( a l t i t u d e ) e f f e c t s , i n l e t d i s t o r - t i o n allowance f o r maneuvering up t o extreme angles o f a t tack and s i d e s l i p , allowance f o r l i g h t i n g and c a n c e l l i n g t h e augmentor segments, and any remaining al lowance f o r unce r ta in t y .

A block diagram o f t h e H I D E C system on t h e

2

The s t a l l margin a v a i l a b l e d u r i n g ADECS opera- t i o n , a l so shown i n Fig. 4, cons i s t s o f t he same engine t o engine, c o n t r o l system, and Reynolds number allowances as f o r normal operation. With ADECS, however, t h e i n l e t d i s t o r t i o n allowance i s reduced t o the amount requ i red f o r t he cu r ren t a i r c r a f t a t t i t u d e and f l i g h t cond i t i on , as opposed t o the worst case condi t ion. The augmentor sequencing allowance i s used a t in termediate and maximum power, but i s not used d u r i n g p a r t i a l a f te rbu rn ing . I n most cases, t h i s excess s t a l l margin a v a i l a b l e f o r u p t r i m i s about 11 t o 13 percent, depending on f l i g h t condi t ion. An a r b i t r a r y 4 percent remaining s t a l l margin f o r u n c e r t a i n t y was retained.

Engine Pressure R a t i o Uptr im Logic

The EPK u p t r i m l o g i c res ides i n t h e d i g i t a l f l i g h t c o n t r o l computer (DFCC) and determines t h e proper EPR command t o send the DEEC t o ob ta in h ighe r thrust .8 To accomplish t h i s , two EPRs are ca l cu la ted : t h e optimum Performance EPR and t h e l i m i t i n g s t a b i l i t y EPH which accounts f o r i n l e t d i s t o r t i o n . The lower o f these two values i s se- l e c t e d as the HIDEC u p t r i m EPR. This command i s passed t o t h e DEEC as a percentage where i t i s checked f o r v a l i d i t y against t he DEEC EPR l i m i t . F igu re 5 shows t h e HIDEC EPR u p t r i m concept on a t y p i c a l f an map. The s t a l l l i n e i s shown as t h e upper l i m i t . The d i s tance between t h e s t a l l l i n e and t h e normal ope ra t i ng l i n e represents t h e s t a l l margin ava i l ab le . The DEEC EPK l i m i t represents t h e maximum EPR al lowed by t h e DEEC d u r i n g uptrim. The s t a b i l i t y EPR considers a l l d e s t a b i l i z i n g fac - t o r s t h a t reduce the fan s t a l l margin from t h e bas i c s teady-state l eve l . As i n l e t d i s t o r t i o n increases, t h e s t a b i l i t y EPK ad jus ts downward t o ma in ta in an adequate s t a l l margin. The optimum performance EPR does not t ake s t a l l margin i n t o account. It represents the optimum EPR based on p red ic ted t h r u s t gains.

EPR i s f i r s t increased along a constant cor- rec ted fan speed l i n e up t o a fan t u r b i n e i n l e t temperature (FTIT) l i m i t . Upon reaching t h e F T I T l i m i t , EPR i s then uptrimmed a lony t h e maximum F T I T l i m i t l i n e . duces a small a d d i t i o n a l b e n e f i t before t h r u s t begins t o decrease because o f t h e reduc t i on i n engine a i r f l o w . During EPR uptr im, the fan oper- a tes c lose r t o t h e s t a l l l i n e . Therefore, excess fan s t a l l margin, no t requ i red f o r i n l e t d i s t o r - t i o n , i s t raded f o r a d d i t i o n a l t h r u s t .

c l o s i n g t h e nozzle u n t i l t he des i red EPR i s reached. The increase i n EPR r e s u l t s i n an i n - crease i n engine th rus t . The u p t r i m l o g i c i s l i m i t e d t o power s e t t i n g s a t which t h e EPR con- t r o l loop i s ac t i ve , above 70' power l e v e r angle (PLA). When u p t r i m i s requested, t h e DEEC ramps i n the u p t r i m value over a per iod o f 1 sec. This a l lows f o r smooth t r a n s i t i o n t o u p t r i m operation.

A f l o w diagram o f t he EPR u p t r i m l o g i c i n the DFCC i s shown i n Fig. 6. The blocks i l l u s t r a t e schedules and c a l c u l a t i o n s whi le the arrows i n d i - ca te the f l o w o f i n p u t data.

Uptr im along t h e F T I T l i m i t pro-

The DEEC responds t o the u p t r i m request by

Optimum Performance EPR

The engine pressure r a t i o f o r optimum performance (EPRP) represents EPR a t which optimum engine t h r u s t was obtained. It was scheduled as a func- t i o n o f co r rec ted f a n speed (NlC2) and t o t a l pressure a t fan i n l e t (PT2), as shown i n block 1 o f Fig. 6. The schedule was determined from exten- s i v e s imu la t i on data and denotes t h e most d e s i r - ab le EPR from a performance standpoint. This data was obtained by us ing t h e s teady-state engine sim- u l a t i o n a t a v a r i e t y o f f l i g h t condi t ions. The EPR was increased inc remen ta l l y f o r each c o n d i t i o n u n t i l t h e peak t h r u s t was reached. This corre- sponded w i t h t h e optimum performance EPR.

Although t h e optimum performance EPH i s t h e most des i rab le i n terms of engine performance, i t i s o f t e n una t ta inab le due t o s t a b i l i t y considera- t i o n s and p r o t e c t i v e l i m i t s i n t h e DEEC.

S t a b i l i t y EPR

An EPR based on engine s t a b i l i t y , which accounts f o r i n l e t d i s t o r t i o n , was ca l cu la ted t o l i m i t t h e amount of u p t r i m du r ing cond i t i ons o f reduced f a n s t a l l margin due t o i n l e t d i s t o r - t i o n . I n l e t d i s t o r t i o n increases a t low Mach numbers, f o r reduced i n l e t a i r f l ows , and a t h igh angles o f a t t a c k o r s i d e s l i p . complex r e l a t i o n s h i p , t h e u p t r i m s t a b i l i t y l o g i c requ i red i n p u t from both a i r c r a f t and engine parameters t o c a l c u l a t e t h e s t a b i l i t y EPR l i m i t .

by c a l c u l a t i n g t h e i n l e t d i s t o r t i o n f a c t o r based on a i r c r a f t and engine condi t ions. d i s t o r t i o n f a c t o r was obta ined by c a l c u l a t i n g a base d i s t o r t i o n f a c t o r f o r t h e cu r ren t Mach num- be r and p r e d i c t e d angle o f a t tack. va lue was co r rec ted f o r e f f e c t s o f s i d e s l i p and engine a i r f l o w .

The change i n fan pressure r a t i o (DFPR), based on t h e s t a l l margin s e n s i t i v i t y t o the ca l cu la ted d i s t o r t i o n f a c t o r , was a l s o ca l cu la ted i n b lock 2. F i r s t , t he d i f f e r e n c e between t h e ca l cu la ted d i s - t o r t i o n f a c t o r and t h e scheduled minimum d i s t o r - t i o n f a c t o r was determined. The minimum d i s t o r - t i o n f a c t o r was scheduled from t h e cu r ren t f l i g h t Mach number. This d i f f e r e n t i a l value o f i n l e t d i s t o r t i o n was m u l t i p l i e d by t h e s t a l l margin s e n s i t i v i t y f a c t o r t o determine t h e c u r r e n t sen- s i t i v i t y o f s t a l l mary in t o d i s t o r t i o n .

pressure r a t i o t o ad jus t t h e fan pressure r a t i o f o r maximum s t a b i l i t y (FPRS). puted i n b lock 3 from t h e maximum s t a b i l i t y engine pressure r a t i o . FPRS and DFPR y i e l d e d t h e adjusted maximum s t a b i l - i t y fan pressure r a t i o (FPRUS). This value was converted back t o an engine pressure r a t i o , as shown i n b lock 4. The r e s u l t was t h e l i m i t i n g s t a b i l i t y engine pressure r a t i o (EPRUS) based on d i s t o r t i o n . The minimum was se lected beween EPRUS and EPRP, r e s u l t i n g i n t h e u p t r i m comnand EPRU.

F igu re 7 shows how t h e EPR c o n t r o l loop was implemented i n t h e DEEC l og i c . The EPR u p t r i m

Because o f t h i s

The s t a b i l i t y l o g i c begins i n block 2, Fig. 6,

The i n l e t

This base

The s t a b i l i t y l o g i c used t h e change i n f a n

The FPRS was com-

The r e s u l t i n g d i f f e r e n c e between

3

l o g i c res ided i n the DFCC and determined the proper EPR comnand t o send t o t h e DEEC. nonuptrimned and uptr imned modes, exhaust nozzle area (AJ) was used t o ma in ta in a des i red EPR. A t h i g h Mach numbers, i f t h e gas generator was oper- a ted on t h e FTIT l i m i t , c o n t r o l was switched t o co r rec ted fan speed (NlC2) t o p r o t e c t t h e i n l e t minimum a i r f l o w and t o opt imize ne t p ropu ls i ve force. PLA and maximum power set t ings. PLA, nozz le area was se t t o a f i x e d value. The scheduled EPR was determined as a f u n c t i o n o f co r rec ted fan r o t o r speed (NlC2) and ca l cu la ted engine i n l e t t o t a l pressure (PT2). The EPH was then maintained by vary ing t h e exhaust nozzle area by means o f a p ropor t i ona l p lus i n t e g r a l c o n t r o l - l e r t o t r i m a bas ic schedule. The bas ic schedule was a f u n c t i o n o f augmentor f u e l - a i r r a t i o , t o t a l temperature a t fan i n l e t (TT2), and PT2. The PT2 was obtained by m u l t i p l y i n g t h e engine i n l e t s ta - t i c pressure (PS2) sensed by the engine noseboom probe, by t h e t o t a l - t o - s t a t i c pressure r a t i o de- f i n e d as a f u n c t i o n o f N1C2 and PS2. During par- t i a l a f te rbu rn ing power, 6 percent was subst racted from the u p t r i m comnand t o a l l o w f o r a f t e r b u r n e r l i g h t o f f and segment sequencing. The DEEC sche- du led EPR was m u l t i p l i e d by t h e EPR command from t h e DFCC as shown i n Fig. 7.

I n t h e

The DEEC c o n t r o l l e d EPR on ly between 70" From i d l e t o 70"

F l i g h t Test Procedures

T h i r t y f l i g h t s have been flown t o assess engine and a i r p l a n e performance. In termediate and maximum power constant a l t i t u d e accelera- t i o n s were conducted between 10,000 and 50,000 ft. S ix in termediate power c l imbs were completed from 10,000 t o 40,000 ft a t airspeeds o f 250 and 350 knots, and two in te rmed ia te power cl imbs were accomplished from 30,000 t o 50,000 f t a t Mach 0.9.

To minimize t h e requ i red co r rec t i ons f o r d i f - ferences i n ambient temperatures and a i r c r a f t gross weight, t he a i r c r a f t acce le ra t i ons and c l imbs were f lown back-to-back, f i r s t w i t h ADECS o f f and then repeated w i t h ADECS on. t i o n o f t he ADECS-off maneuver, t he p i l o t would r e t u r n t o approximately the same l o c a t i o n and f l y the ADECS-on maneuver through approximately t h e same a i r mass.

Upon comple-

Advanced Engine Contro l System F l i g h t Results

Engine Performance Improvements

F igure 8 shows t h e percent improvement i n ne t

The data i s The maneu-

p ropu ls i ve fo rce (FNP) f o r constant a l t i t u d e acce le ra t i ons w i t h i n te rmed ia te power. corrected t o standard day condi t ions. vers were f lown back-to-back w i t h ADECS off and then repeated w i t h ADECS on t o minimize t h e co r - r e c t i o n s f o r ambient temperature and pressure. Constant a l t i t u d e a i r c r a f t acce le ra t i ons were accomplished a t 10,000, 20,000, 30,000, and 40,000 ft. Thrust improvements were c a l c u l a t e d from the i n - f l i g h t t h r u s t deck and ranged from about 8 percent a t 10,000 ft t o 10.5 percent a t 30,000 ft. These 8 t o 10.5 percent improvements i n t h r u s t were l a r g e r than t h e 5 t o 8 percent t h r u s t improvements p red ic ted by Myers and B ~ r c h a m . ~

Another b e n e f i t from t r a d i n g excess s t a l l mar- g i n f o r increased performance i s t o reduce the t h r u s t s p e c i f i c f u e l consumption (TSFC) a t con- s t a n t t h r u s t . F igure 9 shows t h e percent TSFC reduc t i on w i t h ADECS on f o r a constant t h r u s t . A t 30,000 ft, Mach 0.6, and maximum power, a 16 percent reduc t i on i n TSFC was shown. Th is compares we l l w i t h t h e 1 7 percent reduc t i on i n TSFC p red ic ted by Myers and Burcham.5 S i m i l a r r e s u l t s were obtained a t Mach 0.9 and 1.2 a t 30,000 ft. A t Mach 0.9, an 11 percent reduc- t i o n i n TSFC was demonstrated as compared t o t h e 9 percent p red ic ted reduction.5

A i r c r a f t Performance Improvements

The a d d i t i o n a l t h r u s t obta ined w i t h EPR u p t r i m was e f f e c t i v e i n improving a i r c r a f t performance. When angle of a t tack i s low a t t h i s cond i t i on , t h e u p t r i m comnand i s maximized because t h e i n l e t d i s - t o r t i o n i s low. The improvement i n engine and a i r c r a f t performance d u r i n g a constant a l t i t u d e a c c l e r a t i o n a t maximum power a t 50,000 f t i s shown i n Fig. 10. The t ime t o acce le ra te from Mach 0.8 t o 1.5 i s 24 percent f a s t e r w i t h t h e ADECS on. F igure 11 shows t h e improvement i n s p e c i f i c excess power (Ps ) w i t h ADECS on f o r t h i s accelerat ion. The ga in i n Ps ranged from about 10 percent a t Mach 0.8 t o 45 percent a t Mach 1.5. co r rec ted f o r d i f f e r e n c e s i n a i r c r a f t gross weight du r ing t h e accelerat ions.

40,000 ft, constant a l t i t u d e acce le ra t i on from Mach 0.6 t o 0.95. With ADECS on, a 14 percent improvement i n t ime t o acce le ra te was demon- s t ra ted . S p e c i f i c excess power w i t h ADECS on was improved by 14 percent a t Mach 0.9.

The e f f e c t o f EPR u p t r i m on a 350 knot, i n t e r - mediate power c l imb from 10,000 t o 40,000 ft i s shown i n Fig. 13. EPR u p t r i m produced a s i g n i f i - c a n t l y h ighe r r a t e o f c l imb a t a l l a l t i t u d e s , w i t h a 14 percent improvement a t 40,000 ft. upt r im, t h e t ime t o c l imb from 10,000 t o 40,000 f t was reduced 13 percent. The data was co r rec ted f o r a i r c r a f t gross weight d i f f e rences .

Table 1 summarizes t h e improvement i n F-15 a i r c r a f t c l imb performance w i t h two ADECS engines i n s t a l l e d and opera t i ng a t i n te rmed ia te power. Table 2 summarizes t h e improvement i n F-15 a i r c r a f t a c c e l e r a t i o n performance w i t h two ADECS engines.

I n t e n t i o n a l i n - f l i g h t engine s t a l l s were gen- e ra ted by i nc reas ing t h e EPR comnand t o h igh va l - ues t o permi t t he methodology used i n t h e s t a l l margin c a l c u l a t i o n t o be va l idated. A s t a l l margin a u d i t o f an engine s t a l l a t Mach 0.6 and 30,000 f t i s shown i n Fig. 14. The f i g u r e i s an enlarged fan map, rep resen t ing fan pressure r a t i o versus co r rec ted a i r f low. The hashed upper l i n e i s t he u n d i s t o r t e d fan s t a l l l i n e w i t h no i n l e t pressure d i s t o r t i o n . The f i g u r e shows t h e a l lowance f o r d i s t o r t i o n and a l so i n d i c a t e s t h e pre- d i c t e d average engine s t a l l p o i n t w i t h d i s t o r t i o n based on wind tunne l data. A lso shown fo r r e f - erence are t h e p lus and minus two-sigma range f o r engine-to-engine d i f f e r e n c e s and c o n t r o l t o l e r -

The data was

F igu re 12 shows an in te rmed ia te power,

With EPR

4

.

t .

antes. The p red ic ted s t a l l p o i n t i s l ess than 1 percent from t h e ac tua l engine s t a l l po in t , which gives c r e d i b i l i t y t o t h e s t a l l margin a u d i t methodology.

Concluding Remarks

ADECS i s t h e f i r s t i n t e g r a t e d f l i g h t and p ropu ls ion c o n t r o l system t o be demonstrated i n f l i g h t on an a i r c r a f t s p e c i f i c a l l y con f ig - ured f o r i n t e g r a t e d c o n t r o l s research. Engine t h r u s t was increased as much as 11 percent a t subsonic f l i g h t cond i t i ons by uptrimming EPR. The a d d i t i o n a l t h r u s t s i g n i f i c a n t l y improved a i r c r a f t performance. Rate-of-cl imb was increased 14 percent a t 40,000 f t and t h e t ime- to-c l imb from 10,000 t o 40,000 f t was reduced 13 percent. A 14 and 24 percent increase i n constant a l t i t u d e acce le ra t i on was obtained a t in termediate and maximum power, respect ive ly .

ADECS up t r im l o g i c was demonstrated success fu l l y i n f l i g h t t e s t s over the F-15 f l i g h t envelope. The ADECS l o g i c success fu l l y accommodated extreme a i r p l a n e manuevers and r a p i d t h r o t t l e t rans ien ts . I n t e n t i o n a l s t a l l s were generated by i nc reas ing t h e KEPR ( cockp i t ad jus tab le m u l t i p l i e r ) t o h igh values (approximately two times nominal) t o per- m i t t he methodology used i n t h e s t a l l margin c a l - c u l a t i o n s t o be va l idated. Substant ia l t h r u s t i n - creases and f u e l f l ow reduct ions were obtained, as w e l l as s i g n i f i c a n t improvements i n a i r c r a f t performance du r ing a i r c r a f t acce le ra t i ons and climbs.

By us ing the h igh throughput and l a r g e memory o f cu r ren t onboard computers, along w i t h h igh- speed communication data buses, i t w i l l be pos- s i b l e t o implement a wide range o f i n teg ra ted f l i g h t and p ropu ls ion c o n t r o l modes onboard f u - t u r e a i r c r a f t . Such modes w i l l increase t o t a l

T h i r t y f l i g h t t e s t s have been flown. The

veh ic le e f fec t i veness w i thou t s i g n i f i c a n t weight o r cost pena l t i es .

References

lMyers, L.P.; and Burcham, F.W., Jr.: Contro l Experience Used i n the H igh ly In teg ra ted D i g i t a l E l e c t r o n i c Contro l (HIUEC) Proyram.

*Burcham, F.W., Jr.; and Haering, E.A., Jr.: Highly In teg ra ted D i g i t a l Engine Control System on an F-15 Airplane. NASA TM-86040, 1984.

3Burcham, F.W., Jr.; Myers, L.P.; and Ray, R.J.: Predic ted Performance Bene f i t s o f an Adaptive U i g i t a l Engine Contro l System on an F-15 Airplane. A I A A 85-0255, Jan. 1985.

4Myers, L.P.; and Walsh, K.R.: Pre l iminary F l i g h t Results o f an Adaptive Engine Contro l System on an F-15 Airplane.

SMyers, L.P.; and Burcham, F.W., Jr.: F l i g h t Test Results o f t h e FlOO EMD Engine i n an F-15 Airplane. A I A A 84-1332, June 1984.

6Burcham, F.W., Jr.; Myers, L.P.; and Walsh, K.R.: F l i g h t Eva lua t i on Resul ts f o r a D i g i t a l Elec- t r o n i c Engine Contro l i n an F-15 Airplane.

TLandy, R.J.; Yonke, W.A.; and Stewart, J.F.: Development o f HIDEC Adaptive Engine Contro l Systems. ASME 86-GT-252, June 1986.

8Ray, R.J.; and Myers, L.P.: t i o n o f t he HIDEC Engine Uptr im Algorithm. A I A A 86-1676, June 1986.

Propuls ion

NASA TM-85914, 1984.

A I A A 87-1847, June 1987.

P re l im ina ry

NASA TM-84918, 1983.

Test and Evalua-

TABLE 1. - IMPROVEMENT I N F-15 CLIMB PERFORMANCE WITH ADECS A T INTERMEUIATE POWER

Rate-of-cl imb

a t a l t i t u d e , f t T i me -t o -c 1 i mb A l t i t u d e , f t improvement, improvement, %, Airspeed

lU,OOO - 40,000 15 28 a t 30,000 250 knots 10,000 - 40,000 13 14 a t 40,000 350 knots 30,000 - 50,000 30 76 a t 50,000 Mach 0.9

5

TABLE 2. - IMPROVEMENT I N F-15 AIRCRAFT ACCELERATION PERFORMANCE WITH AOECS

Horlzontai situation Indicator

Spec i f i c excess power A'titudes 'Ower Mach range Accelerat ion improvement, t ime (Ps) improvement,

f t s e t t i n g X @ Mach no.

Attitudd

reference set

I n t 0.4 - 0.9 5 19 @ 0.9 Max 0.4 - 0.9 7 I n t 0.4 - 0.9 2 9 @ 0.9 Max 0.4 - 0.9 8

4 Q 0.9

4 Q 0.9 I n t 0.5 - 0.9 11 13 Q 0.9

23 Q 0.9 Max 0.5 - 1.5 24 14 14 @ 0.9

20 Q 0.9 I n t 0.6 - 0.9

13 Max 0.6 - 1.5 Max 0.8 - 1.5 24 45 Q 1.5

10,000

20,000

30,000

40,000

50,000

MIL-STD-1553 data bus I

I1 DEFCS II computer

computer

control HlDEC and control

NASA data

' NASA NASA I auxiliary i '@Ink

Fig. 1 Feature8 of the F-15 reeearoh a i r p h 8 .

and bus control

inertial navigation

system

1

I computer I display I I -------.1

TI

b

Digital

'I *

Navigation

UART Data bus

I , 1 . I I 1 I

F-15 (H009) data bus

Fig. 2 Btook diagram of tho R I D E 8yetM.

6

AThrust 1

p-11=1-=11

/ I AEPRPI

I I performance

1 -

I I RPM - conditions

Determine optimum

1 1 1 1 - 1 1 I uptrim

I I I I I I I I I I

.

Estimate a, B. PLA

WA

Determine inlet

distortion

t, I

1 I l l

]AEPR.'\

D minimum A EPRS

KE'PR

I I I

I I I

f

r------ I I I

I I / I I

-111111111111111111== -1--=11=111111d J L D E E C rtFiight control computer 8113

F i g . 3 Block diagram of the advancd engine control 8ptenr.

Without EPR uptrim With EPR uptrlm

Remaining T 5.5%

Margin available for uptrim

Remaining

Augmentor 5.5% sequencing

Inlet distortion

2.5% En lne varlet ion

8114

7.5%

2.5%

F i g . 4 Stat1 -gin available.

I Stall line 7 FTlT ilmll 7 DEEC EPR Ilmll

FPR - EPR prformance EPR

Stabiilly EPR --- *e/ --- Normal operating itw

SO% NICZ 100% NICZ

c0nrt.d fan apnd. NICZ 8115

7

Optimum- prbrnuncm

Stability EPR

KEPR (Cockpic mulllplkr) + EPRU 8118

I I

TTZ Nl PTZ

8117

F t g . 6 W n e preeeure m t i o uptrim logio in the d tg i ta l f l i g h t o a t r o l oounputer.

FQ. 7 Digital eleotronio engine oontrol (DEEC) 020ad loop c a t r o t of engine preeeure ra t io (EPR) .

l5 r

.9 .8 .? 5

.6 Mach 8118

Advanced englne control system

0- on 0- On

n

I I I 1 1 I

Corrected net thrust, Ib 8118

F i g . 8 Peromtage hprovenent in thrust f o r intormodiota power at d o v e alti tudee.

Fig. @ Peromtoga d u o t i o n i n t h a t epaaifio fuel oonewnptim f o r 4fterburning pow- at Naoh 0.6 and 30,000 f t .

r Advanced engine control system -

1.6 - Advanced ewine

1.4 - --- On

1.3 - Mach l m 2 -

I 100

8120 Time, percent

specific excess power

A 45 percent

, - - - -

/ L- -' I I 1

1 .o 1.2 1.4 1.6 .8 Mach 8121

F i g . 10 N d m power of airoraft aoceleration at 50,000 f t .

F i g . 11 Speoifio uxoeee power hpmmmt f o r mzrimm power of airoraft aooelera t ia a t ti0,000 f t .

Y

50,000 Advanced ermine

c

.5 0 10 20 30 40 50 80 70 80 90 100

Time, percent 8122

35,000

Altitude, 30*000

- -

'111111111111 5 9 0 0 0 ~ 2o 30 50 70 80 9o 1 ~ 1 1 0

8123 Time, percent

F i g . 12 IntunndCate p a r of airoraft aocrrhw- Fig. 13 Int .nndiatr p a r olimb fran 10,000 t o tia amprhwn a t 40,000 f t . 40,000 f t a t 350 knots.

t--z \_Whd ~ t d l point with dlstorlbn

245 243 247 2.18

con.c(ed airflow. Ib/W 8124

Fig. 14 Stal l margin audit of i n t m t b n a l in-flight mginr eta11 a t Naoh 0.6, 30,000 f t and m&wn poorr .

t

9

Report Documentation Page

4. Tw and Subtitle

1. Report No. 2. Gowmmont Accuuion No. 3. Recipient's Catalog No.

5. Report Date I I NASA TM-100431

1. K e y Worda (Suggested by Author(r1) Advanced engine con t ro l system A i r c r a f t performance improvements H 1 DEC Increased engine t h r u s t In tegra ted eng ine- f l i g h t con t ro l system

18. Drtribution Statement Unc lass i f i ed - Unl imi ted

Subject category 07

Performance Improvements o f an F-15 A i rp lane With an In tegra ted Engine-Fl iyht Contro l System

8. Securii Classif. (of thir report) 20. Security Clamif. (of thir page)

Unc lass i f i ed Unc 1 ass i f i ed

May 1988

6. Performing Organization Code

21. No. of pagas 22. Price

10 A02

I

7. Authodrl 1 8. Performing Organization Report No.

Lawrence P. Myers and Kevin H. Walsh 1 H-1470

10. Work Unit No.

9. Potforming Organization Name and Addma

NASA Ames Research Center Dryden F l i yht Research Faci 11 t y P.O. Box 273 Fd CA 93573 - 5000

2. s p o s w c y N m a d A h

Nat ional Aeronautics and Space Admin is t ra t ion Washington, DC 20546

RTOP 533-02-21

11. Contract or Grant No.

13. Type of Report and Period Covered

Technical Memorandum

14. Sponsoring Agency Code

1

5. Supplementary Notea

Prepared f o r p resenta t ion a t the A I A A Fourth F l i g h t Test Conference, May 18-20, 1988, a t San Diego, C a l i f o r n i a .

6. Abatract

and The enY and

An in teg ra ted f l i g h t and propu ls ion con t ro l system has been developed f l i g h t demonstrated on the NASA hes-Dryden F-15 research a i r c r a f t . h i g h l y i n teg ra ted d i g i t a l c o n t r o l (HIDEC) system prov ides a d d i t i o n a l

i n e t h r u s t by inc reas ing engine pressure r a t i o (EPR) a t in te rmed ia te a f te rbu rn ing power. The amount o f EPH up t r im i s modulated based on

a i r p l a n e maneuver requirements, f l i g h t condi t ions, and engine in format ion. Engine t h r u s t was increased as much as 10.5 percent a t subsonic f l i g h t con- d i t i o n s by uptrimming EPR. The add i t i ona l t h r u s t s i g n i f i c a n t l y improved a i r c r a f t performance. Rate o f c l imb was increased 14 percent a t 40,000 ft and t h e t ime t o c l imb from 10,000 t o 40,000 f t was reduced 13 percent. A 14 and 24 percent increase i n acce le ra t i on was obtained a t in te rmed ia te and maximum power, respec t ive ly . The HIDEC l o g i c performed f a u l t f ree. No en- g ine anomalies were encountered f o r EPR increases up t o 12 percent and f o r angles o f a t tack and s i d e s l i p o f 32' and ll', respect ive ly .

I I

\ FORM 1626 OCT M sate by the Rational Technical Information Service, Springfield, Virginia 22161.

Documents

Performance Improvements of an F-15 Airplane With an