X-29A technology demonstrator flight test program overview

NASA Technical Memorandum 86809

X=29A Technology De onstrator

Flight Test Program Overview

Walter J. Sefic and Cleo M. Maxwell

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May 1986 National Aeronautics and Space Administration NASA Technical Memorandum 86809

X-29A Technology De onstrator

Flight Test Program Overview

Waiter J. Sefic and Cleo M. Maxwell Ames Research Center, Dryden Flight Research Eacility, Edwards, California National Aeronautics and Space Administration

Ames Research Center

Dryden Flight Research Facility Edwards, California 93523 X-29A TECHNOLOGY DEMONSTRATOR FLIGHT TEST PROGRAM OVERVIEW Cleo M . Maxwell Walter J . S e f i c X-29A Test Information Engineer X-29A Project Manager NASA Ames Research Center NASA Ames Research Center Oryden F1 i ght Research Faci 1 i t y Dryden F l i g h t Research F a c i l i t y Edwards, C a l i f o r n i a Edwards, Cal i f o r n i a ABSTRACT t o determine i f it was f e a s i b l e t o b u i l d and f l i g h t t e s t a forward-swept wing (FSW) a i r c r a f t .

Results o f t h e f e a s i b i l i t y studies were favorable, This paper presents an overview o f the X-29A and a program c o n s i s t i n g o f preliminary design, functional f l i g h t program and concept eval- f i n a l design, f a b r i c a t i o n , and limited-envelope u a t i o n program, i n c l u d i n g some o f the unique and d i f f e r e n t preparations f o r the f i r s t f l i g h t . f l i g h t t e s t i n g was i n i t i a t e d . The p o t e n t i a l Included are a discussion o f the many organiza- advantages o f an a i r c r a f t w i t h an FSW were iden- t i f i e d during these i n i t i a l studies: t i o n a l r e s p o n s i b i l i t i e s and a d e s c r i p t i o n o f the program management s t r u c t u r e f o r the t e s t team comprised o f NASA, U . S . A i r Force, and Grumman 1 . Improved l a t e r a l control a t high angles o f Corporation personnel. Also discussed are pre- attack r e s u l t i n g from inboard spanwise f l o w f l i g h t ground, f l i g h t functional, envelope expan- and subsequent delayed w i n g t i p s t a l l .

sion, and f l i g h t research t e s t objectives and 2. A reduction i n wing p r o f i l e drag f o r the FSW, q u a l i t a t i v e r e s u l t s t o date f o r both a l i m i t e d - as compared w i t h an aft-swept wing w i t h the envelope f l i g h t c o n t r o l system and an expanded- same shock sweep angle, t h a t r e s u l t s i n a envelope system.

13-percent reduction i n t o t a l drag.

A b r i e f d e s c r i p t i o n o f the a i r c r a f t , i n c l u d i n g t h e 3. A decrease i n wing s t r u c t u r a l box weight instrumentation system and measurements, i s also o r an increase i n aerodynamic e f f i c i e n c y presented. I n addition, a discussion i s included r e s u l t i n g from the geometric differences regarding the use o f major support f a c i l i t i e s , i n FSW and aft-swept wing designs w i t h t h e such as ground and f l i g h t simulators, t h e NASA same shock sweep angle.

Western Aeronautical Test Range and mission con- t r o l center, and t h e Grumman automated telemetry s t a t i o n l i n k e d t o the t e s t s i t e by means o f a 4. Increased fuselage design freedom w i t h a f t s a t e l l i t e data l i n k . An overview o f t h e asso- placement o f the wingbox t h a t permits more c i a t e d real-time and p o s t f l i g h t batch data proc- e f f e c t i v e fuselage contouring t o minimize essing software approaches i s presented. The use wave drag.

o f hardware-in-the-loop simulation f o r independent Reduced t r i m drag r e s u l t i n g from l e s s wing 5 .

v e r i f i c a t i o n and v a l i d a t i o n and mission planning t w i s t required w i t h an FSW design. Less wing and p r a c t i c e i s discussed.

t w i s t a l s o reduces manufacturing complexity and cost.

A discussion i s included regarding t h e approach t o f l i g h t operations f o r the X-29A t h a t was used The experimental a i r c r a f t t h a t was b u i l t as a by t h e Dryden F l i g h t Research F a c i l i t y o f NASA r e s u l t o f t h e DARPA studies was named t h e X-29A.

Ames Research Center. Also included i s a descrip- DARPA manage- t i o n o f the f l i g h t - r e a d i n e s s review, t h e a i r - During preliminary design e f f o r t s , ment stressed t h a t other advanced technologies be worthiness and f l i g h t s a f e t y review, work sched- so t h a t t h e r e t u r n u l i n g , technical b r i e f i n g s , and p r e f l i g h t and incorporated i n t o t h e a i r c r a f t p o s t f l i g h t crew b r i e f i n g s . The c o n f i g u r a t i o n on investment f o r any r e s u l t i n g new experimental c o n t r o l process used on t h e X-29A program i s f l i g h t t e s t vehicle could be maximized. These described, and i t s r e l a t i o n s h i p t o both simula- a d d i t i o n a l technologies , although h i g h l y syner- t i o n and a i r c r a f t operations i s discussed. An g i s t i c w i t h t h e F S W concept, could a l s o be used X-29A schedule overview i s presented w i t h an out- i n comparable aft-swept-wing a i r c r a f t .

l i n e o f a proposed follow-on program.

During the f i n a l design and f a b r i c a t i o n phase, simulation evaluation aided i n ascertaining t h a t INTRODUCTION t h e design goal o f constant f l i g h t c o n t r o l system (FCS) gains f o r the analog reversion backup mode could not be attained. To expedite t h e f l i g h t I n t h e l a t e 1970's, t h e Defense Advanced Research schedule w h i l e FCS redesign was undertaken, it was P r o j e c t Agency (DARPA) sponsored various studies decided f i r s t t o develop the i n i t i a l constant gain covered w i t h a e r o e l a s t i c a l l y t a i l o r e d graphite- system and then t o evaluate the a i r c r a f t w i t h a epoxy covers b o l t e d t o aluminum and t i t a n i u m 1 i m i t e d f l i g h t envelope w i t h constant analog rever- spars. To optimize aerodynamic e f f i c i e n c y over s i o n gains (Figure 1). The f u l l f l i g h t envelope t h e f l i g h t envelope, dual-hinged, t r a i l i n g edge FCS was i n s t a l l e d i n t h e a i r c r a f t i n autumn 1985 flaperons provide h i g h l i f t during t a k e o f f and and i s c u r r e n t l y being flown. landing and during l a t e r a l c o n t r o l and programmed variable-camber operations.

Using the U . S . A i r Force's Aeronautical Systems D i v i s i o n (ASD) as i t s agent, DARPA contracted The a i r c r a f t i s approximately 35-percent s t a t i - Grumman Corporation f o r two X-29A a i r c r a f t . A t c a l l y unstable subsonically about the l o n g i t u d i n a l t h e same time, DARPA arranged t o have t h e Dryden axis. Longitudinal c o n t r o l i s provided by the F l i g h t Research F a c i l i t y o f NASA Ames Research combination o f t h e active, all-movable canards, Center (Ames-Dryden) act as the responsible X-29A

flaperons , and aft-mounted strake flaps. The

t e s t organization. The A i r Force F l i g h t Test canards are b u i l t - u p aluminum assemblies. The Center (AFFTC) and Grumman agreed t o support t h i s single, conventionally constructed v e r t i c a l f i n e f f o r t i f DARPA funding was provided. DARPA's t h a t employs a rudder f o r d i r e c t i o n a l c o n t r o l o v e r a l l program goals were t o ensure t h a t i n t e - provides d i r e c t i o n a l s t a b i l i t y . The surfaces grated technologies were made a v a i l a b l e f o r t h e l e d by an advanced, triple-redundant, are next generation o f f i g h t e r s and t o develop t h e d i g i -by-wi r e FCS.

necessary confidence t o t r a n s i t i o n F S W concepts.

The a i r c r a f t i s powered by a s i n g l e F404-GE-400 A f t e r completion o f f a b r i c a t i o n a t Grumman f a c i l i - t i e s i n Bethpage, New York, the f i r s t X-29A was turbofan engine w i t h afterburner, r a t e d a t wrapped i n a p r o t e c t i v e cover, mounted on a con- 7,258-kg (16,000-lb) t h r u s t a t sea l e v e l . The side i n l e t s and fuselage accommodate t h i s F-18 t a i n e r ship, and transported through t h e Panama Canal t o Ames-Dryden f o r f l i g h t tests. f l i g h t - p r o v e n engine. A i r c r a f t takeoff gross weight i s 8,074 kg (17,800 l b ) , w i t h a f u e l The organizational r e s p o n s i b i l i t i e s and t h e agree- capacity o f 1,814 kg (4,000 l b ) . As w i t h t h e ments between t h e respective agencies appear t o engine, flight-proven equipment i s u t i l i z e d be complex (Figure 2). I n actual p r a c t i c e , the wherever possible t o minimize technical r i s k working r e l a t i o n s h i p between the various agencies and investment costs. This includes an F-5A nose was probl em-free; t h e memoranda o f agreement section and cockpit , nose gear, and environmental (MOA), t h e p r o j e c t management d i r e c t i v e , and the c o n t r o l system, as w e l l as an F-16 main landing gear, emergency power u n i t , j e t f u e l s t a r t e r , contracts were f i l e d and were seldom needed t o c l a r i fy i ssues. aircraft-mounted accessory d r i v e gearbox, and canard-flap-rudder integrated servoactuators.

The objectives f o r the current phase of t h e pro- DATA ACQUISITION SYSTEM gram include envel ope expansion f o r divergence f l u t t e r and loads, t h e determination o f perform- ance and aerodynamic c h a r a c t e r i s t i c s , and eval- 'To meet t h e X-29A research objectives, t h e a i r - u a t i o n o f t h e FCS (1). c r a f t i s h i g h l y instrumented. The sensors include r a t e gyros, accelerometers, s t r a i n gages, aero- AIRCRAFT DESCRIPTION dynamic pressure taps, temperature and pressure monitors9 p i t o t s t a t i c monitors. and p o s i t i o n The X-29A a i r c r a f t (Figure 3) integrates t h e F S W i n d i c a t o r s f o r surface p o s i t i o n s and movements.

concept w i t h t h e f o l l o w i n g advanced technologies: F l i g h t data are integrated w i t h data from t h e 429 data bus onto a s i n g l e pulse code modulation 1. Graphite-epoxy composite wing covers. (PCM) s t ream.

2. A e r o e l a s t i c a l l y t a i l o r e d wing. The X-29A data a c q u i s i t i o n system u t i l i z e s both PCM and constant-bandwidth FM f o r data encoding.

Because o f space constraints on t h e a i r c r a f t , 3. Thin s u p e r c r i t i c a l a i r f o i l cross section.

telemetry i s t h e only source o f data. The PCM 4. Automatic wing camber control. system consists o f f i v e remote u n i t s operating asynchronously and a t d i f f e r e n t frame r a t e s (Fig- 5. F u l l - a u t h o r i t y close-coupled canards. ure 4). Four o f the u n i t s operate a t 800 frames/ sec, w i t h each u n i t having a frame length o f The f i f t h u n i t has a frame r a t e 6 . Three-surface l o n g i t u d i n a l control. 64 words/frame.

o f 25 frames/sec and a frame l e n g t h o f 512 words.

7. Highly relaxed s t a t i c margin. A l l f i v e u n i t s have a word length o f 10 b i t s .

The data bus outputs data from t h e f l i g h t c o n t r o l 8. D i g i t a l fly-by-wi r e control. computers. The data bus contains s i x t y - f o u r 3 2 - b i t words w i t h an update r a t e o f 40 words/sec.

The X-29A s i ngl e-seat f i ghter-type a i r c r a f t employs the F S W w i t h a f i x e d leading edge sweep The outputs o f t h e PCM u n i t s and t h e data bus are i n p u t t o an i n t e r l e a v e r u n i t t h a t merges the i n p u t o f 29.27 deg. The wing aeroelastic t a i l o r i n g i s u t i l i z e d t o c o n t r o l t h e divergence t y p i c a l l y pre- data streams and outputs the data i n a s i n g l e 500-kbps s e r i a l PCM stream. The PCM output has a d i c t e d f o r F S W designs. The wing primary box i s mainframe l e n g t h o f 128 1 0 - b i t words. The main OPERATIONS frame r a t e i s 400 frames/sec w i t h subframe r a t e s o f 200, 100, 50, and 25/sec. The basic assumptions made d u r i n g e a r l y plan- n i n g a c t i v i t i e s f o r t h e X-29A operations were The constant-bandwidth F M system c o n s i s t s o f I n t e r - as follows: Range Instrumentation Group ( I R I G ) channels 1 A through 10A w i t h d e v i a t i o n l i m i t s of +2000 Hz f o r 1 . F l i g h t s a f e t y was paramount.

encoding high-response a c c e l e r a t i o n and v i b r a t i o n data. The output o f t h e F M m u l t i p l e x e r i s routed 2. The f l i g h t r a t e would be two f l i g h t s per week.

t o a premodulation mixer where t h e p i l o t ' s voice There would be progressive b u i l d u p o f Mach, (hot microphone) i s combined w i t h it. 3.

a l t i t u d e , and maneuvering c a p a b i l i t y .

The telemetry transmission system c o n s i s t s o f a d i p l e x e r , d i r e c t i o n a l coupler, two L-band trans- 4. Test planning would i n c l u d e e v a l u a t i o n o f m i t t e r s , and upper and lower fuselage-mounted f l u t t e r and divergence, t h e FCS, s t r u c - L-band antennas. The output of t h e i n t e r l e a v e r t u r e s , propulsion, a i r c r a f t systems, per- modulates one o f t h e t r a n s m i t t e r s , and t h e second formance, f l y i n g q u a l i t i e s , and emergency t r a n s m i t t e r i s modulated by t h e F M m u l t i p l e x e r .

power u n i t l i m i t s .

The t r a n s m i t t e r outputs are then d i p l e x e d and r o u t e d through t h e d i r e c t i o n a l coupler t o t h e The emergency power u n i t c a p a b i l i t y l i m i t i s upper and lower L-band antennas. c e n t r a l t o a l l f l i g h t planning. Under c e r t a i n circumstances i n which complete engine power l o s s F i g u r e 5 i s a summary o f t h e 503 parameters occurs, t h e a i r c r a f t cannot be s a f e l y returned measured on t h e a i r c r a f t . The l o c a t i o n s o f t h e t o base because o f l i m i t e d emergency power u n i t various parameters and block diagrams o f t h e i n - hydrazine f u e l . The reduced f u e l capacity r e s u l t s f l i g h t d e f l e c t i o n measurement system a r e shown i n from t h e use o f a modified F-16 hydrazine tank Figures 6 t o 9. t h a t was made smaller because o f emergency power u n i t space 1 i m i t a t i o n s .

The pressure survey instrumentation and o p t i c a l d e f l e c t i o n measurement l o c a t i o n s are i n d i c a t e d Operations f o r t h e X-29A a i r c r a f t f o r a t y p i c a l There are two rows o f pressure o r i - i n Figure 6. s o r t i e i n c l u d e a t e c h n i c a l b r i e f i n g one week i n f i c e s on t h e l e f t canard, f o u r rows on t h e wing, advance, a f l i g h t t e s t p r o f i l e conducted on t h e and one row on t h e strake. The pressure data are simulator, a mission b r i e f i n g , t h e actual X-29A sampled a t 25 samples/channel/sec. The o p t i c a l f l i g h t t e s t , and a mission debriefing. The f a c i l - d e f l e c t i o n measurement system i s l o c a t e d on t h e i t i e s i n v o l v e d i n t h e t y p i c a l X-29A program opera- r i g h t wing and incorporates a r e c e i v e r and 12 t a r - t i o n s i n c l u d e t h e Western Aeronautical Test Range, gets a t t h r e e span s t a t i o n s . The t a r g e t s i d e n t i - t h e mission c o n t r o l center, s p e c t r a l analysis, and f i e d by s o l i d t r i a n g l e s i n Figure 6 a r e u t i l i z e d s a t e l l i t e data transmission. A more d e t a i l e d d e s c r i p t i o n o f t h e operational sequence i s shown t o determine a reference plane. The o p t i c a l d e f l e c t i o n measurement system i s sampled a t a i n F i g u r e 1 1 .

r a t e o f 13 samples/channel/sec. A block diagram o f t h e o p t i c a l d e f l e c t i o n measurement system i s The X-29A operational sequence was i n i t i a t e d w i t h shown i n Figure 7. The system c o n s i s t s o f t a r - a program plan, f l i g h t t e s t plan, and m i l i t a r y gets t h a t are l i g h t - e m i t t i n g diodes focused on a u t i l i t y plan. A f l i g h t - r e a d i n e s s review (FRR) diode a r r a y through a lens; t h e r e s u l t i n g d i g i t - committee and a f l i g h t t e s t team c o n s i s t i n g o f t h e i z e d i n f o r m a t i o n i s sent t o t h e PCM system. Ames-Dryden, AFFTC, and Grumman personnel were formed. The f l i g h t t e s t team, employing a p r o j e c t The l o c a t i o n s o f s t a t i c s t r u c t u r a l loads i n s t r u - engineer, develops a f l i g h t request t h a t r e s u l t s mentation are shown i n F i g u r e 8. The data c o n s i s t i n a number o f scheduling a c t i v i t i e s i n c l u d i n g c o n f i g u r a t i o n c o n t r o l , a i r c r a f t maintenance, and o f shear, bending moment, and torque measurements s i m u l a t i o n t h a t leads t o a t e c h n i c a l b r i e f i n g on a t t h e r o o t o f t h e l e f t and r i g h t canard, t h e t h e proposed f l i g h t o r group o f f l i g h t s . The fuselage, and v e r t i c a l t a i l ; shear, bending moment, and torque a t f o u r s t a t i o n s on t h e l e f t t e c h n i c a l b r i e f i n g r e s u l t s i n an a g r e e d - t o - f l i g h t wing; actuator loads on a l l c o n t r o l surfaces; and request and an FRR f l i g h t release f o r a f i r s t s t i c k and rudder pedal forces. The s t r u c t u r a l f l i g h t o r a major m o d i f i c a t i o n o f t h e a i r c r a f t .

A f t e r t h e p a r t i c u l a r f l i g h t i s thoroughly con- dynamics instrumentation i s shown i n F i g u r e 9.

Accelerometers a r e l o c a t e d on both wings, t h e ver- ducted on t h e s i m u l a t o r ( i n c l u d i n g p i l o t i n t h e t i c a l t a i l , a l l c o n t r o l surfaces, and t h e fuse- loop), a s e t o f f i n a l f l i g h t cards i s b r i e f e d , lage. The accelerometers are sampled a t a r a t e o f together w i t h t h e f l i g h t operating l i m i t s , a man- 400 samples/channel /sec. datory instrumentation l i s t , a i r c r a f t configu- r a t i o n , and mission c o n t r o l c e n t e r 1 ayout .

A l l data on t h e X-29A are t r a n s m i t t e d t o t h e The f l i g h t c o n t r o l l e r i s t h e primary i n d i v i d u a l ground s t a t i o n u s i n g t h e telemetry system (2) communicating w i t h t h e X-29A p i l o t and t h e chase shown i n Figure 10. During t h e limited-envelope phase o f t h e program, s a t e l l i t e data transmission p i l o t . A l l o t h e r i n d i v i d u a l s communicate through an intercommunication system t o t h e c o n t r o l l e r .

t o t h e Grumman f a c i l i t y i n Calverton, New York, Under c e r t a i n conditions, t h e l e a d f l u t t e r was provided as i n d i c a t e d i n F i g u r e 10.

engineer can communicate d i r e c t l y with t h e p i l o t envelope w i l l be c l e a r e d by September 1986. The A f t e r t h e f l i g h t (Fig- low-speed p o r t i o n w i l l be addressed i n a follow-on w i t h preplanned commands.

high-angle-of-attack program s t a r t i n g i n 1987.

u r e ll), a p o s t f l i g h t b r i e f i n g i s held, data processing i s i n i t i a t e d , and any discrepancies Figures 15 t o 20 present an overview o f t h e key a r e documented and prepared f o r t h e next con- f i g u r a t i o n c o n t r o l meeting. r e s u l t s obtained t o date. Figure 15 i l l u s t r a t e s lift c o e f f i c i e n t as a f u n c t i o n o f drag c o e f f i c i e n t CONFIGURATION CONTROL and compares f l i g h t data w i t h p r e d i c t e d data. The p r e l i m i n a r y f i n d i n g s i n d i c a t e t h a t t h e drag data The c o n f i g u r a t i o n c o n t r o l process (Figure 12) con- q u a l i t y i s t 5 0 counts. There i s a c o n s i s t e n t s i s t s o f change requirements, design, production, magnitude and p o l a r shape over t h e Mach range and t e s t . The process i s i n i t i a t e d by a new t e s t e d thus far. The f l i g h t drag data a r e lower system requirement o r a discrepancy. Analysis than p r e d i c t e d f o r subsonic f l i g h t conditions.

and design are accomplished, and a c o n f i g u r a t i o n

re iir, a more favorable wing l e a d i n g edge

change request i s generated and submitted t o t h e pressura p r o f i l e above a lift c o e f f i c i e n t equal t o c o n f i g u r a t i o n c o n t r o l board. The board members one than t h a t p r e d i c t e d by t h e wind-tunnel data.

i n c l u d e p r o j e c t management and representatives from each t e c h n i c a l d i s c i p l i n e ; t h e p r o j e c t man- F i g u r e 16 shows t y p i c a l r e s u l t s f o r t h e p i t c h ager i s t h e chairman o f t h e board. A hardware s t a t i c s t a b i l i t y parameter as a f u n c t i o n o f Mach c o n f i g u r a t i o n change, i f approved, r e q u i r e s a work number. Results t o date i n d i c a t e t h a t t h e l o n g i - order t h a t r e s u l t s i n a m o d i f i c a t i o n o r f a b r i c a - t u d i n a l s t a b i l i t y i s close t o predictions. The t i o n . !The hardware change i s inspected, documen- l a t e r a l s t a b i l i t y i s s l i g h t l y h i g h e r than pre- t a t i o n i s updated, and t h e system i s tested. For d i c t e d , and d i r e c t i o n a l s t a b i l i t y i s lower than an approved software change, a program change predicted. Typical f l i g h t c o n t r o l data are shown n o t i c e i s generated. A new release t h a t goes i n F i g u r e 17; low-frequency gain and phase margins through v e r i f i c a t i o n t e s t i s accomplished, docu- are p l o t t e d as a f u n c t i o n o f Mach number. I n i t i a l mentation i s updated, and a system v a l i d a t i o n t e s t r e s u l t s i n d i c a t e t h a t FCS performance ( 3 ) i s excel- i s defined. The v a l i d a t i o n t e s t i s then reviewed l e n t . There i s very good c o r r e l a t i o n between f l i g h t by t h e c o n f i g u r a t i o n c o n t r o l board and released and simulation, and t h e o v e r a l l s t a b i l i t y i s equal f o r grpund and f l i g h t t e s t . t o o r b e t t e r than predictions.

Typical r e s u l t s i n t h e s t r u c t u r a l dynamics area S IMULATI ON a r e shown i n Figure 18 i n which s t r u c t u r a l damping Simulatton i s an i n t e g r a l p a r t o f t h e X-29A f l i g h t and frequency are p l o t t e d as a f u n c t i o n o f equiva- t e s t program; t h e program would be severely l e n t v e l o c i t y . No unexpected adverse trends i n constrained without t h e a v a i l a b i l i t y o f a high- s t r u c t u r a l s t a b i l i t y have been observed t o date.

f i d e l i t y hardware-i n-the-1 oop system. The simul a- Good c o r r e l a t i o n i s found between p r e d i c t i o n s and f l i g h t measurements. No unexpected adverse t i o n system (Figure 13) c o n s i s t s o f two primary p a r t s - standard Ames-Dryden equipment and X-29A trends i n f l u t t e r and divergence have been observed, but t h e important t r a n s o n i c region has s p e c i f i e d equipment. The Ames-Dryden equipment includes various computer equipment t h a t contains y e t t o be explored.

and processes t h e aerodynamic data package, a simulated cockpit, and d i s p l a y equipment. The B u f f e t i n t e n s i t y r i s e , i n t h e form o f normal f o r c e X-29A s p e c i f i e d equipment includes t h e f l i g h t c o e f f i c i e n t and center-of-gravi t y normal accel era- c o n t r o l computers, t h e f a i l u r e s t a t u s c o n t r o l t i o n as a f u n c t i o n o f Mach number, i s shown i n F i g u r e 19. The b u f f e t experienced i s regarded as panel, a c t u a t o r models, and o t h e r r e l a t e d equip- l i g h t t o moderate. Canard buffet occurs p r i o r ment. The s p e c i f i e d equipment a l s o includes an t o wing b u f f e t and i s g r e a t l y i n f l u e n c e d by t h e XAIDS system t h a t i s a minicomputer-based device d e f l e c t i o n schedule. A l i g h t t o moderate wing u t i l i z e d t o i n t e r r o g a t e t h e f l i g h t c o n t r o l com- rock phenomenon was experienced f o r t h e low-speed, puters and software f o r systems t e s t i n g and high-angle-of-attack f l i g h t conditions. Typical v e r i f i c a t i o n t e s t s .

r e s u l t s obtained w i t h t h e i n - f l i g h t d e f l e c t i o n FLIGHT RESULTS OVERVIEW measurement system a r e i n d i c a t e d i n F i g u r e 20.

Wingbox t w i s t data obtained from d e f l e c t i o n The X-29A approach used t o develop confidence i n measurements are p l o t t e d as a f u n c t i o n o f wing t h e FSW and r e l a t e d technologies i s t o v a l i d a t e semispan. The i n i t i a l f l i g h t d e f l e c t i o n measure- t h e design, analyses, and t e s t methods by corre- ment data q u a l i t y and q u a n t i t y are very good.

l a t i n g and comparing them w i t h t h e f l i g h t research The Grumman l i f t i n g surface program p r e d i c t i o n s compare we1 1.

r e s u l t s . Careful analyses o f t h e instrumentation requirements, f l i g h t t e s t points, and maneuvers SCHEDULE AND FUTURE PLANS a r e conducted t o ensure t h a t data o f s u f f i c i e n t q u a l i t y and q u a n t i t y are acquired t o v a l i d a t e t h e The goal f o r t h e X-29A program i n 1986 i s t o design, f a b r i c a t i o n , and t e s t process (1).

complete t h e envelope expansion phase f o r a i r - c r a f t one by September. A f t e r completion o f The design f l i g h t envelope i s shown i n F i g u r e 14.

envelope expansion, t h e c u r r e n t p l a n i s t o The shaded area represents t h e p o r t i o n o f t h e f l i g h t envelope t h a t has been cleared. It i s i n s t a l l a c a l i b r a t e d engine and w i n g t i p shaker a n t i c i p a t e d t h a t t h e high-speed p o r t i o n o f t h e system on a i r c r a f t one and conduct a d d i t i o n a l DARPA Defense Advanced Research P r o j e c t

research i n t h e aerodynamics , performance, and

s t r u c t u r e s d i s c i p l i n e s . A i r c r a f t two i s p r e s e n t l y Agency l o c a t e d a t t h e Grumman f a c i l i t y i n Bethpage, New York, where an instrumentation system and s p i n FCS f 1 i ght c o n t r o l system chute are being i n s t a l l e d . The p l a n i s t o conduct a high-angle-of-attack research program, with FRR f l i ght-readiness review f l i g h t t e s t o f a i r c r a f t two beginning i n e a r l y 1987. The f u t u r e technology requirements and F S W forward-swept wing research o b j e c t i v e s f o r both a i r c r a f t a r e sum- marized i n Table 1 . MOA memorandum o f agreement CONCLUDING REMARKS PCM pulse code modulation SIBLINC The X-29A f l i g h t research program i s p r o v i d i n g a scale, i n v e r t , bias, l o g i c , i n t e r f a c e unique and t i m e l y o p p o r t u n i t y t o c l o s e t h e loop consol e on t h e a i r c r a f t analysis, design, f a b r i c a t i o n , and ground and f l i g h t t e s t process. The f l i g h t KEY WORDS research program i s p r o v i d i n g t h e data necessary t o improve t h e e n t i r e a i r c r a f t design, f a b r i - Data a c q u i s i t i o n systems, f l i g h t cation, and t e s t process f o r f u t u r e a i r c r a f t i n c l u d i n g t h e v a l i d a t i o n o f design t o o l s and F1 i ght c o n t r o l s t h e refinement o f a n a l y t i c a l methods. The advanced techno1ogi es incorporated i n t h e X-29A F l i g h t t e s t program are i n t e g r a t e d such t h a t t h e t o t a l bene- fit i s greater than t h e sum o f t h e b e n e f i t s o f Forward-swept wing t h e i n d i v i d u a l technologies.

Instrumentation systems, f l i g h t The i n i t i a l f l i g h t research r e s u l t s are encour- REFERENCES aging. There i s good c o r r e l a t i o n o f t h e aero- dynamics, structures, and c o n t r o l s data with p r e d i c t i o n s . The a i r c r a f t f l i g h t systems a r e (1) Putnam, T . W . , "X-29 F l i g h t Research Program," performing very w e l l . The f l i g h t research pro- NASA TM-86025, Jan. 1984.

gram i s w e l l established and includes follow-on programs f o r two a i r c r a f t .

(2) Cutler, W . , "X-29A Technology Demonstrator, Program Status Review," 16th Annual SFTE NOMENCLATURE Symposium, Sept. 1985, pp. 5.4-1 t o 5.4-10.

AFFTC A i r Force F1i g h t Test Center Gera, J . , "Dynamics and Controls F l i g h t ( 3 ) Testing o f t h e X-29A Airplane," NASA ASD Aeronautical Systems D i v i s i o n (U.S. TM-86803, Jan. 1986.

A i r Force)

TABLE I. - FUTURE TECHNOLOGY REQUIREMENTS AND OBJECTIVES

Research o b j e c t i v e Technology requirement

.--______ --- ---

-- -

X-29A a i r c r a f t one Advanced performance and t h r u s t modeling techniques Advanced f l i g h t t e s t techniques Real-time a n a l y s i s t o o l s developed f o r f l i g h t c o n t r o l s Determination of aerodynamic wing-canard i n t e r a c t i o n Wing-canard c o n f i g u r a t i o n s Boundary l a y e r and pressure d i s t r i b u t i o n c o r r e l a t i o n s w i t h p r e d i c t i o n s D e t a i l e d a i r c r a f t drag and performance determination w i t h FSW c a l i b r a t e d engine Wing divergence determination A e r o s e r v o e l a s t i c i t y F1i g h t c o r r e l a t i o i c t e d s t r u c t u r a l s t a b i l i t y Determination of a s t i c s t a b i l i t y margins Assessment o f v a l i d i t y of c u r r e n t and new f l y i n g F l i g h t c o n t r o l s and handling q u a l i t i e s c r i t e r i a Control o f h i g h l y unstable a i r c r a f t Three-surface c o n t r o l f o r t r i m and maneuverability

-~

X-29A a i r c r a f t two

_- -

Wing-canard c o n f i g u r a t i o n s I n v e s t i g a t i o n o f wing-canard aerodynamic i n t e r a c t i o n through f l o w v i s u a l i z a t i o n Evaluation o f s t a l l c h a r a c t e r i s t i c s and wing rock tendencies Measurement o f instantaneous t u r n i n g performance F S W Assessment o f t a c t i c a l usefulness a t h i g h angles of a t t a c k Determination o f c o n t r o l effectiveness f o r a g i l i t y Three-surface c o n t r o l and c o n t r o l 1abi 1 i t y Evaluation o f three-surface c o n t r o l c h a r a c t e r i s t i c s a t h i g h Large negative s t a b i l i t y margin angles o f a t t a c k Development o f f l i g h t t e s t a n a l y s i s t o o l s Evaluation o f FCS performance compared w i t h present high- angle-of-attack c r i t e r i a and p r e d i c t i v e c a p a b i l i t i e s -__-

----

0 Full flight envelope W Limited envelope Management Directive I I I ' I I I !

Altitude Mach X-29A TEAM ORGANIZATIONAL STRUCTURE FIGURE 1 . X-29A FLIGHT ENVELOPE F O R INITIAL A N D FIGURE 2.

PRESENT FLIGHT CONTROL SYSTEM . . .

4.27 m (14 ft) Height Wingarea 17.2 m2(185 ft2) * Aspect ratio 4.0 0 Static thrust 7,257 kg (16,000 Ib) Empty weight g897 kg (13,000 Ib) * Fuel capacity 1,814 kg (4,000 Ib) F-5A forebody, cockplt, and inlet design * F-18 F404-GE-400engine F-16 main landing gear and actuators FIGURE 3. X-29A KEY CHARACTERISTICS AND FEATURES

I Power and control

I

FIGURE 4. X-29A DATA ACQUISITION SYSTEM Basic parameten (53) * Alrdata(9) * Angles of attack and sldeallp (4) * Pitch, roll, yaw attitudes, rates, end accelerations (13) Center-of-gravityaccelerations (6) * Engine speed, temperature, and nozzle (10) Surface positions (11) FCS (83) * Computer parameters, 429 bus (76) Stick position and forces (5) Cockpit accelerations (2) Flutter and buffet (21) * Accelerometers (21) Structures (118) * Strain gages (106) * Optical deflection measurement system (12) Propulsion (21) * Engine speed, temperatures, and geometry (21) Aerodynamic (173) Wing and strake static pressure (156) Canard static pressures (17) Other systems (76) Hydraulic (6) Environmental control (7) Electrical (7) Temperature (44) * Emergency power unit (10) Aircraft-mountedaccessory drive (2) Total number of channels: SO3 FIGURE 5 . X-29A INSTRUMENTATION PARAMETERS Deflection measurement Referencetargets measurement system receiver Wing station 32.50 Wing station 50.00 148.00 FIGURE 6 . PRESSURE SURVEY INSTRUMENTATION AND OPTICAL DEFLECTION MEASUREMENT SYSTEM FIGURE 7. BLOCK DIAGRAM OF X-29A OPTICAL DEFLECTION MEASUREMENT SYSTEM Butt-line 64 kick rib Forward fuselage

- Upper and lower covers

- Vertical shear

- Axial and shear strains

bending moment, and torque Fin structure

- Root shear, bending

moment, and torque -Rudder actuator Stick and loads Left and right actuators, strake flap structure Wing structure Canard - Left: shear, bending moment,

- Left and right root

and toque at four stations shear, bending

- Right root shear, bending

moment, and torque moment, and toque

- Left and right

actuator loads \Flaperon structure

- Left and right inboard and

outboard actuator loads X-29A STATIC STRUCTURAL MEASUREMENT LOCATIONS FIGURE 8.

A \ \

0 Accelerometer locations

w

X-29A STRUCTURAL DYNAMICS AND BUFFET INSTRUMENTATION FIGURE 9 .

LOCAT IONS

* g : : t Z

Calverlon, NY / Edwards, CA

f

FIGURE 1 0 . X-29A TRANSCONTINENTAL DATA LINK I I I I

i

I I L---

t

Flight request agreement FRR flight release Crew brief

Servicing i - - ~ ~ -

To responsibleengineers I Real-timedata Reports Discrepancies Postflight processeddata Hardware Inspection

modlfication . and quality

or fabrication assurance Assemble Verification .

new test release

- - - -

_ - - - - - - _

' Change '

Design Production Test requirements FIGURE 12. X-29A CONFIGURATION CONTROL PROCESS Computer system A equipment Hardware consde ~~ models FIGURE 13. BLOCK DIAGRAM OF X-29A SIMULATION SYSTEM 1 2

ORIGINAL PAGE IS

OF POOR QUALlrV

0 Full flight envelope W Flight envelope to date Altitude Mach FIGURE 1 4 . PRESENT X-29A EXPANDED FLIGHT ENVELOPE 0 Flight data at lower Mach number 0 Flight data at higher Mach number

- Predicted data for lower Mach number

--- Predicted data for higher Mach number

I I I I I I

Coefficient of drag FIGURE 1 5 . TYPICAL X-29A LIFT AND DRAG COEFFICIENT COMPARISON OF FLIGHT AND PREDICTED DATA 0 Flight data A Predicted 0 Estimated frequency 0 Predicted gain margin .........................

Pitch stability parameter Design Design limit limit Mach margin margin

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

FIGURE 1 6 . TYPICAL X-29A AERODYNAMIC COEFFICIENT ESTI- MATED FROM FLIGHT DATA AND I COMPARED WITH WIND TUNNEL Mach PREDICTIONS FIGURE 17. TYPICAL X-29A FLIGHT STABIL- ITY MARGINS AS A FUNCTION OF MACH NUMBER COMPARED WITH WIND TUNNEL PREDICTIONS SAEL computer program 0 Normal 0 Digital reversion 0 Wing L\ Analog reversion 0 Canard

- Normal

- Wind tunnel

------ Digital reversion

predicted data

--- Analog reversion

Damping coefficient

'Om I

I

i

-

I Acceleration

z -

at center

Of gravity I

Frequency ~ - - -

I

~ , Mach Equivalentvelocity, knots FIGURE 19. TYPICAL X-29A BUFFET INTENSITY TYPICAL X-29A STRUCTURAL DYNAMICS FIGURE 18.

BOUNDARY COMPARISONS O F FLIGHT AND WIND TUNNEL DAMPING AND FREQUENCY COMPARED WITH COMPUTER PREDICTED DATA ANALYSIS 0 Grumman predicted 0 Measured (flight deflection meas- urement system) Wing- box twist, deg

I

Semispan, percent FIGURE 20. TYPICAL X-29A DEFLECTION MEASUREMENT DATA FOR WINGBOX TWIST AS A FUNCTION OF SEMISPAN COMPARED WITH PREDICTED DATA 2. Government Accession No.

3 . Recipient's Catalog No.

1 . Report No.

NASA TM-86809 r 5. Report Date 4 . Title and Subtitle X-29A TECHNOLOGY DEMONSTRATOR FLIGHT TEST PROGRAM OVERVIEW May 1986 6. Performing Organization Code 8. PerformingOrganizationReport No.

7 . Author(s1 Walter J. S e f i c and Cleo M. Maxwell H-1347 1 0 . Work Unit No.

9 . PerformingOrganization Name and Address RTOP 533-02-51 NASA Ames Research Center 1 1 . Contract or Grant No.

Dryden F1 i ght Research Faci 1 i t y

r)C y 9 q

P.O. Box 273 Edwards, CA 93523-5000 1 3 . Type of Report and Period Covered 1 2 . Sponsoring Agency Name and Address Technical Memorandum National Aeronautics and Space Administration 1 4 . Sponsoring Agency Code Washington, D.C. 20546 I 15. Supplementary Notes Prepared as I S A Paper 504 f o r presentation a t I S A Aerospace I n d u s t r i e s / T e s t Measurement Symposium, Seattle, Washington, May 5-8, 1986.

I 16. Abstract

This paper presents an overview of t h e X-29A f u n c t i o n a l f l i g h t program and concept eval- u a t i o n program, i n c l u d i n g some of t h e unique and d i f f e r e n t preparations f o r t h e f i r s t f l i g h t .

Included are a discussion of t h e many organizational r e s p o n s i b i l i t i e s and a d e s c r i p t i o n o f t h e program management s t r u c t u r e f o r t h e t e s t team comprised o f NASA, U.S. A i r Force, and Grumman Corporation personnel. Also discussed are p r e f l i g h t ground, f l i g h t f u n c t i o n a l , envelope expan- sion, and f l i g h t research t e s t o b j e c t i v e s and q u a l i t a t i v e r e s u l t s t o date f o r both a l i m i t e d - envelope f l i g h t c o n t r o l system and an expanded-envelope system.

A b r i e f d e s c r i p t i o n of t h e a i r c r a f t , i n c l u d i n g t h e instrumentation system and measurements, i s a l s o presented. I n addition, a discussion i s included regarding t h e use o f major support f a c i l i t i e s , such as ground and f l i g h t simulators, t h e NASA Western Aeronautical Test Range and mission c o n t r o l center, and t h e Grumman automated telemetry s t a t i o n l i n k e d t o t h e t e s t s i t e by means o f a s a t e l l i t e data l i n k . An overview o f t h e associated r e a l - t i m e and p o s t f l i g h t batch d a t a processing software approaches i s presented. The use o f hardware-in-the-loop s i m u l a t i o n f o r independent v e r i f i c a t i o n and v a l i d a t i o n and mission planning and p r a c t i c e i s discussed.

A discussion i s included regarding t h e approach t o f l i g h t operations f o r t h e X-29A t h a t was used by t h e Dryden F l i g h t Research F a c i l i t y o f NASA Ames Research Center. Also i n c l u d e d i s a d e s c r i p t i o n o f t h e f l i g h t - r e a d i n e s s review, t h e airworthiness and f l i g h t s a f e t y review, work The c o n f i g u r a t i o n scheduling, t e c h n i c a l b r i e f i n g s , and p r e f l i g h t and p o s t f l i g h t crew b r i e f i n g s .

c o n t r o l process used on t h e X-29A program i s described, and i t s r e l a t i o n s h i p t o b o t h s i m u l a t i o n and a i r c r a f t operations i s discussed. An X-29A schedule overview i s presented w i t h an o u t l i n e o f a proposed follow-on program.

1 7 . Key Words (Suggested by Author(s1) 1 8 . Distribution Statement

Data a c q u i s i t i o n systems, f l i g h t U n c l a s s i f i e d - Unlimited

F l i g h t c o n t r o l s F l i g h t t e s t Forward-swept wing STAR category 05 Instrumentation systems, f l i g h t 22. Price* 21. NO. of Pages 1 9 . Security Classif. (of this report) 20. Security Classif. (of this page) U n c l a s s i f i e d Uncl assi f i ed 15 A02