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DEVELOPMENT OF FLIGHT TESTING TECHNIQUES FINAL REPORT Principal Investigator Doral R. Sandlin 10/31/79 - 10/31/84 Aeronautical Engineering Department California Polytechnic State University San Luis Obispo, CA 93407 Grant No. NCC 4-1 -CR- 176996) DEVELOPMENT OF f LIGHT N86-28936 TESTING TECHNIQUES Flcal Beport, 31 .Oct. .
1S79 - 31 Oct., 1984 (California Polytechnic State Univ.), 9 p CSCL 01C Dnclas G3/05 43348 Introduction This is the final report for Grant #NCC 4-1, a graduate student program entitled Flight Analysis and Development sponsored by NASA/Ames and the Dryden Flight Research Facility. The grant was initiated October 1, 1979, and was terminated October 31, 1984.
Several students worked at NASA and took classes at Cal Poly and were supported by this grant. The principal investigator was Dr.
Doral R. Sandlin, a professor in the Aeronautical Engineering Department at Cal Poly.
List of Students and Abstracts The following is a list of students, the title of their research project and abstracts of thesis reports.
(1) Dale Turley LONGITUDINAL STABILITY AND CONTROL DERIVATIVES OBTAINED FROM FLIGHT DATA OF A PA-30 AIRCRAFT This report presents the l o n g i t u d i n a l s t a b i l i t y and c o n t r o l d e r i v a t i v e s obtained from f l i g h t data of a PA-30 a i r c r a f t by u s i n g a maximum l i k e l i h o o d e s t i m a t o r tech- n i q u e . Derivatives were o b t a i n e d at zero f l a p conditions and to show f l a p and t h r u s t e f f e c t s . These d e r i v a t i v e s a r e compared w i t h p r e v i o u s l y o b t a i n e d f l i g h t d e r i v a t i v e s and w i n d t u n n e l e s t i m a t e s . T h e n e w f l i g h t estimates a r e -2- shown to be in much b e t t e r agreement w i t h the w i n d t u n n e l s t a b i l i t y and control d e r i v a t i v e estimates t h a n those of the p r e v i o u s f l i g h t e s t i m a t e s . The moments of i n e r t i a (I , I , I ) of the a i r c r a f t were d e t e r m i n e d for use in the d e r i v a t i v e e s t i m a t i o n analysis u s i n g the swing oscil- l a t i o n method.
( 2 ) R a n d a l l Peterson AERODYNAMIC DRAG REDUCTION TESTS ON A BOX-SHAPED VEHICLE C o a s t - d o w n t e s t s h a v e b e e n p e r f o r m e d o n a b o x - s h a p e d ground vehicle used to s i m u l a t e the aerodynamic drag of high volume transports such as delivery v a n s , motor homes r and t r u c k s . The results of these tests d e f i n e the re- d u c t i o n in aerodynamic drag that can be obtained by the a d d i t i o n of either a f u l l b o a t t a i l or a t r u n c a t e d boat- tail to an otherwise blunt-based v e h i c l e .
i T e s t v e l o c i t i e s r a n g e d u p t o 9 6 . 6 k m / h ( 6 0 m p h ) w i t h R e y n o l d s numbers to 1.3 x 10 . The f u l l boattail pro- vided an average 32-percent r e d u c t i o n in drag at "highway s p e e d s " whereas the t r u n c a t e d b o a t t a i l provided an aver- age 31 p e r c e n t r e d u c t i o n in d r a g as c o m p a r e d to the c o n f i g u r a t i o n h a v i n g the b l u n t base. These results are compared w i t h one-tenth scale w i n d - t u n n e l model d a t a .
-3- ( 3 ) D a n Morrow A MICROPROCESSOR BASED A N T I - A L I A S I N G F I L T E R FOR A PCM SYSTEM T h i s p r o j e c t thesis describes the d e s i g n and e v a l u a t i o n of a microprocessor based d i g i t a l f i l t e r . The f i l t e r was d e s i g n e d t o i n v e s t i g a t e t h e f e a s i b i l i t y o f a d i g i t a l r e p l a c e m e n t for the analog pre-sampling f i l t e r s used in t e l e m e t r y s y s t e m s a t t h e NASA D r y d e n F l i g h t R e s e a r c h F a c i l i t y ( D F R F ) . T h e d i g i t a l f i l t e r w i l l u t i l i z e d a n I n t e l 2 9 2 0 D i g i t a l Signal Processor ( P S F ) c h i p . Testing i n c l u d e s measurements o f ( a ) t h e f i l t e r frequency r e - sponse and (b) the f i l t e r signal r e s o l u t i o n . The evalu- / a t i o n o f t h e d i g i t a l f i l t e r w a s m a d e o n t h e b a s i s o f c i r c u i t s i z e , p r o j e c t e d e n v i r o n m e n t a l s t a b i l i t y a n d f i l t e r r e s o l u t i o n . The 2920 based d i g i t a l f i l t e r was f o u n d to meet or exceed the pre-sampling f i l t e r speci- f i c a t i o n s for limited signal resolution a p p l i c a t i o n s . ; ( 4 ) K e v i n P e n n i n g FLUTTER PREDICTION OF A WING WITH ACTIVE AILERON CONTROL A method of a n a l y z i n g the v i b r a t i o n a l s t a b i l i t y of air- c r a f t w i t h a c t i v e a i l e r o n f l u t t e r s u p p r e s s i o n systems i s e x p l a i n e d . A computer program was w r i t t e n u s i n g this a n a l y s i s . A comparison between p r e d i c t i o n s and f l i g h t t e s t d a t a f o r t h e DAST ARW-1 f l i g h t t e s t v e h i c l e i s s h o w n . Results show the method p r e s e n t e d closely pre- d i c t s f r e q u e n c y a n d damping f o r a i r c r a f t w i t h f l u t t e r -4- s u p p r e s s i o n systems.
(5) J . B l a i r Johnson COMPARISON OF THEORETICAL AND FLIGHT-MEASURED LOCAL FLOW AERODYNAMICS FOR A LOW-ASPECT-RATIO FIN F l i g h t test and t h e o r e t i c a l aerodynamic data were ob- tained for a f l i g h t text f i x t u r e mounted on the underside of an F-104G a i r c r a f t . The theoretical d a t a were gener- ated u s i n g two codes, a t w o - d i m e n s i o n a l t r a n s o n i c code c a l l e d Code H , a n d a t h r e e - d i m e n s i o n a l s u b s o n i c a n d supersonic code called wing-body. Pressure d i s t r i b u t i o n s g e n e r a t e d by the codes for the f l i g h t test f i x t u r e as well as boundary layer displacement thickness generated by the two-dimensional code were compared to the f l i g h t test d a t a . The two-dimensional code pressure d i s t r i b u - t i o n s compared well except at the m i n i m u m pressure p o i n t and the t r a i l i n g edge. Shock locations compared well except at high t r a n s o n i c speeds. The three-dimensional code pressure d i s t r i b u t i o n s compared well except at the t r a i l i n g edge of the f l i g h t test f i x t u r e . The two-di- mensional code does not predict displacement thickness of t h e f l i g h t test f i x t u r e w e l l .
(6) Ronald J. Ray IN-FLIGHT THRUST DETERMINATION ON A REAL-TIME BASIS A real-time computer program was implemented on a F-15 jet fighter to monitor in-flight engine performance of a -5- D i g i t a l E l e c t r o n i c E n g i n e C o n t r o l l e d ( D E E C ) F-100 e n g i n e .
T h i s t h e s i s describes the a p p l i c a t i o n of two gas genera- tor methods to c a l c u l a t e i n - f l i g h t t h r u s t real-time at the NASA/Dryden F l i g h t Research F a c i l i t y . A comparison was made between the actual results and those predicted by an e n g i n e model s i m u l a t i o n . The percent d i f f e r e n c e between the two methods was compared to the predicted u n c e r t a i n t y based on i n s t r u m e n t a t i o n and model uncer- t a i n t y and agreed closely w i t h the results found d u r i n g a l t i t u d e f a c i l i t y t e s t i n g . Data was obtained from accel- eration runs of various altitudes at maximum power set- f tings w i t h a n d w i t h o u t a f t e r b u r n e r .
Real-time i n - f l i g h t t h r u s t measurement was a advancement to f l i g h t test p r o d u c t i v i t y and was accomplished w i t h no loss in accuracy over previous post f l i g h t methods. , i (7) Albion Bowers A COMPARISON OF COMPUTER-GENERATED LIFT AND DRAG POLARS FOR A WORTMANN AIRFOIL TO FLIGHT AND W I N D TUNNEL RESULTS C o m p u t a t i o n s of d r a g p o l a r s for a low-speed W o r t m a n n s a i l p l a n e a i r f o i l are compared to both w i n d t u n n e l and f l i g h t r e s u l t s . E x c e l l e n t c o r r e l a t i o n is shown to exist between computations and f l i g h t results except w h e n s e p a r a t e d flow regimes were e n c o u n t e r e d . W i n d t u n n e l t r a n s i t i o n locations are shown to agree w i t h computed — D "™ p r e d i c t i o n s . Smoothness of the i n p u t c o o r d i n a t e s to the PROFILE a i r f o i l a n a l y s i s computer program was f o u n d to be e s s e n t i a l to o b t a i n a c c u r a t e comparisons of drag polars o r t r a n s i t i o n l o c a t i o n t o e i t h e r t h e f l i g h t o r w i n d t u n n e l results.
(8) Faramarz A. Mahdavi DEEP STALL FLIGHT TESTING OF THE NASA SGS 1-36 Twenty s u c c e s s f u l , manned f l i g h t tests of the m o d i f i e d N A S A SGS 1-36 S a i l p l a n e w e r e c o n d u c t e d at a n g l e s - o f - attack between -5 and 75 degrees. The a i r c r a f t e x h i b i t e d good l o n g i t u d i n a l and l a t e r a l - d i r e c t i o n a l h a n d l i n g q u a l i - t i e s in the normal f l i g h t regime and deep stall angles- of-attack range of ,35 to 55 degrees. At angles-of-attack greater t h a n 55 degrees, the v e h i c l e displayed an un- stable, apparent Dutch-roll o s c i l l a t i o n , as well as l a t e r a l s t i c k f o r c e s ^ T h e o s c i l l a t i o n s , a n d l a t e r a l s t i c k forces appear to be a f u n c t i o n of a n g l e - o f - a t t a c k .
As the angle-of-attack i n c r e a s e d above 55 degrees, so did the m a g n i t u d e of the o s c i l l a t i o n s and the s t i c k forces.
A complete set of f l i g h t d e t e r m i n e d aerodynamic s t a b i l i t y and control d e r i v a t i v e s w a s o b t a i n e d u s i n g t h e M o d i f i e d M a x i m u m Likelihood E s t i m a t i o n program. T h e d e r i v a t i v e s o b t a i n e d from f l i g h t were compared to those o b t a i n e d from the q u a r t e r scale w i n d t u n n e l model tests and the pre- — 7 — d i e t e d rotary d e r i v a t i v e s . G e n e r a l l y , t h e f l i g h t deter- m i n e d s t a t i c d e r i v a t i v e s c o m p a r e d w e l l w i t h t h e w i n d t u n n e l predicted data at low a n g l e s - o f - a t t a c k , but at h i g h angles-of-attack the c o r r e l a t i o n was not good. The d y n a m i c d e r i v a t i v e s o b t a i n e d from f l i g h t d i d n o t compare w e l l w i t h those of the predicted in the deep stall re- g i o n . The p i t c h , roll, and yaw control s u r f a c e e f f e c - tiveness, and the primary damping d e r i v a t i v e s approached z e r o as the a n g l e - o f - a t t a c k was increased to 75 degrees.
S - P l a n e root locus analysis of one of the f l i g h t s at 65 degrees a n g l e - o f - a t t a c k i n d i c a t e d a s t a b l e , coupled, o s c i l l a t o r y r o l l - s p i r a l m o d e a s w e l l a s a n u n s t a b l e Dutch-roll mode. The f l i g h t determined lateral direc- tional o s c i l l a t i o n frequency for this f l i g h t was equal to the Dutch-roll f r e q u e n c y obtained from the root-locus a n a l y s i s .
: Final Comments Copies of the final reports of each of the students are included.
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