Simulator study of conventional general aviation instrument displays in path-following tasks with emphasis on pilot-induced oscillations

TP c . 1

NASA Technical Paper

1.7 7 6

Simulator Study of Conventional

General Aviation Instrument Displays. , in Path-Following ' Tasks. With 'Emphasis . ',:

on. Pilot-Induced'Oscillations

James, J. Adams DECEMBER 1980 TECH LIBRARY KAFB, N M

NASA TechnicalPaper 1776

SimulatorStudy of Conventional

GeneralAviationInstrument Displays

inPath-FollowingTasksWith Emphasis

on Pilot-Induced Oscillations

James J. Adams Laugley Research Cetrter Humnptor.1, Virgirria National Aeronautics and Space Administration Scientific and Technical Information Branch I I I I I I

IIIII I I 1 I 1 l 1 1 l 1 I I 1

SUMMARY A s t u d y of t h e u s e of c o n v e n t i o n a l g e n e r a l a v i a t i o n i n s t r u m e n t s by g e n e r a l a v i a t i o n pilots i n a six-degree-of-freedom,fixed-basesimulatorhasbeencon- ducted. The tasks performed were t r a c k i n g a very high-frequency omnirange (VOR) r a d i a la n d m a k i n ga ni n s t r u m e n tl a n d i n gs y s t e m( I L S )a p p r o a c h to l a n d i n g . A special f e a t u r e of t h e tests was t h a t t h e s e n s i t i v i t y of t h ed i s p l a c e m e n ti n d i - c a t i n gi n s t r u m e n t s ,t h e radio m a g n e t i ci n d i c a t o r ( M I ) , t h ec o u r s ed e v i a t i o n i n d i c a t o r ( C D I ) , a n dt h eh o r i z o n t a ls i t u a t i o ni n d i c a t o r ( H S I ) was kept c o n s t a n t a t v a l u e sc o r r e s p o n d i n g to 5 n. m i . and 1 .25 n. m i . from t h es t a t i o n .B o t h statistical a n dp i l o t - m o d e la n a l y s e s of t h e d a t a were made.

T e s t r e s u l t s show t h a tp e r f o r m a n c ei np a t h - f o l l o w i n g t a s k s improvedwith i n c r e a s e s i n d i s p l a y s e n s i t i v i t y u n t i l t h e h i g h e s t test s e n s i t i v i t y s e t t i n g was reached. A t t h i s maximum test s e n s i t i v i t yv a l u e ,w h i c hc o r r e s p o n d s to t h e s e n s i t i v i t y e x i s t i n g a t 1.25 n. m i . from t h e I L S g l i d e slope t r a n s m i t t e r , track- ingaccuracy was no better t h a n a t 5 n. m i . f r o mt h et r a n s m i t t e r ,a n dt h e pilot- a i r c r a f ts y s t e me x h i b i t e d a marked r e d u c t i o ni nd a m p i n g .I n some cases, a p i l o t - i n d u c e d ,l o n g - p e r i o du n s t a b l eo s c i l l a t i o n occurred.

INTRODUCTION G e n e r a la v i a t i o na c c i d e n t reports ( r e f . 1 )i n d i c a t et h a t many a c c i d e n t s o c c u rd u r i n gt e r m i n a l area f l y i n go p e r a t i o n si ni n s t r u m e n t meteorological con- d i t i o n s . A f a c t o rw h i c h may c o n t r i b u t e to t h i sa c c i d e n t rate is t h e role p l a y e d by t h ei n s t r u m e n tc o n f i g u r a t i o n sa n ds e n s i t i v i t i e si nt h ep i l o t - a i r c r a f ts y s t e m s t a b i l i t y . Pilot r e s p o n s e s t u d i e s andpilot-modeling efforts have shown t h a t t h e p i l o t does respond much l i k e a l i n e a rf e e d b a c kc o n t r o lm e c h a n i s m when con- t r o l l i n ga na i r c r a f t ;t h e r e f o r e ,t h e pilot-aircraft systemcanbeanalyzed as a l i n e a rs y s t e m ,a n dt h es y s t e ms t a b i l i t yc h a r a c t e r i s t i c sc a nb ed e t e r m i n e d .

Aircraft are d e s i g n e d so t h a t i n most cases t h i s s y s t e m s t a b i l i t y is p o s i t i v e (damped) , b u to c c a s i o n s do arise when t h es y s t e m is u n s t a b l e .P i l o t - i n d u c e d u n s t a b l eo s c i l l a t i o n sh a v eb e e na n item of s t u d y for some time. A r e c e n t summary s t u d y is g i v e ni nr e f e r e n c e 2. U n t i lr e c e n t l y ,t h e s es t u d i e sh a v e u s u a l l yc e n t e r e da r o u n ds h o r t - p e r i o d( a r o u n d 2 to 3 sec) i n s t a b i l i t i e s t h a t a t highdynamicpressure,wherethe associated d i v e r g e n c e of a n g l e of occur attack c a nr e s u l ti ns t r u c t u r a lf a i l u r e .L o n g - p e r i o du n s t a b l eo s c i l l a t i o n s can also o c c u rw h i c hi n v o l v eo n l y small v a r i a t i o n s i n a n g l e of attack or side- slip, b u tl a r g ed i s p l a c e m e n t s from t h e d e s i r e d f l i g h t p a t h o f t h e aircraft.

Evidence of s u c h l o n g - p e r i o d i n s t a b i l i t i e s may befoundinmeasurements made d u r i n g s i m u l a t e d i n s t r u m e n t l a n d i n g a p p r o a c h e s . However, i nt h e s ei n s t a n c e s , t h eo s c i l l a t i o n su s u a l l yd on o th a v e time to become f u l l yd e v e l o p e d before t h e p i l o t b r e a k s o u t of t h ew e a t h e rc o n d i t i o n sa n d stable v i s u a l f l i g h t is restored. The p r e s e n ts t u d ye m p h a s i z e st h ee x i s t e n c e of t h e s el o n g - p e r i o d i n s t a b i l i t i e s by u s i n g special test t e c h n i q u e s made possible by t h e f l e x i - b i l i t y of t h es i m u l a t o r computer and relates them to c o n v e n t i o n a lg e n e r a l a v i a t i o n i n s t r u m e n t d i s p l a y c o n f i g u r a t i o n s .

SYMBOLS gust spectrum transferfunctions a l t i t u d e , m pilot-modelgains, rad/m pilot-modelgains,dimensionless gust character istic wavelengths, m mass, k g probabilityof being incorrect i n assuming thatthehypothesis thatthescoresareequal is wrong roll,pitch, and yaw angular rates,rad/sec Laplace operator, persec a i r c r a f t r o l l time constant,sec a i r c r a f t s p i r a l time constant,sec velocity, m/sec lateraldistance, m angles of attack and sideslip, rad aileron and elevatordeflections,rad realroot, persec frequencies,rad/sec, and damping ratiosfor pilot model-aircraf; system mode of motion yaw, pitch, and rollangles, rad gusttransferfunctionamplitudes, m/sec Nondimensional stability derivatives: l i f t coefficient due toelevatordeflection

c u e

rolling-moment coefficient due t o s i d e s l i p

c z f 3

yawing-moment coefficient due t o s i d e s l i p CnB yawing-moment c o e f f i c i e n t d u e to a i l e r o n d e f l e c t i o n Cn6 a s i d e - f o r c ec o e f f i c i e n t due to s i d e s l i p s t a b i l i t y d e r i v a t i v e s : s i d ef o r c ed u e to r o l l i n gv e l o c i t y , N-sec s i d ef o r c ed u e to y a w i n gv e l o c i t y , N-sec s i d ef o r c e due to s i d e s l i p , N gravity,m/sec2 moment o f i n e r t i a , kg-m 2 p r o d u c to fi n e r t i a , kg-m2 r o l l i n g moment due to roll v e l o c i t y , N-m-sec r o l l i n g moment due to y a w i n gv e l o c i t y , N-m-sec r o l l i n g moment due to s i d e s l i p , N-m r o l l i n g moment due to a i l e r o n d e f l e c t i o n , N-m yawing moment due to r o l l i n gv e l o c i t y , N-m-sec MZP yawing moment due to y a w i n gv e l o c i t y , N-m-sec MZr yawing moment due to s i d e s l i p , N-m MZ!3 yawing moment due to a i l e r o n d e f l e c t i o n , N-m M a a A b b r e v i a t i o n s : C D I course d e v i a t i o n i n d i c a t o r de f d e f l e c t i o n HS I h o r i z o n t a l s i t u a t i o n i n d i c a t o r IFR I n s t r u m e n t F l i g h t R u l e s ILS i n s t r u m e n t l a n d i n g , s y s t e m R M I r a d i o m a g n e t i c i n d i c a t o r VOR very high-frequency omnirange S u b s c r i p t s : C comnand DR Dutch roll H heading R r o l l S s p i r a l error E A d o to v e rs y m b o li n d i c a t e sd e r i v a t i v ew i t h respect to time.

EXPERIMENTAL PROCEDURES A s i x - d e g r e e - o f - f r e e d o m ,f i x e d - b a s es i m u l a t i o ne f f o r t was undertaken to examine pilot r e s p o n s e to c o n v e n t i o n a lg e n e r a li n s t r u m e n t s . The tasks i n v o l v e d i n t h e s e tests were to track a g i v e nr a d i a l to a veryhigh-frequencyomnirange (VOR) s t a t i o n or to make a ni n s t r u m e n tl a n d i n gs y s t e m ( I L S ) approach to l a n d i n g .

A s p e c i a l f e a t u r e o f t h e s e tests was to m a i n t a i n c o n s t a n t s e n s i t i v i t y o f t h e d i s p l a c e m e n ti n d i c a t i n gi n s t r u m e n t sd u r i n g a g i v e nr u n .I nt h ea c t u a ls i t u a - t i o no fn a v i g a t i n g to a VOR s t a t i o n or makinganapproach to a nI L Ss t a t i o n , t h e s e n s i t i v i t y of t h ed i s p l a c e m e n ti n s t r u m e n t s ,w i t h respect t o l i n e a r d i s - p l a c e m e n tf r o mt h ed e s i r e dp a t h ,d o e sc h a n g ew i t h linear d i s t a n c e from t h e s t a t i o n .T h i se f f e c tr e s u l t sb e c a u s et h ed i s p l a ys y s t e m sa c t u a l l y show a n angular measure of d i s p l a c e m e n t .T h a t is, t h e y show t h ea n g l eb e t w e e n a l i n e from t h e a i r c r a f t t o t h es t a t i o na n dt h el i n er e p r e s e n t i n gt h ed e s i r e dp a t h .

On t h eo t h e rh a n d ,t h e p i l o t h a sc o n t r o l of l i n e a rd i s p l a c e m e n t .F o ra n yg i v e n i n p u to nt h e part of t h e p i l o t , t h e same d i s p l a c e m e n to u t p u t results r e g a r d - less of a i r c r a f t d i s t a n c e from t h es t a t i o n . As a result, to t h e p i l o t , t h e d i s p l a c e m e n t - i n d i c a t i n gi n s t r u m e n t s appear t o u n d e r g oa n -i n c r e a s ei ns e n s i t i v i t y as t h ea i r c r a f ta p p r o a c h e st h es t a t i o n .

The p u r p o s eo ft h ep r e s e n t tests was t o o b t a i na n accurate measure of t h e p i l o t ' sr e s p o n s e to t h ed i s p l a c e m e n ti n s t r u m e n t su n d e rt h ec o n d i t i o no fc o n s t a n t s e n s i t i v i t y .T h i sp r o c e d u r ee l i m i n a t e st h ec o n f o u n d i n ge f f e c t of changing sen- s i t i v i t y o nd a t aa n a l y s i s . The s e n s i t i v i t y was k e p tc o n s t a n t by t h e simple pro- cedure of using a c o n s t a n tr a n g e to t h es t a t i o n ,e v e nt h o u g ht h e a i r c r a f t was t r a v e l i n ga t some g i v e na i r s p e e d . The s e n s i t i v i t i e sc h o s e n for s t u d y were t h o s e t h a tc o r r e s p o n d to 5 n. m i . and 1 .25 n. m i . from t h es t a t i o n . A t 1 .25 n. m i .

from t h e ILS g l i d e slope s t a t i o n ,t h e a i r c r a f t would still be a t a n a l t i t u d e of 1 2 0 meters; t h u s t h e a i r c r a f t c o u l d still beexpected to be i ni n s t r u m e n t c o n d i t i o n s .

The l a t e r a l course d e v i a t i o ns i g n a lu s e d when t r a c k i n g t o t h e VOR s t a t i o n was computed as follows: AY

Lateral deviation signal = tan-l - (for the 5 n. mi. range)

o r AY

Lateral deviation signal = t a n ' l - (for the 1.25 n. mi. range)

A gain was put on this signal so that a loo deviation would register as a full

deflection on the instrument. While controlling this lateral signal, the pilot was also required to control altitude at 610 meters and airspeed at 135 knots.

The signals used for the ILS landing approach were AY Lateral deviation signal = tan-l

9300 + 2140

or AY Lateral deviation signal = tan-l 2320 + 2140 where the extra 2140 meters is the additional distance from the glide slope station to the localizer station. That is, when the distance from the ILS sta- tion is referred to as either 5 n. mi. or 1.25 n. mi., this value represents the distance from the aircraft to the glide slope ground impact point. The localizer station is an additional 2140 meters away from the aircraft. A gain was put on this signal so that a 2.5O deviation would move the localizer needle to full deflection. The ILS signal is 4 times more sensitive than the VQR signal.

The vertical needle deflection was Ah

Vertical needle deflection = t a n ' l -

o r Ah

= tan-l -

Vertical needle deflection A g a i n was p u t o n t h i s s i g n a l so t h a t a 0.7O d e v i a t i o n w o u l d move t h e g l i d e slope n e e d l e to f u l ld e f l e c t i o n .D u r i n ga n ILS a p p r o a c h ,t h e p i l o t had to c o n t r o l b o t h g l i d e slope a n d l o c a l i z e r w h i l e m a i n t a i n i n g 8 5 k n o t s airspeed.

T h r e ed i f f e r e n td i s p l a c e m e n ti n d i c a t i n gi n s t r u m e n t s were s t u d i e d :t h e c o u r s ed e v i a t i o ni n d i c a t o r (CDI), t h eh o r i z o n t a ls i t u a t i o ni n d i c a t o r( H S I ) ,a n d t h e r a t i o m a g n e t i ci n d i c a t o r (RMI) . B o t ht h e CDI a n dt h e H S I are d e s i g n e d to operate i n c o n j u n c t i o n w i t h e i t h e r VOR or I L S s t a t i o n s ; t h e R M I is d e s i g n e d to operate o n l yw i t h VOR s t a t i o n s .W i t ht h e R M I , t h ea n g u l a rd e v i a t i o ns i g n a l d e s c r i b e di nt h ep r e c e d i n gs e c t i o n was a p p l i e d d i r e c t l y t o t h e s t a t i o n homing n e e d l e .F i g u r e 1 s h o w st h el o c a t i o no fe a c h of t h e s ei n s t r u m e n t si nt h ei n s t r u - m e n tp a n e l of t h e simulator. E a c hd i s p l a c e m e n ti n s t r u m e n t was tested sepa- r a t e l y . When one of them was a c t i v e ,t h eo t h e r t w o were i n a c t i v e .A l o n gw i t h e a c hd i s p l a c e m e n ti n d i c a t i n gi n s t r u m e n t ,t h ea t t i t u d ei n d i c a t o r ,t h ed i r e c t i o n a l g y r oi n d i c a t o r ,a n dt h e airspeed, altimeter, and rate-of-climb i n d i c a t o r s were also o p e r a t i n g .

The s u b j e c t sh a dn od u t i e s to p e r f o r mo t h e rt h a nc o n t r o l l i n g t o t h e d e s i r e df l i g h tp a t h . Prior t o t h e tests, t h es u b j e c t s were i n f o r m e dt h a tt h e test r u n s were 3 minuteslong,andwere asked to d i r e c t t h e i r f u l l a t t e n t i o n to m a i n t a i n i n gp a t hc o n t r o l . Upon completion of t h e tests, a l l subjects r e p o r t e d t h a t t h e y h a d c o n c e n t r a t e d s o l e l y o n t h i s c o n t r o l o b j e c t i v e .

S u b j e c t s Ten s u b j e c t s were u s e di nt h e s e tests. I ne x p e r i e n c e ,t h e yr a n g e d from p i l o t s who f l e w t h e i r a i r c r a f t o n l yo c c a s i o n a l l ya n d who were e i t h e r i n t h e p r o c e s so fo b t a i n i n g or had j u s t r e c e n t l yr e c e i v e dt h e i ri n s t r u m e n tr a t i n g s , to p r o f e s s i o n a l t e s t p i l o t s . A l l t h es u b j e c t sh a dc o n s i d e r a b l es i m u l a t o r e x p e r i e n c e . The s u b j e c t s 'a g ea n da c c u m u l a t e df l i g h th o u r s are listed i nt h e f o l l o w i n g table:

rm T o t a l

I F R h o u r s S u b j e c t

1 Number

Age f l i g h t h o u r s f l i g h t h o u r s i n i t i a l s i n l a s t 1 2 months DH 22 5 200 2 230 53 MM 50 25 250 40 JS 6 2 16 66 360 44 JR

H v

300 1000 31 25 ss 75 1400 43 HB 50 2500 2 8 2500 36 SH 500 15 3500 39 PB 600 15 PD 10 21 00 61 00 45 Test Procedures These 1 0 subjects had a l l t a k e n p a r t i n p r e v i o u s test programsonthe g e n e r a l a v i a t i o n f l i g h t s i m u l a t o r a t t h eL a n g l e yR e s e a r c hC e n t e ra n d ,t h e r e f o r e , were familiar w i t ht h e response of t h es i m u l a t o r .T h e y were, n e v e r t h e l e s s , g i v e n a warmup s e s s i o n a t t h eb e g i n n i n go fe a c h test d a y .T e s t so ft h e CDI a t 5 n. m i . and1.25n. m i . f r o mt h e VOR s t a t i o n w i t h a n i n i t i a l l a t e r a l error and no winds were c o n d u c t e do nt h ef i r s td a y .N e x t ,t h e same c o n d i t i o n sw i t hw i n d s were t e s t e d . Then, t h e same series of tests were r u nw i t ht h e H S I i n s t r u m e n t .

F i n a l l y ,t h e same e i g h tr u n s were made u s i n gt h e I L S s t a t i o n . On t h es e c o n d t e s t d a y ,t h e order of t h e C D I and HSI i n s t r u m e n t s was r e v e r s e d ,a n dt h e nt h e block of f o u rr u n s was p e r f o r m e du s i n gt h e M I .

Aircraft Model A realistic six-degree-of-freedom,nonlinear model was used t o s i m u l a t e a typical high-wing,four place, s i n g l e - e n g i n e ,g e n e r a la v i a t i o na i r p l a n ei nt h i s s t u d y .I na d d i t i o n t o n o n l i n e a rk i n e m a t i c s ,t h ef o l l o w i n gn o n l i n e a ra e r o d y n a m i c f a c t o r sa n do t h e r special f e a t u r e s were i n c l u d e d i n t h es i m u l a t i o n : 1. Nondimensional l i f t a n dd r a gc o e f f i c i e n t s were a f u n c t i o no f cL2 as well a s a.

2. N o n d i m e n s i o n a l s t a b i l i t y c o e f f i c i e n t s C

YB' CLger CZB' C "6, , and C

"6 were a f u n c t i o no f a.

3 . Asynanetric forces and moments a s a f u n c t i o n o f t h r u s t c o e f f i c i e n t were i n c l u d e d .

4 . A h y d r a u l i c c o n t r o l loader t h a t p r o v i d e d c o n t r o l forces a s a f u n c t i o n ofaerodynamichinge moments was included.

5. A s o u n ds y s t e mt h a tp r o v i d e d realistic e n g i n ea n d airstream n o i s e was i n c l u d e d .

Thedynamicresponse of t h i s s i m u l a t i o n model t o step c o n t r o l i n p u t s a t t h e two v a l u e s of airspeed ( 8 5a n d1 3 5k n o t s )t h a t were u s e di nt h e tests are shown i nf i g u r e s 2 and 3 . F i g u r e2 ( a )s h o w st h es h o r t - p e r i o dr e s g o n s e to a 0 . 0 2 - r a de l e v a t o r step a t t h e t w o v a l u e so fa i r s p e e d . The r e s p o n s e is well damped a n dt h ef r e q u e n c i e s are r e a s o n a b l yh i g h , i.e., o nt h e order of 6 rad/sec.

Figure2(b)showsthephugoidresponse to a ni n i t i a lo u t - o f - t r i ma n g l e of attack; t h ep h u g o i d was found t o be s t a b l e w i t h periods of 55and 30 seconds.

The l a t e r a l dynamicresponses a t t h e two a i r s p e e d s are shown i n f i g - u r e 3 . The Dutch r o l l mode is f a i r l y well damped a n dh a sf r e q u e n c i e s of 3 and 2 r a d / s e c .F i g u r e 3 also depicts t h e l a r g e e f f e c t of t h ea d v e r s e yaw o n t h e yaw rate r e s p o n s e .F o rf u r t h e ri n s i g h ti n t ot h e l a t e r a l r e s p o n s e ,t h e l a t e r a l l i n e a r p e r t u r b a t i o n e q u a t i o n s of motion were w r i t t e n , a n d t h e air- craft l a t e r a l r e s p o n s ec h a r a c t e r i s t i c s were a n a l y t i c a l l yd e t e r m i n e d .T h e l i n e a r e q u a t i o n s are P = 2 1x2

Ix - -

IZ At 85 knots,

i = -0.229$ + 0.0065r - 0.0162~ + 0.2254 - r

p = -6.956 + 1.10r - 4 . 8 2 ~ - 8.536, I : = 2.858 - 0.725r - 0.436~ + 0.2166, At 135 knots,

6 = -0.3248 + 0.0065r - 0.0162~ + 0.225Q - r

p = -18.856 + 1.71r - 7.50~ - 20.76, i = 7.916 - 1.13r - 0.677~ + 0.5276, The lateral response characteristics, as determined from these equations, are At 85 knots, TS = 44 sec TR = 0.2sec WDR = 1.95rad/sec <DR = 0.208 At 135 knots, TS = 70 sec TR = 0.13sec WDR = 3.16rad/sec ~ D R = 0.203 T h e s e a n a l y t i c a l r e s u l t s for t h eD u t c h r o l l a g r e e w i t h t h e results n o t e d f o r t h e time h i s t o r i e s ; t h e o t h e r r e s u l t s p r o v i d e f u r t h e r i n f o r m a t i o n on t h e spiral and r o l l time c o n s t a n t s .

Wind I n p u t I n some of t h e tests conducted as part of t h i se x p e r i m e n t , wind i n p u t s were u s e d as f o r c i n gf u n c t i o n s .T h e s ew i n di n p u t sc o n s i s t e d of a s t e a d y cross wind of 1.22 m/sec inmagnitudeand a random i n p u tu s e d to r e p r e s e n tg u s t s .T h r e e g u s ti n p u t s ~ g r ~ g r ~ g were g e n e r a t e du s i n g random-number g e n e r a t o r sa n df i l t e r s based on the Dryden gust model. The f i l t e r s were The scale l e n g t h s were Lu = L, = h ( f o r h 2 535 m) Lu = L, = 44h1i3 (for h < 535 m) & = h The v a l u e s o f t h e i n d i v i d u a l g u s t a m p l i t u d e s were set to occur i n t h e f o l l o w i n g r e l a t i v e v a l u e s : u u = 1.12 Dv = 1.18 Ow = 1.16 I IIIIIIIIII.Il1111111ll During the tests, the overall gust amplitude was adjusted so that the average gust root mean square was 1.22 m/sec at an altitude of 535 meters. The mean value of the gusts was zero.

Method of Analysis A statistical analysis was conducted by measuring the mean and stand deviation of the lateral and vertical errors of the runs made with the wi disturbances. A t-test was conducted between the different range conditions with each instrument, and between the different instruments at each range con- dition to determine the level of significance of the differences.

A pilot-model analysis was performed to provide time histories for co parison with the time histories obtained in the simulation exercise. Block diagrzms of the pilot-modei-aircraft system are shown in figure 4 . Decoupled and linearized diagrams are shown for the separated lateral and longitudin system for simplicity. The pilot is represented by simple gains in the outer displacement loops (y and h) and, for lateral control, in the $ loop. The inner loops @ and 8 contain a gain and a lag function that represent the characteristics of the response used by the pilot to put the control m pulator in the desired position. The second-order form for this response is used because the subsystem represented does involve an inertia, i.e., the manipulator inertia plus the pilot's arm. A perfect-square form is used to represent the critically damped response employed. The 0.2-sec lag time constant used is a preferred lag time constant. It is a long time constant compared with the 0.04-sec time constant that a pilot can use in a simpl control task when required by the system stability considerations. Therefore, the 0.2-sec lag time constant represents an undemanding response as well as the value that pilots use in complicated, multiloop control tasks, where m of the pilot's attention must be directed to reading the instruments.

A lead can also be included in the pilot-model inner loop and would be included if called for by the system stability compensation requirements.

This lead would represent the pilot's response to the rate of change of the inner-loop variable. Lead time constants of 1 sec have been measured in single-loop control tasks. However, in complex, multiloop control tasks, the pilot has very little time available to differentiate the inner-loop variab display. The present study assumes that no inner loop lead is present.

The relations between the aircraft control inputs 6 , and 6 , and the rate of change of the inner loop variables p and q are shown as blocks (labeled "aircraft") in the diagram (fig. 4). These blocks represent complex relations involving many integrations, all of which are interconnected as defined by the equations of motion. The complexity of these relations admits the possibility of large variations in responses of p and q to 6 , and 6 , , which can have a decided influence on the total system response. Investigation of these aircraft response effects is covered by an extensive bodyof published handling-qualities studies. References 3 and 4 cover this areaof research from a pilot-model viewpoint.

The present study is concerned with the dynamic phase lags which are present in the relations of the variables that the pilot is asked to regulate These phase lags are emphasized in the block diagram (fig. 4 ) by showing the integrations that exist between these variables. The 90° phase lag between 8 (or Y) and h, for vertical control, and the 90° between ($ and $ and and y, for lateral control, indicate that the pilot must coordinate his response to these variables to achieve a satisfactory system response. The pilot's ability to provide this coordination is related to the configuration and sensitivity of the display of these variables. This ability is the focal point of the present investigation. The pilot model described in the block diagram was used to obtain time histories that could be used for comparison with the records obtained from the test subjects. These system responses were obtained using the pilot model in conjunction with the six-degree-of-freedom nonlinear aircraft model. Both a lateral pilot model and a vertical pilot model were used. The vertical pilot model was used to maintain a constant altitude. Analytically determined lateral system characteristics were also obtained using the linear pilot model, the linear lateral perturbation equa- tions presented previously, and the following linearized kinematic relations:

; = w

To illustrate the lateral response of the modeled pilot-aircraft system, sample time histories obtained with typical pilot-model gains and the aircraft simulation model are shown in figures 5 to 7. These figures also illustrate the effect of the two different airspeeds used in the study, the effect of the remnant term in the pilot model, and the effect of the wind disturbance.

The time histories of figure 5, for which the pilot model contained no remnant term, show a stable system. The analytically determined system charac- teristics, shown in table I, also indicate that the system is stable. The table indicates a system response which contains four modes of motion. The high-frequency control mode is derived from the pilot-model inner-loop charac-

teristic (0.2s + 1) or (s + 5 ) 2. In the complete system, this mode is

altered slightly. This mode of motion is not noticeable in the time histories.

The next lower frequency mode is the aircraft Dutch roll mode, which also is altered slightly by the additional loop closures of the complete pilot-model- aircraft system. The next lower frequency is an oscillatory mode derived from the combinationof the zero-value heading root and the lower value roll root.

This mode of motion is the oscillatory mode that appears in the time histor The final mode of motion is derived from the zero-value lateral displacement root and the higher roll root. In this sample case, the two roots involved remain real roots rather than combining into an oscillatory model. The lower real root and the roll-heading oscillatory root determine the shape of the time history response.

The d i f f e r e n c e s i n t h e time h i s t o r i e s for t h e t w o airspeeds c o r r e s p o n d to t h ed i f f e r e n c e si nt h e roots ( t a b l e I) for t h e same t w o a i r s p e e d s .S i n c et h e systems are s t a b l e i n e a c h case, t h e time h i s t o r i e s c o n v e r g e t o a c o n s t a n t s t e a d y - s t a t ev a l u e .T h ea s y m m e t r i c a l - e n g i n e - t h r u s t terms t h a t are i n c l u d e di n t h e a i r c r a f t s i m u l a t o r model c a u s et h en o n z e r ov a l u e for t h e s t e a d y s t a t e .

The m i g r a t i o no ft h es y s t e m roots t h a t o c c u r s as t h ep i l o t - m o d e lf e e d b a c k loops are closed is i l l u s t r a t e d i n t h e s e c o n d part o f t a b l e I for the85-knot a i r s p e e d case. With no loops c l o s e d (K@ = 0, K$ = 0 , Ky = 0 ) , t h e s y s t e m c o n s i s t so ft h eu n c h a n g e dD u t c h roll, s p i r a l ,a n d rollroots. When t h eb a n k a n g l e loop is c l o s e d (K@ = -0.16) , t h e s p i r a l root takes on a l a r g en e g a t i v e changeandthe r o l l root is r e d u c e di nv a l u e . When t h eh e a d i n gl o o p is c l o s e d (K@ = -0.16, K+ = 1 .25) , t h e lower r o l l root a n dt h eh e a d i n g root combine t o form a s t a b l eo s c i l l a t o r y root. When t h ed i s p l a c e m e n t loop is c l o s e d ,t h e system takes o n t h e c h a r a c t e r i s t i c s d e s c r i b e d i n t h e p r e v i o u s p a r a g r a p h .

Next, a r e p r e s e n t a t i v e p i l o t remnant was added t o t h e p i l o t model.This remnant was g e n e r a t e d by p a s s i n g a w h i t e - n o i s er a n d o ms i g n a lt h r o u g h a second- o r d e r f i l t e r i d e n t i c a l t o t h ep i l o t - m o d e lc h a r a c t e r i s t i c : Kn (random (0.2s + 112 a n da d j u s t i n gt h eg a i n Kn t o p r o v i d e a t y p i c a l p i l o t remnant amplitude. The effect o fa d d i n gt h er e m n a n t( s h o w ni nf i g .6 ) is to make t h eD u t c hr o l l mode a n dt h er o l l - h e a d i n g mode of motion much more v i s i b l e i n t h e s y s t e m r e s p o n s e .

W i t ht h er e m n a n ts i g n a li n c l u d e d ,t h es y s t e mr e s p o n s e now c o n v e r g e s t o a n a p p r o x i m a t e l yc o n s t a n t - a m p l i t u d eo s c i l l a t o r ys t e a d y - s t a t ec o n d i t i o nr a t h e rt h a n to a c o n s t a n t - v a l u es t e a d ys t a t e . The f r e q u e n c i e so fd i f f e r e n t modes ofmotion are d e t e c t a b l e i n t h e time h i s t o r i e s ,a n dt h ea m p l i t u d eo ft h ed i f f e r e n t modes is dependentonthefrequencyanddamping of t h e modes a n dt h ea m p l i t u d eo ft h e remnantinput.

The e f f e c to fa d d i n gt h e wind d i s t u r b a n c e is shown i n f i g u r e 7. The steady-cross-windcomponentofthewind more t h a n o f f s e t s t h e a s y m m e t r i c t h r u s t moments and causes a p o s i t i v e - v a l u eb i a si nt h ed i s p l a c e m e n t time h i s t o r y . T h er a n d o mc o m p o n e n to ft h ew i n di n c r e a s e st h es t e a d y - s t a t e oscil- l a t o r ya m p l i t u d ei nt h es y s t e mr e s p o n s e .A g a i n ,t h ea m p l i t u d eo ft h es t e a d y - s t a t e o s c i l l a t i o n is a f u n c t i o no ft h ef r e q u e n c ya n dd a m p i n g of t h es y s t e m modes ofmotion.

RESULTS S t a t i s t i c a l A n a l y s i s Time h i s t o r i e s t y p i c a l o f t h e r e s u l t s o b t a i n e d i n t h e s t u d y a r e shown i n f i g u r e s 8 and 9. The l a t e r a l a n dv e r t i c a ld e v i a t i o n sf r o mt h ed e s i r e dp a t hf o r r u n si nw h i c ht h ew i n dd i s t u r b a n c e was i n c l u d e d are shown i n f i g u r e 8. The l a t e r a l d e v i a t i o n for r u n s i n w h i c h t h e r e was a n i n i t i a l l a t e r a l error, b u t n o winds, is shown i n f i g u r e 9. The i n i t i a l l a t e r a l error was set so t h a t t h e i n i t i a l n a v i g a t i o n d i s p l a y n e e d l e d e f l e c t i o n was a l w a y s t h e same, a p p r o x i m a t e l y o n e - t h i r d f u l l d e f l e c t i o n .

A l t h o u g h t h e s e n s i t i v i t y of t h e C D I and H S I are a p p r o x i m a t e l ye q u a l ,t h e s e n s i t i v i t y of t h e R M I to l a t e r a l d i s p l a c e m e n t error is much less t h a n t h a t o f e i t h e rt h e C D I or t h e HSI. The time h i s t o r y records, e s p e c i a l l yt h e records w i t h a n i n i t i a l lateral error, d e m o n s t r a t et h a tt h ef r e q u e n c y of t h e pilot- a i r c r a f t system is v e r y l o w w i t ht h e R M I . W i t ht h e CDI and HSI, s e v e r a l cycles of t h e d o m i n a n t o s c i l l a t o r y mode take place i nt h e3 - m i n u t e time span of t h e test. . W i t ht h e R M I t h es y s t e mf r e q u e n c y is so low t h a t n o t e v e n o n e complete c y c l eo c c u r sw i t h i nt h e time of t h e test. I t was concluded from t h o s e obser- v a t i o n s t h a t p a t h f o l l o w i n g w i t h t h e R M I is much less a c c u r a t e t h a n w i t h e i t h e r t h e CDI or t h e H S I . F u r t h e r m o r e ,t h e mean a n ds t a n d a r dd e v i a t i o nt h a t are m e a s u r e du n d e rt h ec o n d i t i o n so ft h e test d o n o t a c c u r a t e l y d e s c r i b e t h e s y s t e m f o rt h e R M I ; f o rt h i sr e a s o n ,t h e R M I tests were n o tc a r r i e do u tw i t ht h e same d e g r e eo fe f f o r t a s f o r t h e CDI and HSI. Onlyone set ofmeasurementswitheach subject was made w i t h t h e R M I .

The s t a n d a r dd e v i a t i o n sa n dm e a n sf o r t h e l a t e r a l d i s p l a c e m e n t errors are p r e s e n t e di nt a b l e s I1 and 111. S i n c et h es e n s i t i v i t yo f t h e l a t e r a l displace- m e n t si n c r e a s e sw i t h decreases i nr a n g e t o t h e s t a t i o n ,p e r f o r m a n c e may be e x p e c t e d to improve a t s h o r t e rr a n g e .T h i sr a n g ee f f e c t is v e r y clear for t h e e nr o u t e VQR d a t af o rt h e C D I and HSI. The a v e r a g es t a n d a r dd e v i a t i o na n d mean f o re a c ho ft h e s ei n s t r u m e n t s show o b v i o u sr e d u c t i o n si n scores i ng o i n gf r o m t h e 5 n. m i . range t o t h e1 . 2 5n . m i . r a n g e . The scores for t h e R M I d i dn o t v a r y .I nt h e tests w i t ht h e I L S s t a t i o n ,n e i t h e rt h es t a n d a r dd e v i a t i o nn o r t h e mean showed a n ys i g n i f i c a n tc h a n g ef o rt h e two r a n g e s .A d d i t i o n a l t-test c o m p a r i s o n so ft h ed i f f e r e n t pairs o f data were made and show t h a t t h e d i f - f e r e n c e sn o t e db e f o r e were s i g n i f i c a n t . The P-values are l i s t e di nt a b l e s 11 t o V. A P-value of less than0.025canbeused t o i n d i c a t e a s i g n i f i c a n t d i f f e r e n c e .E x c e p tf o rt h e mean o b t a i n e dw i t h t h e H S I t r a c k i n g t o t h e VOR s t a t i o n ,t h eP - v a l u e s show t h a tt h ed i f f e r e n c e sn o t e db e f o r e are indeed s i g n i f i c a n t .

The d i f f e r e n t i n s t r u m e n t s were also compared a t t h e same t r a c k i n gr a n g e .

When t r a c k i n g t o t h e VDR s t a t i o n , t h e b e s t scores were o b t a i n e d w i t h t h e HSI, t h es e c o n d best w i t ht h e C D I , a n dt h e worst w i t ht h e R M I i n b o t h s t a n d a r d I I ( a ) and I I I ( a 1 ) . The t-tests o nt h ed i f f e r e n t d e v i a t i o na n d mean ( t a b l e s p a i r s o fd a t a( t a b l e sI I ( b )a n d I I I ( b ) ) c o n f i r mt h a tt h e s ed i f f e r e n c e s are s i g n i f i c a n t a t t h e 0.025 l e v e l e x c e p t i n t h e case of t h e means for t h e p a i r s CDI-RMI a t 5 n. m i . and CDI-HSI a t 1.25 n. m i . The l a c k of s i g n i f i c a n c ei n t h e f i r s t o f t h e s e two cases may o n l y reflect i n s u f f i c i e n t data f o r t h e R M I .

When t r a c k i n g to t h e ILS s t a t i o n , t h e C D I and HSI were s i g n i f i c a n t l y d i f f e r e n t a t t h e 5 n. m i . r a n g e for s t a n d a r d d e v i a t i o n b u t n o t for t h e mean; HSI d i s p l a y e dt h e better scores. A t 1.25 n. m i . t h e r e were n os i g n i f i c a n t d i f f e r e n c e sb e t w e e nt h e CDI a n dt h e HSI. The time h i s t o r i e s show t h a t w i t h each of t h e s e i n s t r u m e n t s t h e l a t e r a l d i s p l a c e m e n t becomes v e r y erratic a t t h e s h o r tr a n g e . A more d e t a i l e da n a l y s i s of t h i s s i t u a t i o n is p r e s e n t e di n a s u b s e q u e n ts e c t i o n of t h i s s t u d y .

S t a n d a r dd e v i a t i o n sa n dm e a n s were also measured for vertical c o n t r o l (tables I V and VI. When t r a c k i n g to t h e VOR s t a t i o n ,t h e p i l o t c o n t r o l l e d a l t i t u d e by r e f e r r i n g t o t h e altimeter a n da t t e m p t i n g t o h o l d a 610-meter a l t i t u d e . With t h i sc o n f i g u r a t i o nt h e r e is no c h a n g ei ns e n s i t i v i t yi nt h e d i s p l a y of a l t i t u d e error w i t hc h a n g ei nr a n g e ,a n dt h e t-tests onrange effects snow n o s i g n i f i c a n t d i f f e r e n c e s for t h ed i f f e r e n tc o m b i n a t i o n s of lateral d i s p l a c e m e n ti n s t r u m e n ta n d altimeter. The t-test tests, however, d i d show a s i g n i f i c a n td i f f e r e n c eb e t w e e nt h ec o m b i n a t i o n so f C D I and altimeter and HSI and altimeter a t t h e 5 n. m i . range for s t a n d a r dd e v i a t i o n , b u tt h e y showed no d i f f e r e n c e a t 1 .25 n. m i . andno d i f f e r e n c e i n t h e mean a t e i t h e rr a n g e . Tne o n es i g n i f i c a n td i f f e r e n c et h a t was notedcanbe a t t r i - buted to t h e fact t h a t t h e HSI and altimeter are located closer t o g e t h e r on t h ei n s t r u m e n tp a n e lt h a na r et h e C D I and altimeter; c o n s e q u e n t l y , less scan- n i n g is r e q u i r e d to r e a dt h e HSI a n da l t i m e t e rc o m b i n a t i o n .

With t h e I L S s t a t i o n , t h e g l i d e slope i n d i c a t o r so nt h e C D I and HSI i n s t r u m e n t s were used to d i s p l a y v e r t i c a l error; t h e r e f o r e , a c h a n g ei ni n s t r u - ment s e n s i t i v i t yo c c u r r e dw i t hc h a n g ei nr a n g e . The t-tests a p p l i e d t o t h e d a t af o re a c h of t h e s ei n s t r u m e n t s show a s i g n i f i c a n tc h a n g ei ns t a n d a r dd e v i - a t i o nw i t hr a n g e ,b u tn os i g n i f i c a n td i f f e r e n c e si nm e a n s .C o m p a r i s o n of t h e two i n s t r u m e n t s a t e a c hr a n g es h o w st h a t a s i g n i f i c a n t l yb e t t e rs t a n d a r dd e v i - a t i o n is o b t a i n e dw i t ht h e CDI t h a nw i t ht h e HSI a t t h e 5 n. m i . r a n g e ,b u t , a s was t h e case w i t ht h e l a t e r a l scores, no d i f f e r e n c eo c c u r r e d a t t h e 1 .25 n. m i .

range. The b e t t e r CDI score r e s u l t sb e c a u s et h eg l i d e slope n e e d l eo nt h e C D I is much l o n g e rt h a nt h en e e d l e on t h e HSI, and t h em o t i o n of t h en e e d l e is more v i s i b l e ;t h e r e f o r e , it p r o v i d e s a b e t t e ri n d i c a t i o n of v e r t i c a l error.

P i l o t - M o d e lA n a l y s i s L a t e r a lc o n t r o l . - TO o b t a i n a more d e t a i l e d i n s i g h t i n t o p i l o t o p e r a t i o n s i n l a t e r a l c o n t r o l w i t h t h e C D I and H S I d i s p l a y s , a pilot-modelmatchingexer- cise was c a r r i e d o u t . For t h i sa n a l y s i s , some o ft h e time h i s t o r i e so b t a i n e d i n t h e tests were matchedthroughtheuse of a p i l o t model i n t h e p l a c e of t h e p i l o t and through a t r i a l - a n d - e r r o ra d j u s t m e n to ft h e pilot-model g a i n s . The s u b j e c t sc h o s e nf o rm a t c h i n g( s u b j e c t s M M , S H , and PB) r e p r e s e n t low, medium, a n dh i g hd e g r e e so ff l i g h te x p e r i e n c e ,r e s p e c t i v e l y .S u b j e c t "4 r e p r e s e n t e dt h e l m - p e r f o r m a n c e ,l o w - s t a b i l i t y results, w h i l es u b j e c t PB p r o v i d e d some of t h e b e s tr e s u l t so ft h es t u d y .

The time h i s t o r ym a t c h e sa r e shown i nf i g u r e s1 0 t o 14. The l a t e r a l d i s - placement time h i s t o r i e s are shown t o g e t h e rw i t he i t h e rt h eh e a d i n ga n g l e or bank angle time h i s t o r i e s . The c o r r e s p o n d i n gp i l o t - m o d e lm a t c h e sa r e also shown t o g e t h e rw i t ht h ep i l o t - m o d e lg a i n sr e q u i r e df o re a c h particular test. Runs w h i c hs t a r t e dw i t ha ni n i t i a l l a t e r a l error butnowindare shown i nf i g u r e s1 0 t o 1 3 ,a n dr u n sw i t hw i n d sa r e shown i nf i g u r e 1 4 .F i g u r e1 0i n d i c a t e st h a t when t h ed i s p l a c e m e n td i s p l a ys e n s i t i v i t y is l o w , i.e., a t t h e 5 n. m i . range from t h e VOR s t a t i o n ,t h er e s p o n s e sa r ec h a r a c t e r i z e d by a long-period, slow r e s p o n s et h a t is well damped. A s t h ed i s p l a ys e n s i t i v i t y is i n c r e a s e d ,t h e response becomes q u i c k e r ,w i t hs h o r t e rp e r i o d sf o rt h eo s c i l l a t o r y mode, and n o t w e 1 1 damped. T h i st r e n d is r e p r e s e n t e di nt h e p i l o t model by i n c r e a s e si n t h eo u t e r - l o o pp i l o t - m o d e lg a i n Ky. With e i t h e rt h e C D I or HSI, t h e pilot- model g a i ni n c r e a s e sw i t h decrease i nr a n g e .T h i sr e s u l t is t r u e for t h e VOR s t a t i o na n d , to a lesser e x t e n t , for t h e ILS s t a t i o n .

Closed-loop p i l o t - m o d e l - a i r c r a f t s y s t e m c h a r a c t e r i s t i c s were also d e t e r - mined and are shown i n table V I . T h e s es y s t e mc h a r a c t e r i s t i c si n d i c a t ea n i n c r e a s ei nt h ef r e q u e n c y of t h er o l l - h e a d i n go s c i l l a t o r y mode c o r r e s p o n d i n g to t h ei n c r e a s ei np i l o t - m o d e lg a i n Ky. For the tests made when t r a c k i n g to t h e VOR s t a t i o n , t h i s t r e n d is clearly e v i d e n t ;t h ef r e q u e n c y of t h e roll- heading mode i n c r e a s e sw i t ht h e decrease inrange,andthedampingremains c o n s i s t e n t l yh i g h .T h e s ec h a r a c t e r i s t i c sc o r r e s p o n d to the improvement in s y s tern performance noted before.

It h 2 sa l r e a d yb e e nn o t e dt h a tw i t ht h eI L Ss t a t i o ni nu s e ,t h et r a c k i n g a c c u r a c yd i dn o ti m p r o v ew i t hi n c r e a s ei nd i s p l a ys e n s i t i v i t y . Model matching shows t h a tt h eo u t e r - l o o pg a i n Ky does i n c r e a s ew i t h decrease i nr a n g e ,b u t t h a tt h ei n n e r - l o o pg a i n s show a s l i g h tt e n d e n c yt o w a r d a d e c r e a s e . As a r e s u l t of t h i st e n d e n c yt h es y s t e mf r e q u e n c y does n o tc h a n g e ,a n dt h es y s t e m damping r a t i o shows a marked r e d u c t i o n .T h i s decrease i ns y s t e md a m p i n gr a t i o c o r r e s p o n d s to t h e lack ofsystemperformanceimprovementandrepresen.ts a c o n d i t i o n t h a t c o u l d s e r i o u s l y a f f e c t f l i g h t s a f e t y .

The g a i n Ky r e p r e s e n t st h e product o f t h e i n s t r u m e n tg a i na n dt h eg a i n r e p r e s e n t i n gt h ep i l o t ' sr e s p o n s e to t h e i n s t r u m e n t . The i n s t r u m e n ts e n s i t i v i t y changes by a f a c t o r of 1 0 b e t w e e nt h ec o n d i t i o n s , a t 5 n. m i . from t h e VOR s t a - t i o na n dt h o s e a t 1 .25 n. m i . from t h e ILS s t a t i o n . Between t h e s e two condi- t i o n s ,t h eg a i n Ky changes by a f a c t o r of between 2 and 3 . These v a l u e s show t h a t t h e p i l o t is a t t e m p t i n g to a d j u s t h i s g a i n s to accommodate t h ec h a n g ei n i n s t r u m e n t s e n s i t i v i t y b u t is n o t able to do so t o t h e e x t e n t r e q u i r e d t o keep thesystemdamping from f a l l i n g to a l a w v a l u e .

The loss i ns y s t e md a m p i n gi l l u s t r a t e di n t h e c a s e s w i t h nowind is f u r t h e r e s c a l a t e d by t h ea d d i t i o no ft h ew i n d . As shown i nf i g u r e 1 4 and by t h es y s t e m c h a r a c t e r i s t i c s shown i n t a b l e V I (data for subject MM when u s i n gt h e I L S s t a - t i o n ) ,t h es y s t e m is stable a t a range of 5 n. m i . b u t is u n s t a b l e a t a range of 1.25n. m i . The data for s u b j e c t MM w i t h no winds show a r e d u c t i o ni ns y s t e m damping r a t i of r o ma b o u t0 . 2 to 0.1.

A s u b j e c t i v ej u d g m e n t was made by t h ea u t h o ro na l lt h e tests ( 2 0 for each c o n d i t i o n ) a s to w h e t h e rt h es y s t e mr e s p o n s e was s t a b l e ,n e u t r a l l ys t a b l e , or d i v e r g e n t .R e s p o n s e ss u c h as those shown i nf i g u r e 1 3 (b) for s u b j e c t PB were j u d g e ds t a b l e ;t h o s e for subject MM were called n e u t r a l l ys t a b l e ;a n dt h o s e for s u b j e c t SH c a l l e dd i v e r g e n t . It s h o u l db en o t e dt h a tt h e case for s u b j e c t SH, which was c a l l e dd i v e r g e n t , is shown by t h ep i l o t - m o d e la n a l y s i s to b es t a b l e , a l t h o u g hw i t h a l o w damping ratio. The r e s u l t so f these judgments are g i v e n i nt h ef o l l o w i n g table: ... .

I VOR I ILS

i 1.25 n. mi. 5 n. m i . 5 n. m i . 1 1.25 n. m i .

Response I C D I HSI

CDI 1 HSI ; C D I 1 HSI

C D I 1 H S I

I N o wind S t a b l e 18

19 I 18 18 17 12

2 0 N e u t r a l 2 1 4 ’ 1 6 11; 4 , 2 0 D i v e r g e n t 2 1 2 j Withwinds S t a b le 10 1 0 10 18 15 3 4 5 6 2 2 2 N e u t r a l 3 4 1 5 8 0 3 D i v e r g e n t The p r e c e d i n gt a b l es h o w st h es t e a d yi n c r e a s ei nt h ep r o b a b i l i t yo fv e r y low systemdamping or o u t r i g h t i n s t a b i l i t y t h a t occurs w i t hi n c r e a s e i n d i s p l a y s e n s i t i v i t y as range is d e c r e a s e d .

I nt h ef i x e d - b a s ee n v i r o n m e n t of t h e p r e s e n t tests, d i v e r g e n c e so c c u r r e d i n a l a r g ep e r c e n t a g eo ft h er u n s .T h e s ed i v e r g e n c e sr e s u l t e di n p a r t f r o mt h e e x t e n d e dl e n g t h of t h e r u n s (3 m i n u t e s ) ,a n df r o mt h ef a c tt h a tt h es u b j e c t s were asked t o keep t h e error as low as t h e yp o s s i b l yc o u l d .I n actual f l i g h t , t h e c o n d i t i o n s t h a t l e a d most o f t e n to d i v e r g e n c e( t h ei n s t r u m e n ts e n s i t i v i t y c o r r e s p o n d i n g to a d i s t a n c e of 1.25 n. m i . from touchdown) would e x i s t f o r a s h o r t time o n l y . The pilot could beexpected t o b e well s t a b i l i z e do nt h e d e s i r e dp a t hb e f o r er e a c h i n gt h e 1.25 n. m i . rangeand to b r e a k o u t of t h e IFR c o n d i t i o n ss h o r t l yt h e r e a f t e r . I t is t h e r e f o r eu n l i k e l yt h a tt h ef u l l y d e v e l o p e dd i v e r g e n c e sn o t e di nt h ep r e s e n t tests would occur i n a r e a l IFR approach. However, t h e tests show t h a tt h ep o t e n t i a l for a p i l o t - i n d u c e d u n s t a b l eo s c i l l a t i o nd o e se x i s tw i t ht h ep r e s e n ti n s t r u m e n ts y s t e m s .T h e r e is a small p r o b a b i l i t y t h a t a s t h ea i r c r a f ta p p r o a c h e st h em i d d l e marker, t h e p i l o t ‘ s a t t e n t i o n c o u l d become c o m p l e t e l yo c c u p i e dw i t ht h eg r o w i n gi n s t a b i l i t y of t h es y s t e m . H e c o u l d pass t h ed e c i s i o nh e i g h tw i t h o u tn o t i c ea n dc o n t i n u e on t o w a r dt h er u n w a y ,w i t ht h ed i s p l a ys e n s i t i v i t yc o n t i n u i n g t o i n c r e a s e . The s y s t e mi n s t a b i l i t yw o u l dc o n t i n u e t o i n c r e a s e a s t h e a i r c r a f t a p p r o a c h e d t h e g r o u n d .T h i ss i t u a t i o nc o u l de a s i l y result i n a c r a s h .

The p i l o t - i n d u c e du n s t a b l eo s c i l l a t i o n se n c o u n t e r e di nt h ep r e s e n t tests d o n o th a v e t o persist o n c es t a r t e d .T h i s is shown c l e a r l yi nt h e sample test results p r e s e n t e di nf i g u r e 15. I nt h i sp a r t i c u l a rc a s e , a d i v e r g e n c es t a r t s a n dp e r s i s t sf o r 1-1/2 cycles. A t t h a tp o i n t ,t h e p i l o t d e c i d e d t o s t o p responding to t h e l a t e r a l error. H e c o n c e n t r a t e df u l l yo nr e g u l a t i n gt h e bank a n g l e to Oo. D u r i n gt h ep e r i o dt h a th e was s t a b i l i z i n gb a n ka n g l e , a heading error of 5O e x i s t e d .T h i sh e a d i n g error r e m a i n e dn e a r l yc o n s t a n tf o rt h e 40 s e c o n d st h a tt h e p i l o t c o n c e n t r a t e do nb a n ka n g l e .T h i s constant heading error l e d to a ramp c h a n g ei n lateral p o s i t i o nw h i c hc a r r i e dt h e a i r c r a f t from t h er i g h ts i d e of t h ed e s i r e dp a t h to t h e l e f t s i d e . A t t h i sp o i n tt h e pilot decided to r e s u m ec o n t r o l of d i s p l a c e m e n t ,w h i c hh ed i dw i t ha na p p a r e n t l y well- damped response. The r u n was t e r m i n a t e db e f o r e it became clear w h e t h e rh i s second attempt a t c o n t r o l l i n g d i s p l a c e m e n t was s u c c e s s f u l .

P i l o t - m o d e i a n a l y s i s c a n also beused to p r o v i d e a comparisonbetweenthe COI and HSI. A t t h e low s e n s i t i v i t yc o n d i t i o n ( 5 n. m i . f r o mt h e VOR), t h e pilot-model data show t h a t a h i g h e r Ky g a i n is u s e dw i t ht h e HSI t h a nw i t h t h e C D I . O f e v e ng r e a t e rs i g n i f i c a n c e is t h e fact t h a tt h e t o t a l pilot-model forward loop g a i n (K* = KyK$K$,) is also h i g h e r for t h e HSI. A s a r e s u l t ,t h e s y s t e mr o l l - h e a d i n g mode f r e q u e n c y is h i g h e rf o rt h e HSI, and f o re a c hi n s t r u - r a t i o is h i g ha n da p p r o x i m a t e l ye q u a l .T h e s e results corre- ment,thedamping spond to t h eb e t t e rt r a c k i n ga c c u r a c yo b t a i n e dw i t ht h e HSI. A t t h e h i g h e s t s e n s i t i v i t y (1.25 n. m i . f r o mt h eI L Ss t a t i o n ) ,t h es y s t e mf r e q u e n c i e s are n e a r l y t h e same, andthedamping ratios are l o w a n dn e a r l yt h e same, r e s u l t sw h i c h c o r r e s p o n d to t h ee q u a lp e r f o r m a n c ea n dt h e e r r a t i c time h i s t o r i e s o b t a i n e d w i t h b o t hi n s t r u m e n t s .

A t a d i s t a n c e of 5 n. m i . from t h e ILS s t a t i o n , an anomaly appears i n t h e pilot-model data: theperformancemeasures show a s i g n i f i c a n td i f f e r e n c e betweenthe two i n s t r u m e n t s , b u t t h ep i l o t - m o d e ld a t a do n o ts u p p o r tt h i sf i n d - i n g .I nt h e case o ft h e pilot-model data, mixed results are o b t a i n e d ;t h e pilot-model g a i n is h i g h e rf o rt h e H S I , b u tt h es y s t e mf r e q u e n c yf o rt h e H S I is lower. These r e s u l t si n d i c a t et h a t t h e p e r f o r m a n c ew i t ht h e t w o i n s t r u m e n t s s h o u l db ea b o u te q u a l . The anomaly occurs because t h et h r e es u b j e c t sc h o s e n for t h em o d e l - m a t c h i n ge x e r c i s eo b t a i n e de q u a lp e r f o r m a n c ew i t ht h e two i n s t r u - ments, a s opposed to t h e results shown by t h ea v e r a g e of a l l 1 0 s u b j e c t s ,a n d it is t h i se q u a lp e r f o r m a n c e by t h e t h r e e s u b j e c t s t h a t is r e f l e c t e d i n t h e pilot-model data.

As was m e n t i o n e d i n t h e s e c t i o n o n s t a t i s t i c a l a n a l y s i s of t h ep e r f o r m a n c e d a t a , a s u b j e c t i v ej u d g m e n t of t h e time h i s t o r i e so b t a i n e dw i t ht h e R M I i n d i - cates t h a tt h es y s t e mp e r f o r m a n c ew i t ht h e R M I was c o n s i d e r a b l y worse t h a n t h a t o b t a i n e dw i t he i t h e rt h e C D I or t h e HSI. S i n c e t h e r e s u l t sw i t ht h e R M I were so o b v i o u s ,f u r t h e ra n a l y s i so ft h e R M I d a t a were n o tu n d e r t a k e n .

Vertical c o n t r o l . - Vertical c o n t r o lh a s less o v e r a l lp h a s el a gt h a n does l a t e r a l c o n t r o l( o n e less i n t e g r a t o r )a n d is easier to manage. Consequently, s t a b l ev e r t i c a lc o n t r o l was o b t a i n e di n a l l cases. Sample time h i s t o r i e s of v e r t i c a lc o n t r o l are shown i nf i g u r e 8. A pilot-model a n a l y s i s was n o t per- formed for v e r t i c a lc o n t r o l .

CONCLUDING REMARKS A six-degree-of-freedom,fixed-basedsimulationstudy of t h eu s e of con- v e n t i o n a l i n s t r u m e n t s i n a g e n e r a l a v i a t i o n I n s t r u m e n t F l i g h t R u l e s (IFR) environment has been conducted. Ten s u b j e c t s , who v a r i e di nf l i g h te x p e r i e n c e from low-time s t u d e n ti n s t r u m e n t pilots to p r o f e s s i o n a l test pilots, were used i nt h es t u d y . An i m p o r t a n tf e a t u r e of t h es t u d y was t h a t t h e s e n s i t i v i t y of t h ed i s p l a c e m e n ti n d i c a t i n gi n s t r u m e n t s( t h ec o u r s ed e v i a t i o ni n d i c a t o r ( C D I ) , 1 7 t h e h o r i z o n t a l s i t u a t i o n i n d i c a t o r ( H S I ) , a n dt h er a d i om a g n e t i ci n d i c a t o r (RMI)) was f i x e d a t s e v e r a l d i f f e r e n t values to p r o d u c ed i f f e r e n t test cond it i o n s .

A statistical a n a l y s i s of performance for t h ep a t h - f o l l o w i n g task showed t h a t the accuracy of lateral p a t hf o l l o w i n gi m p r o v e dw i t ha ni n c r e a s ei nt h e s e n s i t i v i t y of t h ed i s p l a c e m e n ti n d i c a t i n gi n s t r u m e n t s up to t h eh i g h e s t s e n s i t i v i t y . The maximum s e n s i t i v i t yt e s t e dc o r r e s p o n d e d to t h es e n s i t i v i t y a t 1 .25 n. m i . f r o mt h eg l i d es l o p es t a t i o no f an ILSsystem. The g l i d e slope is 120 meters abovetheground a t t h i sp o i n t . The t r a c k i n gp e r f o r m a n c e was no b e t t e r a t t h i s p o i n t t h a n it was a t 5 n. m i . from t h e g l i d e slope s t a t i o n .

T i n eh i s t o r y plots show t h a t l a t e r a l d i s p l a c e m e n td i v e r g e n c e s occur i n a h i g hp e r c e n t a g eo ft h e tests conducted a t t h e d i s p l a y s e n s i t i v i t y t h a t e x i s t s a t 1.25n. m i . f r o mt h eg l i d es l o p es t a t i o n . A p i l o t - m d e la n a l y s i sc o n f i r m s t h a tt h ep i l o t - m o c l e l - a i r c r a f ts y s t e me x h i b i t s adequate damping a t low d i s p l a y s e n s i t i v i t y b u t n e a r z e r o dampingandevensystem i n s t a b i l i t i e s a t t h e h i g h e s t test s e n s i t i v i t y . The low s y s t e md a m p i n gr e s u l t s from t h eh i g hp i l o t outer- l o o pg a i nc s e di nc o n j u n c t i o nw i t hr e d u c e di n n e r - l o o pg a i n s .T h e s er e s u l t s i n d i c a t e t h a t a p o t e n t i a l l yu n s a f ef l i g h tc o n d i t i o ne x i s t s when t r a c k i n gt h e ILS s i g n a l s a t t h i s d i s t a n c e from t h e s t a t i o n (? .25n. m i . f r o mt h eg l i d e slope t r a n s m i t t e r :2 . 6 5n . m i . f r o mt h el o c a l i z e rt r a n s m i t t e r ; or n e a rt h em i d d l e m r ker , t y p i c a l l y ) .

These tests were a l s o used to r a n kt h ee f f e c t i v e n e s s of t h e d i f f e r e n t i n s t r u m e n t si np r o m t i n ga c c u r a t ep a t hf o l l o w i n g .I nt h e tests u s i n gt h e VOR s t a t i o n ,t h e HSI p r o v i d e dt h eb e s tl a t e r a lp a t h - f o l l o w i n ga c c u r a c y ,t h e C D I was second best, a n dt h e RMI was t h i r d .I n tests w i t ht h e ILS s t a t i o n ,t h e HSI wzs b e t t e rt h z nt h e C D I a t t h e 5 n. m i . r a n g e .A d d i t i o n a l l y , t-tests con- f i r m e dt h a tt h e s ed i f f e r e n c e s were s i g n i f i c a n t a t t h e 0.025 l e v e l . A t t h e 1 .25 n. m i . range,systemdampingdropped to low v a l u e sw i t he a c ho ft h e two i n s t r u m e n t s ,a n dp e r f o r m a n c e s were e q u a l . The t-tests c o n f i r m e dt h a tt h e r e was n os i g n i f i c z n td i f f e r e n c e .I nv e r t i c a lc o n t r o l ,t h e C D I p e r f o r m e db e t t e rt h a n t h e HSI a t t h e c o n d i t i o n of 5 n. m i . from t h e I L S s t a t i o n ,a g a i n a t t h e 0.025 s i g n i f i c a n c el e v e l . A t t h e 1 .25 n. m i . r a n g ec o n d i t i o nt h ep e r f o r m a n c e of t h e two i n s t r u m e n t s were e q u a l .

LangleyResearchCenter N a t i o n a lA e r o n a u t i c sa n dS p a c eA d m i n i s t r a t i o n Hampton, VA 23665 November 26, 1980 1 8 REFERENCES 1 .F o r s y t h , Donna L.; and Shaughnessy, John D.: S i n g l eP i l o t I F R O p e r a t i n g ProblemsDetermined From A c c i d e n t Data A n a l y s i s . NASA T"78773,1978.

2 . Smith, Ralph H.: A Theory for L o n g i t u d i n a lS h o r t - P e r i o dP i l o tI n d u c e d O s c i l l a t i o n s . AE'FDL-TR-77-57, U . S . A i r Force, June 1977. (Available from DTIC a s AD A056 982 .)

3. A d a m s , James J.; andHatch, Howard G., Jr.: A n Approach t o theDetermina- t i o n of A i r c r a f t . H a n d l i n g Q u a l i t i e s by U s i n g P i l o t T r a n s f e r F u n c t i o n s .

NASA TN D-6104, 1971 .

4. Adams, James J.; and Moore, F r e d e r i c k L.: An A n a l y t i c a lS t u d y of Aircraft L a t e r a l - D i r e c t i o n a lH a n d l i n gQ u a l i t i e sU s i n gP i l o tM o d e l s . NASA TN D-8103, 1976.

1 9 TABLE I.- SAMPLE PILOT-MODEL-AIRCRAFT SYSTEM CHARACTERISTICS (a) Complete system ~~~ Pilot-model gains Closed-loop system characteristics

I I

Control mode IDutch roll model Roll-heading mode 1 y mode

Yelocity, knots 135 7.38 3.21 0.192 0.98 -.071 -2.87 85 6.10 .97 1.99 .199 .226 0.176 I 0 : : ; 1-0.2061-2.84 . "" (b) Successive loop closures characteristics Roll-heading mode Control mode Dutch roll mode relocity, knot' W@ Real roots <@ :ad/sec 1.99 0.198 0.25 A = O -0.16 1 . 9 7 1.99 .202 x = o -.16 .97 1.95 .208 x = o - ." ..

- TABLE 11.- LATERAL STANDARD DEVIATIONS, IN METERS (a) Scores, averages, and standard deviations of the scores " ." , ... " VOR station ILS station

I .. - -~ ~-~

~ " " ~ ..

5 n. mi. 1.25 n. mi. 5 n .m i . 1 1.25 n.mi.

Day

I

." -~ ~. ~~ .~ " - .

RMI CDI 1. HSI RMI

CDI HSI CD I HSI 76.6 24.7 56.4 34.2 32.3 16.2 2 61.6 13.1 55.5 60.1 23.2 16.2 24.1 14.6 . . " 1 46.1 79.3 42.7 36.6 54.0 59.5 2 68.9 36.3 52.5 205.9 54.6 111.9 45.1 125.7 . . __ " 37.5 18.9 24.7 20.4

31 .4 . :::: . ." I :::; 50.6 20.4 19.2

37.5 43.0 34.5 24.1 " _ -~ 62.8 54.9 91.2 39.7 50.3 134.8 112.2 54.3 73.5 82.4 84.8 26.2 47.6 - ". . . . " ___. " 20.7 50.3 39.7 29.0 38.1 28.1 53.4 35.4 21 .o 45.8 35.4 18.3 22.3 26.2 " ~- ~ . " - " " - . . . - " - . - - - . . . . .- . ~. . .

39.3 133.9 68.3 42.7 31.1 47.9 84.2 41.8 26.5 59.5 24.7 48.5 29.6 41.8 ..

- 21.4 55.2 29.3 25.6 38.7 26.8 62.5 43.3 23.5 29.6 25.9 18.3 18.9 18.3

:::: 35.7 32.6 34.2

32.0 137.3 95.5 18.9 25.6 69.2 20.7 . . .. ~.

____ ". ".

15.3 27.1 25.0 21.4 27.1

:::i I :::i 19.5

14.0 12.8 -_ 43:6 1 ",:: 27.5 35.4 30.5 18.6 53 7 33.2 51.2 13.1 15.3 18.6 Average 79.26 52.961 31.20 84.1' 35.17 122.63 41 .44 30.01 38.33 34.12 ~~ Standard deviation 38.06 25.461 ~~ 12.15 55.0' 20.34 11.55 24.74 26.09 ~~~ " .

- " . . . .

TABLE 11.- Concluded (b) Results for t-test on lateral standard deviation comparisons Range effects Conditions p-va lue VOR station RYI: 5 n. mi. to 1.25 n. mi. 0.40 .005 CDI: 5 n . mi. to 1.25 n . mi.

.0005 HSI: 5 n. mi. to 1.25 n . m i .

ILS station CDI: 5 n. mi. to 1 .25 n. mi. >0.40 HSI: 5 n. mi. to 1.25 n . mi. >. 40 Display effects Conditions P-value VOR station 5 n . m i . : CDI - HSI 0.0005 .025 CDI - RMI .005 HSI - RMI .005 1.25 n. mi.: (PI - HSI .010 CDI - RMI .Ol 0 HSI - RMI ILS station

5 n. mi.: CDI - HSI 0.005

.20 1.25 n . mi.: CDI - HSI TABLE 111.- LATERAL MEANS, IN METERS ( a )S c o r e s ,a v e r a g e s , and standarddeviations of t h es c o r e s - . .

. .

VOR s t a t i o n I ILS s t a t i o n

f 5 n. m i . 1.25 n . m i . 5 n. m i .

' I 1.25 n. m i .

Subject D a Y ~ -

RMI XMI CDI -1 HSI CDI HSI

I I CDI 1 H S I

~. . ". - ~ ~.

DH 30.8 -50.3 -3.4 -31.7 56.7 -15.9 2 12.2 32.9 98.5 102.8 20.4 7.8 -3.7 18.0 - ~ ~ . . . . " ..~

i

MM 1 -5.2 88.1 16.2 11.9 24.1 15.9 2 -11.6 53.0 123.5 170.5 3.1 -7.6 39.0 34.2 ..... -. - .... ~. - . . - ..... . . .

-1

I 1 9.8 60.4 6.4 3.1 22.9 7.6 I 26.8 i -2.1 JS 2 11.6 90.9 8.8 43.3 10.1 -11.9 -12.8 -15.6 I

. . . . . . . . . . . . . . . . " . - - . . " ~. ~1

J R -88.8 -83.6 -3.1 -6.1 -20.4 29.6 -30.5 '

2 70.8 I 14.0 17.1 4.6 -34.8 I 0.92

99.7 180.9 79.9 3.4 . . . . . . . .~

-+

H v 1 20.4 -36.6 -12.2 -15.6 10.7 7.3 1.83 I 13.7 2 9.2 63.1 -11.0 -3.7 33.2 9.5 I 14.9 ~ 22.6 -1. " - - ....... " t " ~ -7.32 ss 1 -89.1 1.53 -22.3 2.44 54.0 3.05 : 6.10 2 56.4 61.6 2.44 60.7 11.9 3.05 25.9 9.15 ' 18.3 1 -4.27 .... " - . - - -

HE 1 54.3 11.3 7.93 11.9 56.1 48.8 ' 34.8 ' 22.3

2 127.5 52.8 18.3 12.5 -3.05 13.1 28.7 ..

.- . . " 1 68.6 34.8 19.8 2 164.7 39.0 46.4 -12.2 -5.5 22.8 . .

1 44.8 -1.5 43.3 2 10.7 10.9 19.8 1 98.8 85.1 2 66.2 98.5 .. ". ~~ ~ ~. . " Average 89.96 11.86 53.95 . -. . . _. ..

Standarddeviation 42.43 ~. ~ 49.11 I 62.56 . . . . . . . . .

" TABLE 111.- Concluded (b) Results for t-test on lateral means comparisons Range effects Conditions P-value VOR stat ion 5 n . mi. to 1 .25 n . m i . 0.20 RMI: CDI: 5 n. mi. to 1.25 n. mi.

HSI: 5 n . m i . to 1 .25 n . mi.

ILS station CDI: 5 n. mi. to 1 .25 n . m i . 0.20 . 4 0 MI: 5 n. mi. to 1 .25 n. mi.

Display effects Conditions P-value VOR station 5 n. mi.: CDI - HSI 0.0005 CDI - RMI HSI - RMI 1.25 n. mi.: CDI - HSI CDI - RMI HSI - RMI .025 ILS station 0.05 5 n. mi.: CDI - HSI .20 1.25 n . m i . : CDI - HSI 2 4 TABLE 1V.- VERTICALSTANDARD DEVIATION, IN METERS (a) Scores, averages, and standard deviations of the scores . . . .. . . ~ .~ ~ . . . . . " ILS station VOR station

T

- - _ _ _ ~ 5 n. mi.

5 n. mi. I 1.25 n.mi. 1.25 n. mi.

Subject Day

t

~ CDI CDI HSI

CDI 1 HSI RMI HSI

~~~ " ~- ~~ 3.78 6.83 7.20 5.03 6.74 9.91 3.63 5.52 3.57 - ~~ _ _ 7.81 6.80 7.26 10.07 9.52 1 4 . 1 8 11.96 20.53 : 3 . 1 8 - 6 . 7 4 5.37 5.95 8.75 JS iO.01 1 5 . 1 6

6 . 5 9 7.78 4 . 6 1 6.16 9.58 I : 9.39 1 3 . 3 0 9.67 5.73

10.92 7.17 6.38 7.84 16.78 11.83 12.75 6.19 1 0 . 1 0 9.09 7.60 1 7 . 2 0 11.07 " - 8.54 5.86 I 1 - 6 5 H v 5.64 6.47 13.05 4.79 3 . 2 0 3.94 7.47 6.13 9.03 5.98 5.73 1 : 7.53 7.69 8.05 8.14 13.24 ss

7::; 1 9.21 6.68 11.07 13.45 14.67 !1 . 3 2 11 - 2 9

1 ; ___-

c

5.92 6.07 10.58 12.78 8.17 -__ 6.10 4.94 7 . 6 9 8.39 SH 4.76 6 . 2 2 8.60 6 . 4 4 6.07 . -~ " I 5.64 5.64 4.45 5.70 4.73 4.88 10.71 5.86 . ..

7.40 8.67 Average 12.39 - ... . " 2.17 3.68 10.37 Standard deviation " " .

" TABLE 1V.- Concluded (b) Results for t-test on vertical standard deviation comparisons Range effects

I P-value

r" ~ Conditions

VOR station RMI: 5 n. mi. to 1.25 n. mi. 0.30 CDI: 5 n. mi. to 1 .25 n. mi.

.40 HSI: 5 n. mi. to 1 .25 n. mi.

.20 ILS station CDI: 5 n. mi. to 1 .25 n. mi. 0.01 HSI: 5 n . mi. to 1 .25 n. mi.

. 01

Display effects

I Cond it ions

p-value VOR stat ion I

5 n. mi.: CDI - HSI 0.07

CDI - RMI .30

HSI - RMI .05

1.25 n . mi.: CDI - HSI

.10 CDI - RMI .30 .10 ILS station

5 n. mi.: CDI - HSI 0.025

.10 1 .25 n . mi. : CDI - HSI TABLE V . - VERTICAL MEANS, IN METERS (a) Scores, averages, and standard deviations of the scores VOR station

ILS station I

I

~ Subject 1 .25 n . m: i . 5 n. mi.

t 1 I 1 .25 n. mi.

. . ~. . . ~ _ . . ._ . - RMI CDI HS I M I HSI CDI HS I CDI C D I . . - . ." - " " DH 1 -2.75 -5.31 0.43 -7.11 -2.38 -5.37 -1.89 2 -0.95 -2.35 11.65 .88 14.21 -5.34 -2.65 -3.51 -3.57 4.30 _ . . .. .~ . . ~~ . ~.

MM 1 9.91 4.58 7.72 -1 4.98 -1 3.66 10.71 -4.73 2 24.07 -1 -22 -1 .1 7 . 1 6 . 1 0 -8.08 -7.66 -1 8.21 14.06 -8.72 ... . - . .. - - ~. . - . - -~ ~- ". - " - " JS -6.25 -4.27 -3.48 -9.49 1.74 9.61 -4.15 -1.28 1 1

2 I -1 -98 -9.36 -1 -92 5.58 -6.92 -2.78 27.69 .85 -2.1 4

. . . . . - - .- __ ~~ 1 -3.51 -2.20 0.46 27.21 -1 5.34 JR 8.75 10.77

2 ' 12.96 1.10 12.69 9.73 -6.1 3 6.47 -21 .96 -2.72 -. 3 1 ,12.66

. . - 8 . - .~ ~ .- ..~ - . - .__ H v 1 i -4.67 0.55 -3.90 1 .86 -0.46 4.61 -5.98 -0.92 2 ' -3.20 -10.58 1 .31 0.21 -2.87 -2.84 -5.73 16.23 -4.82 .49 -_ " .

. _ . , . .. " . ." . . " " ss 5.89 4.73 -4.12 -1 .56 4.79 8.33 -4.70 -1 -71 1 , 2 ' 35.08 20.31 -3.23 13.1 8 72.29 -1 .16 -33.52 -39.41 -1 6.23 -9.09 ~. " .. . . " . . " - ." . . - - . . .. ~- HB -2.72 -2.41 5.28 0.55 -0.49 -1 8.79 -5.52 -9.55 -7.81 4.79 -8.30 -5.61 -3.29 -5.64 3.05 -1 1 .47 -1 7.69 .. . . . " .___ -4.51 -6.99 -8.54 -5.1 9 2.56 -1 6 . 1 0 -1.34 0.52 -6.44 -9.97 -1 0 . 1 3 -7.99 1.34 -13.24 -7.90 -2.01 -5.77 -, . ~ .. - . . ". . ~- 3.33 -0.92 4.36 2.81 -4.61 -1 7.97 -2.90 2 -8.39 -6.99 -4.48 -7.50 1.74 .55 -4.48 0.89 . - -. - -1 6.99 4.67 - 1 ' . 68 -8.45 -0.67 -0.61 -3.05 0.37 2 1.01 -1.89 -1 4 . 1 2 4.39 12.26 -9.82 -2.26 .09 " ~. ~ . ."

Average I 4.86 -2.32 -2.04 1.35 1.52 -2.55 -2.44 -2.48 -5.28 -2.69

" ". " . . . - ._ " Standard deviation 17.86 8.06 5.72 10.64 17.74 5.37 13.30 15.45 4.26 5.22,

I . . -~ " - ~. . .~ . ". ___. -~

TABLE V . - Concluded (b) Results for t-test on vertical means comparisons Range effects Conditions P-value VOR station RMI: 5 n. mi. to 1 .25 n . m i . 0 . 4 0 CDI: 5 n. mi. to 1 .25 n. mi. .20 . 4 0 HSI: 5 n. mi. to 1 .25 n. mi.

ILS station CDI: 5 n. mi. to 1.25 n. mi. 0.20 >.40 HSI: 5 n. mi. to 1 .25 n. mi.

Display effects

Conditions 1 P-value

VOR station

5 n.mi.:CDI - HSI 0.41

CDI - RMI -20 HSI - FNI -20 1.25 n . m i . : CDI - HSI .40 CDI - RMI .40 HSI - RMI .05 ILS station 5 n. mi.: CDI - HSI < 0 . 4 0

.Ol 1.25 n . m i . : CDI - HSI

'ABLE VI.- PILOT-MODEL-AIRCRAFT SYSTEM CHARACTERISTICS (a) VOR station r ad/m rad/sec rad/sec rad/sec .

5 n. mi. from VOR station, CDI - . - . - . - ~ ~.

- MM -0.24 0.67 0.001 3 1 7.63 0.97 3.21 0.186 0 . 1 00 0.44 -0.611 -2.20 SH -.24 .63 .00082 7.61 .97 3.22 . 1 86 -077 PB

-. 34 1 -33 .00082 7.61 .98 3.21 . 1 86 .157

-. 303 -2.28

Aver age .00098 . 1 1 1 .. ~ - = ~" ~ 5 n. mi. from VOR station, HSI .

0.001 08 0.45 .00108 .45

.00164 l f i ; .1 83 .54

.152 Aver age -00128

- "~ 0 ; ; g 1 -

i2; 1 0 : ; : . . -

1.25 n . mi. from VOR station, CDI ~.

. -. -~ ~ ..

m 0.00246 7.60 0.98 3.21 0.186 0.21 1 SH .00164 7.60 .98 3.21 .l 86 . 1 1 1 PB .00197 7.79 -99 3.23 .l 79 .178 Average .166 .00203 " 1 .25 n. mi. from VOR station, HSI = - MM -0.24 1 .33 0.00246 0.21 1 0.34 -2.27 -0.500 SH

-. 24 .00206 1.33 .199 - 1 86

-2.27 -.476 -42 PB -.16 .00164 2.50 -2.91 -.155 .288 .318 7.40 3 . 1 9 .191 Aver age .00208 -243 ~ TABLE VI.- Continued (b) ILS station Closed-loop system characteristics Pilot-model gains Control mode Roll-heading mode Dutch r o l l mode y-mode ;ub ject KY

''

wc8 W D R ~ A2r A1 rad/m w4)t sDR '4

"

rad/sec sec-1 sec-1 rad/sec rad/sec 5 n. mi. from ILS station, CDI 1.50 6.10 0.00219 0.245 MM -0.16 SH 6.10 .00164 1.50 -.16

6.10 .00164 1.50 -. 16 PB

.00183 .247 iverage 5 n. mi. from ILS station, HSI m 6.10 0.97 0.190 0.199 -2.85 -0.149 -0.16 1.0 0.00246 1.99 0.199 S E I

.97 .189 .33 -. 099 -.16 6.10 .00164 1.0 .200 1.99

-2.85 PE

.96 .315 ,254 -2.56 -.151 -. 24 6.30 .00262 1.67 .193 2.01

.231 Lver age .00217

!

1.25 n. mi. from ILS station, CDI - 0.97 0.104 -0.184 0.297 -2.85 SH .97 -.146 .130 -2.89 .97 -.118 1.99 .198 .246 PE .187 -2.89

I I .229 - 0 0 2 7 8

rverage 1.25 n. mi. from VOR station, HSI I I 1 I I I -0.16 0.248 0.130 -0.146 -2.89 m -.16

-. 221 -2.84 SH

-.16 -. 204 -2.46 PE

.213 ,ver age

TABLE VI .- Concluded

(c) ILS s t a t i o nw i t hw i n d s

Pilot-model g a i n s I C l o s e d l o o p s y s t e m c h a r a c t e r i s t i c s

C o n t r o l mode Dutch roll mode Roll-heading mode y-mode I S u b j e c t KY, q qJ x1 I X2, W ~ ~ p rad/m m@ cDR " r a d / s e c r a d / s e c sec-1 sec-1 r a d / s e c 5 n. m i . from ILS s t a t i o n , CDI withwinds .~ . - ~~~~~~~~~~~~ W 1-0.16 12.00 -2.93 -0.103 0.159

I - .. ~ ... . 0.00202 I 6.10 10.97 I 2.00 10.198 I 0.291

5 n. m i . from ILS s t a t i o n , HSI withwinds ~ ..

m -0.24 1.33 0.00082 6.30 -2.50 -0.410 0.461 2.02 0.96 . . . . . . . .

1.25 n. m i . from ILS s t a t i o n , HSI withwinds -~ ~ -0.108 -0.128 -3.79

m 1-0.04 13.00 I 0.00272 I 5.64 10.99 I 1.96 10.205 I 0.195

~ 1 .25 n. m i . from ILS s t a t i o n , CDI withwinds . " ~ . ~~ . .

-3.38 -0.165 -0.12

m I 1.97 I 0.202 I 0.201 __

~~~ ~ W h) L-80-2370 F i g u r e 1 .- S i m u l a t o r d i s p l a y p a n e l .

. . . . . . . .

. . . . .

. . 1 ; : . .::: . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . .

....... . : : : I . . . . . . . . . .

. . . . .

q , rad/sec . . . . . . . . . . .

-.l .... .,, . . .

. . . . . . . . . . .

. . . . . . . .

. . . . . . . . . .

4 b 2.5 sec

Time Time 85 knots 135 knots (a)Short-periodlongitudinalresponsetoa 0.02-rad elevatorstep.

' r

A V , m/sec Time Time 135 knots 85 knots (b) Phugoid response to an initialout-of-trim a.

Figure 2.- Longitudinalresponse of a i r c r a f t .

I1 I IIIIII I 1

r, rad/sec

- . 2

p , rad/sec :‘t

4 /- 2.5 sec 4 2.5 sec

Time Time (a) 135 knots. (b) 85 knots.

Figure 3 . - Lateral response to a 0.068-rad aileron step.

Remnant (a) Longitudinal system.

Remnant

(b) Lateral system.

Figure 4 .- Pilot-model-aircraft system.

T i m e Time ( a ) 135 k n o t s . (b) 85 k n o t s .

- 100 Time Time (a) 135 knots.

(b) 85 knots.

Figure 6 . - Pilot-modelplus a i r c r a f t response w i t h p i l o t remnant.

K$ -0.16; K-J, = 1.25; Ky = 0.00131 rad/m.

-

-

0 - - -10

-

- 20

4 2 5 s e c 4 25 s e c

T i m e T i m e (a) 135 knots. (b) 85 knots.

Figure 7.- Pilot-model plus aircraft response with wind disturbance.

KQ = -0.16; K$ = 1.25; Ky = 0.00131 rad/m.

Ah, m 2i

-25 200 r Y, % def -200 L Time, s e c Time, s e c Time, sec R M I CDI HS I (a) VOR, 5 n. mi.

"j 25 sec 2 0 0 YY % def

m 10: 1

- 100 -200 Time, s e c Time, s e c Time, s e c R M I CD I HS I (b) VOR, 1.25 n. mi.

Figure 8 . - Sample time histories with winds for subject SH.

Ah, m - 2 5 y, % def m lo: -30 -100 Time, sec Time, sec HS I CD I (c) ILS, 5 n. mi.

-1 25 sec

7 f' 25 sec

y, % def 6 : m -60

- 100

Time, sec Time, sec CDI HS I ( d ) I L S , 1.25 n. m i .

Figure 8.- Concluded.

Y, y , deg 1 m ' lo: % - 100 def .10 - 1 - 200 Time,, s e c Time, s e c Time, s e c F w I C D I HS I ( a ) VOR, 5 n. m i .

Y , %

y' deg O E lo? - 3

- 100 def Time, sec Time, s e c Time, s e c R M I CD I HS I (b) VOR, 1.25 n. m i .

p- 25 s e c

4 k 2 5 s e c

y , % d e i

m lo: 1

-100 - 30 O E Time, s e c Time, sec HS I CD I (c) ILS, 5 n. m i .

y, % def lo:

- 60 o[ -100

Time, s e c Time, s e c C D I HS I (d) ILS, 1.25 n. m i .

F i g u r e 9.- Sample time h i s t o r i e s w i t h i n i t i a l error, nowinds €or s u b j e c t SH.

I

1111 I I YI m - 100 - 200 0.00082 rad/m P i l o t model: K = 0.00131 rad/m 0.00082 rad/m Y K = 0.67 .63 1.33 @ - . 2 4 -0.24 K =-0.24 m

4 25 sec

25 sec

+ 25 sec

20 -

0 - L .

- 20

y , % def 0 - 10 - - 200 l o t 100 T i m e , s e c Time, s e c Time, s e c Subject: MM P B SH ( a ) CDI.

Figure 10.- Responses w i t h VOR s t a t i o n a t 5 n. m i . range.

- 100

-200 lo: 1

0.00164 rad/m 0.00108 rad/m P i l o t model : K = 0.00108 rad/m Y 1.33 1.0 $ = 1.0 -0.12 -0.24 K @ =-0.12

4 b 2 5 s e c

"/ 25 s e c

25 s e c

-4. ; ; .. .. i . "

Time, s e c Time, sec T i m e , s e c PB SH Subject: MM (b) HSI.

F i g u r e 1 0 .- Concluded.

. . .

ii,, deg

- 8 -

P i l o t model: K = 0.00246 rad/m 0.00164 rad/m 0.00197 rad/m Y K = 1.30 0.67 1.25 ii, K = - - 2 4

-. 24 -. 32

4J -30 - Time P B Sub j e c t : m SH (a) C D I .

Figure 11.- Responses with VOR station a t 1.25 n. mi. range.

P i l o t model: K = 0,00246 rad/m 0.00164 rad/m 0.00206 rad/m Y K = 1.33 2.5 1 . 3 3 J I K =-0.24 -0.16 -0.24 @

-I 25 sec

1 k 2 5 sec

7 25 sec

- 8 y , % def .30 - 100 . . . . . . . .

Time, sec Time, sec Time, sec S u b j e c t : MM SH PB (b) H S I .

F i g u r e 11.- Concluded.

- a - 16 P i l o t model: K = 0.00219 rad/rn 0.00164 rad/m 0.00164 rad/m Y K = 1.5 1.5 1.5 4J K =-0.16 -0.16 -0.16 @

+ 25 s e c

. .

- a . 16 . . ... .

Time, s e c Time, s e c Subject: Ffl1 SH (a) CDI.

F i g u r e 12.- R e s p o n s e sw i t h I L S s t a t i o n a t 5 n. m i . range.

Pilot model: K = 0.00246 rad/m 0.00164 rad/m 0.00262 rad/m Y K = 1.0 1.0 1.6 $ K =-0.16 -0.16 -0.24 25 s e c

+ k 2 5 s e c

- a - 10 y , % def Time, s e c Time, s e c Time, s e c

Subject: m 1

PB SH (b) HSI.

Figure 12.- Concluded.

Y, +"# ....

. . . . . .

, . . . . . .

. . . . . .

. . . . .

. . . . . . . . . . . .

. . . . . . . . .

-100 ...

. . . . . . . . . .

. . .

:a P i l o t model: K = 0.00328 rad/m 0.00272 rad/m 0.00270 rad/m Y 1.5 1.5 -0.16 -0.16

1 r - 2 5 s e c 7 25 s e c

Time, s e c Time, s e c Time, s e c PB Subject : MM SH (a) 0 1 .

F i g u r e 13.- Responseswith I L S s t a t i o n a t 1.25 n. m i . range.

0.00272 rad/m Pilot model: K = 0.00272 rad/m 0.00425 rad/m Y 1.0 0.75 K = 1.5 I I , -0.24 -0.16 K =-0.16 @ -a

-16 li

y, % def Time, sec Time, sec Time, s e c PB Subject: m SH (b) HSI.

Figure 1 3 .- Concluded.

Y, m 10: 1

- 100 - 200 0.00272 rad/m Pilot model: K = 0.00202 rad/m Y K . = 2 VJ -0.04 K =-0.16 @

1 y - 2 5 s e c 7 r - 2 5 s e c

y , % d e f m - 100 -60 -200 Time, sec Time, s e c Conditions: ILS, 5 nm ILS, 1.25 n m CD I CDI Figure 14.- Responses with wind disturbancesfor subject M M .

-100 10:[ - 200 P i l o t model: K = 0.00082 rad/m 0.00425 rad/m Y 1.5 K = 1.33 UJ -0.08 K =-0.24 4l

1 25 sec I r 25

y , % def 3: E

6: 3 0 60 -200 Time, sec Time, sec M M MM Conditions: ILS 5 nm ILS 1.25 nm HS I HS I Figure 14.- Concluded.

- l : j 10

- 20

-10 1 1 1 - 20

2oo r

-100

- lo: 200 E

F i g u r e 15.- Sample d i v e r g e n c es t o p p e d a f t e r 1- c y c l e s for s u b j e c t J R .

I 1. Report No. 3. Recipient's C a t a l o g No. 2. Government Accession No.

NASA TP-1776 4. Title and Subtitle 5. Report Date SIMULATOR STUDY OF CONVENTIONAL GENERAL AVIATION December 1 9 8 0 INSTRUMENT DISPLAYS IN PATH-FOLLOWING TASKS WITH 6. PerformingOrganizationCode EMPHASIS ON PILOT-INDUCED OSCILLATIONS 505-41 -73-07 .

7. Author(s) 8. PerformingOrganizationReport No.

James J. Adams L-13785 10. Work Unit No.

9.PerformingOrganizationName and Addrerr

-

NASA Langley Research Center 11. Contract or Grant No.

Hampton, VA 23665 13.Type of ReportandPeriod Covered 12. Sponsoring Agency Name and Address Technical Paper National Aeronautics and Space Administration 14. Sponsoring Agency Code Washington, M3 20546 15. Supplementary Notes I 4 16. Abstract A study of the use of conventional general aviation instruments by general aviation pilots in a six-degree-of-freedom, fixed-base simulator has been conducted. The tasks performed were trackinga VOR radial and making an ILS approach to landing.

A special feature of the tests was that the sensitivity of the displacement indicating instruments (the RMI, C D I , and HSI) was kept constant at values cor- responding to 5 n. mi. and 1.25 n. mi. from the station. Both statistical and pilot-model analyses of the data were made. The results show that performance in path following improved with increases in display sensitivity up to the highest sensitivity tested. At this maximum test sensitivity, which corresponds to the sensitivity existing at 1.25 n . mi. from the ILS glide slope transmitter, tracking accuracy was no better than it was at 5 n. mi. from the station and the pilot- aircraft system exhibited a marked reduction in damping. In some cases, a pilot- induced, long-period unstable oscillation occurred.

17. Key Words (Suggested by Authorls)) 18. Distribution Statement Aircraft display Unclassified - Unlimited Pilot induced oscillations Pilot models Lateral control 19. Security Classif. (of this report1 20. Security Classif. (of this p a g e ) 21. No. of Pages 22. Price Unclassified Unclassified 52 A04 For sale by the National Technical information Servlce, Sprinefield. Virglnla 22161 NASA-Langley, 1980