Design criteria for flightpath and airspeed control for the approach and landing of STOL aircraft

APPENDIX A TURBULENCERESPONSERELATIONSHIPS control of flightpath with thrust. If it is assumed that this References 9 and 10 describe the effect of atmospheric closed-loop control is executedin a manner to provide a turbulence on glide-slope tracking. As noted in reference 9, the aircraft's flightpath response to horizontal and vertical flightpath bandwidth between 0.5 and 1.0 rad/sec, the gusts may be described by the following expressions, assum- closed-loop roots can be approximated by ing thatconstantpitchattitude is maintainedduring the

gust encounter: Ae=const = (s + ~ / ~ Y T ) ( S + l/pe2>

"+ST The modified transfer functions for flightpath response to horizontal and vertical gust become " Y - iZ,lVO>s u g (S + l/fyT><s + l/pe2>

(-Zw/Vo>(S - x , + ~ d , / Z w )

The range of frequencies of the turbulence spectrum over Y = W which the aircraft's flightpath shows significant response is g (s + l / p ~ T ) ( s + 1P'e2) determined by either w e or l/Te,, the flightpath response bandwidth. The magnitude of the response to a unit distur- Contributions of turbulence to rms flightpath response are bance is scaled by the derivative Z, for horizontal gusts and shownin figure 6 3 . Considering typical values of Z, and by Zw for vertical gusts. Z , for powered-lift aircraftoperatingat STOL approach When the pilot is engaged in controlling flightpath to speeds, theflightpathdisturbancesdue to horizontal and track the glide slope in the presence of turbulence, these vertical gusts are of approximately the same magnitude.

relationships that describe the effect of turbulence on Another form of atmospheric disturbance that deserves flightpath response are modifiedtotheextentthatthe attention is the gradient ofhorizontal wind velocity, or wind shear. The transfer-function relationship in this case is characteristic roots of Ae=const are altered by closed-loop SPECTRAL BANDWIDTH V, = 65 knots 2 . c 2 . 0 T '

e2 = 2 sf92

I Vo = 65 knots 0 . 1 1.5 I 1 . 5 T021Ty,g = 0.25 SPECTRAL BANDWIDTH

(&)$ 9 1 . 0

l o . .

" del

1 ::ilk .o

(ftlsec12 .5 .5 I I I I I J 0 .2 .4 . 6 0 .2 .4 . 6 T ' I T ' T ' I T ' ' 2 TT O2 7T a) RESPONSE TO LONGITUDINAL GUSTS b) RESPONSE TO VERTICAL GUSTS Figure 63 .- Contribution oflongitudinal and vertical gusts to closed-loop flightpath control.

4 - 3 - x m E

d"

9 2 - 1 - ~~ 0 .25 .5 .75 1.0 {e Figure 64.- Time to develop flightpath disturbance caused by a longitudinal wind gradient.

The time response can be characterized by the time interval This response is characterizedby thesteady-statedistur- required for the disturbance to reach 90% of its steady-state bance that develops in response toa sustained wind gra- value. Figure 64 illustrates thecontributionsto this time dient and the time required for this disturbance to develop.

factor. Itappears thatfor representativepowered-liftair- From this transfer function it can be shown that the steady-

( { e & 0.9, we & 0.3 rad/sec) the flight-

craft characteristics state flightpath upset is described by 10 sec.Under cir- path disturbance is established in about cumstances of unattendedoperation or when the pilot is not sufficiently aware that wind shear is being encountered, the flightpath disturbance may develop fully and, it it occurs at low altitude, to a dangerous extent. However, if where the first term in the expression is the change in the pilot has sufficient information concerning the aircraft's flightpath required tocounteractthe inertialacceleration situation during theapproach, particularly good quality due to the wind shear, and the second term is the result of vertical speed or flightpath information, and if the aircraft the change in lift-drag ratio associatedwith the airspeed has sufficient performance capability to counter the distur- excursionduring the shear encounter.Thusthe primary bances, thenthere should belittledifficulty in traversing influence of the aircraft's configuration on the response to such wind gradients. However, if the aircraft is operated wind shear is associated with operation on the backside of using only the current generation cockpit instruments, such the drag curve andwith the steady-state airspeed distur- as the IVSI,airspeed, and raw data gIide-slope deviation bance, which is indicators, and if the aircraft'sperformancecapabilityin the landing configuration is marginal, then wind-shear encounters may prove troublesome or even dangerous for STOL approach and landing operations.

APPENDIX B DOCUMENTATION OF EVALUATION CONFIGURATIONS Table 5 presents the longitudinal stability derivatives of which the pertinent flightpath and airspeed response char- the basic aircraft for the nominal approach configuration, acteristics were extracted. Figures 65 and 66 show the time from which the various glide-slope and flare-control config- histories of the glide-slope and flare control configurations, urations are derived. Tables 6 and 7 provide the data from respectively, from which the response data were derived.

TABLE 5 .- LONGITUDINAL STABILITYDERIVATIVES FORTHE AUGMENTOR WING RESEARCH AIRCRAFT Gross weight = 19,522 kg NH = 95% (43,000 lb)

sF = 65"

V = 70knots cO v = 80" a = 3.6" = 28 1,000 kg-m2 (207,000 slug-ft') Xu = -0.056 sec" Zu = -0.36 sec" X , = 0.1 1 sec" Z, = -0.52 sec"

X z

" - 0.0073 " - -0.079 VO VO e e -= 0.016 sec" " - -0.062 sec" VO VO "

- -0.05 sec" zs = o

V VO

z %

" - 0.0015 sec" /%

xs = o

C VO "

- -0.0076 sec" 1% NH

VO Mu = O = -0.43 sec" Ma = -0.46 sec-' Ms = -1.72 sec-' e M = -1.27 sec" I TABLE 6.- GLIDE-SLOPECONTROLCONFIGURATIONS b s s

-

ATmax

-

Config- GW, AT, ’

o . 5 AT^^^^

I/ c o p A7max9 A7SS %s.

TAo* A7ss uration A7ss knots lb knots se c deg deg deg % N H knotsldeg 1 -8 73 42.700 2.2 3.3 3.2 1.5 2.5 0.47 1.03 -2.1 -7.5 73 -3.6 -3.2 2.3 -2.62 1.7 1 5.5 42,500

-8 2.85 1.6 2 .o -2.8 1.8 4 . 5

2 75 2.6 43,600 -7 76 -2.5 -3.5 -2.5 2.2 -2.2 1.4 5.5 43,500 -9 67 4 2.3 2.9 .2 1.7 -30.0 14.5 -6 42,500 -7.5 67 -2.5 6 1.8 -3.53 2.2 -3.7 -1.7 42,300 6 -7.5 75 2.9 3.8 -.31 1.2 -1.5 5.9 4.9 42,600

-7.5 71 7 1.4 2.8 5.2 1.2 1 .o 3.3

2.8 42,000

-7 73 -2.1 4 . 5 -4.5 0 1 .o 0 2.6

41,900 8 -8.5 75 2.5 4.0 1.2 -6.3 2.4 -5.2 3.33 42,000

3 .o

-7 73 -1.1 -1.5 -.4 2.2 -7.5 3.75 41,900 9 4 . 5

-7 75 2.3 2.9 1 .o 2 .o -4.5 2.9

42,500

TABLE 7 .- FLARECONTROL CONFIGURATIONS

-

%s d7

- -

. I Armax 9 Config- V A7rnax GW, 7A0* A7nlax9 A7ss9 A% % s , du ' cO' A8SS ' uration l b deg/knot knots knots/deg deg deg deg deg sec deg A%

- ~ ~~~ ~ -

1 1 45,500 77 0 . 1 -7 2 . 6 - 0 . 8 4.7 -8 0.55 -1.74 1 2 . 8

"_

"_ "_ "_

45,300 75 -7.5 -3.2 -5.9 " .54

"_ "_

44,500 I 5 -8 . 5 -29 8 .062 -2.76 1 0 . 1

"_

12 "_ "_ "_

44,300 77 -9 2.6 3.3 "- .79

"_ "_

44,300 77 - 9 -.3 3 . O - 8 . 5 .035 -2.83 2 2 . 4

"_ "_ "-

44,200 7 5 -9 -2.65 "_ "_

-3.5 . 7 6 " " 44,200 7 5 -9 . O

3 . O 9 .O -3 .o

16.8

"_ "_

13 43,000 68 4 "_ "_ "_

1 . 2 3.2 .38

"_ "_

43,000 68 4

-3.5 3 .o -7 .5

-2.33 6 "-

1 4 "_ "_ "_

43,800 77 - 7 . 5 . 9 5 3 . O .32 8.8 43,700 74 -8 - 2 . 1 1 . 2 -3.8 4.5 . 5 5 . 2 7 -1.2 1 3 . 6

"_ "_ "_

15 44,000 69 -7.5 1.3 "_ "_

2 . 8 .46

"_ "_

44,000 69 -7.5 .1 2 . 6 -3.3 -.03 -1.27 1 2 . 8

"_

"_ "_ "_

43,800 68 -7.5 -2 .o -3.4 -"

. 5 9

"_ "_

43,800 68 "_

- 7 . 5 -1 .o -3.25 -5 .O

-.2 -1.54 1 6 43,700 68 -7 1.5 -3.5 2 . 9 -7.8 .52 .45 -2.69 11.2

"_

"_ -" "_

42,800 68 - 7 . 5 - 1 . 6 -2.8 "_

. 5 7

-" "_

42,800 68 - 7 . 5 1.35 -2.5 13 .lo4 -" -5.2

- ~ " -

AERODYNAMIC FLIGHT PATH deg ANGLE, -10

EQUIVALENT /

AIRSPEED, knots PITCH ATTITUDE, 0 CCCI deg PULL -5 5 L

COLUMN NII[ l':[-

FORCE 100 20 PUSH + l O S e C +

r

RPM,% 95 7

90 t

THROTTLE

J -

deg 20 L

TIME (a) Configuration 1.

Figure 65.- Longitudinal response to a step throttle input.

FLIGHT PATH ANGLE, deg -10

EQUIVALENT /

AIRSPEED, knots PITCH ATTITUDE, o

deg T - -IC

-5 L

PULL COLUMN a FORCE

100 "1 Pusn : , : 20 10sec 4 "

IM) r

RPM,% 95 1

90 t

POSITION, 25 f f

deg 20 L

30 E

TIME (b) Configuration 2 .

Figure 65.- Continued.

AERODYNAMIC O r

ANGLE, FLIGHTPATH deg -5 t-f"----- ~

-1 0 EQUIVALENT knots

70 "----- 60 t

PITCH ATTITUDE, 0

h g -

-b PULL -5 5 L -

FORCE N 0 1 : : : [ [ -

PUSH

+lo set+

RPM, % 95

90 L

THROTTLE 30 J "

POSITION, 25

k g 20 E -

TIME (c) Configuration 4.

Figure 65.- Continued.

AERODYNAMIC FLIGHT PATH -5 [ J "

ANGLE, deg EQUIVALENT AIRSPEED, knots PITCH -5 PULL COLUMNN FORCE 1 o o L 20 L PUSH +lo s e c 4 RPM,% 95

THROTTLE POSITION, r : I-'

des TIME (d) Configuration 6.

Figure 65.- Continued.

AERODYNAMIC FLIGHT PATH

ANGLE, deg -10 -5 I”----

-

EQUIVALENT -

knots AIRSPEED, 70 1 -

PITCH ATTITUDE, 0

wl

PULL -5 ’ t

-

-

FORCE COLUMN N1oIF cb.

PUSH t 4 0 S I ? . +

RPM, % ’ 1 : k ” I , THROTTLE

20 a

TIME (e) Configuration 7 Figure 65.- Continued.

AERODYNAMIC FLIGHT PATH

O r

ANGLE, deg AERODYNAMIC FLIGHT PATH -10 ANGLE, deg -5 1 .

-10 L EQUIVALENT AIRSPEED, knots AIRSPEED.

knots PITCH ATTITUDE, 0 PITCH deg ATTITUDE, 0

PULL -5 't---" deg

-5 1 O O r 20 r PULL COLUMN o / " FORCE

COLUMN N1oI

FORCE n 100L 20L PUSH RPM,% 95 THROTTLE THROTTLE

POSITION, 25 3Q

POSITION, 25 J p

deg

k g 30 E

TIME TIME (g) Configuration 9.

( f ) Configuration 8.

Figure 65.- Concluded.

AERODYNAMIC FLIGHT PATH

ANGLE, deg -5 A

-10 o [ EQUIVALENT AIRSPEED, 70 knots PITCH ATTITUDE, 0 deg

-5 'ti-"

COLUMNN 0 FORCE RPM,% 95 90 L TI ME (a) Configuration 11.

Figure 66.- Longitudinal response to a step pitch input.

AERODYNAMIC FLIGHT PATH -5 1 -

ANGLE, deg EQU IVAL ENT AIRSPEED, 70 knots AERODYNAMIC

FLIGHT PATH -: [

ANGLE, deg

-10 w

PITCH ATTITUDE, 0 5 " - - - - EQUIVALENT deg AIRSPEED, 70 knots

-5 1

PULL PITCH -5 PULL COLUMNN

PUSH +IO sec

FORCE PUSH

loo r

RPM, % 95

RPM'% 90 95 t

TI ME TIME (b) Configuration 12.

(c) Configuration 13.

Figure 66.- Continued.

Figure 66.- Continued.

AERODYNAMIC FLIGHT PATH deg ANGLE, -1 0

EQUIVALENT I"\-, A

AIRSPEED, 70 knots

60 1

PITCH ATTITUDE, 0

PULL -5 ' t i "

RPM,% 95

90 t

TIME (d) Configuration 14.

Figure 66.- Continued.

AERODYNAMIC O r

FLIGHT PATH ~ -5 t

ANGLE, deg -

-1 0 EQUIVALENT

AIRSPEED, Y

knots PITCH ATTITUDE, 0 deg

-5 5 k “ ‘7

PULL l o o r 20 r COLUMN N 0

FORCE -

- 100 20

PUSH + l o set+

RPM, % 95 (e) Ccnfiguration 15.

Figure 66.- Continued.

. . . .. ._ .. ..

. . . .." - - .. . - AERODYNAMIC O r

FLIGHT ANGLE, PATH deg -5 [L

-10 -

EQUIVALENT AIRSPEED, 70 knots PITCH ATTITUDE, 0 de9 P U L L -5 5 L " - l m r 20 r COLUMN FORCE 100 20 PUSH

loo r

- - -

* RPM,% 95

90 t TIME

( f ) Configuration 16.

Figure 66.- Concluded.

APPENDIX C SUMMARY OF PILOT COMMENTS AND RATINGS configuration is provided,including tower-reported winds Tables 8 and 9 present the pilots’ evaluations of each of theexperimentalconfigurations investigated in the flight for individual landings or for a series of landings. The most research program. The tables include evaluations of glide- significant encounters of winds and turbulence, as derived slope control configurations under VFR and IFR condi- from the wind extraction program, are also presented; they 8) and flare- includesustainedheadwindgradients, theirdurationand tions in calm air and in turbulence (table 9). time of encounter during theapproach, and extremes of control configurationsinwinds andturbulence (table Pilot commentaries accompany the opinion ratings. A sum- headwind and vertical gusts, as measured along the aircraft’s flightpath.

mary of a range of wind conditions encountered for each TABLE 8.- SUMMARY OF PILOTS’EVALUATIONS AND WIND CONDITIONS FOR GLIDE-SLOPETRACKING CONFIGURATIONS Pilot ratings, Measured Tower turbulence VFR (IFR)

reported r

Config Pilot comments winds uration U

-

Wmin ow, At, VTD WWmax A B max knots deg knots ft/sec cnots/sec S e C sec

i

lecoupling of flightpath and airspeed 3.5 5 320 response allows approach to be made at 10 3 60 more constant pitch attitude which simpli- 25-30 310 fies tracking task. Glide-slope tracking rea- 20 9 -24 18 3.5 37 320 0.8 8 sonably good. No change to 112 to l rating 37 in turb -1.4 8 unit change in pilot rating for shears and .8 7 45 turbulence encountered. Most deficiencies 10-30 12 320 1.4 8 22 30-38 associated with raw data instrument scan.

1 .o 7

18 0-7 6

5 320 1 .o 7

-1 .o 7 28

4 (4.5) (4.5-5) 20-30 (5-5.5) 3 5-40 320 20 -6 to 7 9 in turb 5 360 -1.1 9 1.5 8 -1.5 7 Flight director does a good job. Makes IFR (2-2.5) 20 320 1 t flight tracking significantly easier. Good ghde- 10 9-19 3 20-25 320 -1 2 7 director slope and localizer tracking performance.

10 340 Pitch commands smooth and easy to follow.

25 320 Throttle and lateral directors seem a little bit busy and perhaps too sensitive.

TABLE 8 .- CONTINUED Pilot ratings, Tower Measured Config- reported turbulence VFR (IFR)

T

Pilot comments uration winds f W

-

'Wan Wmax B UW, TTD A max knots deg knots ft/sec knotslsec sec 2 5 3 60 4.5 Some difficulty with coupled flightpath- 30-38 320 airspeed-angle-of-attack responses to thrust.

(6) 5 3 60 Airspeed variations influence flightpath 8 360 5 response and landing distance. Angle-of- 25-30 270 attack variations influence safety margins.

(5) 3040 310 Sluggish flightpath response when correcting

3 5 4 2 320 -1 .o 10 70 16-30 7.5 (5.5-6) to glide slope from low offset. Easy to get

in turb low/slow due to path-speed coupling. Must 20 350 either control attitude to hold airspeed to 12 obtain acceptable flightpath response during glide-slope corrections, or accept degraded flightpath response if allowing pitch SCAS to hold attitude. Large attitude changes to hold speed. Pitch control required to hold speed while making path corrections with thrust is unconventional (nose-down change in attitude must be coordinated with an increase in thrust for a correction up to the glide slope, and vice versa. Workload evenly divided between glide-slope and localizer tracking tasks. Effects of turbulence and shears encountered degrade ratings by 1/2 to 1 rating unit. Reduced sink rate in strong I headwinds compensates for effect of 11 I turbulence.

TABLE 8 .- CONTINUED ~~ Measured Pilot ratings, Tower turbulence VFR (IFR)

Config- reported l-

-

Pilot comments uration winds U +W

-

Wmin At, TTD Wmax A B UW* max deg knots/sec sec sec knots ft/sec

- -

25-30 -1 .o 9 20 14-23 6 6 Best to maintain constant attitude; otherwise

-1 .o 6 70 15-23 9 large speed and angle-of-attack excursions

-1 .o 6 30 occur. Flightpath overshoot and path-speed

-1 .o 7 15 coupling apparent. Easy to get slow during

6.5 060 glide-slope corrections. Acceptability 7 120 depends on available path control authority.

(6.5) Can make 1-dot glide-slope corrections but response is sluggish. Marginally acceptable if enough flightpath control authority is avail- able. If path corrections not accompanied by large attitude changes, path control is limited.

8 65 16-24 7 7 Unacceptable. Flightpath is not controllable.

25-30 300 -0 9 32 Large adverse path-speed coupling. Can only

1 .o 8

1.5 8 15 15-24 adequately conduct approach if &de-slope corrections are kept small. Corrections from 300 >7 11-15 1-dot high or low causes airspeed excursions of 10-1 5 knots. Difficult to recover from low offset. Speed decays. Lowering nose to regain speed eventually reduces rate of descent, but very sluggish.

3-3.5 Glide-slope tracking OK. Not much different calm in turbulence. About the same as configura- calm (4.5) 35-45 1.4 12 46 18-34 16 (4.5-5) tion 1 for IFR tracking.

-.8 18 33 in turb 1.2 10 15 -2.3 6 30 15-34 21 -1.5 6 20 _.

TABLE 8 .- CONTINUED ~~ ~~ Pilot ratings, Tower Measured

r VFR (IFR)

Config- reported turbulence Pilot comments - uration winds

+”

‘Wmin ~ w , At, Wmax A B TTD max knots knots ft/sec knotslsec ;ec sec

~~ ~~ ~ -

Must be accustomed to making large and 6 300 rapid throttle corrections. Glide-slope con-

35-44 2 .o 9 50 10-32 18

trol noticeably worse than configuration 1.

-2 .o 5 32

Tend to overshoot when capturing glide

-1 .o 9 25

slope. Tracking is oscillatory. Flightpath

090 -2 .o 8 57 -1 to 8 9

response is lightly damped. Initial impres- 1.4 6 40 sion is that response to throttles is too -.7 6 22 sensitive although that impression is dis- 7-10 090 6 -2 to 8 counted with more exposure to this config-

calm -1 .o 9 45 6

(6) 13-28 uration. Tracking is worse close in. Under 3 5 4 0 320 1.5 10 46 18 (7) IFR, it’s difficult to determine appropriate

-1 .o 12 33 in turb

y bar

3 .o 7 60 12-34 24 no glide-slope corrections that are compatible

with flare into touchdown zone. Under -1.4 7 48 (6-1/2) in turb to aim for 1.4 7 40 visual conditions, pilot will begin with y bar touchdown zone earlier and make path -3.3 6 20 9 9 -32 27 adjustments accordingly. Effect of turbu-

-2 .o 50

9 lence fairly neghgible since ground speed

2 .o 40

5 18-43 and sink rate are reduced in strong -4 .O 40 27 6 50 headwind.

4.3 -2.5 6 30 Oscillatory flightpath behavior is still evident 6 t flight 25 320

(5 1

and glide-slope tracking still suffers.

director

-

TABLE 8 .- CONTINUED Tower Measured Pilot ratings, Config- reported turbulence VFR (IFR) Pilot comments uration winds

T

U + -

-

Wrnin At, TTD WWmax A B max knots deg sec sec knots ft/sec -

- -

7 5-10 350 5 . 5 Sluggish flightpath response to throttle. Sen-

10 090 1 .o 8 28 -5 to 7 6 sitive path response to throttle.Difficult to

( 5 - 5 )

-1 .o 10 make s m a l l path corrections. Tend to over-

-1 .o 60 -3 to 7 5 shoot glide-slope corrections. Large speed

1 .o 7 40 changes during path corrections. Must use

35-40 320 1.5 7 60 6-38 coordinated attitude to throttle control

1 .o 10 technique and amount of coordinated con-

4.5 10-20 300 trol required is almost too much. If a good 270 (4.5-5) job of control coordination is not done, 40-45 320 -2.2 9 95 10-34 18 speed excursions are objectionable. Addi- (6)

1 .o 17 83 in turb tional workload to maintain speed is objec-

-3.3 5 30 tionable. Effect of turbulence is pro- 1.7 8 nounced. More difficult to coordinate pitch 70 11-22 4 20 320 1 .o 10 and throttle controls.

22 12-22

-1 .o 8 6

75 3-18 9 8

8 15 320 1 .o 8 Large path speed coupling causes signifcant

-0.8 10 workload. Flightpath control doesn’t seem 0.8 15 much different than configuration 6. Diffi- calm cult to keep speed under control. Easy to get low and slow, difficult to recover.

-

TABLE 8.- CONCLUDED Pilot ratings, Tower Measured VFR (IFR) Config- reported turbulence Pilot comments uration winds U t W Wmin At, Wmax B UW, T T D max

knots 1 deg

knots knotslsec sec sec ft/sec

-1 .o 6-15 5 Difficult t o see much difference from config-

9 10 320 7 12 6. Glide-slope tracking is oscilla-

15 320 -1 .o 10 50 1-15 uration

1 .o 18 10 tory. Tend to overshoot glide slope and

5.5-6 difficult to stabilize the approch.

light and Flightpath-airspeed coupling noticeable but variable not excessive. Airspeed wanders quite a bit calm

-1 .a 7 -3 to 8 45 and it’s difficult to coordinate pitch and

light and throttle controls. Slow correcting from low variable offset.

Poor glide-slope tracking, but not as bad for 10 10-15 090 4 overcontrolling as configuration 6 . Tracking calm (6-6.5) close in to breakoutstill difficult on instruments.

I TABLE 9.- SUMMARY OF PILOT'SEVALUATIONS AND WIND CONDITIONS FOR FLARECONTROL CONFIGURATIONS Measured Pilot ratings, Tower turbulence VFR (IFR)

r reported Config-

r

-

-

Pilot comments winds uration

r

kW 'Wmin At, Wmax TTD U W , A B max

I

knots sec h o t s ftlsec sec knots/sec - 11 5 360 3.5 Flare-control technique - initiate and modu- 25-30 300 late flare with pitch rotation. Use discrete 8 360 thrust inputs to compensate for high sink 3 0 4 0 310 rates. Maintain positive sink rate to touch- down. Gradually reduce thrust when touch- 20 350 down is assured. Landing precision reasonably 4 good. Large pitch rotation required. Use of both pitch and thrust control not objectionable.

2 Flare control primarily with pitch attitude.

12 calm 320 Good, comfortable flare capability. 50 15-37 21 10 3 5 4 2 1.5 10 40 -2.5 7 -1.5 15 calm 12 3 5 4 5 320 4 1.4 46 18-34 16 18 i n turb -.8 33 10 1.2 15 13 10-15 090 4 Response to pitch better than configuration 14.

3-1/24 -7 to 10 7 calm -1.5 7 Necessary to coordinate thrust and attitude.

11 pitch t -1 .I 11 -7 to 8 Occasionally overcontrolled with thrust.

thrust Still inadequate for control withpitch 7-10 090 7-10 alone.

pitch alone - TABLE 9.- CONTINUED Pilot ratings, Tower Measured reported turbulence VFR (IFR) Config- Pilot comments winds uration U f W

-

wmin At, Wmax A U W 9 rTD max knots deg knots ;nots/sec reC sec ft/sec -

-

5 Must control flare with thrust. Flare control 14 15 300 thrust adequate with thrust, and about as good as primary for configuration 11. Occasionally requires -1 .o 9 10 2-14 9 7 nearly maximum thrust to arrest sink rate.

10 350 Essentially no flightpath response to pitch.

-1.5 6 45 0-14 10 in turb Good that aircraft responds primarily to -.8 6 15 5 10-32 18 only one control. Some degradation of

35-44 320 -2 .o 32

rating in turbulence and wind shear.

-1 .o 9 25

calm thrust primary 35-40 320 1.4 7 40 12-34 24 in turb -3.3 6 20 9-32 -2.7 7 8 27 5 18-43 -4 . O 40 27 -2.5 6 30 9-10 7-10 090 pitch alone 15 15 300 3 Can’t see much difference from configura- calm 5 tion 11. Can’t provoke poor flare by over- rotating or flaring early.

20-30 300 3.5 No difference from configuration 11. Flare calm 5 entry conditions and turbulence mask any differences. Can’t provoke poor flare by over-rotating or flaring early. Only slight tendency to drop in from an intentionally extended flare.

TABLE 9.- CONCLUDED I Measured Pilot ratings, Tower

turbulence 1 VFR(1FR)

Config- reported Pilot comments winds uration

T t U

wmin UWP TTD B max knots deg knotslsec sec knots calm Same behavior as configuration 12. Good Calm flare capability with pitch.

Considerable thrust addition required to flare.

18 calm Poor sink rate and touchdown control.

Purposely over-rotated to try toprovoke float. Only subtle difference from configuration 14.

19 15 300 No difference in flare from configuration 14.

May be some tendency to dropin after an unrealistically long float.

10 320 -1 .o 12 6-1 5 Sink rate responds very little to a change in

calm 1.5 10 -2 to 10 attitude. Must use thrust to flare. Flare required from 95% to takeoff thrust at times. Little difference from configura- tion 14.

?

ie

APPENDIX D SYMBOLS complementary filtered vertical above ground level AGL velocity gain of the thrust-to-speed transfer A UT instrument flight rules function instantaneous vertical-speed indicator gain of the thrust-to-flightpath transfer A YT function pitch moment of inertia gain of the attitude-to-flightpath trans- pitching-moment derivative with fer function respect to variable a, I/Zyy(aM/aa) longitudinal body axis acceleration ax prototype microwave landing guidance a lateral body axis acceleration system Y vertical body axis acceleration aircraft mass azJz c.g. center of gravity high-pressure engine rotor rpm distance measuring equipment Cooper-Harper pilot rating DME drag derivative with respect to angle of body axis roll rate D a attack, llm(aD/aa) body axis pitch rate decibel body axis yaw rate change of flightpath angle with air- speed for constant thrust stabilization andcommandaugmenta- tion system EADI electronic attitude-director indicator Laplace operator electrical breakout force for column FBO line of constant thrust column force F C time to touchdown wheel force Fw real root of the numerator of the airspeed-to-longitudinal-gust transfer pedal force FP function GW gross weight real root of the numerator of the gravitational acceleration thrust-to-airspeed transfer function g HSI horizontal situation indicator real root of the numerator of the thrust-to-flightpath transfer function h altitude real root of the numerator of the h vertical velocity from barometric or attitude-to-flightpath transfer function radio altimeter real roots of the attitude fixedlongi- W vertical gust g tudinal characteristic equation maximum vertical wind velocity 'o=const WWmax longitudinal force derivative due to X U time to 50% of the peak flightpath variable u , l/rn(aX/au) response to a step change in thrust decay time for flightpath response to a radar-measured position of aircraftin step change in pitch attitude STOL runway coordinates initial longitudinal velocity for ground speed complementary filter complementary filtered inertial X f velocities rate of change of longitudinal wind (headwind shear with respect to time) raw radar-derived inertial velocities total longitudinal velocity for ( ) components of wind velocity in STOL contribution runway coordinates U perturbation airspeed vertical force derivative due to variable U , I/m(az/aa) longitudinal gust angle of attack ff U minimum and maximum values of Wmin headwind threshold angle of attackforthrottle ffO max flight director calibrated airspeed rate-of-change of angle of attack V initial calibrated airspeed cO angle of sideslip complementary filtered airspeed VF flightpath angle Y VFR visual flight rules aerodynamic flightpath angle YA ground speed initial flightpath angle YO initialairspeed,initiallateral velocity V O for ground speed complementary filter AT incremental change in thrust true airspeed At time duration of longitudinal wind gradient total lateral velocity for ( ) contribution attitude-fixed longitudinalcharacteris- 'e=const tic equation perturbation lateral velocity V ratio of change of steady-state airspeed initial verticd velocity for complemen- to flightpath due to a change in thrust WO (constant pitch attitude) tary fiter total vertical velocity for ( ) ratio of change of steady-state airspeed contribution to pitch attitudeforconstantthrust W perturbation vertical velocity lateraldeviation from localizer beam A Y I wheel position MIA@ ratio of peak sideslip to peak bank angle occurring during a turn entry electrical breakout position for wheel maneuver damping ratioandnaturalfrequency steady-state flightpath perturbation ATSS of engine thrust response tothrottle (Arrnax/A-yss)AT ratioof peak-to-steady-state change of damping ratio and naturalfrequency flightpath angle due to a change in of the attitude-fixed longitudinal char- thrust (constant pitch attitude) acteristic equation (assuming a com- plex pair of roots) AYmay.1 AT peak change in flightpath angle in response to a step change in thrust

e pitch attitude

effective thrust turning angle AYrnaJA'ss peak change in flightpath angle in BT response to a step change in pitch attitude U nozzle position time constant for engine thrust %sf A'ss ratio of change of steady-state flight- rE path angle to pitch attitude response to throttle sum of right and left aileron deflection bank angle 'ATOTAL inboard or outboard augmentor choke heading angle CH position pilot's flightpath control bandwidth 6 , column position amplitude ratio 6 column flight director bar deflection ,FD derivative with respect to time, d( )/dt 6, elevator position 6 pitch SAS series servo position eSAS Subscripts: flap position

&f

A aircraft velocity with respect to 6, rudder position airrnass pedal position 6 P I aircraft velocity with respect to Earth spoiler position &SP W velocity of airrnass with respect to Earth 6T throttle position REFERENCES 12. Franklin, James A.; and Innis, Robert C.: Flight Evalu- ation of Flight-Path Control for the STOL Approach and Landing. J. Aircraft, vol. 15,110. 1, 1. Chalk, C. R.; Neal, T. P.; Harris, T. M.; Pritchard, F.E.; 1978, pp.5-12.

and Woodcock, R. J.: Background Information and User Guide for MIL-F-8785B(ASG), Military 13.Whyte, Patrick H.: An Exploratory Investigation of Specification - Flying Qualities of Piloted Air- theSTOL Landing Maneuver. NASA CR-3191, planes. AFFDL-TR-69-72,Aug. 1969.

1979.

2. Chalk, C. R.; Key, D. L.; Kroll, J. Jr.; Wasserman, R.; 14.Gerken, Gary: USAF FlyingQualities Requirements and Radford, R. C.: Background Information and for a STOL Transport. ASD-TR-78-13,1979.

User Guide for MIL-F-83300, Military Specifica- tion - FlyingQuaiities of Piloted V/STOL Air- 15. Hynes, Charles S . ; Scott, Barry C.; Martin, PaulW.; and craft. AFFDL-TR-70-88,March 1971.

Bryder, Ralph B.: Progress toward Development of Civil AirworthinessCriteria for Powered-Lift Air- 3. Airworthiness Standards: Transport Category Air- craft. NASA TM X-73,124,1976.

planes. Federal Aviation Regulations, Part 25.

June 1974.

16. Quigley, Hervey C.; Innis, Robert C.; and Grossmith, Seth: A Flight Investigation of the STOL Charac- 4. Tentative Airworthiness Standards for Powered-Lift teristics of an Augmented Jet Flap STOL Research Transport Category Aircraft. Federal Aviation Aircraft. NASA TM X-62,334,1974.

Administration, Aug. 1970.

17. Vomaske, Richard F.; Innis, Robert C.; Swan, Brian E.; and Grossmith, Seth W.: A Flight Investigation of 5 . V/STOL Handling Qualities, Part 1. Criteria and Discus- theStability,Control, and Handling Qualities of sion. AGARD R-577-70, Dec. 1970.

an Augmented Jet Flap STOL Airplane. NASA TP-1254,1978.

6. Innis, Robert C.; Holzhauser,Curt A.; and Quigley, Hervey C.: Airworthiness Considerations for STOL 18. Neuman, Frank; Watson, DeLamar M.; and Bradbury, Aircraft. NASA TN D-5594. 1970.

Peter: Operational Description of an Experimental Digital Avionics System for STOL Airplanes.

7.Franklin,James A.;and Innis,RobertC.: Flight-Path NASA TM X-62,448,1975.

and Airspeed Control during Landing Approach for Powered-Lift Aircraft. NASA TN D-7791, 19. Franklin, James A.; Innis, Robert C.; and Hardy, 1974.

Gordon H.: Flight Evaluation of Stabilization and Command Augmentation System Concepts and Cockpit Displays during Approach and Landing of 8. Allison, R. L.; Mack, M.; andRumsey, P. C.:Design a Powered-LiftSTOLAircraft. NASA TP-1551, Evaluation CriteriaforCommercialSTOLTrans- 1980.

ports. NASA CR-114454,1972.

20. Hoh, Roger H.; Klein, Richard H.; and Johnson, 9 . Heffley, Robert K.; Stapleford, Robert L.; and Walter A.: Development of an Integrated Config- Rumold, Robert C.: Airworthiness Criteria Devel- uration Management/Flight Director System for opmentfor Powered-LiftAircraft - A Program Piloted STOL Approaches. NASA CR-2883,1977.

Summary. NASA CR-2791,1977.

21. Kelly, James R.; Garren, John F. Jr.; and Deal, 10. Hoh, Roger H.; Craig, Samuel J.; and Ashkenas, Perry L.: Flight Investigation of V/STOL Height- Irving L.: Identification of Minimum Acceptable Control Requirements for Hovering and Low- Characteristics for Manual STOL Flight-Path Speed Flight under Visual Conditions. NASA Control. Vol. 1 Summary, FAA-RD-75-123, TN D-3977,1967.

June 1976.

22. Wingrove, Rodney C.: Parameter Estimation of 11. Heffley, Robert K.: Closed-Loop Analysis of Manual Powered-Lift STOL Aircraft Characteristics Including Turbulence and Ground Effects. NASA Flare and Landing. J. Aircraft, vol. 13,no. 2, 1976, pp. 83-88. TM X-62,382,1974.

9 3 23. Cooper, George E.; and Harper, Robert P.: The Use of 26. Stevens, Victor C.; and Wingrove, Rodney C.: Ground Effects on STOLAircraft. AIAA Paper 77-576, Pilot Rating in the Evaluation of Aircraft Handling June 1977.

Qualities. NASA TN D-5153,1969.

27. Campbell, John P.; Hassell, James,Jr.; andThomas, 24. Ellis, DavidR.: An In-Flight Simulation of Approach and Landing of a STOLTransport with Adverse J. L.: Recent Research on Powered-Lift STOL Ground Effects. AIAA Paper 77-574, June 1977.

Ground Effect. NASA CR-l54,875,1976.

25. Parks, Edwin K.: Flight-TestMeasurement of Ground Effect for Powered-Lift STOL Airplanes. NASA TM 73,256,1977.

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

NASA TP-1911

L -

4. Title and Subtitle 5. Report Date March 1982 DESIGN CRITERIAFOR FLIGHTPATH AND AIRSPEED CONTROL 6. Performing Organization Code FORTHE APPROACH AND LANDING OFSTOLAIRCRAFT ~ - 7. Author(s) 8. Performing Organization Report No.

James A. Franklin, Robert C. Innis, Gordon H. Hardy, and ~ ~ 10. Work Unit No.

Jack D. Stephenson 9. Performing Organization Name and Address

I 532-02-1 1

11. Contract orGrant No.

Ames Research Center, NASA Moffett Field, Calif. 94035 13.Typeof Report and Period Covered 12. Sponsoring Agency Name and Address T e - 1 PaDer 14. Sponsoring Agency Code National Aeronautics and Space Administration Washington, D.C. 20546 - - ." ." ..

15. Supplementary Notes Point of contact: James A. Franklin, M.S. 2 11-2, NASA-Ames Research Center, Moffett Field, California 94035, (415)965-5009,FTS 448 16. Abstract

I

A flight research program was conducted to assess requirements for flightpath and airspeed control for glide-slope tracking during a precision approach and for flare control, particularly as applied to powered-lift, short takeoff and landing (STOL) aircraft. In some instances, the results are also pertinent to other types of aircraft that execute steep approaches to a flare and landing at low airspeeds. Ames Research Center's Aug- mentor Wing Research Aircraft was used to fly approaches on a 7.5" glide slope to landings on a 30 X 518 m (100 X 1700 ft) STOL runway. The aircraft's research flight control system made it possible to evaluatea wide range of flightpath and airspeed control characteristics. The dominant aircraftresponsecharacteristics that influence flying qualities for approach path tracking were determined to be flightpath overshoot, flightpath-airspeed coupling, and the initial flightpath response time. The significant contribution to control of the landing flare using pitch attitude was the short-term flightpath response. The limiting condition for initial flightpath response time for flare control with thrust was also identified. In general, the range of these characteristics that encompasses satisfactory to unacceptable flying qualities for the approach andlanding was determined. Considering these data, as well as results of other flight and ground-based simulator programs, it is possible to defineflying-qualities design criteria for glide-slope andflare control based on the aforemen- tioned response characteristics.

17. Key Words(Suggested by AuthorW j 18. Distribution Statement

Unclassified - Unlimited

STOL aircraft Handling qualities Approach and landing STAR Category - 08 Flight research I 19. Security Classif. (of this report) I 20. Security Classif. (of this page) I 21. NO. of Pages I 22. Price' A05 Unclassified Unclassified ~~ 'For sale by the National Technic4 Information Service, Springfield, Virginia 22161 NASA-Langley, 1982