The effects of aircraft design on STOL ride quality

E

CHAPTER i INTRODUCTION AND PROGRAM DESCRIPTION Up until the present time, there have been two completely separate ' and independent. efforts to analyze and improve the ride quality and handli"ng qualities of aircraft. The. subject of this dissertation is to define, in a quantitative way, the relationships between these two quanari^ies and to determine what trade-offs exist between the two.

This is accomplished by varying the dynamic characteristics of a simulated aircraft in a mdti^n-based simulator and obtaining simuita- of from test neous measurements ride qualities passengers riding aboard.

,;^, tha,simulator and hanetlittg qualities from a pilotflying the simulator, ;^ Predicted navels of ride quality are a so computed using comfort models.

=k l^ developed by the University of Virginia-based on motion parameters of i j ^? the simulator _and the particular-ai-rcraft design being simulated.

r i Finally, isocontours for both handling qualities and ride qualities -^ are defined<enabing future-designers_of transport. aircraft to weigh ^^ the merits of their de3igns •from both the passenger's,_and pilot's r, ^ In addition, this can help a designer. weigh he relative viewpoints.

^^ , effects which soma modification to an existing design-would have on ^^ , ^,^ ride quality and .passenger acceptance as well as handling quality and: ,, i,^ pilot acceptance.. Also, the. limitations of using grbUnd-based simulators with restricted motion capabilities to maasure ride quality `^ are demons trated.

^; For many years, a considerable amount of work, resources, and time have been spent by military and civil groups in the aeronautical ,^ :^: ,^, 3 i^.

i ,i

_^

li

_.

field to determine what qualities or characteristics an airc,a,^ ^n^u^u have .for it to be most easily and effectively flown. As a result, certain basic criteria have been formulated as guidelines for satis- factory aircraft hand -ling qualities (1)-(8). In general, these criteria .have been determined using variable stability aircraft.

Stability parameters are varied within a limited .range and the opin-ions.

.'.

of numerous pi hots: on the handling qualities of each configuFetion obtained, Handling qualivies measurements are typically made in reasonably calmai,r, and results thus obtained are generally accepted '` to apply to-high turbulence cases as well. This is not necessarily a prudent course to follow, in that turbulence can indeed have an effect.

on pilot opinion.

Gradual"ly, the physical quantities which have a bearing on handling qualities were defined and the range, of these parameters which delineate satisfactory and. unsatisfactory. handling qualities determined. Naturally, aircraft with different.--missions have vastly different requirements, than. a handling qualities re different for-a bomber or transport-type aircraft than for a high performance, highly maneuverable f i gfite r , ', However, even: though much attention hd_'beenj given in the past to deVelop_ng aircraft with good handl_i.ng quail ies, very ti_ttie: '.

^., .

attention has been devoted to developing aircraf with good ride qualities, i.e., aircraft in. which the traveling public find flying '^' pleasant (9). In the recent past., with the evolution of high-altitude ^^ ^.., jet aircraft, this has-not presented serious problems since . passenger on commercial flights, as a whole,. were..not especially annoyed by the- "-` _ _ experience of flying. However,. with the increasing use of short take-off and landing aircraft (STOLE in commercial aper• ation, the question of acceptable levels of ride quality has a^y isen due to the often unpleasant nature of motion encountered on such aircraft (10).

STOL aircraft. often exhibit obJectionable ride qualities due. to .dower wing loadings or higher lift coefficients than aircraft used in conventional operations, Designs which use propulsive. lift or thrust vectoring to attain STOL operat-ions are generally not subject to 'ride-quali y degrad3t pn because during the cruise portion of flight, these craft operate as high-w'sng loading conventional aircraft.

It is not these designs at which this study is directed. Rather, it ^' ,,. is the designs which achieve . STOL performance by using low-wing .

'u Wing loading is a measure ^g^ the lifting ability of a wing.

loading.

^ n is W/S, the pear unit of surface area. (For equilibrium flight, it .

The lower the ^ aircraft weight divided by the wing reference area,) wing loading, the more susceptible the configuration is to external '^ low-wing loading aircraft are more severely disturbances. Thus, dis urbed_by flightthroughrough air than high-wing loading designs, so it is to be expected that STOL aircraft would . have worse. ri^tp it is just such aircraft with qualities than conventional aircraft.

low-wing loadings-which require modifications to improve their ride ^.

qualities.

During _the past decade,. considerable research has been conducted to determine what environmental and psychological factors define ^a R^ More specificaily,.human person's'state of comfort or-discomfort.

k __ .,, response to motions of various forms, noise, temperature, and pressure a levels have been measured and tolerance levels have been defined (11). A .^ '^ recent survey of past work done in this area is contained in Reference -` (12). With regard to the environment experienced by the flying public, y^ the University of Virginia has been involved since 1970 in defining what fac tors are involved in determining passenger comfort, and have ^ developed several comfort models based on aircraft motion param- eters (13). This University of Virginia effort is based on -- .simultaneous in- flight measurements of aircraft motions and sampling .^ of passenger opinion on regional and commuter airlines on the East Coast.

To improve the ride quality of STOL aircraft, several means have (14), beers investigated in general, these methods consist of placing sensors, in the. a i,rcraft which sense aircraft mot ion, usually linear accelerations. and angular rates. These signals :are then used to deflect control surfaces which generate aerodynamic forces ,and moments : which tend to minimize the motion which the passenger feels...: . One-of + the. disadvantages of some of these systems is that they may tend to degrade the handling qualities or controllability of the airplane, ..

making it more diffi-cult or annoying-for the pilot to fly.

In addition to a weight penalty such systems may impose on a design, thc^ failure of such aride-control system may present a safety hazard by severely increasing plot work load due to the. corresponding change in handling qualities, or by exceeding. design structural limits.

,.7 Rather than. using active control systems to control ride quality, .^ one might possibly design aircraft. so that they arse inherently pleasant.

1 :_.a.^-

I I I

_ _I_ I

n

to ride. Thus, the purpose of this study is to determine the relation- ship betwean characteristic aircraft motions and aircraft ride quality.

Most aircraft have five distinct characteristic motions, two ,- longitudinal and three lateral. These motions are determined by .

t aircraft geometry, mass distribution, and flight conditions such as 'c V ^ '^ ^ ^ velocity and air density. The phugoid longitudinal mode and spiral t^..

lateral .mode are normally of such long. period that these pure motions << - ^^ ^< would normally not be sensed by flying passengers. Periods and times..

to double/half amplitude of 30 seconds to two minutes arP common for _.5 these modes. In fact, these modes. are . rarely seen in typical flight because these motions are readily damped out (usually unconsciously) ^^ by the. pi lot. .Likewise, the ^°olli,ng mode is not. deemed important to fi ^^ aircraft ride quality because of the pilot's tendency to keep. the wings !'

level in cruise, and when maneuvering, to keep rolling rates small The two remaining aircraft modes, the (usually .less than 10 deg/sec).

Dutch Roll and,the short-period modes,. are of particular interest in '.' ride-quality studies since their associated periods and amplitudes- x^ fall into the spectrum of motions found most uncomfortable by human ' e beings (0 - 20- Hz) (12). The quantities which usually define the ^.

handTing qualities of these two modes are. the hndamped natural frequency, ca n ,and the damping ratio, ^ s , of the short-period mode, s _ and the number of cycles to half amplitude, C time to half amplitude, ^d ^ .,^ T , and aroll-to-sideslip parameter,. (^/v e ( d , for the Dutch Roll mode.

ltd lJsing the parameters established for defining satisfactory_handl-ing ^^ qualities for these two aircraft motions, the limits which satisfactory ride qualit •/ place on these parameters will be determined by subjecxi>ng :-., _ ^..,..^ ^ ^ _ . ^ _ _. ^ ^ ^w.. s_, =m^. ,._..-__ ti F 3 ... ..

....

^^{ ^ .

L :.human subjects to such motion in aircraft simulators and eliciting ;^, their subjective comfort responses . , and by using comfort models based :^.

on .computed motion parameters for the simulator and the aircraft "` designs-being studied, ' ^i -- The test program is divided Into two distinct phases. The first phase investigated feasibility and the effects of varying certain ^ parameters on ride and handling qualities.

The range of parameter ' ....

r variation and the effects of these variations on ride qual ity were ^^ studied in the University of Virginia's Analog Flight Simulator. ,.

'. ^.

'^ Once these studies.were completed, the second phase was initiated ' at ,NASA's Langley Research Center,.

Here ;rests were conducted on the Visual Motion Simulator (VMS) using aircraft parameters determined to .

..

; ; be important in the first phase, Simul taneous measurements. of both.

` ride and handling qualities were. made :for various aircraft configure- :Y ,.

" tions and finally, he trade-offs between ride and'-handling qualities j ; w defined.- _, ,.

.^ - , !., .r Y G F P .

(} ^^ t 4^ } k . , ...w i r ^: Y ' X 7 „- . , ..

.^ t 4 ?

1 .^ p ^ - { ((Q, ..'. {k k. ^ ^f b ^' r'.

CHAPTER If SIMULATOR EXPERIMENTS AT THE UNIVERSITY OF VIRGINIA The University of Virginia°s-f1<xed-base analog flight simulator ^ „^ .

(Figure 1 and Appendix A) was programmed with the six-degree-of-freedom ^„ ^'': equations of motion (Appendix B) giyeh in Figure 2. .The aircraft used -;, {11,500 pound) Canadian deHavilland ^' in the simulation was a 511.52 N „_ N This particular aircraft was chosen .because. it is OHC -6 Twin' Otter, <.

a typical STOL aircraft and has been in service since .. 1966 in-many - _,:.0 its flying characteristics are well known, and there roles, Also, r_ ^'" are--many pilots available with flying experience in the Twin Otter to .Flight conditions of level ._. validate the ground-based simulations.

flight at 914.4 m (3000 feet) and an equilibrium flight speed of -= m/s (175 mph) wera chosen as the typical . environment in which 78,2 .., this aircraft is operated in present short.-haul commuter service on-- r ^ ' the East Coast. The wing loading of the aircraft in this configuration ,..^ Based on these flight conditions, _ is 405,x' N/m (27.4 lb/ft 2 ).

x stability derivatives were obtained-from an unpubli-shed NASA document ;, ;< containing a mathematical model for the Twin Otter used in a fixed-base ' simulation at the ^.angiey Research Center to study STOL air traffic ^^ - ^ control procedures. These stability derivativesagree well with .ones, u_ : (14) for a Twin Otter in approximately the same contained in Reference The stability derivatives for this flight condition '; flight conditions.

_ u may be found in Tabled using standard NACA notation (see Appendices C ^^ ^ This<condition and its corresponding set of stability der v- and t)).

atives will-be referred to as the "nominal" conditions.

"" ^ ^;, 7;^ ou , ~ ^ _ --'_- '- ''-^~~_ ^^^^ ^^ '-_ '^p^m^^ ~^ .^-^ F|^URE }' THE UN|VER^|TY UF V|RC|NiA/^ ANAL0^ FL|^HT S^MULAT0' cx ', sq„ ax sqo Se^,c a i 0 SgWC ^`^ S te° xax c X ' 7z 1 a + [ o] e - [ gip° l 6T + [zmna 0 a ^^ mU° ^ mUp mU0 -- ---- ' --- + — C ,^,^ _^a . - [sq„ zv ° Sqm za1 S^ {mU + e - --1 9^u l ^s [mU ^°_ r c _°_ ^ c °- ^ c Sqm' 2U ° Sqm 2Un za Sqm 2U° za f ^ za ^F _ ^^, ,^ C CZU , Cza 1 c m6n + [ mU° ^ u + [ mU ° de 1 _ « - I R t ] I m v ° . ] ^° c c c Sqm 2U 0 Cza.

- Sq^ + 2U ° C z . Sqm + 2U0 Cza ti x a a , Sq^cCm ^ ^, Sac SgmCZCm.

u 'u + [- 2U I a 'a + [- i ^ -9 - [ I l Cm.1 'a m Y a Y ° Y ^^, _ ,^ ^^ (; Sq^p w r i Sgmcz m^e ,, _ k° 0 Y 4 Y Sq^Cy^ 5q^b ti Sq^ cy ^ " + ^'u - [mU I ^ [ 2m -^' 1 . ^Y + [- mU 1 6 _6 - - ^'a + ^ c y . ^ 0 0 r 0 ^ .z q^ Sq^b ^ [ 2mU cypl ^ ^ [ mu ° c ys ] 6 r - ^.xE O 2 r Sgaob x S gmba Sgmb ^ ^^ I R 1 ) ^ -^ ` + {- 2U I C 1 ^ - ^ + [- T C t 2U I ^E 0 x r x 6 ^t^ 0 x p !.

- - {, - ^Sq„b CR ^ d a i - ^ S^b CR 1 5r I' x 6 g s dr ^' n .. ..

Sgmb2 Sq^b2 Sq b ^ ^' .

+ .A^\i, n n ^^ _ ^ I- 2U I Cn 1 ^ + [- 2U I C I ^J - f i C 1 P s 0 z p 0 z r z (^ "

^^

Sgmb a^ ~ Sq„b 6 a dr..

z s t ^^ ,7 _ ^; ^μ^i ^ _ FIGURE 2. EQUAT70NS OF MOTION _ , - _ 9 f 1 _.,.,. _. _..

...........,,...w r .. .:-^-^ '. ...:. _....„...,-...... ...

^,n^ ..- +.«w.w..,.w ^..^. ......

..,.. rterse:r.»v...+.v^z^- ^a.-n^^.^ ,.w t }; _ 1 .7 i (^ TABLE 1 FLIGHT CONDITIONS {EQUILIBRIUM) IZ kg-m2 h _ 914.4 m (3000 ft) (level• flfight) = 55031 ^- -ft) (40600 slug 1898 kg - m2 51152 N (11500 lb) I W xZ slug-ft2) (1400 _ -1.3° UD = 78.2 m (256.67 ft/sec, 175 mph) a 0 /s c (0..002177 sl u g f = 1_.98 m (6.5 f t) 1.122..kg/m3 / t3) p

-

b _.19.8m (65 ft)

045'

CT _ 0.

S 39.:0 m 2 (420 ft2) h* = 0.2 22907 kg- (16900 slug.-ft2) I x _ m2 aflap _ 37411 kg-m 2 (27600 slug-f t2) - IY =_ TURBULENCE_COI^D IT I ONS au_0 d v_ o W 0.914m/s (3 f p s.)

NOMINAL STABILITY DERIVATIVcS Longitudinal_Deriya fives Cx =C^ -CD

C L _ 0.3818

CD. _0` °` a a a x .

C D CZ = -C L -

'S.9

C D = 0.045.

_ Cm.

ra ^'

a a

-CD 5.504

C M 0.035

C^ ^ { Cx. ^_

q. a a

CZa = -C^a x CDq = 0 C a 5.7295 (' Cx ` _ -Cp ` ?

Cm ' _ - 23.948

CD _= 0. 1432

F- a C29 _ -C^9 CxQ,= -2 Cp C = -1.9098 ^.

u q q a - C Z _ -2 C L 1.52 ^ L.

a ^_ c iy ^^ ,< _ ..^ 1U

^ ^

i ^{ S _.

^.

TABLE I (C^ntihued) _, f^ j t l . _ Lateral Derivatives - ,, t „ r = -0.89 C = -0.1 C = 0.5 C Yp Ys }; Y ^ _ -0. T2 C^ = -0.5488 : CR = 0. 13 C^ ,; S P= r= _ -0.1855 - 0.1215 C 0.006 C C np nr ^s _ f., ^ ,: ^.

r Control Oerlvatives ^; C = -0.1 C = 0.39 ' yd ns r r C 0.00348. _ -0.01 _Cn Ya '` - 8a a = 0:2055 Cm ' _ -1..79.

CR

s a

a e ^ = 0.0398 C = 0.45 Ra r La e _ t `..

}, .^^

't

;'.

^ ...

is _ , ^ , ..

^. 1 x Y ^^ _l l ^` , — _ ,- :, M ^; a In additioh to the nominal configuration, other stability ;^ conditions. were run. These . conditions were produced by varying Cm ^, a (= aC m/^q ^ 'k (= aCm/8a, the-slope of the pitching moment curve) and ^ m q aCm/a8, the pitch damping derivative) in the longitudinal mode, and h (° 8C /8a, the side-force damping derivative) and C (= aC /a^, C Y

Y^ n^' n

the static directional derivative or weathercock stability derivative) Y; in the lateral mode. The longitudinal parameters. were varied holding ^, the 1-ateral derivatives at the nominal conditions and the lateral '" derivatives were varied holding the longitudinal derivatives at their nominal values.

As an approximation of theshort-period mode {l5), it can be shown t-^ that the natural frequency, w n i given by - ', s ; - mU w ns ^ ( C z Cm) (Cm) q^S ZU a U a q and the damping ratio, ^ s . by -^" ^r I cm _fir -C 2i;swns a ) - za , ZSq„ (-C Sq^c C mq ., where ^;; c =longitudinal reference. length,.. mean aerodynamic chord -^ - iy = moment-of inertia about the pitch axis . .

m = aircraft mass ., } ^ c^ = dynamic. pressure,. ^PU^2 U^ = equilibrium flight speed.

' ;:' 12

I

^ -

I I I_ 1 ^_

I

' and C m a designer could obtain Thus, by judicious choice of ^ m tx q and ^ s for the short-period mode he would desire, any set of w n s x,^ holding all other parameters constant. The primary factor which determines C m is the static margin, the distance which the aircraft.

a :, center of gravity is in front of the center of pressure., For example, the deli-finer, by proper selection of center cf gravity location:, may The value of the stability-derivative select a desired value of C m ^'- N a is determined by the size and location of the horizontal tail.

C mq _ r Therefore, by choosing a horizontal tail of appropriate size and '^.

locating it a specified distance behind the center of'gravty, the f Flence - the des i finerhas designer can obtain a desired value of C m ^ q short-period mode., but he control. Dyer the :defining parameters for the _,_ ^' `.:^^ must be aware of how his variations of C.G, location and . tail-size and w T k (e,g., C m. )' and what location might affect other stability derivatives ,t a <s cost com lexit and h 'at' s ld have on rami cations suc vari on wou p- y, 'fi mission performance of a particular configuration.

!,^ 4y and C are dominant factors .which determine the !_ Likewise, C n^ x yg ,, damping and frequency of the Dutch Roll mode and are therefore ";`k important to the handling qualities of the Dutch Roll mode. For t ^...

and G were used simplicity in this study, only variations in C .: A, yR nf3 „" to modify Du ch.Roll characteristics. However, other stability _ _ >.^ have dJrect effects of Dutch Poll derivatives, such as C^ ..and C n ,. S r __ characteristics and, at the designers option, he may wish to v<<ry:_ ^';^ and C The values of these in addition to, or instead of C .^ y^ ;, ;i nf2 `"" C and C n are largely determined by the size ^.-^:d location of the ys s ^.

^:^ ,, vertical tail; thus the designer, by giving appro^^-l.ate attention to the matter, may choose a design which will give him values .for C y , and C which will result in good handling qualities in the C , C ns n r ^^ - Dutch Roll .mode, For each set of stability derivatives to be investigated, the fourth-degree longitudinal and lateral equations of motion were solved for tfieir characteristic roots. From these characteristic values, the short-period undamped natural: frequency, w^ and-the damping ratio,,^s s were computed from the longitudinal roots. Also,. the number of cycles the time to half amplitude, T and the roll- to half amplitude, C - _ ^d ^d to-sideslip parameter, ^^/v e ^ d for the Du ch Roll .mode were found from the lateral roots. C^ and T^ .are related to the undamped natural d d , and damping ratio, of the Dutch Roll mode by the frequency, w n ^d, d following expressions; ^.

i

It is these quantities which are used to define a d -_^__ _._ .period and Dutch Roll handling qualities (1)-(8). 'ror the longitudinal short-period mode, the natural- frequency and damping ratio describe the response of an aircraft to an abrupt pitch change from equilibrium flight and its subsequent return.; to equilibrium conditions. Similarly, for.. the lateral Dutch Roll mode, C^ and T describe . the. motion of an zd ^d aircraft after being disturbed from'.equilibrium heading, roll, and.

;x sideslip conditions... The roll-to-sideslip parameter is a measure of the roll induced for a unit lateral gust and is a gauge of an aircraft's lateral responsiveness, The analog flight simulator was programmed with various'combina- tions of stability derivatives to cover,. as well as possible, the

re ions in which handl in g g qualities are most often defined for t'he

short-period and Dutch Roll aircraft modes. Coupled to the analog -.

computer was an electronic noise-generator 'adjusted-to disturb the simulated aircraft with ,914 m/s (3 ft /sec) rms turbulent gusts in the

normal and. lateral directions, -This was accomplished by superimposing

_

.^, the random electronic signal on the a and ^ variables in the analog

equa ions of motion. The.. simulated turbulence was essentially random noise with the spectrum shown in figure 3.

^u,v

t ► ^

240 Hz ^, FIGURE 3. GUST INPUT POWER SPECTRUM

^-

:-

e } For each different aircraft configuration, the simulator was operated at Teast 12 times while apilot - flew the simulator attempting to maintain straight and level flight for over 200 seconds. This run duration was chosen to permit the rms normal and transverse accelera- bons computed by the analog computer to stabilize at a steady-state The associated .comfort rating for each flight was found by value.

using-an empirically-derived comfort model developed at the University (See Table ll.)

(16) using their comfort-rating scale. '' of Virginia- z. ,^ ici ty and because ,^ This particular model was chaosen for .its relative simpl - ..

. analog computer with its defining parameters could be obtained from the ^. ^ =The model was derived by simultaneously recording air- „^ , relative ease.

craft-motion and sampling passenger opinion of ride quality on regional -^ ^^ and commuter airilnes during, actual flight operations on the Cast Coast.

^, ', This data was then statistically 'analyzed and 'a best_fit curve deter- mined (13). finally, the average rating for each aircraft configuration ^^ ^^ a ,^^ was found and converted into apassenger satisfaction. level.by statistically-determined transformation (17) shown in Figure 4. This -, relations-hip was formulated byanalysis of questionnaire data recorded '"^` -^ oh the above-mentioned commercial flights asking.. the passengers to i report their comfort levels and their willingness to take another flight - based on their recent flight environment, ; ,^ The values of passenger satisfaction due to variations in the F ^^ ities are plotted in Figur^!5. .The solid '^`` short - period handling qual lines in this figure indicate the presently accepted boundaries for ^^ R.

short:-period. handling qualities. The dashed lines indicate lines of ^.

^ constant ride quality, as suggested by the data points. The trend is ,; i.

?i f:: Mve

r

Y^^;

^^^^^

^^^^

.a^

a

f{ 4^..

TABLE I 1 ti ^ ^ T COMFORT RATING SCALE.

1^ a 1 -Very comfortable ^, 2 -'Comfortable 3 - Neutra 1 c

_ 4 - Uncomfortable

^ ^^

^^ 5 -Very .uncomfortable

^^ ^_ COMFORT MODEL ^.

CR_2 +13.8aN+4,.52aT-2.816_ aNaT ^ _- { } ;' - ^ ,; n :, ^^.^ where aN = normal rms acceleration (g's) :^ ^` aT _transverse rms acceleration (g's) CR =comfort rating,(1-5) } a a s n ^{ l^ s ^ - ,.

fr. _ ^; ., i - 1 - ^^ - - t^ I s j: 1 ^ I E I } ^ i ,: - r ^^ r' _ ^^ ^t ^ 7 f ' 3`i ^{ , d t 1 ^, _ ^^

p 101

W

4.'

N

1-

Q

N W

= 61

W '

H

..\_ Jai ^:' ww:p.^c -.. , «:..... _. .. _ ..._,. ^ -.

...,..,,m.:^ .. .ns.e9'.^nM tW+^ - ^AC i' 11th 1 '::

,^; % °% OF PASSENGERS SATISFIED

HANDLING QUALITY CONTOUR

,^ - ^,4

-- DUALITY CONTOUR

RIDE .

K^ J d

T ^ 1.2 ^

.^ F- ^ ^

a ^ ^

4p _

186.2 , `^

O° ^ a.^ r.

e2.I /°

^

o

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N I.0

87 ^ °i°

L _ ^

^, i HANDLING

^. ^ c ^ O ^

4UALITIES

^ `^ HANDLING 86.6'.%

Q

SATfS.FACTORY

L^ 3

CUALITIES ^ ^ Q /

0.8 i

2 ' ^

^ ACCEPTABLE 1

^

87.5

U

^ t 83.7 % ^

` ,,^..

` o °

\87.2 78.6 `o ^`

O_^ 0.6

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87.5 °

1 ^ 87.5 %e

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8 4. 04 % ^

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^ 87.2 °/o

0.4 ^^ ^ ^ ^ ^O

HANDLING

^"

C

♦ ^ = QUALITLES Bfi.I ,

UNACCEPTABLE

N

E+7."0

°/e O.Z .

TURBULENCE

80.0 ° /o ^

,, 86.0%

Q'- .914 m/s t3 fp=}rm=

Q ! I 1 !

( ^-

0.1 0.2 0.4 0.6 0.8 I.0 2,0

s

_ ^^^ SHORT PERt00 DAMPING RAT10, ^

.: A' ^ r } FIGURE 5, aHORT-PERIOD HANDLING QUALITIES " ,, ^'....

.. ,.. .,-n^ , . _.

^ ..- ^,^,, __ __ _.

.. C i . :^ _

OF PASSENGERS SATISFIED

— HANDLING QUAt_ITIES BOUNDARY

r

.

3 es.o °% p

N

^ 84.5 %

W

U

J ^

U — 0 ^

84.4 °/0

^" ^ 86.1 °/0

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_ 84.7% ^ HANDLING 4UALITIES

.SATISFACTORY _

O 1—

86.I % ^

J

^ eo.4

W

LID

^a

8 4.2 °%

^ Z

HANDLING DUAIiTIES '

W

J

84.2

UNACCEPTABLE

^ ^

O

W ^

^'

82.5

Z

8 2'. 3

_T`URBULENCE .LEVEL

...

•

.91.4 m/s l3f;psl rtes

o

Q 8 5.4 /o

.;_ t

0 1.0 2.0 3.0 4.0 ^_`

;,

. r

^^/ V e ,

tdeg /m/s)

w ;

ROLL'-T0— SIQESLIP PARAMETER ttr

^.

rs.. , ¢, ; , >^ '° FIGURE $. DUTCH-ROLL-HANDLING :QUALITIES _- -_. _ _' _. _..^. x -._ .. _. ^ ^....%.-,^.r. .., ^ ...,,,. ^<:.-.. .,=:3- v=.^. r = :,^.

_.^ --=.: x:a r;:^ T:,.^ dr'......-._y i _;_:^^«i if.:-..,^ ^ 1^ T'°"""'T --- ^ ^...,...^,., 1 _....'ewnwn . a--... a ... _ _- ^. _. - _^ __- L.,.__snu .«......^,. .«.......»^.. :^...^.....+^. ^,..d^ ^.^..+,t: 3..........i r..,.. I.,.....w+.7 ^ ._ ^a ^ ^: ^ °/e % OF PASSENGERS SATISFIES w O W 86.0 °/o

_

^ I.0 p

O

es.o °^°

_ J

86.1 °/°

a

O.$ HANDLING .QUALITIES

_ Q Q SAT'IS FACTORY _ __ ti

I

O

-^ u 0.6

_

._ _-__ 85.5 °/o ^

Q

N

_

v

N

o

Q.4

O

^ 8 6.0 °/o

W

^ 8 4.4 ° ^ _ 8-4, 5 % 8 4.7 °% .^ — "

0.2

4.4 °/° -' ^ _, H

HANDLING QUALITIES-

084.2 °/° ^,. — ^^84.2 °/o

UNACCEPTA$LE

4 /o ^ 2.5 °/°

O' 85. Oe

^^

to

----- ------

0 .—

i ^- — ^

W

^ TURBULENCE LEVfL_

Z

- 0.2 ,_ -

^ rn/s l3fpsl rrr^s .914 __ - .

3.0 -

0 1.0 2.0

'- k

!^/Ve^ (deg/m/s)

ROLL-TO- SIDESLIP PARAMETER, 7.

FIGURE DUTCH ROLL HANDLING QUALITIES .

^ ^ __ ., for increasing passenger satisfaction as the damping ratio and the ^ undamped natural frequency increase.._ These trends are to be expected, since an increase in damping ratio will directly result^,in decreasing ^ normal acceleration and improving ride quality. Further, increasing _ .

the natural frequency tends to make a design more responsive, allowing a pilot_to better maintain control and keep motion to a min imum, also _ improv i ng ride quality.

^ .

x r The effects of variations of Dutch Roll parameters on ride quality t ^ .

^ are shown in Figures 6 and 7.

The solid line indicates boundaries for F ^ re ions of acce table Dutch Roll Y handlin Ride ualit and asse P nger 9^ 9• q Y P

acceptance generally improve as C, T, - and ^^/v ^

.decrease although ^

.

d zd Zd e _ 4 the 'trends are not as clear as those of the short-period mode.

Again,.

; this might fe expected since decreasing the number of cycles to half amplitude and the time to half amp)itude corresponds to increasing

s

the damping of the Dutch Roll mode and reducing .Lateral acceleration.

Likewise, decrea ing the roll-to-sideslip parameter.

implies reduction .

.

of the aircraf t roll res onse to lateral

p gusts resulting inlower lateral ..

accelerations and better ride qualities. Also, it appears that the ^ changes in bongitudinal short-period parameters had a greater effect on

L

' ride quality than did the changes in the Dutch Roll parameters.'

^ No attempt was made in this part of the study to measure pilot __ o inion since a p pi^rot experienced in evaluating handling qualities was not available and. no motion or visual cues are rovided b the simulator..

P Y

i

ry * .: .

n.

, ^'

z° CHAPTER Ill ,.,_ SIMULATOR EXPERLMENTS AT-THE NASA LANGLEY RESEARCH CENTER Using the data and experience gained during the tests on the University of Virginia's Analog Flight Simulator, 27 different sets _.__ - o,f stability derivatives were selected to be studied further at the L NASA Langley Research .Center. Fourteen longitudinal cases and 12 a z' lateral cases were chosen in add'itiom to the "nominal" set of Twin ^^^ ., Otter stability derivatives contained in T^^ble I of the previous section. These cases and the corresponding flight conditions are These cases were chosen: to cover the regions contained in Table III.

>..p f handling e qualities are most often in which longitud.inai and lateral j ^ E ^ r ^ I, ^ defined for - the short-period and Dutch Roll modes by aircraft ^^ designers. Figure 8 shows the contours which define longitudinal I £..

short-period handling qualities as a function,of undamped natural r, frequency, W n and damping ratio, ^S. The numbered points on this a

¢^

s plus the nominal case.

figure indicate the 14 test cases. studied, r__ 9 and 10 depict the '12 lateral test cases studied, Similarly, Figures l pus the .nominal. case plotted in terms in which the Dutch Roll ^ _^ handling qualities are normally defined, namely the number of cycles ^^ to half amplitude, the time to half amplitude, and the roll-to-sideslip t .^ parametor.

p ^.,a The Visual Motion Simulator (VMS) at the NASA Langley Research ^^ Center,. a synergistic motion-based stmutiator with the basic interior ^i ai ^^^ and instruments ion`of a je transport cockpit (Figures 11 and 12), was ^* ,u .

$, programmed with the A schematic diagram of 27 test-cases described, ^.,^ _ ^^ .f; ,.^ , ^a p+ "FABLE 11I (EQUI1_IBRIUM) FLIGHT CONDIT-IONS kg-mz .4 m (3000 ft)(level flight) I = 55031 = 914 h z n.

(40600 s 1 ug-f t 2 } ib) N (11500 W 1152 _ 1898 kg-m2 xz (1400 slug-ft 2 ) 2.56..67 ft/sec).

78.2 'm/s (1'75 mph U 0 ` o p,0 _ -1.'3 p = 1 .122 kg/m 3 .

f c _ (.6.5 1.98 m f t) CT = 0.045 t = 19.8 m (65'ft} b h%, = 0.2 _ S 39.0 m 2 (420 ft2) 22907 kg- m 2 (16900 slug-ft 2 ) I x _ 37411 . kg-m 2 (27600 slug-ft2) l y 8fla P '; TURBULENCE. CONDITIONS I (DP.YDEN MODEL) S e p ctra ^ u.

^ ^ w/U )2 u QUO 1 + (L u 0 ^, ^ [ 1 + (LV /U0)2]2 ^^O 'QUO .

(LwwIUO)2]2 ^w( ) w ^rUO [1 + : t

524 m/s /sec)

a u = w _ aW = T. (5 ft n ^ ^.

_ .

k Lu = L^ _ tW = 762 m (2500 ft) Pos i t lon w:i th Resuect to, A _i rcraf t c. 9. x " Pl to .6 ^ z = 0 x = m (8.8 ft) y = -.49 m (- 1 ft) 2.7 ^ ;;

^

^ _

^ ^

TABLE 111 (Continued) LONGITUDINAL TEST .CASES Short-period Mode w ns C C Case c s ^s Number ^ ^ ^.

- 1 .9098 0 0. 0.332 2 577 _ 3 -40 -20. 0 _ 0.885 0,.

-0.64 -23.948. 0.463 _0.782'

-6.76 -23.948 1. 132. 0.320

6 -3.24 7.0 0.731. 0.193 7.0 0.286 0.49;9 ', -0.64 -1.9098 -70,0 0.796 0.868_ ,^ -4.84 -56.0 1,041 0.568 t0 -0.16 - 101.0 0.677 1..34,7 -2.56.. -119.0 0 1.065 11 .978 0. 846 12 - 5.:76 119.0 1.23) - 13 `-1.9og8 16.0 0.5,14 0...150 ..

19 0,704 0.109 -3.24 16..0 1 .0'j2 0.132 20 ^- 6.76 7 0 ^ ^ -.

^.

^ ^.

- _ ^s ^^ TABLE III (Continued).

{ ^ ^ uutcn Koi^ Moue e 1/T ^d ..

^^7veld Case C C 1/C u Y^ sec-1 nF3 , #d' °/m/s Number ^ 0.62. 2.485 0.260.

14 0.01583 1,699 0.81 -o.8g 0.984 0.766 0,999' r,, ^ i 3.076. 1.184. 0.160 0,1215 -1.875 -1 , 0 2.384 0.171 ^^ 17 0 - 2.736 .

0.86 1.193 1.914 18 0.01417 0.11.5.

.

' 0.743,. 0,165 21 0.1215 0 1..978 0.:82 0..504 0.045' 2...098 22 0.of167 f ; 0.74 ' 1.864 0.186 1 .810 ^ 23 0.015 # 3 2.

0 1.53 0.112 24 -0.75 73':7 x.

x P, 0.194 0:25 3.0 0.107 0.055.. .

0.053. 2.738. ^= 26 0 -0.5 0.721 ^.

0.243 2.231 27 0. 0075 -0.25 2.939 k ..

_.

T ^.

Ct 6t ..

^^ ^« ^, .^ ^ - '. ;i ji W.

k _ ` ^ x^ j t { r.

v..

?6 .; ,i III {ContS-Hued) TABLE i ^^ NOMINAL CONDITIONS i ^ _ a ` w Number 1 Case P -1.9098 C _ p ^^ _ `23.948 mq p ^ = 0.1215 C h n^ Cy = -0.89 Mode ^^ Short- period W n '0.660 cps = s r s = 0.549 Mode' Dutch'Rol1 _ ' 2.501 1 /C^,41 _ d 1/T^a = 0.953/sec e, ^^ 0. 162 ^ °/m/sec ^, $ /ve) d = T;, t x _

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: SHORT PERIOD DAMPLNG RATIO,

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^ FIGURE ^.

SHORT-PERIOD HANDLING QUALITIES BOUNDARLES ' AND LONGLTUDINAL TEST CASES ., ^ __ ^^ w A^ ..

R ., .w>f rei ^6 ^

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^^ - ROLL - TO -SIDESLIP PARAMETER

E, t rr '^.

kt ^ ^i FIGURE DUTCH ROLL FI^NDLING-QUAL6TIES BOUNDARIES• 9, ^; ^ AND _LATERAL TEST CASES, (1/C vs. ^^/ve^) ... w

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^^ p .i `O 15 —^ ^ O 1 : ..

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^^I^`ES LI^P ^'ARA^I^^^^•,

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$ ^ _ jk' .^,.^ _ ^, '.^ a ,, f -- .,,^, -^^ ^ ^ +t - ,^.^ ^„ iJ FIGURE 11. THE VISUAL MOTION SIMULATOR (VMS) AT THE NASA LANG LEY RESEARCH CENTER .the simulator, its control systems, and its data output capabilities is presented in Fi,'gure A CDC-6600 digital computer, used 13.

exclusively to operate the real-time simulators at NASA . Langley, was programmed with the aircraft flight conditions, stability . derivatives, six-degree-of-freedom differential equations of motion, Dryden gust model, a routine for computing rms values for 22 parameters, and a simulator .,washout routine. The-program integrates the__nonlinear six- degree-of-freedom equations of motion 32 times a second to describe the motion of the real aircraft as a function of time... These values are used by the simulator washout routine to determine. the position of the simulator's six moveable legs-as a function of time, providing motion sensations to the occupants aboard the simulator. 0«e to th;e limited displacement of the simulator legs, and the dynamic character- istics of the hydraulic actuators, 'the simulator is not capable of producing the magnitude and duration of displacements,: velocities, and ,; ,, It is the purpose of,the washout ;^ accelerations of the. real aircraft.

redicted motions of the real routine to a pru riatel scale down- the { P P Y P i.+ ,.

^^ airplane to values which the simulator can produce without exceeding one or more of its . design limits., The ` washout routine also attempts ^' - ^, ^` to drive the simulator legs back to their neutral position following a disturbance from equilibrium in antisipation of a future disturbance.

,` ^ :This "centering" . routine is to allow for maximum displacement during $: -some future motion, and the. motion due directly to this portion of the routine is-designed to be of such magnitude that it be sdbliminal to the simulator occupants (1$)., (Time constants of five seconds or ' r -greater are characteristic of such mot Ions.) ^ .

..

, i r^,, f !^'^ {t INTERIOR CABIN OF THE VISUAL MOTION SIMULATOR FIGURE 12.

w

w

_ R, ,.

i h - CONTROL _ CONSOLE ...# .VERBAL COMMUNICATIONS CASE IiNK NUMBER Y `..

CENTRAL DIGITAL COMPUTER RMS QUANTITIES LINE _ ANO COMFORT RATINGS PRINTE^t FLIGHT CONDITIONS FOR EACH TWO MINUTE _ INTERVAL OF OPERATION STABILITY DERIVATIVES SIX DEGREE-OF-FREEDOM EQUATIONS OF MOTION CONTINUOUS STRIP CHART RECORD OF - GUST MODEL RECORDER. PARAMETERS RMS CALCULATIONS WASHOUT SYSTEM ANALOG TO DIGITAL TO DIGITAL ANALOG CONVERTER CONVERTER AIRCRAFT COMMANDS FOR MOTION- BASE COCKPIT CONTROL -- MOTION-BASE SURFACE LEG MOTION .AND DEFLECTIONS COCKPIT INSTRUMENTATION DISPLAY PARAMETERS VMS.

^^ FIGURE 13. BLOCK.DIAGRAM OF MOTION-BASE SIMl1LAT0R APPARATUS ...

^[^ _

..__a^^.,. _._

I

^M.-.

A detailed description of the physical dimensions and the performance specifications of the VMS may be found 1n References.:..:(18), (19), and (20) For all tests the pilot was fio perform an instrument flight rules (IFR) task as;d was given no visual or ' you -the-window" cues. This condition was chosen to provide the pilot with a representative workload of cockpit duties and, at the same time, somewhat simplify the simulation. Aride-quality subject with past

...experience using the U.Va.-developed 5- point ride-quality ruing scale

and. actual in-flight ride-quality evaluation experience rode aboard.

rT ,, a the simulator with the pilot to evaluate the ride quality of each rr I; ^ Like the pilot, the ride-quality suitiject was given configuration.

no visual cues, and the flight-instruments in front. of him were ^_, { The pilot used in the simulations was a fully instrument- covered..

_ : rated pilot with over 3000 hours of fl-fight time, ^ The 27 tes^ cases were. run in random order three times each, with ^^ .:

each test run lasting lb minutes, Each 16- minute segment consisted of

_ For the first 10 minutes, the pilot is the following. subsegmen s.

Y During this time, the ride- J^! instructed to fly straight and level.

quality subject on board the simulator evaluates the ride quality every ^' For the next two minutes, .the pilot execu es atwo-minute M two minutes.

A ^: turn in which the aircraft changes heading by l80°, descending 304.8 m ,` (1000 feet) for the first minute and climbing 304.8 m.(1000 . feet) to r w-.:.; the original altitude in the second minute. The. ride-quality subject ^?- evaluates the ride of this two-minute segment. The pilot is then ,^ ;^...

asked toexecute a second. two-minute turn, identical to-the first, and ^^!

_^; return to the original aircraft heading.. Again, the ride-quality ^, , __ ^^.

^ ^:`'

i_

i

subject evaluates the. :ride of this segment. In the final two minutes of each run, xhe pilot is instructed to separately pulse the elevator, better evaluate the handling aileron, and rudder to enable him to .

qualities of the particular configuration being investigated. Simul- taneously, the ride-quality subject evaluates the comfort levels of the motions produced by each of the control pulses. For the study-at hand, only the ride-quality evaluations taken during the straight and level portions. of each run will be used_for analysis. ..Evaluations taken during the turns and control pulses are recorded for ,possible future use. Following the run, the pilot`is asked to complete a questionnaire rating his ability to maintain straight and level flight, and give his opinion of, the overall handling qualities of the case - - being studieri using the Cooper-Harper :rating scale (21). The Cooper- Harper scale is a 10-point rating scale used by test pilots to quantify pilot opinion of aircraft handling qualities, with 1-being _ ; ,: most desirable and l0 .being almost unflyable. Also, the ride-quality.

subject is asked to -give an overall rating of the ride quality of the t.

..

cruise portion of this configuration. Samples of the rating forms used t by thepilot and subjects are presented as Figures 74 and 15. ,: During each run, continuous strip-chart recordings are made ., displaying time histories of various aircraft parameters. These- nciude the .three: linear acceleratonsand three angular. rates of the aircraft in the body axes, eleva or, aileron, and .rudder deflections, throttle position, attitude,. - rate of climb, airspeed, and heading, as , :, ...

well a a time channel indicating fibs times when .ride-qual"iiy responses r^ ^^ are taken. A sample output is shown in Figure 16.

. - F ._ Case Number Date Rate the following using the Cooper-Harper scale: Your ability to maintain straight and level flight

s

Your opinion of overall handling qualities Do you have any particular comments regarding the handling qualities of this configuration?

Cooper-Harper Scale DEMANDS ON THE PtIO T PICQT ADEOUAC`/ i0i1 SEL(CTED TA:,If OR ^ AiRt,RAFT CsW RAC TER15T1C5 ^ SE t.EC TfD IASrc 011 RE OU^RED Iw AAr,ON• AT _ RLOVIRID OP`_RAi ION •

u

C E•cdient gaol caroeMatrwr not • IKta la -- Il,gnty des^roWe • oes^e0 pe^ramona I Chid ^---'---- -^ Pdpl cornpinfOlrpn not o tetta to 2 Neyluppk dthaenUes ^ OeareO ptrlamance rnw Sore mildl y -- — M^rlrmol pap compeMOUOn rtewred to unpleosom dNrcanaes dewed p«tamonct ^

a M^rvv Dul ortoyvtq

res Des^re0 Dt r lamonce reQuvee mooerote WIrC4rr.Re p101 CompeMOl^pn Is ^t DeLaencnes Mpdtr0l^ pDlec lrpnoDle A7lOuOte Dlr lOr mOnC! rtpo^rff sot^sbcray .annul ^ onl .wir • cons^OtroDl! D^iot comoensol^on ^ ,nprOVlmtM 7 O[IKrcmcaM ^mpr o. emMt OOKC1rOnODtt Dut Aoepuat! DNlamonCf reQWH l^tMw•e

0 VMy

tderoDk dthUenUtt • plot cOmpcnfOtron ^e s A^feouole perlamonct nil onanode w^tn ma.^mum roWoDk p^bl compenson pn 7 Mapr del,caenuel

0 CaurdbDrldy not .n euest,on

s a0eouot —., Datornmre Orhutnckf — -- _ No Cons^OtraDle Dtbl co mDensorron s repuned 7t,obk w^tn a rokrogt ' to"" e Mu,a oe6oencw•s ^ P'd .asbod^^ to caurd To •o.emerr ImMSe gent cpmpMSOt^on n reewred to Moto oelKyrrues 9 relOm control

^^

Is ^ of rMwed' No ImprovwnreM qsl yr^nq sane pprrrpn .t wnlrouaDkJ Mn,a rfelKrw+caes ^^ aluyi^^ ,ll Df t0 mon0otpr ^Dehmnon pt rlowred oplror^On ^nvrdrts Oes^Qnpt.M of 1b^M d+oU ono/a su0pn asr5 +^tn Rbl OlC^SgM OCCnmponyinQ copd^hpnS FIGURE 14. EVALUATION PILOT'S HPNDLING QUALITIES RATING SHEET

t

4^^h P^GL^

r

^?U^ ► ^, Case Number Date What is your overall opinion of the ride quality of thts configuration '^ ^.-x this configuration `^ Rate the overall ride quality of ,, t - _ _ !.

t F Case-Number ^ Date ^; '' is your overall opinion of the ride quality of his configuration? y^^ ^; What { .- a .

;, -- L ^.

t this co^tfig^^ration Rate the overall ride q^ai-ity of ^ :^.

,.

t r ...

y ^ i (.

_, P ..

s`?

.; ; ^ t ^ ..

1' X..

^4 ^^ '^ A FIGURE 15. R I DE-QUAL LTY TEST SUBJECT" S^ ict1T1 NG SHEET - 38 ^: '.^.

^r^ ^ ^^^

6e - Elewtor - _ ^ - _ -_^ I pn DeEIK[ion _ _ ^ v Acu I Net _ ^-`^- _ t I ^y ) t ^- y leeyrees "^ ^ _ y`__ _ _ - 0.1 1 ^ _ - _ - ----L.:.

8 9 6 e -Aileron `--.. __ _

Del I t i on -^''^-' _ y'`^ry^ _ __ - AccelNet ion _ K (eeyrHet) _ _ ^` -10• _...

^: - - - __ t0 - - _._ _ ^.t^ + - Nveeer 2 - wrttul ^{^,t^ ^MMw...'w^.^M. ^'Y' 1, Mi^t^NAI•Ar^^`St^'r'`/"'''^+.Lr^'^Mj'+1•^\ Oef I K t i on --..'—^--^ ^+.-^- Acc''Net{ p 1 i/1 (eeg r p f ) -/0+ - r ^ -e.1- t _.____ 1..

._. __ ,^.

15- dt - TMOtt le hell

r _ ^a. ^, .^

root ion --- - - --_- INSreee/ tK l (percent) 90• •1 ^' i I _._-_-. -- ^ --. ___'-^ ^ _.__ ^.

2000• {10 1[- - IYE TE•S1 h - Al titu0e e _ d eek Mte /Av.^n (eyreet i sec ) Ifoet) - -{10 -1000 • ^ -H' f_ 1_ x - -- .^^ ^ _ _- ^ -- • 10.1{ 1H _ ,- .^_ _.

— _. _._ j Ir[f[R!/1[C 1 ^ ^_ - ^ -Mete of r - tit twb . ' - — Cl iwk - -^ - — -.^ -a /sK) (u/rhs ..r4. -._-. ._ (feet /wIn) - - -- - - -_ -_ +-u u -[000- _- t so- Alr - _ - - - — ^ - r - so..^ n«+ Ikrots l -30` . ^ ....- ..

-- -^ w.

- ^.

_ - ...

- -_^ } - IbM I ry Tlro (M7rNf) - - .ice , .,.

_ _ .

_I^p- `` to to s[c scc FIGURE 16. TYPICAL STRIP-CHART OUTPUT OF FLIGHT PARAMETERS (LEVEL FLIGHT, Q = 1.524 m/sec (5 fps))

w

^D ^.-._. _ t ^.-.. _ r( ^^ ,.

In addition to these measurements, the main program which controls ` the simulator computes rms values for the three linear accelerations, three angular accelerations, three angular rates, and a'll control ^^: deflections for each two-minute segment of each run. A sample output is shown in Figure 17. Rms values of the motion parameters are evaluated for both the values predicted far the real aircraft by the six-degree-of-freedom equations ,of motion, and the values computed to drive the simulator after accounting ..for the washout system. Using- real aircraft and simulator rms acceleration variables, comfort ratings are computed for each two-minute segment by empirically-determined linear comfort: models contained. in Table.LV (22) .-..The-particular (23) comfort models used in this portion of the study were chosen because they were. more advanced than the one used. in the preliminary study.

.:The first mode} incorporates motion in all six degrees-of-freedom and the second applies for cases where lateral motion dominates. Both models use rms accelerations as the defining parameters, end-use. of morn complex models . would not. be warranted for this. study; Finally, an ;inertial package is placed aboard the simulator to sense and record the motion of thesimutator itself for comparison with the values of the computed parameters and to evaluate the errors "between the driving signa,Ts after washout and-the actual motion sensed in the cabih of the ^t .- _simulator.

:# .W.

i^ f ^i _ Y.; ; r ^^^ }^ ^^.

^.^^ .

,._ " z 4U ., x

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CASE NO. 17 Rl^l__ ► ^W. ♦ _ _ GATE Oe/21/14 _ _ - b - - 9 Ti u d^TlGl ► IRU / / ► / / vOJfl61 rOJfIGI SECT _ JIRD SECT t, IRO/SEC! DOTIR 521 pOQTIR Stl ROJTIR 21 C.R.

-- - - `+ DEl E OEL A DEl R OEL T MIEOlCIEO ^ .02126 .Oe)S• .06506 .05456 .Ol2W .02055 .0• 4 .04 .3^I^4b z.17 u u ._ .ot ul .o3sa4 .00elb_ .01947 .00sbt .oosss .o344t .oz24a .0 93) .7I 1.13Y17 .ee47[ .34901 5.86934 ^-I.^! __ ___ Mf01CiE0 ^ _ __.01582 .05199 .05837 .03526 .01254 .01004 .07536 .04409 .00%B AtTUA: .00186 .0224tl .OJtl84 .01419 .00571 .00451 .J 90tl .J 2 -^ 6T3^4^^Z4 .16260 5.96915 1.23)itl .S 127 ► REOICTEO 01554 .06666 . 164 .6^Td- 3Ii^I =.72 .01523 . 05560 .01312 l er.tilA^ -"-^ Z.S6 ^^^.00812 .029W - .JOe17 .01813 .00 6 L.26407 .6639) .2e698 S .e3 67S vwtOlC f0 .u2o23 .07469 .0559 .046 .0 _ _ ___ ^LTUAI . 00976 . 0)021 . JOel6 . 01631 . 00538 . JO6AS . 0 2 .J Z f.bu _ .71486 . S.d 183 - ---^- - ^ - ^- - L108)6 ?1523 lf7 .06345 .07984 .0!971 .01619 .5141 c ^ICIfO .J1111 ^ .02581 .W Sl .0164_ .0 b 0 ^- _____ ^^ _ __ •01109 _.____ _. ___^ 1.21205 .• 816 .24194 .8eb59 ^i I11f01CTF0 .o4tlss .14111 .15450 .06693 .026 6 .13155- Ti I'b .

a^IY^A _ ____ .o2ase .oss14 .00ess to __ o .oa^ 5'3 bf^ . ^ _ _ 1.32233 1.88327 .x131• S.e2328 _ nrso lclEO . oslos .143zb .12211 .os 4 .o2ro .w .otbes .osws -- .ooess .o w• .00 -^6^ .o s -T.TT- ^Gf^Al _ - .92308 L.640T3 5.99040 .e2524 - -- - - ------ - - - ► 'REOICTEO .03951 46Y .tb2 ^ .09207 .ON2l .0 645 .l -^T^ -- .0• 4 __ 9 .0 U ACTUAI .02lJ6 .04SJ3 .01001 .02062 1414 .00912 .04 6 .0 1.71015 2.07675 .55912 5.70115 FIGURE 17. TYPICAL COMPUTER OUTPUT OF RMS MOTION VARIABLES AND PREDICTED COMFORT RATINGS t r TABLE IV COMFORT MODEL T = 1.85. + 11. S a N _CR + 5.7 a + 1.O a^ + 0.2 a + 0.2 a + 1.5 a ROLL PITCH YAW (aN > 1.6 a T ) ^, a N ,^ 20.9 a T ^ (aN ^ 1,6 aT) P;R = 1.9 + $.1 ..^ where aN = normal. rms acceleration (g's) 4,' =transverse aT rms acceleration (gds) _ " longitudinal rms acceleration (g's) a^ = angular acceleration about X body fixed axis ^ -rms a ROLL .^ (rad=ans/sec t ) '€, a _ rms angular acceleration abou Y body fixed axis ^.

,k PITCH (radians/sect) =rms angular acceleration about Z body fixed axis aYAW F (radians/sect) ^ s^ CR = comfort . rating where: 1 -very comfortable _, ^ -: 2 -comfortable 3 -neutral w^^ 4 -'uncomfortable 5 - *ver uncomfortable Y ,( ^ ^^ t ^.

; n Y om .

r 1.

.< i(

;, 42

^^ CHAPTER IV RE5ULTS AND CONCLUSIONS ^g From the data collected on the VMS, several statistical quantitlies .

^x were computed for each separate test. case, i.e., each unique set of stability derivatives and aircraft :handling qualities. Computed were -- means and standard deviations of the comfort ratings of each; test case, `" These quantities were found .for. the comfort ratings predicted for the actual aircraft, the ratings predicted based on the actual simulator :^ J motion, and the comfort. ratings elicited from the test subjects riding y^ aboard the simulator. These quantities are tabulated 'in Table V.

Also, typical .power spectra of the three linear accelerations obtained from measurements made by the inertial package. placed aboard t'he .,, ^^' simulator are . presented in Figures and 20. The rms acceleration 18, 19, ., .^ uu quantities obtained from. this inertial package agreed within 10% of ^' those computed fir the simulator after washout by the .central computer, ^^^^ indicating the computer-generated quant ities were valid. Only the- ;^ ^i ^^" values comput^^d and recorded during the straight and level: portions of ^^; each simulator run were used when computing these statistics since it is ^^ the ride quality during the cruise portion of flight which is of primary r^ ,:^ ^^ interest in this ^2udy. Thus each mean and standard deviation is based ^: ,^,^ on 15, data points since each test case was run. three different occasions, ^ ^ `, *^ and five ride-quality measurements were .taken during the 10 minutes of ^; straight and level fl ight'of each. run.

Comparing the mean comfort ratings for the 27 test cases. as i; .. ,, computed from the er^uations of motion of the real aircraft wi th the

w^,,_.. ,_.._.._

j Based on Actual Based. on Predicted Simulato ► Motion Subjective Response Reap. Aircraft Motion Case CR CR Number CR _Q CR Cit Q CR

.13 ' 2:.03 .04 2.00 .00

1 2.70

2.07 .26 2 2.97 .12 2. 13 .0$

.08 2 . oo . 38

2.7 t ,13 2.11 .10 2.00 .00 4 .13 2.10 2.91 - .#6 2.U8 .08 2.27 .l0 _5 2.53 6 .08 2.07 .05 2.13 2.88 .35 .00 7 3.60 ,62 2.06 .04 2.00 .08 2.00 .00 8 2.64 2.09 _.OS 2.i1 .08 2.00 .00 9 2.60 .14 .07 2,.03 05 2.07 .26 10 2 .80 .

.06 2.00 .00 11 2.63 .06 2.09 2.07 .07 2.13 T2 .35 2,'57 .09 ,^9 .51 2.16 .08 2.40 13 3.61 .16 .49 14 3.04 .65 2.34 2.33 .Og 2.17 .05 2.87 .35 3.39

2.2 7 .46

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^ ratings based on the commands to actuate the simulator motion,-one R finds very little agreement between these two quantities (see Table V).

-_ ^.

Tfiese results are due to the physical limitations of the motion-base cockpit and the corresponding washout routine which controls the move- .merit of the simulator's six moveable legs.

This implies that the VMS was not capable of reproducing the ride quality of a given aircraft configuration on a one-to-one basis for the present study.. This is, of course, due to the washout system and the displacement, velocity, and acceleration limits of the simulator. .The correlation coefficient -as computed, by n ^ ^xi-x) ^Y i ;Y) n-1 i=1 r = q a o xy between these .two quantities is r 0.75 however, indicating that q although the motion is .not.. being exactly reproduced as intended, there z s is a definite relation-between the simulator ride quality and that of an actual aircraft.

s Comparing the mean comfort. rani rigs computed from the commands to- move the simulator legs with the . mean of the comfort ratings recorded ^.

^ by_theride-qualtysubjects riding aboard the simulator, one finds theagreement for most cases to be quite good (see Table V). The f correlation coefficient for this data is r O.:^sO. Part of the.: ,^ it ' discrepancy between the two seas of mean comfort.. ratings may be } ;, accounted for by the. fact that. the comfort. model used to pred ict ;; `` comfort ratings based on rms accelerations is a continuous function ^.

- - - - ^ ^; while the actua rating scale_as defined and used by the test subjects >4 '` ^; 48 ,, I I

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is an integer scale. This also accounts for the low correlation ,,.

coefficient 'For this data. Also the number of responses used in it x:.

f ,^ 1n spite of these determining each mean was somewhat small' (n = 15).

^^- - limitations, the. .agreement between these two suggests that the experi- enced ride-quality subjects were indeed responding in the "proper'' T, (predicted) manner to the motions to which they were subjected, and further validates the empirical comfort models, This tends to support- -the theory that ground-based simulations for ride-quality studies may be of significant value .,. if the desired motions and environmental ^- ^" conditions being simulated are acceptably reproduced 'in":the laboratory.

Using the previously-described transformation (22) which translates i' ..:-; a comfort rating to the percent of tfie population satisfied with the .^ ride, the satisfaction Tevels of . the comfort predictedfor the real ,» aircraft for the cases when the longitudinal short-period handling ,^ qualities were varied, are plotted in Figure 21, superimposed upon the contours of short-period handling qualities. In arsimilar manner, ^^n .M variations in the lateral Dutch Roll mode handling qualities resulted in the. satisfaction levels shown in Figures 22 and 23, platted along with contours of accepted handling qualities for the Dutch Rol.1 mode.

`^ ^;^: From the data of Figure 21, lines of constant satisfaction 1eve1_have ^^ been drawn and are shown. in Figure 24`along with .the contours of constant handling qualities for the longitudinal short-period mode.

^ ^^` It is recognized from this .figure that ride. quality is indeed a function ^" of the parameters which define: short-period handling qualities, namely W n and ^ s . Thus atrade-off exists between longitudinal handling s qualities and rile quality. Hence., from a design standpoint, the .: ^.

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designer can choose an operating point and know how both the-handling qualities of the short-period mode and the corresponding level of ride quality would compare with some other design point. This would enable the designer to weigh the trade-offs between ride and handling qualities and help him make an intelligent choice of an operating point for good.

handling qualities and give him an idea of what level of passenger satisfaction to expect from his design.

'Similarly, from Figures 22 and 23, one can identify trends of improving ride quality as. defined by parameters in which lateral Dutch Roll handling qualities are defined. While it is difficult to con- struct contours of constant. ride quality due to the sparsity of data available_, the previously-observed trends hold. Namely, decreasing C ,^ T,^ and l^/ve l d tends to improve ride quality and raise the d ^ percentage of the population satisfied. with the quality of the ride.

Thus in the lateral mode, good ride quality is complimentary to good handling qualities of the. Dutch Roll mode. It is worthy to note here, however, that..while these regions are complimentary, there is a sg- nificant amount of varianion -in the percentage of passengers sat isfied over the region where Dutch Roll handling qualities are judged satin- -factory (68 - 85 %). The-.designer should note .here that .simply _ designing an aircraft with _satisfactory Dutc h_Rol 1 handling character- ' istics is not all he should strive for from the ride-quality standpoint.- He should realize from these. figures that the further he can. move his ^' operating point away from the boundary between-acceptable and unaccept- ,' -able handling qualities, the more he can improve. passenger satisfaction as well as improve handling qualities; he may be able to .improve _ passenger satisfaction by up to 20% of the total pas g ingers carried for a design of similar wing loading and equivalent turbulence conditions It should be re-emphasi2ed that all the measurements as the test case.

taken . we re on-one particular design, one flight condition, and one turbulence level. One would not expect the values produced by this • study to be universal, applying to all conditions and .turbulence levels; f . and. the however, the general .nature of the isocontours for ride quality .'

other trends outlined should hold regardless . of wing loading, turbulence level, and flight conditions.

Ifi one takes the linearized longitudinal equations of motion for the free airplane with controls fixed, eliminates the forceequation in- +^ the X body axis direction, and assumes variations in u are negligible, „^ A one obtains an approximation of the short-period mode (24). From these equations, one may develop an expression for the normal acceleration as a functionof w, the forcing frequency of an imposed sinusoidal gust ^^ oscillation. integration over all forcing frequencies, one obtains the following relations for the rms normal accelerations as a function of the. gust magnitude, wg, the short-period undamped natural frequency, ^"' wn and the hort-period damping ratio, ^s s _. - Kt^W^ (t-k^5)2 l^ - - - ^ _^ ^ .^ ^l I K3'wq (1-k^ )2 s N a ^ ^S > 1 ^ s2-1 ^n s where K l , K 2 , K3 , and k are constants. Derivation of these relations may be found in Appendix E.

These relations, while derived by using the assumptions of controls fixed and allowing only sinusoidal variations in gust velocities., _: exhibit the contours found experimentally, Holding constant, these ^s equations all predict that as theshort-period undamped natural i s increased , a frequency W n N i s decreased resu 1 t i ng i n an increase i n s passenger satisfaction. Similarly holding w n constant, a N is decreased s as increases. below ^S i ; s = 1, predicting an increase in satisfaction '< 1 . Also, a N i s i ncreas^d as for i increases above 1 s ^S ^s > 1. These trends agree predicting a decrease in satisfaction for ^ s with those observed experimentally in Figure 24.

The effect that variation of the turbulence level could have on the ,contours of constant ride quality may be studied using this mathematical model. _For a givenconstantpassenger satisfaction contour, the corresponding comfort rating may be found using Figure 4.- Tfie rms acceleration required to produce this Tevel of comfort. is determined from the simplified comfort model (Tab1e'lI) neglecting _ - ^ transverse acceleration-.terms, Since the normal.. acceleration -is ;^ dierectly proporr_ional to rms turbulence level, one may find, by an` ^: inverse method, contours of cons ant passenger satisfaction for any- t ,.

;^ turbulence .level; For example,. 6W = 0.914 and 2. 134 m/s {3 and 7 fps) _, .

;..

;, result' in-the following ;satisfaction levels: y .

+y Ql if E t^ k ow ,s Satisfied (3 89.6 a$,7 86.9 0.914 m/s fps) 8z.o 1 ,, .^ :R 1,524 m/s (5 fps) 87.0 85,0 80.0 63.0 /s (7 fps) 83,6 2.1 34 m 82.,1 '72,0 44.0 ^_a Y These results are .plotted in Figures 25 and 26. For fhe contours shown, Y::s passenger satisfaction varies. only 7.6% for Qw = .914 m1s (3 fps}; how- ^.

ever, fo^^ a w = 2.134 m/s (7 fps), passenger satisfaction varies 39.6%.

,^ ^_ Thus, for flight in regions of heavy turbulence, the selection of short-period characteristics could markedly affect the degree of ^' passenger satisfaction.

a ' ;.

^ ^,,p The pilot's evaluations of his ability to maintain straight and ^2 level flight, and his opinion of overall handling qualities for all test ^.

.cases are tabulated in Table V1. The pilot made several trial runs on ^R ^.

seYeral test cases before-actual testing was begun, and these are also ^, included in the table. Thfis was done to le.t the pilot gain familiarity ^,; with the. simulator, its controls and instrumentation, and use of the a- Cooper-Harper pilot-rating scale. The results compiled in thee. table - contain the pilot ratings for all test cases listed in the order in .^ which they were taken> dncluded,are the trial run .cases as well as the three test cases, dur;ng which ride-quality measurements were taken.

tteferring to Table 11t,'one can see that for most cases, the pilot was E^ consistent- among the three ratings he used to evaluate a particular case, or agreed closely on-two of the. - three , evaluations, Ony on one r p, case, number 25, did the pilot return.. three substantially different ratings for-each test run. finale. column #tr:^ The in Table Vi 'lists the . ,F_ ^.., ;:.

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TABLE V I (- PILOT RATINGS (COOPER-HARPER SCALE) Ability to Maintain Opinion of Predicted Case Straight and Level Overall Cooper-Harper ^ Handling Qualities Number Flight Rating 4, 2 3.5, 5, 3 3, 3.5, 3 1 2 , 2 , 5, .

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predicted value which should be expected for each test case, These.

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.^ by the two are in good agreement.

^. # (' For the short-period . mode, the cases with good handling qualities ' (ratings of 4 and less) . were not as close to the predicted values as F^ 'a^aw I were the cases where t,he handling qualities were not good ( ratings of r r^ ` or more), 5 For the Dutch Roll mode, the recorded ratingsagree. well ^; F with.: the predicted ratings for low Cooper-Harper ratingis (be low 4) aid ^ ry' >; high Cooper-Harper ratings (above 7); however, agreemet,t for marginal F ^; `' t' ratings (betw5een 4 and 7) was poor.

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^

-Also, there appeared to be a qualitative relationship between control activity and pilot opinion of handling qualities. Figure depicts the variation of elevator activity for typical cases in which.

the longitudinal short-period characteristics were varied.. As is { evidenced from. .these traces, average Cooper-Harper rating of handling E^( qualities increased as greater elevator activity was required to ^^ maintain level flight. The activity of the other control surfaces E remained essentially constant while the short-period characteristics were varied,. Similarly, variation of the Dutch Roll mode character- M .,^ istics (Figure 31) were accompanied by changes. _in aileron activity, ^^ Higher Cooper-Harper ratings were accompanied by increased aileron ac vity necessary to maintain straight and level flight. Thee P^ apparent activity levels of the remaining control surfaces were ^- constant as Dutch Roll characteristics were varied.

- .The only quantitative measures of control activity obtained were ^.

rms values of the control surface deflections,. This measure was.

. ; Bound to be unsatisfactory for determining-control activity, due . to thetime averaging process involved in computing an rms of a parameter ,: which is very small or zero for a substantial portion of the averaging _ _ ^- ^.

period.

case of elevator rms Also, in the deflection, i-t was not possible ^ to exactly determine the equilibrium elevator deflection and bias this.

- value out of the rms calculation. Another measure of control activity i` should be used in the future to quantify the. activity level.

Such ^` a i quantihies as the ,percentage._of time the control'surface`deflecton .

i •

i

I

i ,' r ^ I , ^ i, l ^ ! ^r ^^ ^ ^ ^ ^ FR .I l^

I

S -Elevator ^.

r.

1^ 1 e Deflection (( « i (degrees) ;I -10—^ ^ ^' .: Light Activity, Case #1, Average Cooper-Harper Rating •- 3.0 Predicted Cooper-Harper Rating 3.0 ^— 30 sec. ----•^ r , 1 ^: ^ rr^ 1 ^^^ ^^^ !',^ ^^^ ^ ,`^' `^ ^ ii il^ ' i . ' alt: 10 r{r- , ^ ! , T' ,^ i (^ ^ ^^

G:{^ r t t- .t^ ^', ^` ^ ^. ^= ^ ^

U — Elevator ^ _ .,^^^._.^- :I^ ` ,,.

1 ^.1

e ., Deflectior^y^ ^, ;j ^.^ ;^^ r~^ (degrees) ..^ . ^ . , ^ ^ ^ :., j t . G ' ^ i. ^ ' t s.

t^ 1 ^. t ^1^^^^^.^^_....^^ i w-^._^,.^1.r'f I^.^ Moderate Activity, Case #6, Average Cooper- . Harper Rating =_S.0 Predicted Cooper-Harper Rating = 5.5 l0 w.^^ ^^ ^ ^ ^i ^) r ^ 1 i c f ^ .a ^.._. _^: ^ r ' ^ III 1 I '}, ti .1.' .i '1 t d j _ ^ ^^ ^, ys: ^ ^ ,1 I ^^ ' '+ ^^^!^^^.

Elevator , _ ^.: ^.

'.^ •{ ., se ^ ^" Deflect ion - -^1 ^, ^-, ` t ,- . , _ :.^ ' e _ ^ r.

(degrees) ^ '^ j ^ , ^ ^ , r ..

^ .

Heavy Activity, Case #20, Average Cooper-Harper Rating '= 6.0 Predicted Cooper-.Harper Rating = 8.0 Fi_GURE 30, TYPICAL ELEVATOR ACTIVITY VARIATJONS '' ..., ..3 a p ..

E ^^ , ' 'k ^._. .'. ^._s.;_.^ A Pt Rv F j ^ (i ^ ' 'I t ^^^ ;' a 3 t t f^f^ I ' a 1 t :; ..a r ,: 10- .. } ^ ^^ I ^fi" i, ^ It'" -,; ..^.^ ti :.^ :.1J , ^. c..^ , ^t .^ t - 1 ► 1 i ll ^' y` f1,{.t.. It^t ^ ^ L ... ^ aikl i '^ .4 ;1, 4,;! ^{ Sa - A i 1 e ron .^^ •'' ,. i{ ^1 ' 3^ , ^ i ^ ^ : i :^ Deflection a't .s .i ^ ^--^ ^^ ^a^ J ^ ^^ r ,• t7^ tv ^' r ^1.^ ^Ir a id ii ` t } ^i ^ t.l i ^^ LT * t '^ t (degrees) t X 3 1 a^.j7 i^^ a ^1 ^^ u _^ ` tks ^ ^ ^. a l` ^' -^ ^^ tr;.^^i } ) ^ i ^ ^`^. 3't h ^i 1 Ili t^ ! 1 1^ 4 a ^1 ^( ^ ` a 3 r^ i 1 tt a i ^ t ..f ^'..

1 ,.^t ±^ L a ^I fff ^1{ ` I 1 ' i.'

t^ ."t'^ } i 11 ii ,t! ^`t ^ I ^ { -1^- V^ ` il 1a t' . .

,..L^^.^ j . t- !^^^ _ ^.^1 ^I...^,L.

. 3 . .^. i_:J ^ 1 1;.^^ ilr.l Light Activity, Case #1, Ave rage. Cooper-Harper Rating = 3.0 " Predicted Cooper-Harper Rating = 3.0 sec _ ^•-- 30 ^^'^^l, .^ ;^ .tom ^ .i^. ^t 1 ^h h IS ..4 ^ .I ^ ^ ' t iJa ^ 3 ^^^ i 3.^ i k i f.;` ^ }ti .t.

:, 'j,. ^,^ ; MI ;, !

:' ^.,. ,^,. ^ .x -Aileron ^^ '^ ;] i.''^ a .. Deflection '^ 1 ^ ^ i t ^: '^,^ ^ ! ,^ ^-r .^ ,'+'^ -' _ (degrees) '" " '' ' ' ^ ^^` .!. ^ 1 ` i , , ; a ^ ,'^ iii ^ r _1.

fir; , i-^ ^: 1 1 `'- ' :r t, i i i ^l f `^ ^ ° 1 f'-1 '^ ,^' , ^,, ^ a ` ^ Activity, Case#15, Average Cooper-Harper Rating = 5.7 Moderate Predicted. Cooper-Harper Rating = -6,0 —r f 10 -+ ^ -^ i a ^ .^ ,..,^.

: ^. 4 1 a ^ i ' 1 . fit.

^ ^ _^ I. ^ .^ ^ 4 3 i T_'r..

t Y : i t ^ ::.i w.

S a -Aileron ,i^ T^ Def l ec tion I i , ' ...

^ (degrees) ! d i t^ 3 I -z.^.; ^.,,.. a ^ ^'!, .:.r.° .. ^ +t:.

.. }.'° f ' ?^ .3.'

^ ^'^t ..^ ^ -^oJ .t ^ ...

^ I I +; r ....,...

9.7 Heavy Activity, Case #26, Average Cooper-Harper Rating ^^ '^-' Predicted Cooker-Harper Rating _ 9.0 ^ F1GURE-31. TYPICAL AILERON. ACTIVITY VARIAT"OHS k ;% , . a ^^ axce.eds a specified value or the number of peaks (max or minj per unit r time experienced by a control surface may be more meaningful than rms i for defining controlactvity,.

Taking tfie latter measure and wing a 1.5° threshold for both-the elevator and ailerons, the total number of exceedances was determined.

Figure ,32 shows how elevator activity varied ^5 the short-period handling qualities varied. As seen, this measure of pilot ac ivity increases with undamped natural frequency and is not complimentary with the-handling qualities eontours. The trend implies that. the pilot uses more elevator motion to maintain straight .end level flight when.

the short-period frequencies were high, possibly because he is not physiologically able to react rapidly enough to control a disturbance.

In a s imi lar manner, the number - of times the aileron exceeded: 1 .5° in magnitude is .plotted in Figures 33 and 34 versus the .Dutch Roll handling qualities. In thi case, this measure of pilot activity is directly related to handling quaiities and the .region are complimentary; that is, pilot opinion of a configuration is worse when more aileron activity is required• s t u t -.

'„ ' 68 ,^ -, , ^^ 1.4 !

u ^ UNACCEPTABLE _ ;

HANDLING

1J 23.3

O

Q !.2

QUALITIES

^^ ?

:: O

t•-

^

13.3

z ,,,,, 30.0

O10

N 10 p

p6.

W T

SATISFACTORY

p, ^ HANDLING

c

QUALITIES

12.3_

a

0.8 0

_ p ACCEPTABLE

4.3 0.3

HANDLING

Z ^

p O 'S'.6ODUALITIES

O 2.T

Z

O

^ 0.6 ^

o°

a 2.0

W ;w 0.2.0

a^

O

^ 04

O O _ n .^

^ UNACCEPTABLE

0.2

N L HA D ING

QUALITIES

0^

_ 0.1 0.2 0.4 0.6 0 8 L0 2.0

n ;^ ;,

'^ ` SHORT PERIOD DAMPING RATIO, S

^^ — {' .,

x^

^

`' FIGURE 32. ELEVATOR. ACTIVITY, SHORT-PERIOD HANDLING QUALITIES

^^ ^ _._ [-, ,

I- i f

LL. 3.3

E

5.6

..

J

O

a

.

O

a. 2

s. o

O

~ O

12.6

SATISFACTnRY

W

HANDLING

s

J

QUALITIES

3,p ^

U

>- 3 2.5 ^

c.^ ^, p

3a.o

o w

o ^

W

= UNACCEPTABLE

I"" m_

HAN DLIN G

^ ^ QUALITIES

^ z g

Q 66.6

W ^

50.6

O

-I^.!

z

_ 1 T. 0

^

0 1,0

2.0 ^.0 4.0

,

^^

^/ Ve I (deg

/m/s )

r R(J

LL- T0-SIDESLIP PARAMETER °^

;.

_ _

;, ^^.

;^ FI'GURE 33.

_AILERON ACTIVITY,-DUTCH ROLL HANDLING QUALITIES ^, (11C^ vs. ^^ /ve^ ^; _ ^;, ;; 7O ` ^ ^ a,, _ .,^ .^:a. s_.,... . , ^ a .

.... __ _ _. __,. ,- .._ . ^_^. -,^.m,^...^ ..^ .^-^.....

-;^

p

3.3

1.0

8.0

O

p 4.2

_ 1^ ^

^ 0.8

Q

0 3.0

N

SATISFACTORY

0.6

F-.

HANDLING

W

^ QUALITIES

0.4

w

__

W ^

9.0

^ to ^ 5.6

_

^ 0.2

p 32.5

^ 12.6 ^.-^'

UNACCEPTA81_E

W -

016.5

-^' 034.0 _^^•

^ NANDLIN^

d

17.0 066.6

O QUALITIES

z _^^..- ^

=

'^50 6

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

Q

,

0.2

_:

3.0 1.0 2.4

{^/ Ve1 /m/s)

ROLL-TO-^S'IDESL IP PARAM ETER, (o^g

HANDLING QUALITIES, (1/T^ vs.

FIGURE 34; AtIERON ACTIVITY,, Ol1TCN ROLL I^Ive+ v •q.t`} , '^ t CHAPTER V SUMMARY AND RECOMMENDATIONS The interaction between ride and handling qualities fora typical STUL aircraft has been investigated, Simultaneous measurements of ride and handling qualities were :made using amotion-based aircraft -simulator and varying the short-period and Dutch Roll characteristics.

{ of the basic design. After platting the ride quality associated with each test configuration along with the present :requirements for short- period and Dutch Roll handling. qualities, several imp^r • tant trends have been found. There appears to be a distinct trade-off .between longitudinal short-period handling qualities and ride quality. Good Dutch Ra'll handling qualities and ride quali ty seem to be somewhat complimentary, but are, nevertheless, strongly related. It is up to the designers of future aircraft, particularly low-wing loading ' aircraft., to be aware of a vehicle's ride qualities as well as its handling qualities, and the results presented here should begin to guide him in these areas.

Future work. is recommended to .investigate. these interrelation- ships in a much more comprehensive manner.

.More test cases should be chosen to obtain measurements to better define how ride qualities very as handl i'ng qualities are varied over their acceptable regions, Other stability derivatives than the ones used in this stud could Y ^, be, chosen to vary the short-period and Dutch :Roll handling character- sties to determine if individual derivatives have unique effects ors '; ^^^.^LAN^ ^9^^^- C,^ g^i,FJCED^N_ ^ ^, I I I I the levels of ride quality measured. This is particularly important to investigate for the lateral Dutch Roll mode..

Likewise, the. effects of variations in wing loading, turbulence level and power spectra, and flight conditions should be determined by repeating the tests as these additional parameters are changed.

Ultimately,: a general relationship could be developed to define the t _.._t_ _.f ^:J_ ^..^tla.. a.^ Lam. ^...^^^i. .^J ^.G .. ^.. ..^.^..^^L!^.. .^^. i'!.^.^ .. .. ..

,^ ^^ - _ ._ __ .. ^ ^_^.. _._-._ _ - -r^ _ .

- _ __ ,; APPEND I X A UNIVERSITY OF VIRGINIA ANALOG FLIGHT SIMULATOR The simulator used in the preliminary studies consists of a fixed- base cockpit with rudder, stick, ar^d throttle controls.. The cockpit instrumentation includes artificial horizon,. altimeter, rate of climb indicator, airspeed indicator, heading indicator (compass), and glide slope and localizer indications (ILS). The cockpit is connected to two.

analog computers, an EAI-580 anJ Pace TR-20, programmed with the six- degree.-of-freedom. equations of motion, ILS equations, and equations to compute the sum-^of-squares of the. lateral and vertical accelerations.

A photograph of the instrumentation and tfie entire apparatus is ` Figure 1 in the text.. Amore thorough description presented as of - the equipment may be found in references and (26).

(25) ^ ^ ^ Y ^ ..

;^ §^ - ,^ ^._' ; ,` : r ..

•F I -

APPENDIX B DERfVATION OF ANALOG EQUATIONS . OF MOTION The six-degree -^of-freedom equations of motion in Eulerian .axes for a rigid body with an x-z plane of mirror symmetry are as follows {27):

-RU+g sin0 =E X/max

U+QW

V+RU - PW-g sink cos0 =E Y/m=aY

W+PV- QU-gcos^cosp=E Z/ma

z

•-

^ I xz

+ RQ ( I z ^) _ ^^

a^ ^ P - (R + PQ)

x x x r,,.

Iz) (P 2 - R 2 ) I xz _ EM Q + (Ix + PR Y Y Y ^^ (i', z z z r<-^ ^; ,^ ^-, Y .Jl Using the .standard.. perturbation technique (24), the following.

r ^ nondimensional equations are obtoined: ,^ .

..

r ^ - - .^ S ^ Sq' u °+ C _Sq a + ^ C Sq '^ + ^ C Sq a; + ^ - Sq ^ ^ xs ^ e x u xa ^ 2U0 x q ^ 2U0 x a e + C x s Sq^BT = mg6 + mU O C'u + 8a — ;^ ^Vsl T G Sq°°^ + 2U C Sq^^ + 2U C Sq^,^ + C Sq^B r + C Sq^Ba Y Yp r Yaa ^ Y Y^ r s o _ ^^ + cy sq^^ muo C^ + ^ u ^a + V^] T ^ ^ 77 ,

^^^^s WAGE gig

NOT ^ ^: ,.rye_...."

-,. _ _..._ _ p I` Cz Sc^;u + Cz Z Sq^6 + 2U Sq^a + C z Sq^Se C z Sq °° a + 2U C .^ a u 0 0 ^ q se T m^ + C z Sq^S = mU 0 [ec ± ^(^ - 8' u - 6^ dT ^^ C Q Q R bS9^^ + CQ bSq^^r bSq^$ + 2U C bSq °° S + 2U C ^j R 0 p 0 r Sr .. .

^^ a + C Q bSc^S e)I Iy) = ^Ix - (^ + ^ xz + e ^ (1 z - ^^ a ^^ ; m cSq^d e ,^^ Cm cSq ^u `'' ^^^ cSq°°a {. ZU Cm cSc^6 + 2U + C C m. c s^ a a u 0 q 0 a 8e ^»^ Cm cSq^d T = , 81 + (^2 - ^2) z ) ^^ x - I I xz + ^^ ^ I y d e^^ T ^^, , n bSq^^ +, 2U C bSq^^ + C Cn bS9^s + 2U C n n b5q^&r ^ 0 p 0 r dr.

+ C n bSq Sa = biz + (8^ - ^^) I + ^ xy (1y - IZ) °° a These are rearranged .for ease in analog pro-yramming.: An order of ..magnitude. analysis allows the products of inertia and differences in momen*.s of inertia terms. to be neglected compared to other terms in t the moment:'equations,-yielding C x Sq Cx cSq Cx ^ & Sq ^

a a

-' u = - ^VR + 8a - mU^ ^ u - 2mU 2 mU0 :^ p - gq C C Sq ^ ^ ^ ; C cS xd q^ ^ x x'd e _ T z C - —^-- 2 9 + ^ 6 - 3 mU Se m U 8T 2mU^ 0 0 0 t '^.

'^ 7g CYrbSq^ CY Sq^ ^y S`^ ^^ mU0 mU0 r 2mU 2 C S q^ C bS C Ys 40 S qo, _ a _ _ Yp ' mU Sa 2 ^ mU ^ 0 2mU0 - mU 0 /Sq^ + c/2UOCz mU /Sq _ _ - a q6- ^ 0'u mU 0 /Sq^ - c/2UOCz, mU0/Sq^ - c/2UOCz

a

'"^" ^

E' mU^/S Czu ^ . 'app + — ' u mU 0 /Sq^ - c/2U^C z mU^/Sq^a - c/2UOCz.

a a

C

z

Cza d e

a -

,^,. - mU0/Sq^ - c /2U O CZ . mU0/Sq^ - c/2UOCz.

a C ^a z _ aT d ^,- { - T mU 0 /Sq^ - c/2UOCz.

..

bSG^ ^ C^, GQ b2Sq^ C^ b2Sq^ _ r R a - ^ _ - ^ 2UOLx ^ ^ Ix 2UOIx ^^ CR bSq^ CQn bSq^ S _ a_ a r A d Ix a _ Ix ^ ^ ^ ;^ •. Cm cS -« μ Cm cSq^ 9^ ^. Cm c2Sq^ a u , c^ e -,e=- u- I a^ -, 2U 1 I 4; Y.

0 Y Y ,° ^ Y C c2 Sq ^ Cm cSq^ Cm cSq^ ^ ^ a Se 2U 1 i I aT Y Y Y ` ^ ^.

C^ bSq^ Cn ' ^ b2Sq^ C^ b2Sq^

L

-.^_-

S ^ 2U 1 -^- i 2U ^ z 0z '^' 0z :.

C bSq^ n C^ bSq^ d r a'_"_' _ 8 d l z r a Iz ^

APPENDIX C DEFINITION OF STABILITY DERIVATIVES P i ^.

R Y.

aF ^ ^: s Lateral-directional Equations _ n

C y s - = ,^- Cna

aB

;;; ac `^ ac _ = n C C y p (pb/2UC np {pb/2UC ^^ ac ac _ n c y (rb d /2U) ^` Cn (rb/2U p_ r 4 r ac ac n _ C _ _ t., y^ »^^ ; ^ nsr ^ ac .

ac =^Y .^*^ =,^ Cy Cn r Sa S r a t ac ^ ^ .'

_^ <, c

88a

Y d

a ^^ acR c R ^ - a^ .

} acQ ^^ a pb/2U C ) ; ..

,^^ CQp .} ., acQ °^ ^, ^ a rb/2UC C^'r .^, ac Q_ ^^ ^; CRS asr r r ^ ^^ acQ ^, ' CkS - ada x- a, .^ :^ F ^..

4: ;; ^, ..:.: :; ^^ APPEND IX D ^:^ SIGN CONVENTIl1N5 and Sign conventions for forces, moments, angular rates, linear ^.^^ velocities are shown in the sketch below.. The positive sense. of each variable is shown.

Y,V Q,^ rye - ^^ ^' ^: ^^ P,L R,IJ ^^;..

Z, W - Y (Reference 14) ^.^ Sign .conventions for control deflections are listed below: Control Surface Positive Deflection Elevator Trailing edge down Ailerons Left aileron trailing edge down edge up Right aiheron trailing - Rudder Trailing edge kaft ^ g3 .

F .. a .^..^.,t._..,. ^.

,.

^ ^ ^}^ #„ ^.

t. - i APPENDIX E }:. .

^, DERIVATION OF EXPRESSION FOR NORMAL ACCELERATION ' DUE TO TURBULENCE t If one eliminates the force equation in the X .body axis direction,.

and C 2, and Z assumes variations in u to be negligible, neglects C 4 : q a assumes a sinusoidal forcing function, the following equations (24) result w r ' a a w = {-C - C s + sC

s + C )a + (i s - C ) q

- (C

B - mq, ^0 a a a a mq where = m/pSQ u IY/pSQ 3 ' i B c/2 R, ,..

_Laplace operator s input magnitude.

' wg = gust g and q/w9 by Cramer's rule One may solve these expressions for d,/w ;', to find r a { _

s) ( Bs - Cm )

- C m s + C m ) - CZ (i

- ^ ^ (-C 2 l 1

w

a

O q

q

9 ^ ^

p

^^; _

_s) - C sC

^-= I(2hs - C C - C s +C

1 (C )^

)(-

ma: , mq '" U ^Ix O p a Za a a ^•: g :`' $5 • P B D C E ^p II^T(^ p^,^ BLANK NOT FTGMN^ ^ .r..^__ , ,_ ^_ ..

._ IYF^ }i =.

{;, Ve 11' .

^^ (-2uC - i C - 2uC ) 2 - 4^ i (C C - 2uC ) ' ` ^ ,: B B mq za m^ m^ a b; _ B - 4U2i 2 B ^,..^ Following the development in Reference (24) for an approximation ^; of the short-per'iad mode, the following relations are obtained for '` ",x ^ ;` n w and ^ s '' " y s C C - 2u C k " , Za m q ma, 3 :._ _ - wns 2u i6 atu ^ '; 2uCm + i + 2uC m. B C z ^ _ - a q 2^ s w ns - 2u i6 ' ^~ ^.

and By use ofthe two previous expressions for wn it .can be ^ s w n rr s s Y.'

t t ,, seert that ^_ Y i^ A = w and n s , ^ , { ;" s _ 5 ^: a i r• - " Solving ^ ^ ^ i w dw T 1` ^, ^: ^^' we attempt to writo this in the form ^^ GJ 2 dW -^ (E + w2 ) ^ F + ^2) -.: where 4A B t B ^ - E,F $ 7 Ty. _.. _ _ l _ l _l I l 1 ^,.. '^ K^. 1 _ ^ We now examine the quantity 6 2 - 4A: z E 2 -1)1 2_ # 4^ 2^^2-1) (2x 62•-- 4AL2w 2 ^ n s s ns ns s s From this, we may identify three different case for the roots of the characteristic denominat+^r.

.Case 1 . < 1 ^ s 2 Complex roots exist since 6 2 - 4a ^ 0. Integrating ^.

..

w 2 dw ^_ ^— over the complex plane, we_obtain the following result after much .

^. k complex arithmetic . * ^ _ l - ^ + w 2w n -^ A + Bw 2 s ^s2 = 1 Case 2, roots ex i s ^ since B 4A = Integrating , we' find } .Two real equal 2 - 0 . - , ^ +`^ - II S .

• -.

Zw^s + w^ =^ A + Bw ^.^ ^; ^; ..

,. .

r ' `^ .^ , i Case 3. 1 ^S > ^, !4 «. , t, > ^' Two real unequal roots exist sinde 6 2 - 4A 0. Again, integrating ^_ ,,.

^^ _ _ we find ..

^ ^ ^ ^, ^_ . , - _ t _.

e w2dw _ ^r (E 3 ^ - F,/E') P° ^^ 2 2 ^r[2^ s - l + 2^s -1 ] 1 - 2^s -1 ]^

[2^s - ^s

^s Ow n ^ s ^s2-1 s 2 - 1 - 2^ [2^ s s ^5 -1][2 ^ s 2 - 1 + 2^ s ^s -1^^ ; - O w n ^ s t; s -1 _s If one plots the numerator-function over the range 1.1 < ^ < 2.0, We may then . write nne finds. it nearly linear in ^ s , ,-} ^.r w2dw K^r _ ^^ f °° "^ s ns ,.,^.

,E ^^ ;; N , a constant K appeared which was _, In the original expression for a 2.

is held fixed '^ a function of the product C .2C In this study C z a m q za ,^ is used as a variable to modify the short-period character- ;^^^; and. C . r ^. ^ m q ^^ - 1.8098) i'stics. Art examination of test zases 1, 2, and 13 {Cm = '^ reveals that there is almost a linear relationship between C m .and ^S.

q + 0.332 or , ^,^ A mathematical fit to this trend. is CS = -0.011 C m Cm - 3^ s ). Lncorporating this function intothe three ^^^ ^ 33 ( 1 ,, ^ q ^ expressions gives ^ ,.

^ s, ^^ ^;:.`

l

^' is j; ".

i w9(l - 3^s)2 ^KI ^ < 1 aN _ 2 s

i ns

l w ^.

..9.

aN = i; s - l K .2 w ns •, w (1 - 3^ )2 s aN=K3^ ^s> 1.

w m ns - i ^ s , and K 3 are-functions of flight conditions, ^ ^' where the constants K l , K 2 aircraft mass, pitch moment of inertia, and the stability derivative C'Za .

n , Expanding the radicals by the binomial expansions yields

^2 + 8 ^4 +

(t/ 1 - i; 5 2 ) = l - H.o.r.

°° ^3 ^5 ^_w Thus ,(1 3^s) i 1 - ^^: (i: - 3^s) Y 4 ^2- l 5 Z^ 5 _^.

i.

i:, rY ^ ^, r ^.,.

:t a.

r 's .Y..,^--_ ,,r ,_.__ _ _ -, J , ^„ k_ t and simplified expressions for a H are ^' w = - a N K l ^^-- (1 6^ s + + H.O.T.)

8.52

^s ^ l ns w ^_ a N = K Z ^ ^s = 1 n s - w n ^s s _ Q it should be noted fiere that thc: mathematical fit for C m versus q :' ^s is unique to the particular value of C m chosen. However, fits for a other values of C m =constant exhibited the same trends as above, a that is f,^ m ^ (1 - ks) where k is a .positive constant. Therefore, q ^«, i n genera 1 ^1 w (; - k^ )2

s

s

a N Kl = ^s ^ 1 l - ^s wn s w ^ 2 ^ ^s = 1 _ aN = K ^'s ; <, w (i - k^ ) 2 ^ ^; ^ wns \ ^ S l ^^` ri' r 5..

^ ^:: ,^.,,j __ . _ - __,, _ .

__ _ _ REFERENCES 1. Anonymous, "Flying !'.^^lities of Piloted Airplanes," Military Specification MIL-F-8785{ASG), September 1 954.

2. Anonymous,. "Flying Qualities of Piloted Airplanes," Mi litary Specification MIL-F-87856 (ASG) , August 1969.

Anonymous, "Flying Qualities of Piloted V/STOL Airplanes," 3.

Military Specification MIL-'F-83300, December 1970.

Newell , F. and. Campbell , G. , "Might Evaluations of Variable 4.

Short Period and Phugoid in a B-26," Cornell Aeronautical 1954.

Laboratory (CAL) Report TB-757-F-11, Investiga ion of Acceptable Roll to Yaw Ratio G., "A Flight 5..Bull, of the Dutch Roll and Acceptable Spiral Divergence," Cornel l Aeronautical Laboratory (CAL) Report TB -574- F -6, 1952.

F., "Handling Criteria," J. Ro al Aeronautical 5ociet , 6. O'Hara, Vol. 71, No. 676, pp. 271-291, 19 7.

^" ^ Flight Standards Service, "Tentative Airworthiness Standards for 7.

',^, Powered Lift Transport Category Aircraft," Federal Aviation Administration, Department of Transportation,. August 1970.

$. Advisory Group for Aeronautical Research and Development, "Recommendations for V/STOL Handling Qualities," North Atlantic. Treaty Organization Report 408A, October 1964.

9. Stone,: Ralph W., Jr., "Ride-Quality Overview,".Symposium on Vehicle Ride Quality, NASA Langley Research Center, Hampton,, Virginia, July 6 -7, 1972, NASA Technical Memorandum NASA TM X-2620, October 1972.

K ^^ STOL Demonstra- i0. Eastern Air Lines and McDonnell Aircraft Company, tion Program," EAL Flight Ai;D 68-315., MDC-G-984, March 1969.

International Standards Organization Technical. Committee lA8 11.

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