NACA P-51X Wing Data With Various Trailing Edge Modifications

8/9/2019 NACA P-51X Wing Data With Various Trailing Edge Modifications

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NATIONAL ADVISORY C ITTEE FOR AER

Memorandum Report

AILERONS WITH VARIOUS M O D I F I C AT l i O N S

ON A NORTH AMERICAN XP-51 AIRPLMYE

(AAF N O. 1~1-38)

By Maurice D. Vhite and Herbert H. Hoover

Langley Memorial Aeronautical LaboratovyLangley Field, Va .

NACA WfiRTIME REPORTS are rep rin ts of papers originally issue d to provide rapid distribut ion of edvmce research results to an authorized group requiring them for the war effort. They were pre -viously held under a security st atus but are now unclassified. Some of these report s were not tech -aiczl\y edited. Al l have been reproduced without change in order to expedite general distribution.


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NATIONAL ADVISORY COJ'lZMITTEEFOR AERONAUTICS

MEMOEIANDUMREPORT_- .I -f o r t h e

*

Army Air F o r c e s , Materiel Command

FLI GHT TESTS OF' BEVELED - TRAILING - EDGE

AILEXONS WITH VARIOUS MODIFICATIONS

ON A NORTH AMXRICAN XP- 51 AIRPLANE

By nIaurice D. V!hite and H e r b e r t H. Koover

SUMMARY

Fl ig h t t e s t s have been conducted on a North AmericanXP-51 a i r p la ne wi th sever a l a rrangements of beveled -t r a . i l i n g - e d g e a i l e r o n s t o determine the m o s t s a t i s f a c -t o r y arrangement for use on t h i s a i r p l a ne , The a i l e r onc o n t r o l f o r c e and e f f e c t i v e n e s s c h a r a c t e r i s t i c s w e r e

i n v e s t f g a t e d f o r average bevel a n g l e s o f 25', 272 , and32" , and f o r several arrangements o f balancing t a b s ,The t e s t p rogram inc luded , i n add i t ion , the de te rmina -t i o n o f a s u i t a b l e means f o r trimming the beveled -t r a i l i n g - e d g e a i l e r o n s .

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The r e s u l t s i n d i c a t e t h a t , as t h e bevel angles wereincreased above 2 5 ' , the hlnge-moment slopes were reduceda t smal l c o n t r o l d e f l e c t i o n s , b u t w e r e i n c r e a s e d a tl a r g e c o n tr o l d e f l e c t i o n s ; as a r e s u l t t he v a r i a t i o n of stick f o r c e w i t h a i l e r o n d e f l e c t i o n d e v i a t e d p r o g r e s s i v e l yf r o m t h e a pp ro xi ma te ly l i n e a r r e l a t i o n s h i p of t h e 25'-

bevel-

a ng le a i l e r o n s , p a r t i c u l a r l y a t h i gh s pee ds . Witha bevel angle o f 32' the a i le ro ns were overba lanced a-tindicated ai rspeeds above 200 miles . p e r hour for a i l e r o nde f l ec t i ons be low s b o u t k 7 O .

The addition of s e a l e d i n s e t b a l a n c i n g tabs o f chordequal t o o r g r e a t e r t h a n t h e b e v el ch or d i n s t a l l e d onthe 25*-bevel-angle a i l e rons r educed t h e hinge momentswithout s e r f o u s e f f e c t o n t h e v a r i a t i o n s o f s t i c k f o rc ew i t h a i l e r o n d e f l e c t i o n . W.th an arrangement o f balanc ing t a b s of chord equal to t h e bevel chord on the25-bevel -angle a i l e r o n s , a v a l a e o f pb/2V of 0,095was ob ta ined a t an i nd i ca t ed a i r speed of 20 0 miles per

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hour with full coni;rol deflectfon; with a 50 - pound stickforce, values cf pb/ZV of 0.086 and 0.041, respectively,were obtained Et indicated airspeeds of 280 and 400m i l e s per hour.

Adequate trimming effectiveness was obtained witha sealed inset tab. Pixed external tabs were lesseffective and increased the aileron operating forceswith the tabs either deflected or undeflected,

During the investigation, it was found that suchfactors as rnisalinement of the ailerons, location of anexperimental airspeed boom on the wing ahead of anaileron, and other itens tending to disturb the symmetry .

of boundary - layer flow over the two ailerons causedexcessive trfm forces anG differences in aileron% operating forces required for right and left ~ 0 1 1 s .

INTRODUCTION

The results of previous NACA flight tests of theXP - 51 airplane with beveled - trailing - edge ailerons havinga trailing - edge angle of 25' showed that, with this modi -fication, a marked improvement in lateral colntral char -acteristics was obtained as a result of a

largereduction

in aileron hinge moments. At the same time, however,it was found that an unsealed inset tab of a size whichgave satisfactory trimming effects with the original cuspailerons was inadequate for trimming the beveled - trailing -edge ailerons .

The present report gives the results of a more com -plete flight investigation to develop an arrangenent of

b ev l e d - ai ling - e ge ai 1 e ons that would provide furtherimprovement in the c o n t r o l characteristics of the P - 51airplane

Three bevel angles and several arrangements ofbalancing tabs were tested, The investigation alsoincluded tests to determine a suitable means for trimmingthe beveled - trailing - edge controls


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The wing o f t he XP-51 a i r p l a n e h a s a span of 37.03f e e t , an a rea of 235.75 squa re f ee t , and a t a p e r r a t i oof 0.1:5. The wtng i s of the low - drag type w i t h t h ep o i n t of minimum pressure a t O.j.+c and w i t h a cuspedt r a f l i n g edge. The wing plan form i s shown i n f i g -u r e 1.

In t h e course o f t h e i n v e s t i g a t i o n , a large numberof modif ica t ions were tes ted . The f l i g h t c o n d i t i o n scompris'ing various combinations of these modi f i c a t i o n sare d e f i n e d i n t ab l e I; e a c h f l i g h t c o r i d i t i o n has been

a ss ig ne d a l e t t e r a s a convenient means of' i d e n t i f i c a -t i o n i n p r es e nt i ng t h e t e s t ' r e s u l t s .

The span of ' all ?he a i l e ro n s t e s t e d was 8 3 - 2 fnchesl61and the chord tapered f r o m about 1 3 inches t o 9;-

4-inche s; the average rat1.o o f a i l e ron cho rd t o wing chord

f was about 0 .19 .

Four a i le ro n conf i gur a t i ons , which have been de -r\

1" 0s : ?>mt~c ' : 25~- , 7-=;-, 32 - bevel - ang le a i l e rons and. cusp

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ai le ro ns were te s t ed , The bevel angle i s de f ined asthe ' inc luded angle a t the t r a i l f n g edge o f tne a t l e r o n s .A s i n d i c a t e d f n f i g u r e 2 ( a ) , where the se c t io ns a t theinboard and outboard ends of the a i lerons are shownt t h edesfgna . t ion f o r tw o o f t he beve l ed - t r a i l i ng - e d g e a i l e r o n sr e f e r s t o the average beve l ang le a long the a i le ron s-pan.Fo r t h e 27- - bevel - a n g l e a i l e r o n s , t h e bevel angle was

uniform alo ng th e span. The cilsp a i l e r o n s , w i t h whfcht h e a i r p l a n e was o r f g i n a l l y equipped, ha 6 concave s ur -faces conforming t o the normal a L r f o i l s e c t i o n s of t h e

wlng; unsealed balancing tabs were used on these a i leronsfor. a l l t e s t s . S e c t i o n s o f t h o cusp Eiilerons a r e shownIn f i g u r e 2 ( b ) .

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1 "The 27, - and j2O-bevel-angle ai le ro ns were con -

s t r u c t e d by a t t a c h i n g wood f a l s e r l b s t o t h o o r i g i n a lGU S? a i l e r o n s ; a n a1w-inu.m coverlng was t hen f a s t ened t ot h e ribs r r i t h wood screws and. riveted t o t h e o r i g i n a lcover ing a long the lend ing edge ( re fe rence I). The

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25 - bevel - angle a l l e r o n s were _ f a b r i c a t e d s l r x l l a r l g t oth e o r f g i n a l cusp a i l e ro ns , t h a t I s , x i t h a l-m in un : a l l o yribs anG cove r ing ( r e f e r enc e 2 )

t o de t e rmine t he e f f ec t s of sea l5r ig the nose gags of theai le ro ns . The s e a l i n g was accomplished w i t h d3pedf a b r i c betjveen t h e t r a i l i n g edge of t he f i xed p o r t f o n o ft h e and the hinge a x l s o f t h e a i l e ron .

Some t e s t s were made of t h e ~ 2 - b e v e l - m g l e a i l e r o n s

3 w f n g t h e t e s t p r o ~ = a m h e a v a E l a b l e d e f l e c t i o nrange of the a i Z e r o n s wss changed several t lmes withr e s u l t a x t changes i n t h e mechanical advantage of the con -t r o l system. The va r i ou s r e l a t i o n s h f p s S s t n e e n a i l e r o n

d e f l e c t i m and stfck - g r i p p o s i t i o n %sed a r e shown f nf l & u r e 3 , and i n t s b l e I the p a r t l c u l a r c o n t r o l sys teml inkage used f o r e a c h f l i g h t i s l i s t e d .

Two s e t s of i n s e t b a l a n c i n g t a b s , which have beend-esfgna ted normal - chord and large - chord balancing t a b s ,were t e s t e d on the 25*-beve l -&ng le a l l . e rons . The nosegsps o f b o t h s e t s o f t a b s were s e s l e d with doped fabr ic .

The noxnab-chord tabs had 3pDroxlxiately t h 9 s m eplan - form dimens tons as t h e b a l a n c f n g t a b s on the o r i g i - n a lcusp a i l - e rons . They were 2,!4.-5- i n c h a s I n span (C),2(! of

16 1the a i le ro n span) and were tapered i n chord f r o m Lkf- Inchest o 3 5 Inches (O.3k of t h e a i l e r o n c h or d) ( f j - g s . I- And 4).These t ab s were t e s t ed a t l E n k a g e r a t l o s of 0.61, 0.77,and 0.78, 1l.nkage r a t i o being d e f l n e d as t h e ratio of t a b d e f l e c t i o n t o a i l c r o n d e f l e c t i o n .

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The large - chord t a b s had t h e same span as the normal -chord t a b s , bu t viieret h e t o t a l a i le ro n chord .) , the a d d l t i o n a l chord p r o j e c t r n gbehind the t r a f l i n g edges of t h e a i l e r o n s (figs. 1, 4,and 5 ) . These tabs were t 2 s t e d a t a l i n k a g e r a t i o of

1 f n c h g r e a t e r i n chord (0.39 of

0 .78 .

Durfng t h e t e s t s of t h e i n s e t b a la n ci n g t a b s , t h et a b on th e l e f t a i l er o n was emplQged 5 0 t h as a trfmrningtab and a s a ba l anc ing t a b . Some t e s t s were a l s o madew i t h a normal - chord ns e t t a b i n s t d l e d o n l y on the 1 e 2 ta f l e r o n 8 s a trfimning t a b .


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Tests were conduc d w i t h a s e t of f i x e d et abs on the 32-bevel - ns . These tc o ns i st e d of f l a t s h e et s i n s t a l l e d oninbo ard end of each ai le ro n, were 12 i nches i n span

and l& i nches i n chorr? ( f i g . l}, When these tabs wered e f l e c t e d t o balance an ex is t ing t r i m f o r c e , t h e t a bt h e l e f t a i l e ro n was de fl ec te d up and the ta b o n theaileron was deflected down.

Dur ing t he ea r ly t e s t s o f t h e i n v e s t i g a t i o n , i t wasfound t h a t r a t h e r l a r g e s t i c k f o r c e s were required f o rl a t e r a l t r l m arid th a t th er e were cons ider ab le d i ff e re nc esi n s t i c k f o rc e s r eq ui re d f o r l e f t and r i g h t rolls.Seve ra l pos s ib l e cause3 o f these condi t ions were in v es t i -ga t ed i nc l ud in g a i l e ron a li nement and f a c t o r s t h a t mightproduce d i ffe ren ces i n th e boundary l ay er over the twoa i l e r o n s . A d e s c r i p t i o n of t h e f a c t o r s i n v e s t i g a t e df OllO%I!S :

F o r some o f th e t e s t s , an ai rs pe ed head was mountedon a boom f a s t e n e d t o the lower sur face of t h e l e f t wingahead o f t h e a i l e r o n ( f i g s . 1 and 6) T o determine thee f f e c t o f t h i s i n s t a l l a t t o n , t e s t s w e r e mqde w i t h theboom rsm.oved.

The f i r s t t e s t s o f the p res en t s e r i e s were madew i t h r e g ul a t i on s t a r i n s i g n i a p a i n te d on the upl3er s u r f a c eof th e l e f t wing and on the lower su r f ace o f t h e r i g h twing ( f ig . I); the edges of th ese i ns ig n i a were qu i t esharp and about 0 .008 i nch h igh . La t e r t e s t s weremade with the edges of t h e two In s ign i a s anded smooth,no changes being made t o the remaining surfaces whichwere covered w i t h camouflage paint.

Some t e s t s were made with spanwise s t r i i3s f a s t e n e dt o th.e wing surfaces ahead of t he a i l e r o n s i n an e f f o r tt o c a u s e t r a n s i t i o n of the boundary la y e r a t the same

po in t on b o t h l e f t and r i g h t Ki9gs. These s t r i p s con -s i s t e d of l e n g t h s of double - th ickness fabr ic doped t o t h ewing s u r f a c e ( f i g . 1 ) . On the l ower su r f ace s , t he s t r i p swere located about 7- pe rcen t of the chord, nzeasureda long the sur face , a . f t o f the leading edge and were 0.018inch th i ck and 1 inch wide . On the upper sur facest h e s t r i p s were located about LO percent of the chord,measured a long t he su r f ace , z f t o f the leading edge and

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12 were 0.018 inch t h l c k and - n c h wide.

were always located s y m n s t r i c a l l y , e i t h e rsur faces of b o t h l e f t and r i g h t w-ings, o rupper and lower surfaces of b o t h l e f t and

F o r most of t h e t e s t s of the var ious

The s t r ips

on the lower011 b o t h t h er igh t wings

a i le ron a r range -ments , t h e l e f t a i l e r on was o u t o f a l l n e m e n t v e r t i c a l l yw i t h res pec t t o the wing due t o t h e l o c a t i o n of t h e hTngef i t t i - n g s i n t he wing ( f i g , 7 ) . To i n v e s t i g a t e t h ee f f e c t o f t h i s mfsa l inernent , t e s t s were made w i t h woodenwedges approximately half the a i l e r o n span i n l eng th ,

I t 'inches wide, arid t a p er e d i n h e i g h t from

feather edge, located spanwise on the wing d i rec t ly aheadof the outboard h a l v e s of the a i lerons t o s imula te o r t of a i r fn t h e misa l fnemen t (f5.g. l I b One wedge wasin s t a l l e d on t he l ower su r f ace of t h e r i g h t wing t os imula te the m i s a l i n e m e n t o f t he l e f t a i l e r on ; t he ot h erwedge was i n s t a l l e d on the upper surface of t h e l e f t t of a i r i n the misal inernent . For s e v q p a l of t h e t e s t s with

the 2.5'- and 27&'-bevel-angle a i l e r o n s t h e al inernent wasc o r r e c t e d by 3.oweri.ng the outboard end of t h e a i l e r o n

1 inch t o a8

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6b- inch , w i t h the inboard end unchanged (fig. 7) The

hinge axf s remained unchanged.

TESTS

The procedu rz used f o r t h e t e s t s w q s s i d l a r t o t h a tused i n t he t e s t s o f r e f e r en ces 1 and 2 ; t h a t i s , recordswere o S t a i n e d of a f r s g e c d , a i l e r o n d e f l e ct i o n s , s t i c k fo rce , and ra t e o f roll. as t h e a i l e r o n c o n t r o l w a s ab -r u p t l y d e f l e c t e d v a r i o u s a m u n t s and he ld , the othe rc o n t r o l s b e l n g h e l d Fixed.

Standard N A C A recording instruments were used.These included a s t i c k - f o r c e r e c o r d e r , c o n t r o l - p o s f t i o nrecorders co i i i~ec tod t o b o t h a f l e r o n s , and an airspeedrecorder. The a i rs peed rec ord er was connected t o th eNACA airspeed head when t h i s was avai lable ; o therwise ,i t was connected t o t h e a i r p l ane a i r speed head . F l i g h tca l i b r a t io ns were ob ta ined f o r both th es e heads. Forseve ra l f l i g h t s , n ot ed i n t a b l e 11, a n a i r s p e e d i n d i c a t o rwas u se d i n s t ead o f t h e recorder.


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The majority o f t h e t e s t s werd made over a range of i n d i c a t e d a . i r speeds from about 110 m f l e s p e r hour t o

about 30 0 ln i les pe r hou r. With the cusp a i le rons andf o r sone tes t s o f the 25O-bevel-angle a i l e r o n s , t h espeed range was extended t o about ,!!1.0 miles per hour.Because the 27,-: - and the 32O-bevel-angle a i l e ro ns werecons id-erably hea-v ier i n weigh t t han t he o r ig ina l cuspa i l e r o n s a n d i t was unc er t a in what e f f e c t t h i s i n c r e a s e dweigh t would have on t he f l u t t e r ch a r ac t e r i s t i c s o f thewing, t he t e s t s of t he se a i l e ron s were r e s t r i c t e d t oind ica ted airspeeds below approximately 300 mi le s pe rhour. The in d ic a te d a i r s peed s of the t e s t s of each of t h e arrang emen ts l i s t e d i n t a b l e I a r e given I n t a b l e 11.

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FESTJLTS ANT3 DI CUSSI ON

The resu l t s of the tes t s a re shown in f i g u r e s 8 t o29, t he da t a be ing p re sen t ed l a r ge ly i n t he form of curves o f a i l e r o n s t i c k f q r c e and the e ffec t ivenessparameter pb/2V a g a i n s t change i n t o t a l a i l e r o nd e f l e c t i o n f r o m t r i m f o r s e v e r a l i n d i c a t e d a i r s p e e d s .The parameter pb/2V i s defined by

P a n gu l ar v e l o c i t y i n roll, radians per secondb wing span, feet

v t r u e a i r s p e e d , f e e t p e r se cond

The average in di ca te d ai r sp eed f o r each group of curves 4 s i n d - i c a t e d on t h e f i g u r e s .

Ind ica ted ai rspe ed, as used throughout t h i s r e p o r t ,-i s def ined as Vi = 0.681JZ

where

Ind- ica ted a i r speed , m i l e s pe r hour

Y dynamic gressure, pounds per square f o o t

vi

s ea - l e v e l d e n s i t y, slugs per cubic f o o t


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The va lues ob tai ned from t h i s d e f i n i t i o n d l f f e rsomewhat from the va lues given En ref ere nce s 1 and 2 .where in d i ca te d a i r s peed was d e f i n e d a s

Vi = 0,681 E-, , being the impac t p ressure .cond i t i on P a r e r e pe a te d i n a l l th e curves . Condi tionPspeed boom removed-, the i n s i g n i a smoothed, and no t r a n s i -t i o n s t r i p s on the wing.

1To serve as a basis f o r Comparison, the r e s u l t s f o r

r e p r e s e n t s t h e 25-bevel-angle a i l e r o n s slrith t he a i r -

Af le ron Conf igura t ion

The resu l t s of t e s t s of var ious a i le ron a r rangementsin tended t o give improved stick - fo r ce and e f f ec t i venes sc h a r a c t e r f s t l c s ar e shown i n f i g u r e s 8 t o 18.

...----Bevel a n g l e . - Jn f i g u r e s 8 and 9 t h e c h a r a c t e r i s t i c so f the 32T-TGa-- -angle a i le rons a re shown,f i g u r e 8 snow t h a t t he se a f l e r o n s a r e u n s a t i s f a c t o r ybecause they become overbalanced f o r s m a l l c o n t r o l de-f l e c t l o n s a t no rmal f i f g h t speeds .

The da ta i n

Th.e da ta shown i n f i g u r e 10 afford a comparison of

t h e s t i c k - f o r e 3 c h a r a c t e r i s t i c s of t he2J - and

t he272 - bevel - angle a i l e r o n s . The r e s u l t s i n d i c a t e t h a t ,i n g e ne r a l, t h e a i l e r o n s h av in g th e 25 bevel angle are

%he 1 0s u p e r i o r t o those having/272 beve l ang le , The s t i c k f o r c e s f o r t he 25 -bqve l - ang le a i l e r o n s a r e h ig he r a tsmall c o n t x l d e f l e c t i o n s , b u t a r e , on the average, equalt o o r l o w e r o a t t h e l a r g e r c o n t r o l d e f l e c t i o n t h a n t h o s ef o r t h e 275. b e v e l - a n g l e a i l e r o n s Also, t h e v a r i a t i o nof stick f:jrce ?vj$jh a i l e r o n d e f l e c t i o n i s more n e a r l yl i nea , - f o r t h e 25 - bevel - ang le a i l e rons t han f o r t he272 - bevel - a n g l e a i l e r o n s w i t h t he con t ro l l i nkage u sed .G r e a t o r s e n s i t i v i t y of s t i c k - f o rc e c h a r a c t e r i s t i c s t o

changes f n a i l e r o n a li ne me nt f o r t h e 27- - bevel - angle

a i l e r o n s as coxrmared with t h e 25 -beve l - ang le a f l e ro i i si s i n d i c a t e d i n f i g u r o 10.

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A coinparison of t h e d a t a i n f i g u r e s 8 and 10 w i t h9 and 11 f n d i c a t e s t h a t b e v e l - ang le mod i f i ca t i ons t ha tr educe t he s t i ck fo r ce s a l s o tend t o reduce the e ffec t ive -ness . A s a consequence the effect iveness of t h e

a

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32 ' - bevel - angle a i l e rons i s l e s s than t h a t of t h e 25"10

and the 2'72 -bevelmangle a i l e r o n s .Sea led a i l e ron nose gaps . - Dur ing t h e t e s t s of t h e

32'-b=el-angle a i l e r o n s ,' t h e e f f e c t s o f s e a l i n g t h enose gaps of th e ai le ro ns were in ve st ig at ed . The re -s u l t s p r es e nt ed i n f i g u r e 12 i n d i c a t e t h a t t h i s m o d i f i -c a t i o n e f f e c t i v e l y r ed uc ed , b u t d i d n o t e n t i r e l ye l imi na te the overba lance no ted a t smal l c on t ro l de f lec -t i o n s , Q u a l i t a t i v e l y, th3.s r e s u l t i s i n agreement w i t hwind - t u n n e l r e s u l t s ( r e f e r e n c e 3 )

The d a t a i n f i g u r e 13 i n d i c a t e t h a t t h e a i l e r o n e f -

a g a in s t a i l er o n d e fl e c t i on , i s i n c re as e d s l i g h t l yf ec t i venes s , a s de f i ned by the s lop e of t h e curve of pb/2Vby sea l ing the nose gags o f t h e a i l e r o ns .

A n i n t e r e s t i n g f r e e - c o n t r o l o s c i l l a t i o n of t h eai le ro ns was recorded at m i n d i c a t e d a i r s p e e d of approxi -mately 320 m i l e s p e r hour f o r the sealed - gap condi t ionwhen the control s t i c k was r81eased . A t ime h i s to ry o f t h i s o s c i l l a t i o n showPng a i l e ro n p os i t i on , a i r s pee d , andr o l l i n g v e l o c i t y i s given i n f i g u r e 14.

The p i l o t was unable t o i nd uc e s i m i l a r o s c i l l a t i o n sa t lower speeds.

Balancing tabs. - Prev ious t e s t s hav ing i nd i ca t ed t h e25O-bevel-angle contour t o be the most s a t i s f a c t o r y of t h e t h r e e c on to ur s t e s t e d , t e s t s o f s e a l ed ba lan c ing t a b s ,designed t o improve s t i l l f u r t h e r t h e s t i c k - f o r ce c har -a c t e r i s t i c s of these ailerons, were made only w i t h t h e25-beve l -angle a i l e r o n s ,

The s t i ck - f o r c e charac t e r i s t i c s of 25'- bevel - angleai.llerons w i t h normal - chord tabs and large - ch o rd t ab s ,e ac h s e t o p e r a t i n g a t a l i n k a g e r a t i o of about 9.78, a r ecompared i n f i g u r e 15; d a t a a r e a l s o gi ve n f o r t h enormal - chord tabs opera t i ng a t a l i n k a g e r a t i o o f 0.61.I n t he se t e s t s , t h e ta b was not used f o r trlmming. Withb o t h t ab - l i n k a g e r a t i o s the normal - chord. balancing tabse ff ec t ed a marked r educ t ion i n s t i c k fo r ce s as coalparedw i t h t h e a i l e rons w i t h n o t a b s . The magnitude o f t hehinge - moment r e d u c t i o r , i s even grea te r t h a n would bei nd ic at ed by a simple comparison o f t h e s t i c k f o r ce sb ecau se , s imu l taneously w i th t he i n s t a l l a t i o n o f t h eba lanc ing tabs , the def lec t ion range of t h e a i l e r o n swas i nc r ea sed f o r t h e same s t i c k t r a v e l , t he re by r e -ducing the mechanical advantage of the control system.

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A f u r t h e r d ecr eas e i n s t i c k f o r c e s was accomplishedby incr eas ing the chord of tne ba lanc ing tab s , th e ad -d f t i o n a l chord p r o j e c t i n g be hin d t h e a i l e r o n t r a i l i n gedge

A s shown i n f i g u r e 16, t h e e f f e c t i v e n e s s p e r u n i tc o n t r o l d e f l e c t i o n was reduced by the ad d i t i on of ba l -ancing tab s , the average redu ct io n being about the samef o r a l l t a b a r r a n ements. A n i t em of a d d i ti o n a l i n t e r e s t

balaizcing t a b s t o e l imina te an a s g m e t r y In e f f e c t i v e n e s ss lopes between r ig h t and l e f t rolls experienced. with t henormal - chord tabs,

shown i n f i g ur e 1. i s the tendency o f t h e l a rg e - c h o r d '

E f f e c t i v e n e s s __1of p r in c ipa l m od i f i c a t i ons e - I n o r d ert o provide a comparison o f t h e fmprovgment i r r c h a r a c t e r -i s t i c s e ff ec te d by t h e p r i n c i p a l m o d i f i c a t i o n s , d a t a f o rthe cusp a i l e rons ac d the 25"-bevcl-angle a i l e r o n s w i t hba lanc ing tabs and t h e 25C-beve l - ang le a i l e r o n s w i th o utba lanc ing tabs a re FTesented in f i g u r e s 1 7 , 12, a i d 1 9 .The balancing tabs on b o t h s e t s of a i le ro ns were thes i z e d e s i g n a t e d as normal - chord tabs. I n f i g u r e s 1 7and 18, t h e s t i ck - f o r c e and e f f e c t i v e n e s s c h a r a c t e r i s t i c sa re p l o t t e d a g a i n s t c o c t r o l def lec t fon , and i n figure 19t h e v a l u e s of ?b/2V ob t a in ab l e w i t h a 30-pownd s t i c k f o r c e m d 8 50-pound s t i c k fo r ce a r e shown p l o t t e d aga in s t

i n d i c a t e d a i r s g e e d f o r each i n s t a l l a t i o n , In some casesi t was necessa ry t o e x t r a p o l a t e the d a t a o f f i g u r e s 1 7and 16 t o f u l l d e fl ec t io n o r t o 'a s t i c k f o r s e of 50 pounds,as i nd i c a t ed by t he do t t ed ex t ens ions t o the curves , i no r d e r t o pe rmi t cons t ruc t i on of t h e c u rve s o f f i gu re 19.It should be noted t h a t t h e mechanical advantage of thea i l e ro n c on t ro l sys tem used i n o b t a in i n g t h e da t a shounIn t h e se f i gu re s f o r t he 25-bevel -angle a i le rons wasg r e a t e r t ha n t h a t u se d i n o d t a i n i n g t h e d a t a o f f i g -u r e s 1 5 and 1 6 w i t h t h e r e s u l t t h a t l ow er s t i c k f o r c e swere obtained f o r a given condi t ion. Inasmuch asknown sources of d i s - p n e t r y d i s cu s sed i n a l a t e r S ec ti on

of t h i s r e g o r t were eliminated, th e causes o f d i ffe rencesi n s t f ck - f o r c e c h a r a c t e r i s t i c s between r i g h t and l e f trolls, eviclent i n f i g ur e 17 , are not known.

The data of f i g u r e 19 i n d i c a te t h a t , w i t h beveledt r a i l i n g - edge a i lerons and normal - chord balancing tabs ,a value of pb/2VI n d i c a t e d a i r sp e e d of 200 miles per hour wi th f u l l con -t r o l d e f l e c t i o n . ? 5 t h a s t i c k f o r c e of 50 pounds,va lues of pb/2V of 0.086 and 0.041 were obta ined a t

o f about 0.095 was obtained at an

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i n d i c a t e d a i r s p e e d s o f 280 and 400 m f l e s per hour, respec -t i v e l y . These v a lu e s r e p r e s e n t i n c r e a s e s i n r a t e o f r Q l l o f 100 p e r c e n t a t 280 mi le s pe r hour and 37 pe rcen ta t 400 miles per hour over t ha t ob ta ined wi th the cuspa i l e ron - balancing tab arrangement

fo r t he cusp a i l e rons and t he 25-bevel-angle a i l e r o n sp r e s e n t e d i n t h i s r epo r t and t he da t a p re sen t ed i r , r e f -erences 1 and 2 . This i s probab ly due t o t h e f a c t t h a t ,because of m a n u f a c t u r i n g i r r e g u l a r i t i e s , n e i t h e r of t h es e t s o f a i l e r o n s t e s t e d h e re was i d e n t i c a l w i t h thosep r e v i o u s l y t e s t e d ,

Some minor di ff er en ce s a r e evi den t between the d at a

Trimming Tabs

Several arrangements o f t ab s we re i nves t i ga t ed t odete rmine a su i tab le means f o r trimming th e be vel edt r a i l i n g - e d g e a i l e r o n s . The r e s u l t s o f t he se t e s t s a r ei n d i c a t e d i n f i g u r e s 20 through 23,

I n s e t t a b s . - I n f i e u r e 20 t h e t r i m - f o r c e v a r i a t i o nw i t h a i r s p e e d f o r s e v e r a l d e f l e c t i o n s o f a normal - chordt a b i s shown. With a s e a l e d i n s e t t a b i n s t a l l e d on t h el e f t a i l e r o n on ly ( f i g . 2 O ( c ) ) , s u b s t a n t i a l changes i nt r i m for ce were ob ta ined by de f l ec t i ng the tab . Thea v a i l a b l e t ab d e f l e c t i o n r an ge of 57 was i n su ff i c i en t ,however, t o t r i m o u t t h e f o r c e s ca us ed b y t h e i n s t a l l a t i o no f an NACA a i r s p e e d boom on one w i n g .

With s e a l e d i n s e t b a l a n c i n g tabs on b o t h a i l e r o n s ,and w i t h wing conditions symmetr ica l except f o r t h emlsa l inemen t o f t he l e f t a i l e r o n , t h e t a b o n t h e l e f ta i l e ron prov ided comple te t r i m as I n di c at e d i n f i g u r e ZO(b).

An o b se r va t io n p e r t i n e n t t o t he p r e sen t d i s c u s s i o n Iw a s made when a very pebbly coa t ing o f paint was inad -

ve r t en t l y app l i ed on t he uppe r su r f ace o f t he r i gh t w ing ,I t was found that, a l l o ther condi t ions cor responding t othose o f f i g u r e 20(b), a tab d e f l e c t i o n of approximately8 O w a s t h e n r e q u i r e d f o r t r i m . T h i s r e s u l t i s o f i n t e r e s t as an in d i ca t i on of t he t rimming tab def le c t io nrange t h a t should be provided with t h e b ev el ed t r a i l i n g -edge a i le rons .

A s a mat te r o f i n t e r e s t , d z t a f r o m r e f e r e n c e 2,showing th e re l a t i v e c h a r a c t e r i s t f c s of completelysea led and imper fec t ly sea l ed tabs , a r e shown i n f i -ure 2 0 ( a ) , These da t a i nd i ca t e t ha t t he impe r f ec t 9ysea l ed t ab i t s e l f i n t roduces asymmetry such t h a t

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approximately 7 O of d e f l e c t i o n i s required! of t h e t ab t ot r i m out I t s own e f f e c t ,

The actual trimrning e f f e c t i v e n e s s was n o t i n v e s t i -ga t ed f o r t h e s ea l ed l a rge - cho rd t ab s , bu t t he 2 a t a f o rthese t abs i n f i g u r e 15 i n d . i c a t e t h c i r e f f e c t i v e n e s s a sa t r i m t a b would be about t h e same as t h a t of the normal -chord tabs .

I n connec t ton w i t h the use of d e f l e c t ed i n s e t t ab sf o r t r i m , t h e s t i c k - f o rc e c h a r a c t e r i s t i c s i n rolls a r eof I n t e r e s t . A s shom7n by the d-a ta f o r 201 miles perhour in f igure 22 and i n r e fe r en ce 2 , d e f l e c t f n g an i n s e tt a b i n c r e a s e s t h e s t i c k f o i a c e s i n rolls t o one s i d e and

r educ es t h e s t i ck fo r ce s I n r o l l s t o t h e o t h e r s i d e .The direct ion o f t 3 e e ff ec t co r r e spon ds t o a p e r s f s t e n c eof the t r f m - f o r c e change, but the magnitude o f t h e f o r cechange appears t o i n c r e a s e w i t h i n c r e a s i n g a i l e r o n de-f l ee -t ion . This behavior I s i n agreen?ent w i t h wind-tunnel d a t a ( r e f e r e n c e 3 )

f o r t e s t s of f i x e d e x t e r n a l t a b s on t h e 32c'-bevel--anclea i l e r o n s I n d i c a t e t h a t some trimming e f f e c t can be obtainedw i t h t h e f i x e d e x t e r n a l t a b s . Their p r a c t i c a l v a l u e I s ,however, d iminished by the f a c t t h a t , e i t fner d e f l e c t e d

o r wid .e f l ec t ed , these t abs cause a co ns ide r ab l e I n c r e a s e2n s t i c k f o r c s f n rolls ( f i g . 2 2 ) . These resu l t s arei n agreement with wind- tunnel d a t a ( r e f e r e n c e 3 ) .

no d i ffe rence i n e f f e c t ; i v e n e s s c h a r a c t e r i s t l c s -to becaused b y the f ixed e x t e r f l a l t abs .

F i x ed ex t e rna l t ab s . - The r e s u l t s shown i n figure 21

The a i l e r o n e f f a c t i v e n e s s d a t a i n f i z u r e 23 i n d i c a t e

Fac to r s A ff ec t i n g Symmetry o f

A i 1 e o c Char ac b r i s t i c s

Reference t o the t e s t r e s u l t s p r e v i o u s l y discussed-i n d i c a t e s % h a t e x c e s sr v e t r i m f o r c e s a.nd a d i f f e r e n c ebe tween the s t i ck f o r c e s ?eyuSred i n r i g h t a n d l e f t rollexisted. I n o r d e r to determine and s l i m i n a t e the causeof t h e se v a r i a t i o n s , t he e f f e c t s o f g e v e r a l f a c t o r s whfchinc luded the N A C A a i r spe e d boom, the wing i n s l g n f a ,t r a n s i t i o n s t r i p s f a s t e n e d ' t o th e l e a d h i ? e C g e of thewing sur face , and ver t i ca l n l i n e n e n t 03 t he c . i le ron wereinve s t f g a t e d . R e s u lt s of t e s t s o f t he se i t ems a r e showni r , f i g u r e s 10 and 11 and 24- through 29.

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T r i m f o r c e s . -11 A l l t h e f a c t o r s i n v e s t i g a t e d hapbsome effect on the asymmetric forces experienced, Thep r in c ipa l sou rce o f t he e xce s s i ve t r i a l forces, however,was the NACA a i r spee d boom as shown i n f ig u re 24. Thet r a n s i t i o n s t r i p s whj-ch were a lways ins ta l led sxJmmetri-c a l l y r educed s l i gh t l y t h e t r f m fo rces caused by th eairspeed. boom, Figure 26 shows the effect o f the rough -ness caused by the wing in s ig ni a on th e t r i m force . Therough edges of the wing insignia tended. t o co un t e r a c tt h e e f f e c t s o f the boom as shown by t h e f a c t t h a tsmoothing the edges o f th e I . n s ign i a i n c r e a s e d t h e f o r c e s

requf red f o r t r i m wi th t he a i r s pee d boom i n place. Thesei n s i g n i a , i t w i l l be noted, were located unsysflznetrically,one o f t he f n s l g n i a being on the wing surface oppositet h a t t o which the airspeed boom was attached.

F igu re 10 shows t h a t t h e e f f e c t of a i l e ro nreal inement on t r i m f o r c e s mras r a t h e r l a r g e , p a r t i c u l a r l y

w i t h the 27- - bevel - a ng l e a i l e ro ns . This t rim - f orce

change i s i n q u a l i t a t i v e agreement w f t h t h e e f f e c t s of cove r - pla te rea l inement ind ica ted i i ? r e f e r en c e 3 . Thep i l o t ' s obse rva t i ons o f the e f f e c t s of a l inement changes

s imula ted by wedges indicated that these rnad i f i ca t fonswere r e l a t i v e l y i n e f f e c t i v e as coi??x,ared with a c t u a l r e -alinement of t h e a i l e r o n .

lo2

Symmetry of f o r c e s I n r o l l s . - A s regards theasymmetry T f o r c e v a r i a t i o n s E r o T s , the d a t a i n f i g -u r e s 2k and 22 i n d i c a t e t h a t t h e e f f e c t s prod.uced- 'by t hea i r s p e ed boom and wing i n s ig n i a a r e , w i t h the excep t ionsnoted, co ns i s te n t and exp la inab le on the ba s i s o f p r e -mature se pa ra t i on over the a i l er on bulge, caused by theboom o r t h e I n s ign i a . In rolls in t h e d i r e c t i o n of t h et r i m - f o r c e change ( tha t i s , i n ri , h t r o l l s where the

modif icat ion r equ i r ed m o m r i g h t t r i m f o r c e ) t h e f o r s e sob ta ined w i t h and without the a m d i f f c a t i o n approachede ac h o t h er a t l a r g e c o n t r o l d e f l e c t i o n s , I n rolls t ot h e o p p o si t e d i r e c t i o n , t h e d i f f e r e n c e i n trim force wasmafntafned a t a l l c o n t r o l def lec t idns . Excep t ions t ot h i s behavior were no ted i n l e f t r o l l s a t moderatespeeds Setween the conditions of rough and s m o o t h wingf n s i g n i a m

Transftj .oii s t r i p s f n s t a l l e d symmetr ical ly, Ingene r a l , r educed t he f o r ce s i n rolls f o r both the 25'-and the 27- - bevel - ang l e a i l e rons (figs. 2k and 26:."

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Tr a n s i t i o n s t r i p s on only the lower surfaces gave aboutthe same effect as s t r i p s on b o t h ui2per and lower sur -f a c e s ( f i g , 24).

i n rolls were d i f f e r en t for t h e two a i le ron a r rangementst e s t e d , With t h e 25-bevel-angle a i l e r o n s t h e d f f f e r -ence In trim f o r c e w a s ma'intained a t a11 c o n t r o l de-

f l e c t i o n s , whi le wi th the 27- - bevel - a n g l e a i l e r o n s , t h e2f o r c e s i n rolls t o b o t h d i r e c t i o n s were l e s s for t h e r e -a l ined a i le rons than they had been foxa the o r i g l n a l a l f n e -rtient a t l a r g e d e f le c t io n s ,

The effects of ai leron rnisal inement on f o r c e s

lo

E f f e c t i v e n e s s . - As shown i n f i g u re s 11, 25, 2 7 ,and 29 t h e - X F E 5 5 f f c a t i o n s df scus sed i n t h i ss e c t i o n o f t he r e p or t r e s u l t e d i n d i f f e re n c e s i n e f f e c -t i v en e s s c h a r a c t e r i s t i c s t h a t were c o n s i s t e n t w i t h thes t i c k - force changes; t h a t i s , lower e ffec t iveness wasg e n e r a l l y a s s o c i a t e d with l o w e r s t i c k f o r c e s .

c !3NCLUSI NS

The resu l t s of f l i g h t t e s t s o f beve led t r a i l i n g -edge ai lerons w i t h va r ious mod i f i ca t i ons on a MorthAmerican Xp-51 a i r p l m e may be summarized as fo l l ows :

du ct io n i n hinge moments a s conpared t o the o r i g i n a lcusp a l l e r o n - b a l a n c i n g tab arrangement, and gave anapp rox ima te ly l i nea r va r i a t i on o f s t i c k f o r ce witha i l e r o n d e f l e c t i o n f o r the con t ro l l inkage used, In -creas ing the beve l ang le above 25' caused g rea t e r r e -ductions In hinge - moment s lopes a t small de f l ec t i on s ,but increased the hinge - moment s lop es a t I u r g e d e f l e c -

t i o n s s s o t h a t t h e v a r i a t i o n o f s t i c k f o r c e w i t h a i l e r o nd e f l e c t i o n d e p a r t e d i n c r e a s i n g l y f r o m a l i n e a r r e l a t i o n -s h i p , p a r t i c u . l a r l y a t h ig h speeda. Wfth a bevel angleof 3 z 0 , the a i le ro ns were overbalanced a t indr ica ted a i r -speeds above 200 miles per hour for a i l e r o n d e f l e c t i o n sbelow about $7'

2. Fur ther reduct - lons i n h in ge moments were

I. The 25-bevs l -angle a i le ro ns gave a l a rg e re -

obta ined w i t h sea led i n s s t ba l a - c l c ing t abs o f chordequal t o o r l a r g e r t h a n t he beve l cho rd i n s t a l l ed onthe 25-bevel -angle a i l e r o n s .


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3 . The 25-bevel -angle a i l e r o n s w i t h s e a l e d i n s e t3 b a l a n c i n g t a b s of span e q u h l t o 0.29 o f t h e a i l e r o n s p a n

and chord equal t o th e bevel chord, geared t o a l i i ikager a t f a of 0.78 t o 1, gave E 'value o f pb/2V o f O.C(35 forf u l l c on tr ol d e f l e ct i o n a t an i nd i ca t ed a i r s p e e d of 200

0 - pound stfcl i : f o r c e , v a l u e s o f mi le s pe r hou r ;pb/2Va i r speeds of 280 and 400 rdlles per b 7 w , r e s p e c t i v e l y.These values r e 7 r e s e n t i n c r e a s e s i n r a t e of roll o f 100percent and 37 p e r c m t a t 289 and I.@O miles per hour,re sp ec t i ve ly , as compared w i t h t h e o r i g i n a l c u s p a i l e r o n sw i t h ba l anc ing t abs .

7of 0 ,066 and 0.041 were obtained a t i n d i c a t e d

14.. A s e a l e d i n s e t t a b gave adequate trimming e f f e c t

and appears t obe 8 s a t i s f a . c t o r y d e v i c e f o r trlmw-ing beveled -t r a i l f n g - e d g e c o n t r o l s . F ix ed e x t e r n a l t r imming tabswere l e s s e f f e c t i v e a nd in c r e a se d t h e s t i c k f o r c e s I nrolls whether t h e t a b s were d e f l e c t e d or u a d e f l e c t e d ,

5. An asymmetry i n s t i c? . c - fo rce c h a r a c t e r i s t i c s f o rthe beve led - t ra i l ing - edge a i le rons , ev idenced as excess ivet r i m f o r c e s and a s d i f f e r e n c e s betweeli t h e s t i c ' : f o r c e sr eq u ir ed i n r i g h t and l e f t rolls, was found t o be due t oseve ra l f a c t o r s . These f ac to r ' s i ? i c lud ed misa lfne rnen tof t h e a i l e r o n s , l o c a t i o n o f an expe r imen te l airspeedboom on the wing ahend of an a i leron, znd o t h e r i t e n i s

tending t o d i s t u r b t h e synzrrie t r y of bound-ary-layer flowove r t he two a i l e r o n s .

Langley lllcrnori a1 Aeronautic a 1 Laboratory,l f a t i o n a l Advisory Conmlt tee for Aeronaut ics

Langley Field, Va., December 7, l q ! ~ 3 .


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16

'WSErnRrnGES

1. White, & IG D., and Hoover, Herbest Ne: F l l g h t Tes t sof Modiffcations to Improve the Aileron ControlCharacteristics of a North American XP- 1 Alrplans( A . C . No, 41-38), NACA MR, Aane 20, 19

2 , loover, Herbert H., and White, Maurice 13,: Lateral -Control Characterfstics o f North Amem?%can XP-5X A i r -plane ( A , C , No, 41-58) w i t h Beve lBd TrailSng-Edge

Ailerons in Hfgh-Speed F l i g h t , NACA MR, Now. 2TP1942

3 . RogabLo, F. M a p and Crandall, Stewart M,: W n d -Tunnel Investfgation of Trimming Tabs on a Thickenedand Beveled Aileron on a Tapered Low - Drag Vdng,NACA A,C.R, , March 1943.

J


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I I

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-utboard

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Figure 20.- End s m t i o n s o f beveled trailing - edge ailerons . X P - 5 1 ai rp lane.

d


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Figure 5.- Views of large - chord balancing tabs on 25' bevel - angleailerons. North American XP - 51 airplane.


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-Figure 6.- View of NACA airspeed boom mounted on left wing of North American XP - 51 airplane.


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NATIONAL ADVISORY

COMMlTTEE FOR AERONAUTICS/Distances m efrDm outboard end of f/dp.

Plan view of l e f t wiuy

Orig ind posit ion - - - -@+u/igned position

Section 0

Orig ind posit ion - - - -@+u/igned position

- < = ; I - - - - - -- -1Section 0

--

1S e c t i o n 0

showing ori i n o landre-dL ned position o f l e f t Q L e r o nLn2 19iqure7dections o f l e f t

N o r t h 2 erican X P - 5 1 airplane


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C ond i t i on Aileron Airspeed

t a b l e I ) angle,

-+- A

+ P


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NACA P-51X Wing Data With Various Trailing Edge Modifications

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