low speed wind tunnel tests on a buccaneer mk with blown le slats, flaps and ailerons

8/13/2019 Low Speed Wind Tunnel Tests on a Buccaneer MK With Blown LE Slats, Flaps and Ailerons

1/53

t g 3g}

~z

N . M . N o , 3 6 5 5

. . . . y

J U : i l k ~ . ' ~ , '%j ~

M I N I S T R Y O F V I T I O N S U P P L YAERONAUTICAL RESEARCH COUNCIL

REPORTS AND MEMORANDA

L o w - S p e e d W i n d - T u n n e l T e s t s o n a S w e p t b a c kW i n g M o d e l B u c c a n e e r M a r k I) w i t h B l o w i n g a t t h eW i n g L e a d i n g E d g e a n d B l o w i n g o v e r t h e F l a p s a n d

D r o o p e d A i l e r o n sBy S. F. J. BUTLER

Aerodynamics Dept., R.A.E., Farnborough

LONDON: HER MAJESTY'S STATIONERY OFFICE1971

PRICE 1 8S 0d[1 40] NET


2/53

Low-Speed Wind-Tunne l Tes t s on a SweptbackW ing M od e l Buccaneer M ark I) wi th B lowing a t theW ing Leading Edge and B lowing over the F laps and

D r o o p e d A i l e r o n sB y S . F . J . B U T L E R

A e r o d y n a m i c s D e p t . , R . A . E . , F a r n b o r o u g h

Repor t s and Memoranda No . 3655September 1967

SummaryLow-speed longi tudina l s tabi l i ty measurements a re descr ibed on a f i f th- sca le ha l f -model , inc l f fding

som e c om pa r i sons w i th c om ple t e - m ode l t e s t s a nd t he m e a sur e d a i r c r a f t pe r f o r m a nc e .Shr o ud b lowing ove r t he t r a il i ng- e dge f la p a nd d r oo pe d a i l e ron ne a r ly dou b le d t he Czincrement , to asm u c h a s 1 .0 , w i th a d e qua t e a i l e r on r o l l c on t r o l e f fe c ti ve ne ss a t a m e a n a i l e r on a ng l e o f up t o 30 . T r im -m ing r e du c e d t he l i ft i nc r e m e nt s by a bo u t 20 pe r c en t .De sp i t e c ons ide r a b l e a e r od yn a m ic ob j e c t i on s a s soc i a t e d w i th t he t h in w ing a nd sm a l l nose r a d i i, a nintegra l non-def lec t ing) leading-ed ge blow ing ar rangem ent w as spec i f ied for a i rc ra f t s t ruc tura l r easons .A l thou gh a n a c c e p t a b l e a r r a nge m e nt wa s de ve lope d , th is ne c e ss i ta t e d t he se l e ct i on o f a s a fe c om p r om isepos i t i on f o r t he b low ing noz z l e t o a vo id a dve r se c om pr e ss ib i l i ty e ff ec ts a t a i r cr a f t t a ke - of f a nd l a nd ingspeeds . Ty pica l ly , a s ta l l ing inc idenc e of 20 CLmox= 1 .8 ) wa s a c h i e ve d f o r t he p r op ose d t a ke - o f f c on-f igur a t i on 30 fl a p ; 20 m e a n a i l e r on d r oo p) . W i th t he p r e sc r ibe d i n t e gra l l e a d ing e dge , w ing p i t c h- up a tt he s t a ll wa s no t a vo ide d , a l t hough in i ti a l w ing f low se pa r a t i ons w e r e c onf ine d t o t he i nb oa r d w ing .In genera l , the a i rc ra f t high-l i ft per fo rma nce conf i rm s the resul t s of the tes t s on this ha l f -model .

*Re pla c e s RAE T e c h . Re por t No . 67 223- - A .R .C . 29 976 .


3/53

S e c t i o n1

2

3

.

L I S T O F C O N T E N T S

I n t r o d u c t i o nM o d e l D e t a i l sT e s t P r o c e d u r e3 .1 . T he e ff e ct o f b lowing ai r supp ly on ba l a nc e z er os3 .2 . Spe c i f ic a t ion o f b lowing m o m e ntu m coe f fi c ie n t3 . 3 . C o r r e c t i o n sT e s t s w i th Shr oud Blow ing ove r t he T r a i l ing- E dge F l a p a nd D r oo pe d A i l e r on w i thou t L e a d ing-E d g e D e v i c e s4 . 1 . S c o p e4.2. Lift4 . 3 . D r a g4 . 4 . P i t c h in g m o m e n t s a n d d o w n w a s h a t t h e t a il p la n e4.5. The e ffec t of loca l nozz le block age represent ing f lap and supp or t gear4 .6 . T he ef fe ct o f t he a i r b r a ke a nd the m a in unde r c a r r i a ge a s se m blyT e s t s w i th L e a d ing- E dge De vic e s5 . 1 . S c o p e5 .2 . P r e l im ina r y te s t s w i th m e c ha n ic a l l e a d ing-e dge de v ic e s5 .3 . T e s t s w i th f ir s t i n t egr a l l e a d ing-e dge b lowing a s se m bly5 .4 . T e s t s w i th se c ond in t e gra l l e a d ing- edge b low ing a s se m b ly

6 . C o n c l u d i n g R e m a r k sA c k n o w l e d g e m e n t sL i s t o f S y m b o l sReferencesA p p e n d i x AA p p e n d i x B

C o m p a r i s o n o f h a l f- m o d e l a n d c o m p l e t e - m o d e l t e s t re s u lt sCo m p a r i son o f m o de l a nd a i r c ra f t te s t re su l ts

T a b l e 1 M o d e l d a t aI l l u s t r a t i o n s - F i g s . 1 t o 29D e t a c h a b l e A b s t r ac t C a r d s


4/53

1 . In t roduc t ion .T he a pp l i c a t i on o f bou nda r y- l a y e r c on t r o l x by b lowing f o r h igh l if t ha s be e n t he sub j e c t o f a s e r i es o finvest iga t ion s in the R.A.E. N o. 2 11ft x 8f t win d tunnel . M od el tes t s have been com ple te d on s lot -b lowin g a r r a nge m e nt s f o r the D e Ha v i l l a nd Se a Ve no m 2 , t he Sa u nde r s - R oe P . 1773 , a nd t he Supe r m a r ineSc im i t a r 4 , a s we l l a s t he e xpe r im e nt s c ons ide r e d he r e in on a n e x i s ti ng o ne - fi ft h sc a l e ha l f- m ode l o f t he

Buc c a n e e r M a r k I a ir c r af t .E xp lor a to r y i nve s t i ga ti ons w e r e f ir s t m a de o n t h i s m ode l by t he f i rm in the i r 7 ft x 5 ft t unne l a t B r ough ,unde r c on d i t i ons o f se ve r e t unne l c on s t r a in t . T he p r e se n t r e po r t d i sc usses the f o r c e a nd m om e nt m e a sur e -m e nt s , subse q ue n t ly m a d e i n t he la r ge r R .A .E . tunne l b e twe e n 1957 a nd 1962 , w i th r e a r wa r d t a nge n t i a lb lowin g a t t he l e ad ing e dge o f t he i n t e gr a l t h in w ing a nd sh r ou d b lowin g ove r t he t ra i l ing- e dge f l a p a ndd r o o p e d a il e ro n . ~T he e ff ec t o f sh r ou d b lowing o ve r t he t r ai l ing- e dge f l a p a nd d r oo pe d a i l e r on on t he ba s i c w ing c ha r a c te r -i s ti c s a nd on t he do wn wa sh a t t he t a i l p l a ne i s c ons ide r e d f ir st , i n t he a bse nc e o f l e a d ing- e dge de v i c es .T he e ff ec t o f l oc a l noz z l e b loc ka g e r e pr e se n t ing t yp i c a l f la p a nd a i l e r on supp or t ge a r, a nd t he e f f ec t s o fthe p r e se nc e o f t he m a in unde r c a r r i a ge a nd t he a i r b r a ke a r e a l so p r e se n t e d .T he m a in d i sc uss ion c onc e r ns the de ve lop m e n t a nd op t im i sa t i on o f a su i ta b l e le a d ing- e dge s lo t- b lowinga r r a nge m e nt . For s t r uc tu r a l r e a sons , a l e a d ing- e dge f l a p w i th b lowing a t t he knuc k le c ou ld no t be i n -c or por a t e d on t he a i r c r a f t , a l t hough c l e a r ly p r e f e r a b l e f r om a e r odyna m ic c ons ide r a t i ons . Wi th t he t h inwing se c t i on ( typ i c a l ly 8 pe r c e n t RA E 101 , w i th som e a dd e d nose c a m be r ) , t he p r e sc r ibe d i n t e gra l l e a d ing-e dge a r r a nge m e nt ( i. e. no m o va b le su r fa c e s) wa s i ne v i t a b ly a s soc i a t e d w i th h igh ne ga t ive p r e s sur e pe a ksa nd se ve r e a dve r se p r e s sur e g r a d i e n t s und e r h igh l if t c ond i t i ons . E ve n a t t he c om pa r a t i ve ly l ow m a in-s t r e a m M a c h nu m b e r ( M ~ 0 .2 ) r e pr e se n t a t i ve o f a i r cr a f t t a ke - of f a nd l a nd ing c ond i t i ons , t he loc a lp e a k v e l o c it y a p p r o a c h e d s o n i c c o n d i ti o n s .Un de r t he se c i rc um s ta nc e s , t he e f f e ct i vene ss o f t he l e a d ing- e dge b lowing a r r a nge m e nt wa s f oun d tod e p e n d n o t o n l y o n c h o r d w i s e l o c a t i o n b u t a l s o o n t h e m a i n - s tr e a m M a c h n u m b e r a n d n o z z l e p re s s u rer a t io , t hu s ne c e ss i t a t ing t he c ho i c e o f a s a fe c om pr om ise a r r a nge m e nt f o r t he a ir c r af t .

Som e c om p a r i sons a r e p r e se n t e d be tw e e n the te s t re su l ts ob t a ine d on t h i s ha lf - m ode l , a nd on t he 1 /12 th -sc a le c om p le t e m ode l use d by t he f ir m f o r ge ne r a l s t a b i l it y a nd pe r f o r m a nc e m e a sur e m e nt s . A f li gh t-t unne l c o m p a r i son i s a l so inc lude d .

2 . M o d e l D e t a i l s.Th e one- f i f th sca le por t -wing ha l f -mo del was or igina l ly cons t ruc ted by H.S.A. (Broug h) for tes t s in the i r7 ft 5 ft l ow- spe e d t unne l . For t he p r e se n t t e s ts , i t wa s m ou nte d on t he v i r t ua l - c e n t re l owe r ba l a nc e o f t heR.A.E. N o. 2 11ft x 8ft w ind tu nn el see Figs . 1 a nd 2 ). T he m ode l wa s m a de m a in ly f r om wo od , e xc e p tf o r t he m oun t ing b r a c ke t s , b lowing du c t s a nd noz z le s , whic h w e r e c ons t r uc t e d f r om s te el , dur a lum in , a nd

brass .P r io r t o t he R .A .E . t e s t s, t he m od e l wa s m odi f i e d see Figs . 1 a nd 2 ) t o b e m o r e r e pr e se n t a t i ve o f t heBuc c a n e e r M a r k I a i rc r a ft . I n pa r t i c u l a r , t he f use l a ge wa s l e ng the ne d , w i th p r ov i s ion f o r r e pr e se n t a t i onof t he pe t a l - t ype a i r b r a ke a t t he r e a r o f t he f use l age a nd t he m a in unde r c a r r i a ge . A f i a t- p l a te f m wa spr ov ide d , t o suppor t t he ha l f - t a i l p l a ne whe n f i t t e d ; t he a l l - m oving t a i l p l a ne i nc or por a t e d a t r im m ingf la p , bu t t he a i r cr a f t t a i lp l a ne l e a d ing- e dge b lowin g a r r a nge m e nt wa s no t r e pr e se n t e d . As p r e v ious ly , fr eef low wa s a l l owe d th r oug h the s im ula t e d m a in e ng ine na c e ll e duc t .

T he w ing , o f fu ll a spe c t r a t io 3 - 55 a nd t a pe r r a t i o 0 .59 ha d a c on s t a n t t r ai l ing- e dge swe e p ba c k o f 20 ;t he q ua r t e r - c hor d swe e pba c k wa s 30 .2 ove r m os t o f the e xpose d spa n , i nc r e as ing p r ogr e s s ive ly t o 38 .6 i n b o a r d o f t h e w i n g p l a n fo r m b l e n d r e g i o n see Fig. 1). Th e wing, which h ad z ero twis t , was m ou nte d a t am id- f use l a ge pos i t i on , w i th z e r o d ihe dr a l a nd + 2 5 w ing-f use la ge a ng l e. T h e w ing se c t i on va r i e d a c r ossthe spa n , w i th a 9 .25 pe r c e n t t h i c k R AE 100 sym m e t r i c a l s e c t i on a t t he f use l a ge c e n tr e li ne , a n 8 pe r c e n tth i c k R AE 101 se c t ion w i th nose c a m b e r a t 55 pe r c e n t se m i - span , a nd a 6 pe r c e n t t h i c k RA E 102 se c t ionwi th nose c a m be r a t t he t i p : t yp i c al nose p r o f il e s a re show n in F ig . 4.

*Th e tes t r esul t s were ana ly sed a t the t im e and rece ived a l imi ted c i rcula t ion in the form o f H.S.A.(Brough) inte rna l repor ts .


5/53

T h e w i n g t r a i l in g - e d g e f l ap a n d l a r g e - sp a n a i l e r o n see F ig . 1 a n d T a b l e 1 ), w h ic h w e r e s u p p o r t e d b yl o w e r s u r f a c e b r a c k e t s p r o v i d i n g a r b i t r a r i l y p r e s c r ib e d a n g u l a r s e t ti n g s o f u p t o 7 5 a n d 4 5 r e s p e ct i v e l y( n o r m a l t o h i n g e -l i ne ) , w e r e g e n e r a l l y r e p r e s e n t a t iv e o f t h e a i r c ra f t a r r a n g e m e n t , w i t h r o u n d - n o s e dc o n t r o l s c e n t r a l l y - h i n g e d a t a b o u t 7 6 p e r c e n t w i n g c h o r d see F ig . 3 a ) . I n a d d i t i o n t o t h e l e a d in g - e d g eb l o w i n g a r r a n g e m e n t s f o r t h e i n t e g r al w i n g n o s e , p r o v i s i o n w a s m a d e see T a b le 1 ) f o r a l e a d in g - e d g e s l a tsee F ig . 1 2 ) , w i th 1 5 p e r c e n t c h o r d w i s e a r e a e x t e n s io n a n d 1 5 a n g u l a r s e t ti n g , a n d a l e a d in g - e d g e f l a ph in g e d a t 1 5 p e r c e n t c h o r d o n t h e w in g l o w e r s u r f a c e w i th 3 0 d e f l e c t i o n ( n o r m a l t o h in g e - l i n e ) .

T h e w i n g w a s f i t te d w i t h t w o f u l l- s p a n m a i n a i r d u c t s s ee F ig . 1 ) c o n v e y in g t h e h ig h - p r e s s u r e a i r t on o z z l e s a t t h e w i n g n o s e a n d i n t h e w i n g s h r o u d a h e a d o f t h e t r a i li n g - e d g e fl a p a n d a i l e r o n . T h e s h r o u d -b l o w i n g i n s t a l l a t i o n w a s c o n v e n t i o n a l see F ig . 3 a ) , w i th t h e n o z z l e p a r a l l e l t o t h e w in g c h o r d p l a n e a n dth e l o w e r fa c e o f t h e n o z z l e a l i g n e d t a n g e n t i a l l y w i th t h e n o s e o f t h e f l a p a n d t h e a i l e r o n . U s u a l l y , t h en o z z l e d e p th w a s r e g u l a t e d b y s ma l l s p a c e r s a t 2 - i n c h i n t e r v a l s a c r o s s t h e s p a n . T o s imu la t e t h e e f f e c to f p r o p o s e d f l a p a n d a i l e r o n s u p p o r t - g e a r a r r a n g e m e n t s , a l t e r n a t i v e la r g e r - s p a n s p a c e r s w e r e p r o v i d e dt o s e a l t h e a p p r o p r i a t e s e c t io n s o f t h e n o z z l e s p a n .

F o r a i r c r a f t d e s i g n r e as o n s , t h e i n b o a r d l i m i t o f t h e l e a d i n g - e d g e b l o w i n g n o z z l e w a s d e t e r m i n e d b y t h ew i n g f o l d a t 4 4 p e r c e n t s e m i - s p a n . T h e l e a d i n g - e d g e b l o w i n g a r r a n g e m e n t o r i g i n a l l y t e s t e d b y H . S . A .( B r o u g h ) , p r o v id e d a n o z z l e a t 5 p e r c e n t c h o r d , i n c l i n e d a t a b o u t 3 0 t o t h e l o c a l w in g s u r f a c e see Fig. 3b).F o r t h e i n i t i a l R . A .E . t es t s , a d d i t i o n a l n o z z l e s a t 1 p e r c e n t - 2 p e r c e n t c h o r d ( w i th t a n g e n t i a l e j e c t i o n )w e r e a r r a n g e d b y t h e a d d i t i o n o f a u x i l i a r y b r as s n o s e - p l a t e s , w i t h s m a l l s p a c e r s t o r e g u l a t e t h e n o z z l ed e p t h see F ig . 3 c ) . I n a d d i t i o n , a n o z z l e a t p e r c e n t c h o r d w a s c o n t r i v e d b y t h e u s e o f a f u r t h e r b r a s sn o s e p l a t e i n c o r p o r a t i n g a s e r ie s o f n o z z l e s f o r m e d b y s a w - c u t s i n c l i n e d a t a b o u t 3 0 t o t h e l o c a l s u r f a c e( F ig . 3 d ) . F o r t h e f i n a l R . A . E . t e s t s , a s i n g l e n o s e u n i t w a s ma n u f a c tu r e d i n c o r p o r a t i n g tw o a l t e r n a t i v en o z z l e s ( a t p e r c e n t a n d 1 p e r c e n t c h o r d ) , e a c h n o z z l e i n c l i n e d a t 3 0 to the loca l sur face (F igs . 3ea n d 3 f) . T h e n o z z l e d e p t h w a s r e g u l a t e d b y i n t e r n a l s p a c e r s u p s t r e a m o f th e f i n al c o n t r a c t i o n , s o t h a t t h ea c t u a l n o z z l e s w c r c u n o b s t r u c t e d . B y t h e c a r e fn l u s e o f a s t if f A r a l d i te m i x t u r e o f m i n i m u m a d h e s i v es t r e n g th , i t w a s p o s s ib l e t o s e a l a n d o p e n e a c h n o z z l e i n t u r n , a s d e s i r e d .

M o s t o f t h e t e s ts w e r e m a d e a t 2 0 0 ft /s e c, c o r r e s p o n d i n g t o a R e y n o l d s n u m b e r o f 3 .0 x 1 06 b a s ed o ns t a n d a r d m e a n c ho rd ~, b u t t h e s p e e d w a s r e d u c e d t o 1 4 0 f t /s e c f o r c e r t a i n t e s ts a t r e d u c e d M a c h n u m b e r .T h r o u g h o u t , t r a n s i t i o n w a s l ef t f r e e o n t h e w in g a n d t h e t a i l p l a n e , b u t f i xe d o n t h e f u s e l a g e n o s e .

3. Test Procedure.3.1. Th e Ef fect o f Blowing Air Su pply on Balance Zeros .

F o r t h e f i rs t s er i e s o f t e s t s a t R . A .E . , a s imi l a r a i r s u p p ly a r r a n g e m e n t s w a s a d o p t e d a s f o r th e e a r l i e rb lo w in g t e s t s 2 3 4 , u s in g a c a n v a s - s l e e v e n e c k e d c o n n e c to r . F o r t h e l a t e r t e s t s , t h e a i r c o n n e c t i o n w a se f fe c te d b y a n a i r - b e a r in g c o n n e c t o r 6. T h e z e r o s f o r b l o w - o n r u n s w e r e t a k e n w i t h t h e a p p r o p r i a t e s t at i c-p r e s s u r e c o n d i t i o n s i n t h e c o n n e c t o r s . T h e z e r o s c a t t e r w a s n o t a p p r e c i a b l y g r e a t e r t h a n t h a t w h i c h w o u l dh a v e o c c u r r e d w i t h a c o n v e n t i o n a l ( u n b l o w n ) m o d e l o n t h i s b a l a n ce .

3.2. Specif ica t ion o f Blowing M om entu m Coef fi c ient .T h e g r o s s b l o w i n g m o m e n t u m c o e ff i ci e n t, C , , w a s d e f i n e d 5 i n t e r m s o f t h e m e a s u r e d m a s s - f lo w r a t e,a n d t h e t h e o r e t i c a l v e l o c i t y a f t e r i s e n t r o p i c e x p a n s i o n t o f r e e - s t re a m s t a ti c p r e s s u r e see L is t o f S y mb o l s ) .

S p a n w i s e t r a v e r s e s o f n o z z l e t o t a l h e a d w e r e m a d e see F i g . 5) t o d e t e r m i n e m e a n v a l u e s f ro m w h i c h t h el et v e l o ci t y c o u l d b e c a l c u l a t ed . T h e m o m e n t u m - c o e f f i c i e n t v a l u e s o b t a i n e d f r o m t h e m e a s u r e d m a s s - f l o wr a t e a n d j e t v e l o c i ty w e r e c o n s i s t e n t w i t h t h e s l i g h t ly l a r g e r v a l u e s d e r iv e d f r o m t h e n o m i n a l n o z z l e a r e aa n d t h e j e t v e lo c i t y .

S u f fi c e s h a v e b e e n u s e d t o d i s t i n g u i s h b e tw e e n n o s e b lo w in g ( C ~,,) a n d r e a r s h r o u d b lo w in g ( C ,R ).M e a n s e c t i o n a l c o e f f ic i e n t s , C ~N a n d C u R w e r e d e f i n e d l i k e w i s e , w i th t h e g r o s s w in g a r e a r e p l a c e d b y t h ea r e a , S , o f t h e w i n g c o r r e s p o n d i n g t o t h e s p a n o f th e b l o w i n g n o z z l e . T h u s :

4


6/53

SC z~ = C ,~ ~ , = 2 .6 Cz ~, f o r t he f i nal l ea d ing- e dge a r r a nge m e ntoNSC~r = Cz ~ ~ = 1 - 55 Cz r .

Fo r t he a va i l a b l e p r e s sur e r a t i o o f a bo u t 3 :1 , t he m a xim um va lue s o f CgN a nd C ,~ w e r e a ppr o x im a te ly0 .045, 0 .07 r e spe c t i ve ly ( e a c h c or r e spo nd in g t o se c t iona l va lue s o f a bo u t 0 .11), a t t he usua l t e s t spe e d o f200 f t / sec . For the a i rc ra f t , engine thrus t considera t ions res t r ic ted the va lue of (C,N + C~R)to 0 '065 for thet a ke - of f c o nf igur a t ion .T he noz z l e w id th wa s va r i e d spa nwise , b r oa d ly i n p r opor t i on t o t he l oc a l w ing c hor d , a nd t he noz z l et o t a l h e a d d i d n o t v a r y m u c h a c r o s s th e s p a n o f e a c h n o z z le (see Fig . 5 ). T hus , t he l oc a l s e c t i ona l m om e n-tum c oe f fi c ie n t s e ns ib ly r e m a ine d e q ua l t o t he m e a n se c t i ona l m om e ntu m c oe f fi c ie n t a c r oss t he spa n o feach nozz le .

3.3. Corrections.I n a d d i t i on t o t he usua l a l l owa n c e s f o r so l i d b loc ka ge , su i t a b le corrections h a v e b e e n a p p l i e d t o a l l o w

f or i nc r e a se d w a ke b lo c ka ge w he n f l ow se pa r a t ions a r e p r e se n t 7 . T he r e su l t i ng c ha nge s i n t he nom ina lt e s t v al u e s o f m a i n s t r e a m d y n a m i c h e a d , Po V0 , a m ou nte d t o 2 p e r c e n t -3 5 pe r c e n t ( a t o r be low thes ta l l) and up to 12 per ce nt (ab ove the s ta ll ).T h e f o ll o w i n g tu n n e l c o n s t r a i n t* c o r r e c ti o n s w e r e a d d e d s u b s e q u e n t l y :

A O ~ d e g r e e s 0 83 7 Cr. . .. ,p~anoACoo = 0 0145 C~ . . . .plano

( T a i lp l a ne -on r uns ) ACm = - 0 4 3 5 ( ~ ) CL . . . ,p t~no ( r/ r i n de gr e e s) T o a s s i st d i r ec t c om pa r i son w i th t he f i r m ' s m od e l t e s t s fo r t h is a i rc r a ft , t he p i t c h ing- m om e nt c oe f fi c ie n t s

h a v e b e e n b a s e d o n t h e s t a n d a r d m e a n c h o r d ~ , r a t h e r t h a n t h e a e r o d y n a m i c m e a n c h o r d ~, a n d h a v e b e e nr e f e rr e d t o 0 .25 ~ ( N .B . ~ = 0 946 ) .

4. Tests with Shroud Blowing over the.Trailing-Edge Flap and Droop ed Aileron, without Leading-EdfleDevices.4.1. Scope.

In the pre l imin ary tes ts by the f i rm in thei r 7f t x 5f t tunne l , the e f fec t of t r a i l ing-edg e sh rou d b low ingove r t he f l a p a nd a i l e r on wa s s tud i e d i n som e de t a i l . A l though the se t e s t s we r e sub j e c t t o qu i t e l a r getunne l c ons t r a in t e ff ec ts , by nor m a l r e se a r c h s t a nda r ds , use f u l r e su l ts we r e ne ve r the l e s s ob t a ine d a t l owinc ide nc e s . Conse q ue n t ly , t he R .A .E . t e s t s we r e m a in ly c o nf ine d t o a c onf i r m a t ion o f t he ge ne r al e f f e c tso f sh r ou d b low ing und e r c ond i t i ons o f r e duc e d t unne l c ons t r a in t ( Se c t ions 4.2, 4.3, a nd 4 .4 ). I n a dd i t i on ,i t w a s n o w f e as ib l e to m a k e m e a s u r e m e n t s o f m e a n d o w n w a s h a t t h e t a i lp l a n e ( S e c t io n 4 .4 ). F o r t h e set e s ts , a s t a nda r d m o de l c o nf igur a t i on wa s a do p te d , w i th t he f in p l a t e p r e se n t, t he t a i l p l a ne o f f ( un le s so the r w i se spe ci fi ed ), t he a i r b r a k e r e t r a c t e d , a n d t he unde r c a r r i a ge a s se m bly r e m ove d . T he ba s i c un-de f l e c te d w ing l e a d ing e dge wa s use d , w i tho u t l e a d ing- e dge b lowing . T he sh r o ud noz z l e wa s unob s t r uc t e d ,e xc e p t f o r sm a l l , r e gu l a t ing spa c e r s .T he e ff ec t o f pa r t i a l noz z l e b loc k a ge , r e pr e se n t ing p oss ib l e obs t r u c t i on by a i r c r a ft f l a p a nd a i l e r onsup por t ge a r , wa s s im ula t e d f o r c e r ta in r e pr e se n t a t i ve c a se s ( Se c t ion 4 .5) . F ina l ly , a f e w t e s t s we r e m a d ewi th t he pe t a l - t ype a i r - b r a ke a t t he r e a r o f the f use l a ge f u ll y e x t e nde d , a nd w i th t he m a in unde r c a r r i a gea sse m bly a dd e d ( Se c t ion 4 .6) .

T he c or r e spon d ing c or r e c t i ons f o r t he e xp lo r a to r y t e s t s by t he f ir m we r e som e th r e e t im e s t h i s s iz e(S/C = 0.34, com pa red wi th 0 .11 for the R.A.E. tes ts ).


7/53

4.2. L i f t .T h e p o s i t i o n o f t h e w i n g f o l d r e l a ti v e t o t h e e x p o s e d w i n g s e v e r e ly li m i t e d t h e s p a n w i s e e x t e n t o f th e

a i r c r a f t f la p i n b o a r d o f t h e f o l d , w h i l e p r a c t i c a l d e s i g n c o n s i d e r a t i o n s f a v o u r e d t h e u s e o f a l a r g e - s p a nc o n s t a n t d e f l e c t i o n a i l e r o n o u t b o a r d o f t h e f o ld . I n o r d e r t o me e t t h e t a k e - o f f a n d l a n d i n g li ft r e q u i r e -me n t s , th e r e f o r e , m e a n d r o o p w a s a p p l i e d t o t h e a i l e r o n , t o g e t h e r w i t h t h e u s u a l p r o v i s i o n f o r d i f f e re n t i a lmo v e m e n t o f th e a i l e r o n s f o r r o l l c o n t r o l , w i t h i n t h e o v e r a l l d e s i g n d e f l e c t i o n li m i t o f a b o u t 4 5 . Co n s i d e r -a t i o n o f r o l l in g c o n t r o l r e q u i r e m e n t s s u g g e s t e d a p r o v i s i o n a l l i m i t o f 3 0 o n m e a n a i l er o n d r o o p , o n t h ea s s u m p t i o n t h a t b l o w i n g B . L . C . w o u l d e n s u r e a r e a s o n a b l e c o n t r i b u t i o n t o r o l l i n g m o m e n t f r o m t h ed o w n - g o i n g a i le r o n w i t h t h is v a l u e o f m e a n d r o o p s e e Se c t i o n 4 .5 a n d A p p e n d i x B) .

T h e g e n e r a l e f fe c t o f s h r o u d b l o w i n g o v e r t h e f l a p a n d t h e d r o o p e d a i l e r o n i s s h o w n i n F i g . 6 f o r re p -r e s e n t a t i v e f l a p a n d a i l e r o n s e t t i n g s. A t t h e l o w e s t C , R- v a l u e s e x a m i n e d ( C , R = 0 -0 2 0, e q u i v a l e n t t oC~R = 0 0 32 ), t u f t s in d i c a t e d t h a t a t t a c h e d f l o w w a s a c h i e v e d o v e r mo s t o f t h e s p a n o f th e c o n t r o l s , a sw o u l d b e e x p e c t e d i n v i e w o f t h e i n c r e a s e o f 6 0 p e r c e n t t o 8 0 p e r c e n t i n t h e e f f e c ti v e n e ss o f th e c o mb i n e df l a p a n d a i l e r o n , r e la t i v e t o t h e u n b l o w n c o n d i t i o n . T h u s , t h e v a l u e o f C , R = 0 ' 0 4 p r o p o s e d f o r th e a i r -c r a f t w a s s u f f ic i e n t t o e n s u r e w e l l - a t t a c h e d f l o w , w i t h a d e q u a t e s a f e t y ma r g i n s . F u r t h e r i n c r e a se s i n l if t a tc o n s t a n t i n c i d e n c e w o u l d n a t u r a l l y r e s u l t f r o m l a r g e r v a lu e s o f C , R , b u t a t a r e d u c e d r a t e see Fig. 6).M o r e o v e r , c o m p a r a b l e l if t i n c r e m e n t i n c re a s e s c o u l d b e a c h i e v e d a n y w a y w i t h l e a d i n g - ed g e b l o w i n g *see Sect ion 5 .4 ) , w i th a dd i t ion a l ben ef i c i a l e ffec t s on s t a l l i ng inc id ence an d CLr .,~

Be c a u s e o f t h e s p a n o f t h e f la p , t h e v a r i a t i o n o f li ft w i t h f l a p a n g l e a t a p r e s c r i b e d v a l u e o f C , R ( F i g . 8 a)w a s i n e v i t a b l y s ma l l, c o m p a r e d w i t h th e c o r r e s p o n d i n g v a r i a t i o n w i t h a i le r o n a n g l e ( F i g. 9 a ). I n a d d i t i o n ,t u f t s s h o w e d t h a t c o mp l e t e l y a t t a c h e d f l o w c o u l d n o t b e a c h i e v e d o n t h e s ma l l - s p a n f l a p , p a r t i c u l a r l ya t l a r g e f l a p a n g l es . T h u s , f r o m t h e p o i n t o f v i e w o f li ft , t h e o p t i m u m f l a p a n g l e w a s r a t h e r l o w , a b o u t 4 5 see Fi g . 8 a) , c o m p a r e d w i t h p r e v i o u s e x p e r i e n c e o n l a r g e r - s p a n i n b o a r d f l a p s 2 3 4 .

I n t h e c h o i c e o f t h e a i r c r a f t t a k e - o f f c o n f i g u r a t i o n , e n g i n e t h r u s t c o n s i d e r a t i o n s n e c e s s i t a t e d a c o m -p r o mi s e b e t w e e n t h e c o n f l i c t i n g r e q u i r e me n t s f o r h i g h l i f t a n d l o w d r a g s e e Sect ion 4 .3 ) . Thu s , t he f l apa n d me a n a i l e r o n d r o o p s e t t in g s w e r e i n i t i a l l y l i m i t e d t o 3 0 a n d 2 0 r e sp e c t iv e l y . Fo r l a n d i n g t h e c o r r e s -p ~md i n g s e t t in g s o f 4 5 a n d 3 0 e n s u r e d h i g h e r li ft . w i t h t h e r e t e n t i o n o f a d e q u a l e a i l e r o n e f fe c t iv e n e s s f o rro l l con t ro l ~ i th the b as i c u n in t e r ru p te d t~l ,,~ ~ng nozz le ( see F ig . 9a and Sec t ion 4 .5~.

W i t h t h e a p p l i c a t i o n o f th e a p p r o p r i a t e a s p e c t r a t i o a n d p a r t - s p a n li ft c o n v e r s i o n f a c t o r s , t h e e x p e r i-me n t a l l if t i n c r e m e n t s c o m p a r e r e a s o n a b l y w e l l w i t h t h e c o r r e s p o n d i n g r e s u l ts f o r a s i m i l a r c o n f i g u r a t i o n( S. R. 1 7 7 ) w i t h s h r o u d b l o w i n g o v e r t h e f l a p a n d t h e a i l e r o n s e e Fig. 33b o f Ref. 3) .B e c a u se o f t h e m a g n i t u d e o f t h e n o s e - d o w n p i t c h i n g - m o m e n t c h a n g e s d u e t o t h e b l o w n f la p a n d a i l e r o n ,a n d t h e s h o r t t a i l - a r m , t h e a s s o c i a t e d t r i m mi n g l o s s e s w e r e a p p r e c i a b l e . T y p i c a l l y , f o r fl = 3 0 , ~ = 2 0 and Cu ,, = 0 .04 . t he li ft pen a l ly am ou nte d to ~( 'L~ = -0 .14 . ab ou t 2 (I pcr cen t o f the li ft increm ent du et o t h e f la p a n d d r o o p e d a i l e ro n {see Se ct ion 4 .4 an d Vig. I I I .

4.3. Drag .T h e g e n e r a l e f f e c t o f s h r o u d b l o w i n g o n t h e C D v . C L ( n o t a i l) c u r v e s i s s h o w n i n F i g . 7 , f or r e p r e s e n t a t i v e

s e t t in g s o f t h e f l a p a n d d r o o p e d a i l e r o n . T h e v a r i a t i o n o f d r a g w i t h f l a p a n g l e a n d w i t h a i l e r o n a n g l e iss h o w n i n F i g s . 8 b a n d 9 b r e s p e c t i v e ly , f o r p r e s c r i b e d v a l u e s o f CuR . T h e m e a s u r e d d r a g c o e f f i c ie n t s i n c l u d ea n y je t t h r u s t w h i c h m a y b e r e c o v e r e d .

F o r t h e u n b l o w n f la p a n d a i le r o n , t he d r a g p e n a l t y a t a c o n s t a n t l o w C L - v al u e i n c re a s e d w i t h f l ap a n da i l e r o n a n g l e , a m o u n t i n g t o a b o u t A CD = + 0. 02 a t / 3 = 3 0 , ~ = 2 0 . A t s u c h m o d e r a t e c o n t r o l a n g l e s ,t h e r e d u c t i o n i n C D a t c o n s t a n t CL d u e t o b l o w i n g w a s n e a r l y e q u a l t o t h e a p p l i e d v a l u e o f C ,R . H o w e v e r ,a t h i g h e r d e f le c t i o n s , t h e r e w a s a n e t p e n a l t y a s s o c i a t e d w i t h t h e a p p l i c a t i o n o f b l o w i n g a s w e l l a s ah i g h e r A C o f o r t h e u n b l o w n c a s e . T h u s , s i g n i f i c a n t v a r i a t i o n s i n d r a g o c c u r r e d a s t h e a n g l e o f t h e s ma l l -s p a n b l o w n f l a p w a s v a r i e d , a l t h o u g h t h e c o r r e s p o n d i n g l i f t c h a n g e s w e r e s ma l l see Figs . 8a and 8b) .T h e c o r r e s p o n d i n g v a r i a t i o n o f d r a g w i t h a i le r o n s e t t in g s e e Fi g . 9 b ) w o u l d b e e x p e c t e d t o r e s u l t i ns i g n i f ic a n t y a w i n g mo m e n t s , o n t h e a p p l i c a t i o n o f a i l e r o n d i f f e r e n ti a l i n t h e p r e s e n c e o f s h r o u d b l o w i n g .

*A ssum ing a l im i t a t io n on the to t a l va lues o f CuN + CuR of 0.065 .


8/53

T he va r i a t i on o f CD wi th C~ r e m a ine d e s se n t ia l l y li ne a r ov e r a w ide i nc ide nc e r a nge see Fig. 7d) , wi thdCDt he va lue o f ~zA 5 - ~ de c r e a s ing s ign i fi c a n tly w i th de f l e c t ion o f tr a i li ng- e dge c on t r o l s a nd a pp l i c a t i on o fd C Lblo win g f rom 1.26 (f laps up) to 1 .15 ( fl = 45 , ~ = 30 , C~R = 0-04).As usua l , t he r e wa s a ne e d to op t im i se t he f l a p / a i l e ron b low ing c onf igur a t ion a t t a ke - off , t o m in im isedr a g . For t he l a nd ing c onf igur a t i on , a dd i t i ona l d r a g c ou ld be p r ov ide d , w i th be ne f i c i a l r e duc t ions i nm in im um dr a g spe e d , by su i t a b l e i nc r e a se s i n t he d i ff e re nc e be tw e e n the f la p a ng le a nd the m e a n a i l e r ondr oo p angle 1 'a '4 .

4.4. P i t c h i n g M o m e n t s a n d D o wn w a s h a t t h e Ta i l p la n e .Pi t c h ing m o m e nt s a r e r e f e rr e d to t he t e s t c g a t 0 .25 ~ on the w ing c hor d p l a ne a nd the f use l age da tum .T o f a c il i ta t e d ir e c t c om pa r i son w i th t e s t s by the fi rm , t he p i t c h ing - m om e nt coef f i c i en t s ha ve b e e n r e f er r ed

to s t a nda r d m e a n c ho r d c ~ = 0 .946 . T he ge ne r a l e ff ec t o f sh r ou d b lowing on the Cm v . C L c ur ve s isshow n in F ig . 7 f o r va r ious f l a p a nd a i l e r on se t t ings . A f e w r e pr e se n ta t ive c ur ve s a r e g ive n w i th t he t a il -p l a ne p r e se n t , i nc lud ing t e s t s w i th t he t a i l p l a ne t r im m ing f l ap de f l ec t e d .

De f l e c t i on o f t he f l ap a nd d r oo pe d a i le r on , t oge the r w i th t he a pp l i c a t i on o f sh r ou d b lowing , r e su lt e din the e xpe c t e d nose - do wn p i t c h ing- m om e nt c ha nge s f o r t he w ing w i thou t t he t a i lp l a ne . Be c a u se o f t hed i f fe r e nc e i n spa n a nd the sw e e pba c k o f t he c on t r o l h inge -l ine , t he va r i a t i on o f p i t c h ing m o m e nt w i th f l a pa ng le ( Fig. 8c) wa s na tu r a l l y m uc h sm a l l e r tha n the c or r e spon ding va r i a t i on w i th m e a n a i l e r on d r oo p( Fig. 9c ). T he p i t c h ing- m om e nt a nd l if t i nc r e m e nt s d ue to m e a n a i l e r on d r o op w e r e p r opo r t i ona l , so t ha tthe a pp l i c a t i on o f a i l e r on d i f fe r e n ti a l fo r r o l l c on t r o l w ould n o t b e e xpe c t e d to r e su l t i n l a rge p i t c h ing-m om e nt va r i a t i ons a t a g ive n m e a n a i l e r on de f l e c t i on .

An inc r e a se i n s t a t ic s t a b i l i t y ge ne r a ll y r e su l t ed f r om the a pp l i c a t i on o f b low ing in t he a bse n c e o f thet a i lp l a ne , t oge th e r w i th a n i nc r e a se in t he se ve r i ty o f t he w ing p i t c h- up a t t he s t al l. T h e va r i a t i on o f m e a ndow nw a sh a t t he t a i l p l a ne ( Fig. 10) wa s de d uc e d f r om c o m p a r i son o f r e su lt s w i th a nd w i thou t t he t ai l-p l a ne . T he a pp l i c a t i on o f b low ing inc r e a se d the dow nw a sh a t t he t a i l p l a ne b y a bo .u t 2 , s l igh t ly inc r e a se dthe t a i l p l a ne c on t r ibu t ion to s t a t i c s t a b i l i t y , bu t d id no t se e m to a f f e c t t he t a i l p l a ne powe r

t t/----~- ~ -0 .0 12 per deg ree to a s igni f icant exten t ; in mo st cases , there w as a gradual redu c t ion of thet a i l p l a ne po we r w i th i nc r e a s ing inc ide nc e .T h e m a g n i t u d e o f t h e n o s e - d o w n p i t c h i n g - m o m e n t i n c re m e n t s d u e t o t h e b l o w n f la p a n d d r o o p e da i l e ron , t oge the r w i th t he sm a l l t af t a r m ( 1.96 ~ ), ne c e ss i t a t e d c om bine d use o f a n a l l - m oving t a i l p l a nea nd a t a i l p l a ne f la p f o r t r im m ing . T he a s s oc i a t e d l if t l os se s due to t r im m ing we r e a ppr e c i a b l e . T hus , w i thB = 30, ~ = 20 a nd C ,R = 0 .04 ( the o r ig ina l a i r c r a f t t a ke - of f c onf igur a ti on) , t he l os s a m oun te d toACL~ = - 0 - 1 4 w i t h t h e cg at 0-32 ~ see Fig. I1) , som e 20 per cent of the to ta l l if t increm ent du e to f lapa n d d r o o p e d a i l er o n .T he p r e se n t t e s t s showe d a m a xim um t a i lp l a ne i nc r e m e nt ( w i th t ai l p l a ne f l a p de f l ec t e d) o f a bo u tACmt = 0.4, fol low ed by a gent le ta i lplane s ta l l see Fig . 7 ). A t a h ighe r R e yno lds num be r , w i th l e a d ing-e dge b low ing on the t a i l p l a ne a s we l l a s a t r im m ing f la p , o the r t e s t s sugge s t e d tha t t he a i r c ra f t t a i l p l a neshould achieve at least a Cr.m~xof - 1 5 ( ba se d on t a i lp l a ne a r ea ) , c o r r e spondin g to ACm ~ = 0 .44 a ndACL t = - 0 .2 2 . T h e a i r c ra f t cg l im i t s we r e c hose n a c c or d ing ly , t o e nsur e a n a de qu a te m a r g in a ga ins t t he

pos sibi l i ty of an ina dver ten t ta i lplan e neg a t ive s ta l l a t high l i f t . Also. the nega t ive ta i lplane m ov em enta va i l a b l e ( som e - 2 0 se l at i ve t o da tum ) w a s a de q ua te t o a l l ow t rim m ing th r ou gho ut t he usa b le inc ide nc er a nge . A t t he r e a r m os t cg con tem pla te d (0.32 ~), the s ta t ic s tab i l i ty margin was ab ou t 0 .08 ~ in a typica lc a s e

4.5. Th e E f f e c t o f Lo c a l N o z z l e B l o c k a g e , R e p r e s e n ti n g F l a p a n d S u p p o r t G e a r .T he e f f e ct o f pa r t i a l noz z l e b loc ka ge , r e pr e se n t ing the po ss ib l e obs t r uc t ions c a u se d b y p r opo se da i r c ra f t a r r a nge m e nt s f o r t he fl a p a nd a i l e r on sup por t ge a r , wa s de t e r m ine d by in t r oduc ing w ide spa c e r s

in to t he sh r o ud b low ing noz z l e a t t he a pp r op r i a t e spa nwise pos i t i ons . A t m o de l sc a le , t h r e e 0 .48-inc h


9/53

w i d e s p a c e r s w e r e i n s e r t ed a c r o s s t h e s p a n o f t h e a i l e r o n a n d o n e 0 . 3 2 - i n ch w i d e s p a c e r o p p o s i t e t h e f l a p .A l t o g e t h e r , th i s b l o c k a g e a m o u n t e d t o o n l y a 4 p e r c e n t r e d u c t i o n i n t o t a l n o z z l e a r e a . T h e s h r o u d b l o w i n gp r e s s u r e w a s i n c r e a s e d b y a s u i t a b l e a m o u n t t o r e s t o r e t h e o r i g i n a l v a l u e o f C ~R .

T h e d e t r im e n ta l e f f e c t o f s u c h b lo c k a g e i n c r e a s e d a t l a r g e d e f l e c t i o n a n g l e s (F ig . 9 ), a s f o u n d p r e v io u s ly 3 .P a r t i c u l a r l y s e r io u s w a s t h e i m p l i c a t i o n o f an a l m o s t c o m p l e t e l o s s o f e f fe c ti v e n es s f o r ro l l c o n t r o l * o f th ed o w n w a r d - m o v i n g a i l e ro n , f o r t h e p r o p o s e d a i r c r a ft l a n d i n g c o n f i g u r a t i o n w i t h a m e a n a i l e r o n d r o o p o f3 0 . C o n s e q u e n t l y , a p a r t i a ll y s u c ce s sf u l a t t e m p t w a s m a d e t o m o d i f y t h e d e s i g n o f t h e f l ap a n d a i l e r o ng e a r t o m i n i m i s e s u c h i n t e r r u p t i o n s o f t h e s h r o u d n o z z l e o n t h e a i r c ra f t .T o a c h i e v e m a x i m u m b e n e f it f r o m a B . L .C . b l o w i n g i n s t a l l a t io n , i t is e ss e n t ia l t o m i n i m i s e d i s c o n t i n -u i t i e s i n t h e b lo w in g n o z z l e ef f lu x , o r i n t h e u p p e r s u r f a c e c o n to u r o f t h e d e f l e c t e d c o n t r o l s 2 .

4.6. T h e E f f e c t o f t he A i rb ra k e and the M a in U nde rc ar r iage A s se m b ly .T h e a d d i t i o n o f t h e m a i n u n d e r c a r r i a g e a s s e m b l y ( w i th o r w i t h o u t t h e d o o r ) c a u s e d a r e d u c t i o n i n l if t

a t c o n s t a n t i n c i d e n c e . T h e l i f t l o s s i n c r e a s e d w i t h C , R , a m o u n t i n g t o A C L = - - 0 ' 0 7 f o r t h e t a k e - o f fcon f ig ura t io n f l = 30 , ~ = 20 , CuR = 0 04; the loss w i th f l = 60 , ~ = 30 , CuR = 0 04 was Similar inm a g n i t u d e . I n e i t h e r c a se , th e a s s o c i a t e d d r a g i n c r e m e n t a t c o n s t a n t C L a m o u n t e d t o A C D - '- 0 .0 2 . T h eo v e r a l l t r im c h a n g e s w e r e s ma l l , a s t h e p o s i t i v e n o - t a i l p l a n e p i t c h in g - m o m e n t i n c r e m e n t ( A C , , ----- + 0 -0 3 )w a s a c c o m p a n i e d b y a r e d u c t i o n i n d o w n w a s h a t th e t ai l p la n e .E x t e n s io n o f t h c p e t a l - t y p e a i r b r a k e s ( w i th s t r a k e s ) d id n o t c a u s e a n y a p p r e c i a b l e c h a n g e s i n l i f t . T h ed r a g i n c r e m e n t a t c o n s t a n t C~. a m o u n te d t o A C D -----0 0 9 . T h e r e w a s a l s o a s ma l l n o s e - d o w n p i t c h in g -m o m e n t i n c r e me n t , A C ,, --~ ~ 0 .0 2, w i lh a n d w i th o u t t h e t a i l p l a n e p r e s e n t , f o r t h e c a s e s e x a m in e d .

a. Tes ts w i th Lead ing-E dge Dev ices .5.1. Scope.

A l th o u g h t h e p r e l imin a r y t e s t s in t h e 7 ft x 5 f t t u n n e l i n c lu d e d e x t e n s iv e s t a l l in g i n v e s t i g a t i o n s , t h e s ew e r e n e c e s sa r i ly e x p l o r a t o r y i n n a t u r e i n v ie w o f t h e m a g n i t u d e o f t h e t u n n e l c o n s t r a i n t c o r r e c t i o n sa n d t h e p o s s i b i l it y o f u n r e p r e s e n t a t i v e e f f e ct s o n t h e s t a l li n g b e h a v i o u r (see A p p e n d i x A ).

F o r c o m p a r a t i v e p u r p o s e s , a f e w p r e l i m i n a r y t e s t s (S e c t i o n 5.2 ) w e r e m a d e a t R . A .E . w i t h s o m e e x i s t in gc o n v e n t i o n a l m e c h a n i c a l h i g h - l i f t l e a d i n g - e d g e d e v i c e s , i n c l u d i n g a p a r t - s p a n l e a d i n g - e d g e s l a t w i t hc h o r d e x t e n s io n , a n d a p a r t - s p a n l e a d in g - e d g e f l a p . H o w e v e r , t h e ma in t e s t s ( S e c t i o n s 5 . 3 a n d 5 . 4 ) c o n -c e r n e d t h e d e v e l o p m e n t a n d o p t i m i s a t i o n o f a s u i t a b le B . L .C . b l o w i n g a r r a n g e m e n t f o r t h e p r e s c ri b e da i r c r a f t inte,qrati l e a d i n g -e d g e c o n f i g u r a t i o n . F o r t h e p r e s e n t c o m p a s a t i v e l y t h i n w i n g ( t y p ic a l ly 8 p e r c e n tR . A .E . 1 01 s t r e am w i s e , w i t h s o m e l o c a l a d d e d n o s e c a m b e r ) , t h is i n v o l v e d n o t o n l y t h e d e t e r m i n a t i o n o ft h e b e s t b l o w i n g n o z z l e p o s i t i o n , a n d d e t a i le d m o d i f i c a t i o n s t o t h e w i n g n o s e s h a p e , b u t a l so t h e i n v e s t i g a t-i o n o f m a i n s t r e a m M a c h n u m b e r e f fe ct s.

5.2. P re l im inary T e s t s w i th M e c han ic a l L e a d ing - E dge D e v ic e s.T h e r e s u l t s o f b r i e f t e s t s o n a n e x i s t i n g le a d in g - e d g e s l a t a r r a n g e m e n t a r e s u m ma r i s e d i n F ig . 1 2 . T h i s

s l a t , w h i c h o n l y e x t e n d e d f r o m 5 5 p e r c e n t s e m i - s p a n t o t h e w i n g t i p , p r o v i d e d a n a v e r a g e c h o r d w i s ee x t e n s io n o f s o me 1 5 p e r c e n t a n d w a s s e t a t 1 5 d e f l e c t i o n .F o r t h e v a r i o u s f l a p a n d a i l e r o n c o n f i g u r a t i o n s w i t h o u t t r a i l i n g - e d g e s h r o u d b l o w i n g (CuR = 0) , thea d d i t i o n o f t h e s l a t imp r o v e d C Lmoxa n d s u b s t a n t i a l l y d e l a y e d t h e o n s e t o f st a ll , r e l a t i v e t o t h e b a s i cu n d e f l e c t e d a n d u n b l o w n w i n g n o s e . A t t h e h i g h e r r e a r l o a d i n g s w h i c h o c c u r r e d w i t h s h r o u d b l o w i n g o v e rt h e t r a i li n g - e d g e f la p a n d d r o o p e d a i l e r o n , h o w e v e r , th i s p a r t - s p a n s l at d i d n o t i m p r o v e C L m , x b ec a us e o fi n b o a r d w in g f l o w s e p a r a t i o n s . H o w e v e r , t h e s e v e r i t y o f t h e p o s t - s t a l l li ft l o s se s w e r e r e d u c e d b e c a u s e o f

* I t is n e c e s s a r y t o a s s u me , w i th a h a l f mo d e l , t h a t t h e e f f e c t i v e n e s s o f a il e r o n d i f f e re n t i a l f o r r o l l c o n t r o lc a n b e i n f e r r e d f r o m t e s t s w i th a r a n g e o i s y mme t r ] c a ] d r o o p s e t t i n g s .

t A I t h o u g h s u p e r i o r a n d m o s e s t r a i g h t f o r w a r d a e r o d y n a m i c a l l y ( see S e c t i o n 5 . 2 ) t h e a l t e r n a t i v e o f al e a d in g - e d g e f l a p w i th B . L . C . a t t h e k n u c k l e w a s n o t i n v e s t i g a t e d , b e in g r e j e c t e d a s u n a c c e p t a b l e f o rs t r u c t u r a l r e a s o n s i n t h e p r e s e n t c a s e .


10/53

t he im pr o ve d ou t e r - w ing f l ow , a nd t he r e wa s som e a l le v i a t i on o f t he se ve r i t y o f t he p i t ch- up . N o a t t e m p twa s m a d e t o im pr o ve t he s l a t a rr a nge m e nt , o r t o va r y i ts spa nwise e x te n t .Fu r the r e xpe r im e nt s , w i th a s im ple unb low n de f l e c t e d l e a d ing- e dge f la p ( no a re a e x t e ns ion) on t he

ou te r pa r t o f t he w ing spa n p r o du c e d r e su l t s ge ne r a l ly r e se m bl ing t hose ob t a ine d f o r t he pa r t - spa n s la t.t he s t a ll s t a r t ing . e i t he r on t he i n bo a r d w ing o r a t t he j unc t i on w i th t he l e a d ing- e dge f la p . Be t t e r re su l tswe r e ob t a ine d w i th t he l e a d ing- e dge f l a p e x t e nde d inb oa r d , t he r e su l t s f rom the m os t p r om is ing c on-f igur a t ion be ing sum m a r i se d i n F ig . 13. He r e , t he unb low n l e a d ing- e dge f l a p e x t e nde d f r om 32 pe r c e n tsemi-span to the t ip , wi th 30 def lec t ion normal to the f r inge- l ine (on the wing lower sur face) . Over theou te r p a r t o f t he w ing , the h inge - l ine w a s a t 15 pe r c e n t c hor d , b u t du e t o t he i nc r e a se d l e a d ing- e dgeswe e p ba c k t he f l ap c hor d wa s a pp r e c i a b ly g r e a t e r a t t he i n boa r d e nd o f t he f la p . T o a c h i e ve t he r e su lt ssho wn in Fig. 13, a nos e fence was ne cessary a t th e inb oard end of this f lap.

I n t he p r e se nc e o f sh r ou d b low ing ove r t he t r a il i ng-e dge f l a p a nd d r oo pe d a i le r on , t h i s l e a d ing- e dgef lap was (not surpr is ingly) m ore e f fec t ive than the par t - sp an s la t spec i fica l ly considered . Thus , for thepr o pos e d a i r c r a f t t a ke - of f c onf igur a t i on ( fl = 30 , ~ = 20 , CUN+ CUR = 0 065) , def lec tion o f the leading -edge f lap resul ted in s igni f icant improvements in CLmoxa nd s t a l l i ng i nc ide nc e , a dm i t t e d ly w i th som er e duc t ion i n l if t a t c o ns t a n t i nc ide nc e . T he w ing no w s t a ll e d a s t he r e su l t o f f l ow se pa r a t i ons f r om theknuc k le o f t he l e a d ing- e dge f la p , r a the r t ha n t he w ing nose .As t e st e d , how e ve r , e ve n t he l a r ge - spa n unb low n l e a d ing- e dge f l a p on ly j us t a c h i e ve d t he m in im umobje c t i ve CLm~~> 1-8, ~ ,ta~l /> 20) for the pso po sed take-o f f a r rangem ent . M ore ov er , any k i n d o f n o n -in t e gr a l w ing l e a d ing- e dge a r r a nge m e nt wa s c ons ide r e d una c c e p t a b l e f o r s t r uc tu r a l r e a sons i n t hepr e se n t c a se. A lm os t c e r t a in ly , ha d t h i s no t be e n so , t he l e a d ing- e dge f la p a r r a nge m e nt t es te d , c ou ld ha vebee n dev e lop ed by the inc orp ora t ion of a sui table B.L .C. ~ ,9,~o a r rang em ent a t the lead ing-edg e k~auckle ,t o e xc e e d t he a bov e ob j e c t i ve by a n a pp r e c i a b l e m a r g in , t hus a l l owing m or e c on s ide r a t i on o f s t al l a ndpost - s ta l l charac te r i s t ics .

5.3. Tests with First Integral Leading-Edge Blowing Assembly.E ngine t h r us t c ons ide r a t i ons a t t a ke - of f l e d t o t he i n i ti a l r e s tr i c ti on o f f l ap a nd m e a n a i l e ron d r o op to

f l = 30 , ~ = 20 , and a lso to a n o vera l l l imi t on blow ing ra te o f Cu~ + CuR ~< 0.065. Con sidera t ions of ther e l a ti ve c on t r i bu t ions o f t r a il i ng- edge b low a nd l e a d ing- e dge b~ow in r e l a ti on t o t he spe c if ie d m in im umaero dy nam ic objec t ive (CLm,x~> 1 8, ~s taa > / 20), tog e ther wi th the resul t s of pre l imin ary tes ts b y thef i rm a nd the R .A .E . t e s t s w i thou t l e a d ing- e dge de v i c es , sugge s t e d t ha t a bo u t 60 pe r c e n t o f the a v a i l a b l eb low ing a i r see Se c t ion 4 .2 ) shou ld be a pp l i e d a t t he t r ai l ing- e dge CuR = 0.04) and the remainder a t thel e a d ing e dge (CuN = 0 .025). T h is r a t i o be twe e n no se a nd r e a r b low ing r a t e s wa s use d p r ov i s iona l l y f o r thet e s t s de sc r ibe d i n t h i s s e c t i on . Howe ve r , t he nose a nd r e a r r a t e s we r e subse que n t ly va r i e d i nd iv idua l lydur ing the f ina l check tes ts descr ibed in Sec t ion 5.4.

T he o r ig ina l l e a d ing- e dge b lowing a s se m bly , a s de s igne d a nd t e s t e d by t he f i r m f o r t he i n t e gr a l - nosea i rc ra f t ins ta l la t ion, enta i led a nozz le a t 5 per cent chord, extending f rom 47 per cent semi-span (de te r -m ine d by w ing- f o ld pos i t i on a t 44 pe s c e n t s e m i -spa n) t o t he w ing t ip . Co ns ide r a t i ons o f t he pe a k suc t i onpos i t i on a t h igh i nc ide nc e s le d t o t he p r ov i s ion o f al t e r na ti ve n oz z l e pos i t i ons a t 2 pe r cent, 1 per cent and pe r c e n t c ho r d f o r t he R .A .E . t e s t s o n t h is a s se m bly . As e xp l a ine d e a r l ie r see Sect ion 2) , th is involvedthe j ud i c io us use o f c a re f u l l y - fo r m e d m e ta l nose f a i ri ngs i nc or por a t i ng t he r e qu i r e d noz z l e s see Fig. 3).Al th oug h tangen t ia l je t ef flux was a r ran ged for the 1 per cent and 2 per cent chord nozz les , the pe r c e n tnozz le and the or igina l 5 per cent ch ord nozz le w ere inc l ined a t ab ou t 30 to the loca l w ing surfz~cc .-Be cau se of the sensi t ivi ty to loca l nose shape , i t prov ed ra th er di f f icul t to achieve ident ica l s ta l l ingbe h a v io ur f o r t he d i f f e r e n t l e a d ing- e dge noz z l e a r ra nge m e nt s a t Cu~ = 0 . A l thou gh pa r t l y due t o t hesmal l nose rad i i invo lved (6 per cen t R.A.E. 102 a t wing t ip), such di f ficul ties were agg rava ted by thec om ple x i ty o f the w ing p l a nf or m a nd se c t i on va r i a t i ons i n t he v i c in i ty o f the nose . T he ba s i c , so l i d l ea d ing-e dge a r r a nge m e nt r e ga r de d a s a da tum ge ne r a l l y p r ove d supe r io r t o t he m odi f i e d l e a d ing- e dge b lowinga sse m bly i n t he a bse nc e o f l e a d ing- e dge b lowing* see Fig. 14) . Par t icu la r ly in the cas e of the 11 per c ent

*Check tes ts wi th the leading-edge nozz les sea led and fa i red conf i rmed tha t these da tum var ia t ionswere assoc ia ted wi th wing contour var ia t ions ra ther than loca l nozz le f lows.


11/53

c h o r d n o z z l e , i t w a s f o u n d n e c e s s a r y t o i mp r o v e t h e n o s e s h a p e , i n o r d e r t o r e s t o r e t h e o r i g i n a l c o n t o u rsee Fi g . 4 ) a n d t o a c h i e v e a d a t u m b e h a v i o u r a t Cu N = 0 c o mp a r a b l e w i t h t h e b a s i c l e a d i n g e d g e . T h er e s u l t i n g a r r a n g e m e n t , C3 , w a s p r e f e r r e d t o C 1 a n d C 2.T h e t h r e e c o n f i g u r a t i o n s A 1 , B I a n d C3, wi th noz z les a t 5 per cen t . 2 per cen t and 11 per cen t ch ordrespec t ive ly , exh ib i t ed s imi la r ch arac te r i s t i cs a t Cu~, = 0 see Fig . 14) . t he w ing s t a l l ing as the resu l t o ft h e s p r e a d o f l e a d in g - e d g e s e p a r a t i o n s c h o r d w i s e a n d s p a n w i s e f r o m t h e o u t e r w i n g n o se . T h e r e w a s ap r o g r e s s i v e i mp r o v e me n t i n t h e e ff e c t iv e n e s s o f l e a d i n g - e d g e b l o w i n g a s t h e n o z z l e p o s i t i o n w a s mo v e df o r w a r d s . I n f a c t, f o r c o n f i g u r a t i o n C a w i t h l e a d i n g - e d g e b l o w i n g ( C ~ , - - 0 .0 24 ), t h e o n s e t o f w i n g s t a l lw a s n o w d e t e r m i n e d b y s e p a r a t i o n s o r i g i n a t in g i n b o a r d o f t h e l e a d i n g -e d g e b l o w i n g n oz z l e, s o th a t a n yf u r t h e r i m p r o v e m e n t s n e c e s s i ta t e d i n b o a r d w i n g m o d i f i c a t io n s .T h e p o s s i b l e s c o p e f o r s u c h mo d i f i c a t i o n s w a s s e v e r e ly r e s t ri c t e d b y c o n s i d e r a t i o n s o f c r u i s i n g d r a ga n d b y s t r u c t u r a l l i m i t a t i o n s , a s w e l l a s b y t h e d e s i r a b i l i ty o f p r e s e r v i n g a r o o t s t a l l, a n d e n s u r i n g s o m ed e l a y i n t h e s p r e a d o f th e s t a ll t o t h e o u t e r w i n g . T h e m o d i f i c a t i o n a d o p t e d , c o n f i g u r a t i o n C 4 see Fig . 4) ,r e s u l t e d i n a s ma l l f u r t h e r i mp r o v e m e n t i n CL m, x a n d s t a l li n g i n c i d e n c e see Fi g . 1 4 c ) i n t h e p r e s e n c e o fl e a d i n g - e d g e b l o w i n g . T h i s m o d i f i c a t i o n w a s r e t a i n e d f o r t h e t e s ts w i t h t h e p e r c e n t c h o r d n o z z l e .H o w e v e r , s o m e d e t a il e d i m p r o v e m e n t s i n c o r it o u r w e r e a g a i n f o u n d d e s i ra b l e, r e s u l t in g i n c o n f i g u r a t i o nD 2T h e p r e f e r r e d c o n f i g u r a t i o n s A ~ , B1 , C4 a n d D 2 h a v e b e e n u s e d t o i l l u s tr a t e t h e c o m b i n e d e f f ec t o fn o z z l e p o s i t i o n a n d CuN o n t h e C L v . % c u r v e s ( F i g . 1 5 ) . H e r e , t h e b a s i c s o l i d l e a d i n g e d g e h a s b e e nt a k e n a s th e s t a n d a r d d a t u m a t C , N = 0 . I n g e n e r a l , t h e r e w a s a p r o g r e s s iv e i mp r o v e m e n t i n s t a l l in gi n c i d e n c e a n d CL m~x as h e l e a d i n g - e d g e n o z z l e p o s i t i o n w a s mo v e d f o r w a r d s t o w a r d s t h e n o s e . Pa r t o f t h ei n c r e a s e i n CL m,x w as t h e r es ult o f i n c r e a s e d l if t a t c o n s t a n t i n c i d e n c e , d u e t o i m p r o v e m e n t s i n t h e w i n gb o u n d a r y - l a y e r c o n d i t i o n i n t h e v i c i n i ty o f t h e t r a il i n g -e d g e f la p a n d d r o o p e d a i l e ro n w h i c h r e s u l te d f r o mt h e a p p l i c a t i o n o f l e a d i n g - e d g e b l o w i n g .

W i t h t h e e x c e p t i o n o f th e p e r c e n t c h o r d n o z z l e , t h e r e s u l t s c o r r e l a t e d i n th e n o r m a l w a y , w i t h p r o -g r e s si v e i n c r e a s e s i n s t a l l i n g i n c i d e n c e a s t h e v a l u e o f Cu ~, w a s i n c r e a s e d . H o w e v e r , t h e r e s u l t s w i t h t h e per ce n t cho rd nozz le ~ ll t he no rm al l es t speed o f 200 ft / sec showed a d i f fe ren t t rend (Fig . 15d) , wi thp r o g r e s s i v e r e d u c t i o n o f st a l l in g i n c i d e n c e a n d C L . .. . as CuN wa s inc rea sed fro m 0.012 to 0 .024 an d 0.040.W hen the t es t speed t~ l s redu ced to 140 f t / sec , the usua l var i a t ion w i th C~,N w a s a c h i e v e d . S i mi l a r r e s u l t sw e r e f o u n d w i t h t h e o t h e r p e r c e n t c h o r d n o z z l e c o n f i g u r a t i o n , D r . A t t h e h i g h e r t e s t s p e ed , w i n g t u f tss h o w e d t h a t a p r e m a t u r e f l o w s e p a r a t i o n f r o m t h e o u t b o a r d w i n g le a d i n g e d g e o c c u r r e d a t t he h i g h e rv a l u e s o f Cu , , . T h e v a r i a t i o n s o f Cu .,, w e r e n e c e s s a r i ly a c h i e v e d a s u s u a l b y v a r i a t i o n o f n o z z l e p r e s s u r er a t i o a t a p r e s c r i b e d g a p s iz e. so t h a l l h e f l o w b r e a k d o w n a p p e a r e d t o i n c r e a se i n s e v e r it y a s t h e p r e s s u r er a t i o w a s i n c r e a s e d . Fo r t h e a i r c r a f t a p p l i c a t i o n , e v e n h i g h e r p r e s s u r e r a t i o s w e r e c o n t e mp l a t e d , a n dt h u s m o r e a d v e r s e c o m p r e s s i b i l i t y e f f ec t s s e e m e d p o s s i b le .Prov i s iona l ly , i t was dec ided to loca te the a i rc ra f t nozz le a t 11 per cen t chord , to avo id such e f fec t s .O n c o m p a r i s o n o f F ig . 1 5c a n d F i g . 1 3 a. i t i s a p p a r e n t t h a t t h i s b l o w i n g a r r a n g e m e n t f o r a n i n t e g r a lw i n g w a s g e n e r a l ly c o m p a r a b l e i n p e r f o r m a n c e w i t h t h e c o n v e n t i o n a l u n b l o w n d e f le c t e d le a d i n g -e d g ef l a p, a t t h e p r e s c r i b e d t a k e - o f f v a l u e o f C~,~+ C u ~ = 0 .0 65 . T y p i c a l d r a g a n d p i t c h i n g - m o m e n t d a t a f o r th ec h o s e n l e a d i n g - e d g e b l o w i n g a r r a n g e m e n t a r e g i v e n in F i g . 1 6, w h i c h c o n f i r ms t h e g e n e r a l e f f e c ti v e n e ss o fl e a d i n g - e d g e b l o w i n g i n d e l a y i n g t h e o n s e t o f t h e s t a ll . H o w e v e r , i t s h o u l d b e n o t e d t h a t t h e a p p l i c a t i o no f le a d i n g - e d g e b l o w i n g , a l t h o u g h e n s u r i n g a s ta l l e m a n a t i n g f r o m t h e i n n e r w i n g , d id n o t p r e c l u d e aw i n g p i t c h - u p . T h i s r e s u l t e d f r o m t h e l a r g e l o s s o f l if t o v e r t h e r e a r o f th e w i n g w h e n e v e r s i g n i f i c a n t f l o ws e p a r a t i o n s w e r e p r e s e n t a t t h e w i n g l e a d i n g e d g e .As d i scussed ear l i e r (Sec t ion 4 .4 ) , t he a i rc ra f t c9 r a n g e h a d t o b e c h o s e n t o a v o i d a n e g a t i v e t a i l p l a n es ta l l a t a h i g h l if t. S o m e m a r g i n w a s t h e r e f o r e a ll o w e d f r o m t h e a v a i la b l e t r i m m i n g m o m e n t i n c r e m e n t o f0 .44 wi th t a i lp l a ne f l ap def l ec ted . 'F u r t h e r g e n e r a l i n d i c a ti o n s o f t h e r a t h e r c r i ti c a l n a t u r e o f th e w i n g l e a d in g - e d g e s h a p e , t o g e t h e r w i t h ap o s s i b l e e x p l a n a t i o n o f t h e a p p a r e n t a d v e r s e c o mp r e s s i b i l i ty e f fe c t s w i t h t h e p e r c e n t c h o r d n o z z l e , a r eg i v e n b y s o m e l e a d i n g - e d g e p r e s s u r e d i s t r i b u t i o n s a t 7 5 p e r c e n t s e m i - s p a n see Fi g s . 1 7 a n d 1 8 ). W i t h t h eb a s i c u n b l o w n l e a d i n g e d g e , a p r e s s u r e c o e f f i c i e n t o f a b o u t - 1 0 w a s a c h i e v e d , c o m p a r e d w i t h a v a l u e o fo n l y - 7 ( f o r a r e d u c e d s t a l li n g in c i d e n c e ) f o r o n e o f t h e p e r c e n t c h o r d n o z z l e a r r a n g e m e n t s a t Cu , = 0

10


12/53

(Fig. 17). On the application of leading edge blowing (Cu~, = 0.024) at the lower test speed of 140 ft/sec, thevalue of the pressure coefficient which could be achieved was now about -22 (Fig. 18), compared with thecritical value ( ~ = -4 2) for local sonic flow at this mainstream speed. However, at the higher test speedof 200 ft/sec (M = 0.18) the onset of premature leading-edge flow separations limited the pressure co-efficient to only -15, compared with Cp = -2 0. Comparable compressibil ity effects have been en-countered in two-dimensional tests of a blown cylinder at low mainstream Mach numbers 8.Thus, the location of the blowing nozzle at, or very close to, the min imum pressure posit ion appearedto result in flow separations i f the jet efflux induced local supersonic regions in the airflow around the nose.It is not known whether such flow separations emanated from the main wing nose ahead of the nozzle, orwhether they resulted from the breakdown of the Coanda effect, which was relied upon to tu rn theinclined jet efflux through a moderate angle (about 30 ) to flow tangentially rearwards over the main wingsurface. From this point of view, it should be no ted that the rear face of the per cent chord nozzle wasfinished with a large radius to blend with the local external surface and assist the turning process.5.4. Tes ts wi th Second In tegral Leading-Edge Blowing Assembly .Although a provisional decision was taken to fit a 1 per cent chord nozzle to the aircraft, confirmatorytests were obviously advisable, with a leading-edge unit which accurately represented the final aircraft1 per cent chord nozzle design arrangement . At the same time, it was desired to effect a more satisfactorycomparison between the chosen 1 per cent chord nozzle and the more critical per cent chord nozzle.

Accordingly, a second leading-edge assembly was constructed by the firm incorporating two alternativenozzles, each nozzle inclined at 30 to the local surface see Fig. 3). Arrangements were made for thesealing by choice of either, or both, of these nozzles, each of which was unobstructed by spacers along itslength see Section 2). Although the nozzle depth was somewhat reduced for this leading-edge, the aircraftnozzle depth/chord ratio was still no t fully represented.The wing leading-edge contour was carefully constructed to Mark I aircraft product ion design. It wasnot found feasible to incorporate on the aircraft the full inboard wing modification, as used for con-figurations C4 and D 2 in the earlier tests, except in the vicinity of the wing break see Fig. 4). Nevertheless,there was a close comparison between the performance of configuration C4 and the 1 per cent chordnozzle of the second leading edge see Fig. 19). It can be seen that the latter ar rangement was slightlyinferior, in terms of Ct. ..... in the presence of leading-edge blowing, probably as a result o f the differencesbetween the inboard leading-edge geometry noted above. On the other hand, the variations of C z abovethe stall were less pronounced on the second leading-edge assembly, probably as a result o f the improvedoutboard wing contour accuracy and a more refmed nozzle design. Certainly, the spanwise rate of spreadof the inboard wing stall in the presence of leading-edge blowing was much reduced, as can be judged fromFig. 20. It is also interesting that the hysteresis, as determined by static tests with increasing and decreasingwing incidence, was not pronounced. In fact, usually the value of Czmaxwas not affected, although therewere small changes in the lift coefficient at a given post-stall incidence. Figs. 20 and 21 show that furthergains in CLm,xwould be expected to result from increase in the mean aileron droop angle at take-off,without unacceptable adverse effects on aircraft drag characteristics. The direct variation with Cu,, isshown in Figs. 22 and 23, at a constant value of CuR. The favourable effect of leading-edge blowing on theboundary-layer condition at the trailing-edge controls is shown clearly. On comparison with Fig. 6,leading-edge blowing is seen to be nearly as efficient as trailing-edge shroud blowing in producing super-circulat ion lift increments.

The general effect of aileron differential on wing stalling incidence and the variation of aileron rollcontrol power with incidence and C~,., + CuR ) can be inferred from Fig. 24. The favourable influence ofblowing on aileron power was maintained up to the stall. However, the wing stalling incidence fell as theaileron was deflected and the post-stall lift losses increased. Tufts showed that the wing still stalled fromthe root.A detailed comparison between the chosen aircraft nozzle position at 1 per cent chord and the alterna-tive per cent chord nozzle position is given in Figs. 25 and 26. Even with the 1 per cent chord nozzle.minor adverse compressibility effects were found (Fig. 25d). However, these effects were much morepronounced for the per cent chord nozzle (Figs. 25 a-c), particularly with a discontinui ty between the

11


13/53

rear face of the nozzle and the external surface of the aerofoil. The adverse compressibility effects, as shownby the difference in the behaviour at the two test speeds, were once again found to increase with C,~,.Considerable alleviation was obtained by blending the rear face of the nozzle with the aerofoil surface(see Fig. 3f) to assist the turning process. Nevertheless, the performance of the blended per cent chordnozzle still remained markedly inferior to that of the 1 per cent chord nozzle at the higher test speed.The precise mechanism of this phenomenon is still not understood.The results at the lower speed showed that the per cent chord nozzle would be superior in the absenceof such compressibility effects. Thus, the post-stall lift loss was postponed to much higher incidencesand the margin between the stall of the unblown inner wing and the stall of the blown outer wing wasincreased correspondingly. This was confirmed by some wing tuft studies of the incidence at whichleading-edge separations occurred on the outer wing (Fig. 26). In the absence of compressibility limitations.at the lower speed, the per cent chord nozzle resulted in smaller minimum values for C~,, and muchhigher sectional stalling incidences. The chosen 1 per cent chord nozzle was much inferior at this speed,even with higher values for C , , . although vastly superior to the original 5 per cent chord nozzle.In general, these results confirmcd the prox isional conclusions drawn from the tests on the first leading-edge blowing assembly, particularly as regards the choice of a compromise nozzle position for the aircraft.Reasonable agreement has been obtained between predictions based on tests with a 1 per cent chordnozzle position and the l]ight pcrfornmncc of the Buccaneer aircraft ( s ee Appendix By. Obviously, sincethe wing stall commenced on the inboard unblown wing, limited scope remained for further leading-edgedevelopment, for instance by extension of the leading-edge blowing nozzle towards the wing root. How-ever, further attention to the outboard wing could well prove necessary, in order to preserve a root stall.More generally, although a reasonably satisfactory compromise has been achieved for the presentapplication, within the prescribed aircraft design limitations, it is apparent that a fully effective leading-edge blowing arrangement necessitates a carefully-designed nose conl ,mr ~hape to ensure the avoidanceof local supercritical free-stream regions under high lift conditions. Particularly' x~ith small nose radii, the

additional complexity of, say, a leading-edge flap with B.I..('. at the flap knuckle 1 9 ~o would seem prefer-able usually to an integral leading-edge arrangement, so as to allow a more straightforward developmentprocess and to avoid compromising the cruise configuration. Further, a more powerful and flexibleaerodynamic performance at high lift could be anticipated, particularly as regards the achievement ofspecified stall and post-stall characteristics.Some further guidance on possible compressibility effects for high-lift B.L.C. blowing arrangements,and the flow phenomenon involved, may result from comparative sectional tests at R.A.E. on a four-footchord pressure-plotting model, with alternative normal and high pressure-ratio (up to 9:1) nozzles,initially for leading-edge knuckle and trailing-edge shroud blowing arrangements.

6. Concluding Remarks.Low speed longitudinal stability measurements are described on a half-model of the BlackburnBuccaneer Mark I, with blowing at the integral wing leading edge and shroud blowing over the trailing-edge flap and drooped aileron. Some comparisons with complete-model tests by the firm generallyconfirm the usefulness of the large-scale half-model for detailed wing development testing.By the application of shroud blowing over the trailing-edge flap and drooped aileron, the lift incrementat constant incidence was nearly doubled. Because of the large spanwise extent of aileron, increases ofmean aileron droop angle were particularly beneficial. The presence of shroud blowing permitted mean

aileron droop angles as high as 30 , subject to aircraft thrust, yawing moment and rolling moment con-siderations, with total (flap +drooped aileron) lift increments approaching 1.0, and the preservation ofaileron control capability up to the maximum aileron deflection of 45 . Because of the wing sweepbackand small tail-arm, the trimming lift losses typicallyamounted to some 20per cent of the total lift increment.The main tests concerned the development and optimisation of a suitable leading-edge blowing arrange-ment for the Mark I aircraft. For structural reasons, an integral leading edge was specified, although therelatively thin wing (typically 8 per cent R.A.E. 101 with some nose camber) necessitated by cruise dragconsiderations inevitably led to very high negative pressure peaks and severe adverse pressure gradientsunder high-lift conditions. The spanwise extent of leading-edge blowing was limited to the main wing,

12


14/53

o u t b o a r d o f t h e w i n g f o l d p o s it i o n .T he m in im um a i r c ra f t t a ke - of f ob j e c t i ve , o f CLm~ > 1 8 and as t~l i> 20 , wi th a l imi t on a i le ron me andr o op to 20 f r om e ng ine t h r us t c ons ide r a t i ons , w a s a c h i e ve d w i th som e d if fi cu lt y. Ho we v e r , the e f f e ct ive -n e s s o f t h e l e ad i n g -e d g e b l o w i n g a r r a n g e m e n t w a s f o u n d t o d e p e n d n o t o n l y o n c h o r d w i s e p o s i ti o n a n dC ,N , b u t a l s o o n m a i n - s t re a m M a c h n u m b e r a n d b l o w i n g p r e s s u re r a t io , b e c a u s e o f t h e p r o x i m i t y t osupe r c r i t i c a l l oc a l f r e e - s t r e a m ve loc i t i e s a t r e p r e se n t a t i ve m a in- s t r e a m spe e ds . A sa f e c om pr om ise wa scho sen for the a i rc ra f t , wi th so m e loss of e ffec t iveness . The ch osen lead ing-edge a r ran gem ent ensu red ar oo t s t al l, w i th som e de l a y be f or e t he sp r e a d o f t he s t~ ll t o t he r e m a inde r o f t he w ing , a nd on ly m o de r a t epos t - s t a l l r e duc t ions i n l i f t , e ve n a t e x t r e m e a i l e r on de f l e c t i ons . Howe ve r , p i t c h - up a t t he s t a l l wa s no ta vo ide d a nd go od pos t - s t a l l c ha r a c te r i s ti c s c ou ld no t be e nsur e d w i th the p r e sc r ibe d i n t e gra l l e a d ing e dge .T he Buc c a n e e r M a r k I a i rc r a f t shows f li gh t pe r f o r m a nc e u nde r h igh-l if t c ond i t i ons whic h i s i n goodge ne r a l a g r e e m e nt w i th t he m ode l t e s t s w i th t he a i r c ra f t l e a d ing- e dge noz z l e pos i ti on . S inc e the o nse t o fw ing s t a ll i s de t e r m ine d by f l ow se pa r a t i ons on t he unb low n in boa r d w ing , t he r e i s som e sc ope f o r f u r the rde ve lop m e n t , f o r i ns t a nc e by e x t e ns ion o f t he spa nw ise e x t e n t o f t he l e a d ing- e dge b lowing noz z le . Ho w-ever , to preserve the prese nt ro ot s ta ll , wi th ou t increas ing the ra te o f spread of the ini t ia l f low sepa ra t ions ,f u r th e r a t t e n t io n t o t h e o u t b o a r d w i n g n o s e m a y a l s o p r o v e n e c e s sa r y .

I n s im i l a r a pp l i c a ti ons t o h igh- spe e d t h in - w ing a i r cr a ft , t he a dd i t i ona l m e c ha n ic a l c o m p le x i ty o f al e a d ing-e dge f l a p w i th B .L .C . wou ld se e m pr e f e r a b l e t o t he p r e se n t i n t e gra l l e a d ing- e dge a r r a nge m e nt , t oa v o i d c o m p r o m i s i n g t h e c r u i s e c o n f i g u r a t i o n a n d t o a l l o w m o r e s t r a i g h t f o r w a r d d e v e l o p m e n t . T h ep r o b l e m s o f o p ti m i s in g t h e n o z z le p o s i t i o n w o u l d b e m u c h r e d u c e d a s a ls o w o u l d t h e f lo w r e q u ir e m e n ts ,e spe c i a ll y if a dve r se c om pr e ss ib i l i t y ef fe ct s we r e thus a vo ide d . E qua l ly im po r t a n t , a m or e powe r f u l a ndf le x ib le a e r od yna m ic pe r f o r m a n c e c ou ld be e xpe c t e d , pa r t ic u l a r ly a s r e ga r ds t he a c h i e ve m e n t o f spe c if ie ds ta l l and post - s taU charac te r i s t ics .

Some fur ther guidance on compress ibi l i ty e f fec ts for high- l i f t B.L .C. a r rangements should resul t . f romc om pa r a t i ve se c t i ona l t e s t s a t R .A .E . on a f our - f oo t c hor d p r e s sur e - p lo t t i ng m ode l , w i th a l te r na t i ve nor m a la nd h igh- pr e s sur e r a t i o noz z l e s ( up t o 9 :1 ) , i n i t i a l l y f o r l e a d ing- e dge knuc k le a nd t r a i l i ng- e dge sh r oudb low ing c onf igur a t i ons .

Acknowledgements.H.S.A . ( Br ough) c ons t r u c t e d t he m ode l a nd a s s i s te d w i th t he t e s t ing a nd a na lys i s o f r e su lt s , a s we ll a s

p r ov id ing da t a f o r the t unne l a nd f li gh t c om pa r i son s p r e se n t e d i n t he Appe nd ic e s .

13


15/53

LIST OF SYMBOLS

Ab

CoACD

ACDcC L, CLm a;l ~-- L

A C LACL,

C,.AC.,

A C m cA C m ,

C~,, CuR

c . c . .N~

C pCp

gm

MPo

S

s .S~

VoV j

O~

Wing aspect ratioTotal wing spanLocal wing chordStandard mean chordAerodynamic mean chordTotal drag coefficient including jet thrustDrag coefficient increment at constant CLTunnel constraint correction to drag coefficientLift coefficient, maximum lift coefficient, tr immed lift coefficientLift coefficient increment at constant ~wLift coefficient increment due to trimmingPitching-moment coefficient, based on ~, referred to 0-25Pitching-moment coefficient increment at constant Cr~Pitching-moment coefficient tunnel constraint correction (tailplane-on runs)Pitching-moment coefficient increment due to tailplane

m vj)N m vj)RPo U~ SO ~ Po U~ Sg ; blowing momentum coefficients based on gross wing area,for nose and rear nozzles

c . . sCuN-1,~ Sh ; average sectional blowing momentum coefficients based on blownwing area S~, Sh for nose and rear nozzles

Surface static pressure coefficientCritical value of Cp for sonic conditions at main-stream Mach number MAcceleration due to gravityMeasured mass flow rate of blowing airMainstream Mach numberMean total pressure of blowing airGross area of half wingWing area spanned by blowing nozzle at wing noseWing area spanned by blowing nozzle at wing shroudGross area of half tailplaneMainstream speedMean jet velocity after expansion to free-stream static pressureWing incidence

14


16/53


17/53

No . Au thor s )l J . W i l l ia m s a n d S. F . J . B u t l e r . .

2 S . F . J . B u t l e r a n d M . B . G u y e t t

3 S . F . J . B u t l er a n d M . B . G u y e t t

A . A n s c o m b e , S . F . J. Bu t l e r . .a n d M . B . G u y e t t

5 A . A n s c o m b e a n d J. W i l l i a m s . .

6 S . F . J . B u t l e r a n d J . W i l l i a m s . .

7 E . C . M a s k e l l . . . . . .

A . F . J o n e s a n d . .W . R . B u c k i n g h a m

9 S . F . J . B u tl e r a n d J . L a w f o r d . .

l 0 R . C . W . E y r e a n d S . F . J . B u t l e r

11 A . M . H . D u n n . . . .

R E F E R E N C E STit le , etc.

A e r o d y n a m i c a s p e ct s o f b o u n d a r y - l a y e r c o n t r o l f o r h ig h l if t a tl o w s p e e d s .Journ . Roy . Ae . Soe ., Vol. 67, pp 2 01-2 23 (1963).A G A R D R e p o r t N o . 4 1 4 (1 96 3) .L o w - s p e e d w i n d - t u n n e l t e st s o n t h e d e H a v i l l a n d S e a V e n o m w i t hb l o w i n g o v e r t h e f l a ps .A . R . C . R . M . 3 1 2 9 ( 19 5 7) .L o w - s p e e d w i n d - t u n n e l t e s t s o n a d e l t a - w i n g a i r c r a f t m o d e l

( S. R. 1 7 7 ) w i t h b l o w i n g o v e r t h e t r a i l in g - e d g e f l a ps a n d a i l e r o n s .A . R . C . C . P . 7 1 0 (1 9 62 ).L o w - s p e e d w i n d - t u n n e l t e s ts o n t h e V i c k e r s - S u p e r m a r i n e N . 1 13

( Sc i mi t a r) w i t h b l o w i n g o v e r t h e t r a i l in g - e d g e f la p s .R.A.E . Te chn ica l N o te 2905 (1963). A .R.C. 25417 .S o m e c o m m e n t s o n h i g h - li ft te s t in g i n w i n d t u n n e l s w i t h p a r t ic u l a r

r e f e r e n c e t o j e t - b l o w i n g mo d e l s .A G A R D R e p o r t N o . 6 3 (1 95 6).R.A.E . Tech n ica l No te A ero 2460 (1956). A .R.C . 18664 .F u r t h e r c o m m e n t s o n h i g h - l i f t t e s t i n g i n w i n d t u n n e l s w i t h

p a r t i c u l a r r e f e r e n c e to j e t - b l o w i n g mo d e l s .R.A.E . Tech n ica l N o te Ae ro 2632 (1959) . A .R.C . 21690.Aero Quar t. Vol . XI , pp 285-308 (1960).A G A R D R e p o r t N o . 3 0 4 (1 95 9) .A t h e o r y o f t h e b l o c k a g e e f f ec t s o n b l u f f b o d i e s a n d s t a l le d w i n g si n a c l o s e d w i n d t u n n e l .A . R . C . R . M . 3 4 0 0 ( 19 6 3) .S o m e e x p l o r a t o r y t e s t s o n a t w o - d i m e n s i o n a l b l o w n - c y l i n d e r

m o d e l i n t h e R . A . E . 2 ft 1 ft t r a n s o n i c w i n d t u n n e l .R.A.E . Techn ica l Repor t 64090 (A.R.C. 26850) (1964) .L o w - s p e e d w i n d - t u n n e l t e s ts o n a w i n g -f u s e la g e m o d e l w i t h a r e a

s u c t i o n t h r o u g h p e r f o r a t i o n s a t t h e l e a d i n g - ed g e f la p k n e e .R.A.E . Techn ica l Repor t 67153 (1967) .L o w - s p e e d w i n d - t u n n e l t e s t s o n a n A R 8 s w e p t w i n g s u b s o n i c

t r a n s p o r t r e s e a rc h m o d e l w i t h B . L .C . b l o w i n g ov e r n o s e a n drear f l aps fo r h ig h l i f t.R .A.E . Tec hn ic a l R epo r t 67112 (1967) . A .R.C . 29389 .B l o w i n g t h e B u c c a n e e r .Fl igh t In terna t iona l , pp 754-756 (1966) .

16


18/53

A P P E N D I X AComparison o~CH a l f - M o d e l a n d C o m p l e t e -M o d e l T e s t R e s u l t s.

D ur in g the ini t ia l tes ts on the 1 /5-sca le ha l f -m odel in the H.S.A. (Broug h) 7ft x 5f t wind tun nel , thef use la ge ha d to be f o r e shor t e ne d a nd the va l id i t y o f t unne l c ons t r a in t a nd b loc ka ge e s t im a te ss )= 0 .34 i s ope n to que s t i on pa r t i c u l a r ly ne a r t o t he s ta ll . How e ve r , c om pa r i son s c a n use f u lly bea t t e m pte d be tw e e n the p r e se n t t e s t s on th i s m od e l i n t he R .A .E. l l f t x 8 ft t unne l a nd on a 1 /12- sc al ec om ple t e m ode l i n t he H .S .A . 7 f t x 5 ft t unne l. F or tun a t e ly , t he e s t im a te d l if t c ons t r a in t a nd b loc ka gec or r e c t ions a r e v i r t ua l ly i de n t i c a l f o r t he two c a se s a nd o f a c c e p ta b l e m a gn i tud e ( e .g .Ae = l 65a t CL = 2 ).

C l o s e a g r e e m e n t i s a c h i e v e d b e t w e e n t h e c o r r e s p o n d i n g CL VS. ew curves be low the s ta l l (Fig. 27) ,c onf i r m ing the va l id i t y o f t he ha l f - m ode l t e c hn ique a nd the ge ne r a l c om pa ta b i l i t y o f t he t e s t p r oc e dur e sa do p te d in t he two f a ci li ti es , f o r ins t a nc e , a s r e ga r ds m e a sur e m e nt o f C , - va lue s . Ho we v e r , the sm a l l s c al eo f t h e c o m p l e t e m o d e l a n d t h e l im i t e d R . N . ( a b o u t 1 .2 5 x 1 0 6 ) c o m b i n e d t o p r e c l u d e t h e a ch i e v e m e n t o fr e pr e se n ta t i ve s t a ll de ve lopm e nt , w i thou t o r w i th l e a d ing- e dge b lowing .D r a g a n d p i t c h i n g - m o m e n t c o m p a r i s o n s i n d i c a t e r e d u c e d p i t c h i n g - m o m e n t i n c r e m e n t s a n d l o w e r

od CDva lue s OId--~L a nd CDo f o r t he c o m p le t e m o de l . O n the o the r ha nd , su r pr i s ing ly g ood a gr e e m e nt i nva r i a t i ons o f m e a n do wn wa sh a t t he t a il p l a ne i s a c h i e ve d see Fig . 10) de sp i t e t he pa r t i a l im m e r s ion o fthe ha l f -t a i lp l a ne i n t he t unne l f l oor bo un da r y l a ye r .T he ha l f -m ode l t e c hn ique c a n use f u l ly be a pp l i e d f o r de t a i l e d h igh-l if t w ing de ve lop m e n t , pa r t i c u l a r lywhe r e t he use o f a c om ple t e m ode l ~vou ld ne c e ss it a t e an i na dc qo a te m ode l sca le o r R .N . N a tur a l l y , ac om ple t e m o de l o f a de q ua te sc a le would be p r e fe r a b l e t o t he ha l f- m ode l , pa r t l y t o m in im ise t he unc e r t a in -t ie s i n t ro d u c e d b y u s e o f a h a l f -m o d e l t e c h n i q u e , b u t m o r e t o a l lo w w i d e r a e ro d y n a m i c i n v e s ti g a ti o n s(e.g . a i le ron pow er , la te ra l s tabi l i ty , super s ta ll , gr ou nd ef fec t) . In the p resen t ins tance , a 1/5-sca le com ple tem o de l w ould be f e a sib l e w i th a w ind tunne l ha v ing a c r oss - se c t iona l a r e a o f o r de r 200 sq fe e t ( e .g .H .S .A .15f t x 15f t V ST O L tunnel ).

A P P E N D I X BCo m p a r i so n o f M o d e l a n d A i r c r a f t Te s t R e s u l t s.

W ith the a p pr op r i a t e c o r r e c t ions a pp l i e d , t he p r e se n t r e su lt s a g r e e we l l w i th f u r the r a i r c ra f t de ve lop m e ntt e s ts on the sa m e m o de l i n t he ne w H .S .A . (Ha t f i eld ) 15ft x 15ft t unne l . I n o r de r t o m a ke va l id f l i gh t -t unne l c om pa r i sons , t he H .S .A . p r og r a m m e inc lude d t e s t s w i th c e r t a in spe c if ic f e a tu r es o f t he f li gh t te s ta i rc r a ft . W i th due a l l owa n c e f o r t he v a r i a t i on o f C~ wi th ~ ,~ f o r t he a i r c ra f t, e xc e l l e n t a g r e e m e nt wa sachiev ed by H.S.A. for the li f t -inc idence curv e (Fig. 28). This a greem ent p ers is ted a t w ing inc idences o f theo r d e r o f 1 8 , represe nt ing the l imi t ing u sab le CL for this a i rc ra f t and c lose to the m od el s ta l l ing inc idence .In the abse nce of s ta ll tes ts for the a i rc ra f t ac tu a l co m par i son s o f CLm~xa nd s t a l l i ng i nc ide nc e a r e no tpossible .T he f u r the r c om pa r i so n o f t a i l p la ne t r im se t ti ngs f o r two c9 posi t ions (Fig. 29) aga in conf i rms thede gr e e o f a gr e e m e nt b e twe e n tunne l a nd f li gh t r e su lt s , w i th in t he l im i t s se t by e xpe r im e n ta l a c c ur a c y .

F l igh t t e s t s ha ve ge ne r a l l y c o nf i r m e d tha t b low ing B .L .C . wa s a s e f fe c ti ve a s e xp e c t e d 11 a l l owing f o rl im i t a ti ons on spa nwise c on t inu i ty o f e ff lux a r is ing f r om e ng ine e r ing c o ns ide r a t i on s r e l a t e d t o c o n t r o lsup po r t ge a r . I n pa r t i c u l a r, t he d r o op e d a i l e r ons r e m a ine d r e l a ti ve ly e f fe c t ive a t h igh inc ide nc e s , e na b l inginc ip i e n t w ing d r op to be c or r e c t e d .

17


19/53

T A B L E 1M

low speed wind tunnel tests on a buccaneer mk with blown le slats, flaps and ailerons

Documents