merlin46_naca

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f

M I N I S T R Y O F S U P P L Y

f ' -g . ~ - - ~ & M . No. 2213, :~ ~i,~,,~',~, (7151)A.R.C. T echnical Report

A E R O N A U T I C A L R E S E A R C H C O U N C I LR E P O R T S A N D ~ M E M O R A N D A

T h e V a r ia tio n o f P o w e r w i th H e ig h t o f aM e r l in 4 6 E n g i n e as d e t e r m i n e d b y

F l i g h t T e s t s o n a S p it fir e V c8y

G . 8 . H i s L ov , P h . D . , B . S c ., A . R . T . C .

C ro ~ z C o p y 'i # t R e ~ t d

L O N D O N : H I S M A J E S T Y 'S S T A T I O N E R Y O F F IC EPri ce 3 s . o d . n e t

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T h eE n g i n e

N A T IO N A L AERO,~ .'A~ .~ IT~C;:'. L EL M , , .ALISHMEN-t '

V a r i a t i o n o f P o w e r w itL tl B , Ae l g n t o f aas d e t e r m i n e d b y F l i g h t T e s t s o n a

ByG . S . H I S L O P , P h . D . , B . S c . , A . R . T . C .

M e r l in 4 6S pi t f i re V c ....

C O M M U N I C A T ED B Y T H E P R I N C I P A L DIRECTOR O F S C I E N T I F I C R E S E A R C H (AII~),M I N I S T R Y O F S U P P L Y

Reports and Memoranda No. 2213September 1943"

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Summ ary.--Reasonsfor E nquiry.--The variation of full thro tt le engine power with heigh t was required on a Spitfire Vc(Mell in 46) for compar ison wi th t ha t obta ined previous ly by the same meth od on a Hur r icane I I (Merl in XX ) .Range of Investigation.--This, the locked prope l le r meth od, g ives the ra t io of fu l l thro t t le powers a t any two a l t i tudesand in th e present te s ts th e ra t io was obta ined a t the fo l lowing a l t i tudes : - -37,000 f t . and 16,000 f t .35,000 f t . and 16,000 I t .83,000 f t . and 16,000 f t .

37 ,000 f t . r epresents the m axim um he igh t a t w hich accura te pe r formance measurements can be m ade w i th th is a i rcra f t.Conclusions.--(i) The variation of full thrott le power with height of the Merlin 46 engine under st i l l a ir conditions,expressed as a functio n of dens ity isP cc (1-10 a -- 0"10).

Th is result is vir tu ally th e Same. as o btained from previo us f l ight tests on M erlin engines.( ii) Th e observed supe rcharger compression ratio tem pera ture coefficient is 0.00248 wh ich compares with th e acc eptedvalue of 0.002 fc . r Merlin engines.( ii i) In th e absence of a torqu em eter the electr ic c0nstan t-speed propeller which can be locked in pitch provides a ve ryuseful appara tus for de te rmining the pow er law of an engine .Further Developments.--None c on te m pla t e d .1 . I n t r o d u c t i o n . - - - 1 . 1 . Th e e s t a b l i s h m e n t o f t h e l a w g o v e r n i n g t h e v a r i a t io n o f f u ll t h r o t t l ee n g i n e p o w e r w i t h h e i g h t i s o f c o n s i d e r a b le i m p o r t a n c e a n d i n t h e a b s e n c e o f t o r q u e m e t e r sv a r i o u s m e t h o d s o f m e a s u r e m e n t h a v e b e e n p r o p o s e d . P r e v i o u s f li g ht t e s ts c a rr i ed o u t a tt h i s E s t a b l i s h m e n t o n t h e s u b j e c t a r e d e s c r i b e d i n R e fs . 1 , 2 a n d 3 .1 .2 . I n t h e r e p o r t o n t h e l o c k e d p r o p e l l e r m e t h o d 1 t h e h o p e w a s e x p r e s s e d t h a t t h e t e s t w o u l db e r e p e a t e d o n a S p i t fi r e h a v i n g a M e r l i n 4 7 e n g i n e . S u c h a n a i r c ra f t w a s p r o v i d e d , e q u i p p e dw i t h a R o t o l e l e ct r ic v a r i a b l e p i t c h p r o p e l l e r o f N o . 5 h u b s iz e a n d m e t a l b l a d e s , c a p a b l e o f b e i n gl o c k e d i n p i t c h d u r i n g f l ig h t . I t w a s e x p e c t e d t h a t t h i s a i r cr a f t w o u l d b e a b le t o r e a c h 3 8 , 0 0 0 o r3 9 , 0 0 0 ft . w h e n f l o w n li g h t a n d t h a t t h e f i t m e n t o f t h e e l e ct r ic p r o p e l l e r a n d a n a d d i t i o n a l f u e lt a n k w o u l d p e r m i t o f t h e h i g h a l t i t u d e fu l l t h r o t t l e l e v el a n d t h e m e d i u m a l t i t u d e t h r o t t l e dp a r t ia l s b e i n g d o n e o n t h e s a m e f l i gh t . S u c h a p r o c e d u r e w o u l d h a v e o b v i a t e d t h e n e c e s s i t yf o r r e f u e ll i n g b e t w e e n t h e t w o s t a g e s in q u e s t i o n a n d t h u s h a v i n g t o t a k e o ff w i t h t h e p r o p e l l e ri n f i x e d p i t c h . H o w e v e r , e v e n w i t h o u t t h e e x t r a f u el t a n k w h i c h c o u l d n o t b e i n s t al l e d e a si l y,t h e c l i m b p e r f o r m a n c e o f t h e a i r c ra f t w a s r a t h e r d i s a p p o i n t i n g , p o s s i b ly d u e t o t h e s m a l l d i a m e t e ro f p r o p e l l e r, a n d c o n s i d e r a b l e d i f f i c u l ty w a s e n c o u n t e r e d i n re a c h i n g e v e n 3 7 , 0 0 0 f t. w i t h t h er e s u l t t h a t t h e r e w a s i n s u f f i c i en t f u e l r e m a i n i n g to c a r r y o u t t h e t h r o t t l e d p a r t i a ls , a n d a s e p a r a t ef l ig h t w a s r e q u i r e d f o r t h e l a t t e r.

*R epo rt No. A. & A.E.E . /Res. /190 received 25th October, 1943.(80417) A


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1.3. Thus t he genera l tec hni que re mai ned nluch as described in R. & M. 2212 ~, the principa lchange with, and advantage of, the electric propeller being that it dispensed with the necessityof doing a number of preliminary high altitude levels in order to obtain the correct fixed-pitchsetting for maximum power at those conditions.2 . Theor y . - - Th i s is given fully in R. & M. 2212 t and need n ot be r eca pitu late d here.2.2. The ratio of full thro ttle powe r at two widely different altitudes is obtain ed by de termi ningthe J and n for full thro ttle level flight at high altitude, and the n by th rott ling th e engine,realising the same J and n at a suitable low altitude. This thr ott led power is adjuste d to fullthrottle at the same boost and r.p.m, by a suitable correction.That is,

F . T . P . H . A . F . T . P . H . A . T .P .M . A.,~F . T . P . M . A . 1 T . P . M . A . = F . T . P . M . A . ~F . T . P . H . A . ~ ( H . A .) ~P,, sav,o r F,TIP_MTA. = x < x x =

where the symbols have the same meaning as'in R. & M. 22121.Corrections a~ and aa are related to b.h.p, in accordance with the formula

11pb.h.p, cc (p,~ -- -G- ~) T q- 127'where P, = boost pressure absolute,

P~.: := back pressure abs.,T := intake temp. deg. C. abs.

It should be noted that the power ratio, P, is referred to the air intake densities, ~,, corre-sponding to the appropriate full throttle high altitude level and full throttle at medium altitude1.

3. Condi t ion of Airc raf t dur i~zg Tes ts. (S ee photographs).--3.1. The aircraft, a Spitfire Vc,was lighten ed by re moval of all guns and amm uni tion and certain a rmour but the radio equip-ment was reta ine d; the take-off weight was 6,160 lb. with the C.G. at 6. 9 in. aft of datu m,undercarria ge down. Apart from the stub exhausts, which were fitted to eliminate the thrustpower obtained from the ejector type of exhaust, and the electric propeller the aircraft was anormal Spitfire Vc.

3.2. The instr mnent s fitted were similar to those employe d on the earlier tests except tha t aCambridge type of electrical resistance thermometer was used in the air intake instead of thecapillary type. No autom atic observer was employed. The total head of the air entering theintake was read on an altimeter connected to the intake pitot-static tube, whilst the local speedwas also obtained from this source.

3.3. Eug i ue . - - M er l i n 46 No. A.314195/78141. The boost control was inopera tive thro ugho utto ensure tha t full thr ottl e conditions were obtain ed as necessary. Mag net os- -Ro tax NSE 12/4.Rich mixture was used at all times.3.4. P r @ e l l e r . - - R o t o l Electric V.P. Type E5 RW -R M- FB . Serial No. EE.171. No. ofblades, 3 (Magnesium) to Drg. No. RA.630. Diamet er 10 ft. 3.8 in. Direc tion of rotat ion, R.H.Serial Nos. of blades A.4154 -5-6. Fine pitch angle 28 deg. 10 min. Fea the rin g angle 87 deg.15 min. Spinner No. RA.7355 No. 49. Red uct ion gear R.125.


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34 . F l i gh t Te s t s . - - The t e c h n i q u e w h i c h w a s e m p l o y e d i s g i v e n b e lo w : - -4 .1 . Hi gh A l t i t ude Le v e l . - - The a i r c r a ft w a s f lo w n le v e l a t m a x i m u m p o w e r f o r 3 , 0 0 0 r. p . m .a t 3 7 ,0 0 0 ft . w i t h t h e p r o p e l l e r c o n s t a n t s p e e d i n g ; t o w a r d s t h e e n d o f t h e r u n t h e p i t c h w a sl o c k e d a n d t h e n e c e s s a r y o b s e rv a t i o n s m a d e o n c o m p l e t i o n o f t h e l ev e l. T h e a i r c ra f t w a s l a n d e da n d t h e p r o p e ll e r p i t c h m e a s u r e d .4 .2 . M e di u m A l t i tude Thr o tt le d Pa r t i a l s . - - A t t h e s a m e p i t c h a s a b o v e t h e a i r c r a f t w a s f lo w nt h r o u g h t h e . h e i g h t r a n g e o f 1 5, 00 0 t o 1 7 ,0 0 0 f t. a t a n u m b e r o f a i r s p e e d a n d t h r o t t l e o p e n i n g st o in c l u d e t h e s a m e V a n d n as a t h i g h a l t i t u d e . T h e p r i n c i p a l o b s e r v a t i o n s w e r e m a d e a t1 6 ,0 0 0 f t. t h o u g h s e c o n d a r y S et s w e r e t a k e n o n e i t h e r s id e o f t h i s h e i g h t t o p r o v i d e a c h e c ko n t h e c o n s i s t e n c y .4 .3 . Ful l Throt t l e He ight De terminat ior~. - -Wi th t h e p r o p e l l e r c o n s t a n t s p e e d i n g a t 3 ,0 0 0 r. p . m .t h e a i r c r a ft w a s c l i m b e d a t f u ll t h r o t t l e f r o m 1 6 ,0 0 0 t o 2 4 , 0 0 0 ft . o v e r a w i d e r a n g e o f s p e e d s ,t h e o b s e r v a t i o n s b e i n g m a d e e a c h 1 ,0 0 0 f t.4 .4 . R e p e a t T e s t s . - - T h e h i g h a l t i t u d e l e v e l a n d m e d i u m a l t i t u d e t h r o t t l e d p a r t i a ls w e r er e p e a t e d a t p i t c h s e t t i n g s a p p r o p r i a t e t o a l l o u t l e v e l a t 3 5 , 0 0 0 a n d 3 3 , 0 0 0 ft . w h i l s t a c h e c k

w a s m a d e o f t h e 3 7 ,0 0 0 f t. r e s u l t s.I n a d d i t i o n t h e fu ll t h r o t t l e h e i g h t d e t e r m i n a t i o n w a s c h e c k e d t o w a r d s t h e e n d o f t h ep r o g r a m m e .4 .5 . P o s i t i o n E r r o r M e a s u r e m e n t . - - T h o u g h w e l l - k n o w n o n S p i t fi r e a ir c r a f t t h e p o s i t i o n e r r o ro f t h e n o r m a l M k . V I I I e l e ct r ic a l ly h e a t e d p i t o t - s t a t i c h e a d w a s c h e c k e d o n th i s p a r t i c u l a ra i r c r a f t .5. Resul t s . - -5 .1 . M o s t o f t h e o b s e r v e d r e s u l t s h a v e n o t b e e n g iv e n i n t a b u l a r f o r m b u t a r ep r e s e n t e d i n t h e f o r m o t c u r v e s o n F ig s . 3 - 7 .T h e h i g h a l t i t u d e l e v e l r e s u l t s a n d t h e p r i n c i p a l m e d i u m a l t i t u d e r e s u l t s a r e g i v e n i n T a b l e 1 ;T a b l e 2 i s t h e p o s i t i o n e r r o r c o r r e c t i o n .T h e c h a n g e i n p r o p e l l e r p o w e r c o e f f ic i e n t Cp w i t h Vt/a a t c o n s t a n t J w a s c a l c u l a t e d f o r c e r t a i ns p e c if ic c o n d i t i o n s f o r t h e A e r o D e p t . o f t h e R o y a l A i r c r a f t E s t a b l i s h m e n t a n d t h e i r r e s u l t s a r eg i v e n i n T a b l e 3 . T a b l e 4 g i v e s t h e p i t c h s e t t i n g s o f t h e p r o p e l l e r as m e a s u r e d a f t e r e a c h f l ig h t .5 .2 . A s a m p l e c a l c u l a t io n o f t h e m e t h o d s e m p l o y e d i n c a l c u l a ti n g t h e p o w e r r a t i o f o r ea c ht e s t h a s n o t b e e n g i v e n h e r e a s t h e t h e o r y s h o w s q u i t e c l e a r l y h o w i t is d o n e a n d T a b l e 1 g i v e st h e n u m e r i c a l v a l u e s a t e a c h s ta g e . I f r e f e r d n c e t o a n a c t u a l c a l c u l a t i o n is r e q u i r e d r e c o u r s ec a n b e h a d t o t h a t g i v e n i n R . & M . 22 12 1.5 .3 . F r o m t h e e x p e r i m e n t a l r e su l ts t h e p o w e r l aw o f t h e e n g i n e h a s b e e n p l o t t e d i n F i g. 1a s s u m i n g a l i n e a r v a r i a t i o n w i t h d e n s i t y . T h i s re s u l t c a n be c o m p a r e d w i t h t h o s e fr o m o t h e re n g i n e s a s q u o t e d b e l o w : -

Present tests, b.h.p, cc (1.10 a -- 0.10 ), M erli n 46, Locked propellerRef. 1 b.h.p, cc (1.08 a -- 0.08 ), Merlin XX , Locked propellerRef. 2 b.h.p, oc (1.094 ~ -- 0.094), Merlin XX , Fag e m etho d ~Ref. 4 b.h.p, cc (1.074 a -- 0.074), M erli n 46, RA E Bench testsA s w i l l b e s e e n t h e p r e s e n t r e s u l t s g i v e v i r t u a l l y t h e s a m e e x p r e s s i o n a s w i t h t h e o t h e r f l i g h t t e s tsa n d a r e i n f a ir a g r e e m e n t w i t h t h e R . A . E . b e n c h t es ts , a n d t h u s l i t t le f u r th e r c o m m e n t is ne c e s s ar y .I t m i g h t b e p o i n t e d o u t t h o u g h , t h a t t h e l a r g e d i s c r e p a n c y i n t h e 3 3 , 0 00 f t . r e s u l t s i n F i g . 1 c a nb e a t t r i b u t e d t o t h e e x c e s s i v e c h a r g e i n p r o p e l l e r p i t c h (1~ - d e g .) w h i c h o c c u r r e d d u r i n g t h i sp a r t o f t h e t e s t s . F u r t h e r r e f e r e n c e t o t h i s i s m a d e i n S e c t i o n 6 of th e r e p o r t ,


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45.4. In R. & M. 2212 ~ an analysis of the like ly errors was mad e and though the air int aketemper ature measu rement has been considerably improved in the present tests the increase inaccuracy has pro bably be en offset by the small propeller pitch changes which occurred.Thus the probable accuracy which might be expected for the quoted power law is as before,

i . e . it lies within the rangeP~ 1"115 ~- -0 "1 15

and p cc 1.085 a -- 0"085 approximately.This is equ iva lent to an error of about q: 10 b.h.p, at 37,000 ft.

5.5. The full thro ttle height dete rmin atio n was checked at the end of the tests, and as will beseen from Fig. 7A and B, a small change has appar ent ly tak en place. In view of the fact tha t acylinder block change was made during the test schedule, it seemed advisable to use the firstdete rmin atio n for those tests mad e prior to the block change and the second dete rmin atio n forthe later ones.Unde r still air I.C.A.N. conditions the mean full thr ottl e hei ght for 9 lb./sq, in. boost at

3,000 r.p.m, is 17,500 ft., which compares with the value of 18,000 ft. quoted by the R.A.E.from bench testsL5.6. Sufficient full thrott le da ta being available the superchar ger compressions ration correctionC in the formu la R~ = R0 [1 + C (to -- t~)] has been ob tai ned by p lot ting observed compressionratio, boost/intake total head v e r s u s intake temperature for a number of different conditionsas shown in Fig. 2.The value of C so derived is 0. 00248 which compares with t he figure of 0.002 comm only usedon Merlin engines. The results from Ref. 5 on a Merlin 45 engine gave a C of 0.0027, a figurewith which the present results agree quite closely.5.7. The measured total h ead of the slipstream has been compared wi th that expected from

the theoretical slipstream speed

Several cases were ta ken includ ing the high altitude levels and one or two points from the fullthrottle height determin ation and in each case the ratio of the measured total head to thecalcu lated was withJn + one or two per cent. of unity .6 . N o t e s o u P r o p e l l e r O p e r a t i o ~ . - - 6 . 1 . It has been found to be much quicker and easier to carryout the foregoing test schedule with this type of propeller tha n was the case with the ordina ryprope ller used earlier. The Spitfire, however, does not carry sufficient fuel to do t he tairly

len gthy schedule of climb and high alti tude level, followed by thr ott led partials, all in one flight,and thu~ the undo ubt ed adva ntag e of the propeller could not be fully exploited. In the absenceof satisfactory torque meters , however, there seems to be no reason why the power variationof new types of engine should not be measured by this methc,d using this type of propeller.6.2. Thc propeller was fitted with an elec trical pitch indic ator but in the first few flights this(lid not seem to be giving the pitch to the re quired accuracy, and thus no use was made of theindicator. Whe n it eventua lly failed to work no atte mpt was made to put it right owing to thedelay which would have been caused. There seems to be no fun dam ent al reason, however,why this design could not be modified to give pitch indicati ons to the require d order of accuracy.


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56 .3 . I n g e n e r a l t h r o u g h o u t t h e t e s t s t h e r e w a s a t e n d e n c y f o r t h e p r o p e l l e r to " c r e e p " a b o u t~-4 d e g . fro m . it,s l o c k e d p o s i t i o n t h o u g h t h e d i r e c t i o n o f m o v e m e n t w a s n o t a l w a y s c o n s i s t e n t .T h i s c h a n g e i n pi L ch w a s t h u s l i a b l e t o i n t r o d u c e a fa i r e r r o r i n t o t h e r e s u l ts . L a t e r t e s t s o n t h i sp r o p e ll e r h a v e s h o w n a m o r e s a t i s f a c t o r y te c h n i q u e w h i c h i s a d v o c a t e d f o r t h i s o r a n y t e s t so f a s i m i l a r n a t u r e , v i z . I n s t e a d o f l o c k i n g t h e p r o p e l l e r o n t h e h i g h a l t i t u d e l e v e l s a n d k e e p i n g i t l o c k e d f o r t h es u b s e q u e n t t h r o t t l e d p a r t i a l c l i m b s , t h e p i t c h s h o u l d b e m e a s u r e d o n d e s c e n t f r o m t h e h i g ha l t i t u d e l e v e l s a n d o n e o r o t h e r o f t h e p i t c h r a n g e s to p s a d j u s t e d t o t h i s v a l u e T h e e n s u i n gt a k e -o f f a n d c l i m b c a n t h e n b e m a d e w i t h t h e p r o p e ll e r c o n s t a n t s p e e d i n g . P r i o r to c o m m e n c e -m e n t o f t h e a c t u a l p a r t i a l s t h e e n g i n e c o n t ro l s c a n b e a d j u s t e d t o m a k e t h e p r o p e l l e r g o t o t h ea p p r o p r i a t e s t o p , w h e r e i t c a n b e l o c k e d a n d t h e t e s t c a r r i e d o u t . S u c h a p r o c e d u r e o b v i a t e st h e n e c e s s i t y o f t a k i n g o f f a n d c l i m b i n g i n a n u n s u i t a b l e f i x e d p i tc h .7 . C o n c l u s i o n s . - - 7 . 1 . T h e v a r i a t i o n o f f u l l t h r o t t l e p o w e r w i t h h e i g h t o f t h e M e r l i n 4 6 e n g i n eu n d e r s t i ll a i r c o n d i t i o n s f o ll o w s t h e l a w : - - P cc ( 1 .1 0 ~ - - 0 . 1 0 ) . T h i s r e s u l t i s a p p r o x i m a t e l yt h e s a m e a s o b t a i n e d f r o m o t h e r t e s t s o n M e r l i n e n g i n e s .7 .2 . T h e s u p e r c h a r g e r c o m p r e s s i o n r a t i o c o r r e c t i o n h a s b e e n e v a l u a t e d a s 0 . 0 0 2 4 8 w h i c hc o m p a r e s w i t h t h e a c c e p t e d v a l u e o f 0 . 0 0 2 f o r M e r li n e n g i n e s.7 .3 . I n t h e a b s e n c e o f a t o r q u e m e t e r t h e e l e c tr i c v a r i a b l e p i t c h p r o p e l l e r p r o v i d e s a v e r yu s e f u l m e t h o d o f d e t e r m i n i n g t h e p o w e r l a w o f a n e n g i n e .

N o . A u t h o r1 G . S . H i s l o p a n d R . H . W e i r . .

2 A . F a g e . . . . . . . .

3 C . V . A b b o t t a n d G . S . H i s l o p . . . .

4 B . M a r l o w a n d J . M . S h a w . . . .5 W . J . D . A n n a n d a n d J . D . H a y h u r s t . .

R E F E R E N C E STi t l e , e t c .

T h e V a r i a t i o n o f P o w e r w i t h H e i g h t o f t h e M e r l in X X E n g i n e a sd e t e r m i n e d b y F l i g h t T e s t s o n a H u r r i c a n e I I . R . & M . 2 2 1 2.J a n u a r y , 1 9 4 2 .

D e t e r m i n a t i o n o f t h e V a r i a t i o n o f P o w e r w i t h H e i g h t o f a M e r li n X Xb y D r a g A n a l y s i s of F l i g h t T r i a l s m a d e fc , a H u r r i c a n e I I .R . & M. 1977. Sep t em be r , 1942 .T h e V a r i a t i o n o f P c w e r w i t h H e i g h t o f a M e r l in X l I E n g i n e a sd e t e r m i n e d b y F l ig h t T e s t s o n a S p i tf i re I I . R e p o r t N o .A . & A .E .E . / R es . / 1 66 . A .R .C . 5934 . Ma y , 1942 . ( U npu b l i s hed ) .Mer l i n 46 Eng i ne . A r t i f i c ia l A l t i t ud e Tes t s . R .A .E . R epo r t E .3952 .A . R . C . . 6 1 2 0 . A u g u s t , 1 94 2. ( U n p u b l i s h ed ) .P e r f o r m a n c e R e d u c t io n M e t h o d s - - I V . A n a l y s is o f P e r f o r m a n c e o fS p i t fi r e V B W . 3 1 3 4 a t v a r y i n g A i r T e m p e r a t u r e s . R e p o r t N o .A . & A .E .E . / R es . / 1 48 / 4 . A .R .C . 5776 . A pr i l , 1942 . ( U npu b l i s hed ) .


7/16

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16/16

Publ ica6ons ofA e r o n a u t i c a l R e s e a r c hT E C F I N I C A L R E P O R T S O F T H ER E S E A R C R G O M M I T T E E ~x934-35 V ol L A erodynam ics . 4os . (4os . 8do)VoL I I . Seaplanes , S t ructu res , En gine s , Mater ia ls~ eteo

4os . (4os . ~ d . )x935-36 V ol . L A erodynam ics . 3os . (3os . 7d . )V oL I I . S t ruc tu res , F lu t t e r , E ng ines , S eap lanes, e t c .3os. (3os. 7d-)x 93 6 V ol. L A e r o d y n a m i c s G e n e r a l , P e r f o r m a n c e ,' A i r screw s , F lu t t e r and S p in n ing .4os. (4os. 9do)V ol . IL S tab i l i t y and C on t ro l , S t ruc tu res , S eap lan%En gines , e tc . 5os . (5os , Iod . )x 93 7 V oL L A e r o d y n a m i c s G e n e r a l , P e r f o r m a n c e ,A i r sc rew s , F lu t t e r and S p inn ing .4 o s . ( C o s . 9 d . )Vol . 11I, S tab i l i ty and Con trol ) , S t ru ct ur % Seaplm~es ,Eng ines , e tc. 6os . (6 ~n )

A N N U A L R E P O R T S O F T H E A E R O N A U T I C A L R E S E A R C HC O M M I T T E E ~x9 33 -3 4 xso 6d. (xs. 8do)x93 4-35 I t . 6d . ( I s , , 8d . )A pr i l x , x935 to D e cem ber 3 I , x936 . 4~. (4d . +d . )x93 7 as. (~ ,s . ad . )~938 is . 6d. (xs. 8d.)I N D E X E S T O T H E T E C H N I C A L R E P O R T S O F "][ 'H EA D V IS O R Y C O M M I T T E E O N A E R O N A U T I [ C S ~

D e ce m b er I, x 9 3 6 - - J u n e 3o , x939R ep or t s & : M em oran da N o . I85oo xs. 3 d . ( I s . 5d .)J u l y x , x 9 39 ~ j u n e 3 0 , I 9 4 5R e p o r t s & M e m o r a n d a N o . I 9 5 0 . x s. (~ s 2 d .)Pr ices i n b racke t s b~c lude p 'o s tage .

O b t a i n a b l e f r o m" O f [ icei s M a j e s t y ' s S t a u o n e r yLondon W oC.2 : York }louse, Kingsway[Po~t Orders- -P .O. Box No. 569, Lonaon, 8.E.L]Edin burg h 2: I3A Ca stle Street Manch ester 2: 39-4~ K ing StreetCardiff: ~ St. And rew's Crescent Bristol x: Tow er LaneBelf~,t : 8o Ch iche gter S t ree tor throug h any bo okseller .

~ . & N. N). 2'2113(TXhX)A.R.O. Technical Regox*

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A E R O N A U T I C A L

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