naca rm l6j25 rudder tests

8/9/2019 NACA RM L6J25 Rudder Tests

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NATIONAL ADVISORY COMMITTEEFOR AERONAUTICS

WASHINGTON

UNAVAILABLE


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2 NACA, RMno. L6J25

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occurred a t 25,000 f e e t a l t i t u d e was not a t t r i b u t e d t o the charac-t e r i s t i c s of the horn-balanced rudder because th e rudder returnedt o n e u t r a l a n d remained t he re Wing the o s c i l l a t i m .

A t the r eques t d h e A i r Mater ie l Cananand, Axmy A i r Forces,flfght tests were conducted an a P-5 lD-20-XA (AAF No. 44-63826)ai rp lane equipped with a horn-balmce'd ruclder. Ths rudder wasf i t t e d w i t h an unbalancing k b s was th e or ig ina l product fanrudder. Tes ts were made both with the unbalmc5ng ta b fn operat ionand with the unbalancing ta b locked. The modif ica t ion to th eo r i g i n a l v e r t i c a l tail cons is ted of removing the cap from the topof the fin and add- 1.91 square feet of m e a t o the rudder asthe horn balance and 0.82 square f o o t of a r e a to the top of the

rudder aft of the hinge line .A canparison of the d i r e c t i c m a l s t a b i l i t y an d control charac-

t e r i s t i c s of the P - 5 D airplane with t h r e e d i f f e r e n t v e r t i c a l - t a i lconf igura t ions - th e horn balance. origjnal production, and extend&tail (with unbalancing ta0 lockedj . conf'Qurations a r e presentedhere in . The tests of th e horn-balanced rudder were conducted atthe L w ~ gaboratory i n 1945. The t e s t a o f the ariginal-ta$lcan f igu ra tion were p r e ~ i o t ~ s l y onducted a t t h e Ams AeronauticalLaboratory roference 1) Testa of the ex tended- t a i l con f igu ra t ionwere cmducted a t the Langley Laboratory an d a m epor ted Inreference 2 .

The P-51D-20-MA airplane i 8 a eingle-place; low w i n g , fighter-type monoplane. A three-view drawing af th e ai rp lane as t e s t e d i s

shown in figure 1, A side view of t h e ai rp lane l e shown i n f i gu re 2.Figures 3 and 4 show th e cmp arieo n between t h e original production,extended tail and horn-balanced rudder configurations t e s t ed .Figure 5 is a drawing comparing the rudders ai? th e t h r e e airplanes.

General Spoci f ica t fon and Dimensicme

Engine . . . ' . . . . . . . . . . . . . . . . . Packard V-1650-7

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NACA RMNo. L6J25 3

P r o p e l l e r . . . . . . . . . . . . . . . . Hamilton Standard mdrcmaatlcWmbar of blades . . . . . . . . . . . . . . . . . . . . . 4Gear r a t i o . . . . . . . . . . . . . . . . . . . . . . . 2 .@:IDiam3ter . . . . . . . . . . . . . . . . . . . . . I l f t 2 i n .

Gross weight 88 t ea t ed (at take-off ) lb . . . . . . . . . . 874.2Center-&-gravi ty position (wheels dom) percent M.A.C . 25 5

W i n g :span . . . . . . . . . . . . . . . . . . . . . . 37 ft 5 in.A r e a , s q f t . . . . . . . . . . . . . . . . . . . . . . . 240Sect ion . * . . . . . - - . . . u - WACA low drag airfoilD F h e d r a l , d e g . . . . . . . . . . . . . . . . . . . . . . . . .Sweepback (leading edge) . . . . . . . . . . . . 30 35 32

. Taper r ak lo . . . . . . . . . . . . . . . . . . . . . . . 2.16:1

...

Ver t i ca l tail (productton) :

T o t a l a r e a , e q f t . . . . . . . . . . . . . . . . . . . . 20.02Fin a r e a (exclusive ,& dorsal f fn, sg P t ) . . . 51-61F in offset fram fu@elage cen t e r lfne . . . . . . . . . . . o l e f tRudder d e f l e o t f a n , f r m f i n , deg . . . . . . . . . . . . 230Rudder t r h tab area, eq ft . . . . . . . . . . . . . . . 0.81Rudder trb tab de f l ec t i on , deg.,. . . . . . . . . . . . . . . 210Ratio .f UnbaUmcing, -l;ab e f l ec t i on t o m a e r deflection;.

approrimste . . . . . . fght rudder 0.6.:1i , _ ". - , . . . . . . . . . . . : - . .: - .l&t rudder o 4 il

Ver t i ca f t r i i l '(hob balanced) : . , ..

To t ' d area , sq f t 20.75. . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . .. , - . . . . '. . ..

Note: ,. A3'1 o the r cti2mnsions. m e the 8 m 8 for t h e probuctlmcokf igura t ion . . . . . . ' .


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where

f o t h e cciupmssib i l i ty co r r ec t ion ac to r a t se a l e v e l

q c the impact pressure, measured a s th e difference between totalhead and s t a t i c p r e s s u r e I n inches of water

The yaw vane for w e with the recorder was mounted 1. chordlength ahead of t h e l e f t w i n g t i p .

Measurements wire made i n f l i g h t of th e d i r ec t iona l a t a b i l i t yFn s i d e s l i p s an d th e change ' i n rucder-trim orce with speed a t10,000 an d 25,000 f e e t a l t i t u d e of th e P-51.D-5-MA with the horn-

balanced rudder and f i t t e d with an unbalancbg t ab * Additional t e s t sa t 10,000 f e e t a l t i t u d e =re niade with the unbalancing tab locked.AU tests were made ' i n the climbing condition (normal; r a t ed power,f laps and lasdixig g e e up) . To maintain a n o m 1 csri ter-of-gravitypos i t ion of 25.5 pe rc en t of 't he mean.aerodynamic chord throughout' the e s s 't2ie fuselage f u e l tank w88 kept empty The charge of-h e n t e ~ - o f - ~ a v i t ' p o s i t ~ ~ ue t o fuel ccmeumptian dwk?ing f l i g h t

, was negl. igible.. .

. . . .. . .

The d i r ec t iona l s t a b i l i t q w a s determined bg measuring the rudderdef lec t ion , pedal fo rce and s i d e s l i p angle slow cantinuouas ides l ip s , in which the rudder was deflected a t a continuom rate Int h o r i g h t 'and l e f t at given i r i d i c a t e d airspeeds of approxlmtely103, 200, an d 350 miles per hour at 10,000 f e e t a l t i t u d e and100, 250, and 350 miles per hour a t 25,000 f e e t altitude. D a t aobtained a t t hose a l t i t u d e s for the horn-balanced rudder, the originalv e r t i c a l - t a i l conf igura t iom, an d the extended- ta i l configurationsa r e given in cmparieon in figures 6 t o 8 and 9 to 11, respectively.Figures 12 to 14 are th e data f o r the horn-balanced rudder with the

unbalancing tab locked a t 10,000 f e s t A l l rudder angles a r e givenin degrees from the center llne of th e airplane.

' The horn-balanced rudder increased the rudder- free s t a b i l l t ybut gave a negligible ncrease t h e r u d d e r- f l x e d s t a b i l i t q whencompared,with the [email protected] tail. A comparison of th e n l u e a ofvariatian 'of rudder a n g l e with s i d e s l i p d$/dP and the v a r i a t i mcf rudder orce w i t h s i d e s l i p dFy/f@ for all. t h e e of t h econfigurations is given in t ab l e I . The value of d%/d@ is a

measurement of the rudder-fixs8 d i r e c t i o n a l stabAlity, and the value

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NACA R MNo ., 5 5

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of dF,/df3 ie a measurement of the rudder-free directional e t a b i l i t y .From table I it appears tha t . h e value8 of dB,/* f o r the horn-balanced rudder decreased with increaslpg speed and a t high speedbecame less than those f o r t h e origfnal-tafl c m f i g u r a t f o n . Thevalue of dS,/aS f o r al l tail ccmfigura t ims tended to decreasesl5ght.J.y in going frcm 10,000 to 25,000 fee t altitude. Because ofth e d i f f i c u l t y in a c c u r a t e u m e a s u r i n g the d o p e 8 af the c u r v e s ofrudder deflection a g a l n e t sihesltp angle over a mall range ofs i d e s l i p angles, t h e vaLusa given in t a b l e I a re mI-7 approximate.

Va l u e s of dF,/df3 fo r the horn-balanced rudder end Bxtendedtail showed a normal increase with increasing speed while th evalues for the o r i g i n a l tail decmaeeb 8 8 the speed increased fram200 t o 35 0 a l e s per hour at 10,OOO f e e t altitude. The value of&Fr/d13 f o r the horn-balanced rudder wae gsnere3J.y equal t o thatof the extended tail whereas, th e value for t h e original t a i l wasconsiderably l e s s .

For th e horn-baancea rudder w i t h unba lanc ing tab locked at10,000 f e t a l t i t u d e , the value of aS,/i@ tiecreased as t h e a p e dincreased frcxn 200 t o 350 m 3 . l ~ ~e r hour ThQ valug o f . dF,/dpshared a normil. increa8.e with increasing a-peed. Tha value of d%/dSwas grea te r with the u n W a n c l n g tab..locked han with .it In aperation.This increaee 1.e due to the fact t h a t ruddsr e f f e c t i v e n e p is reducedwith :the tab locked. AB expected, the y a l w. of d??,/.fip was ' ,decraa.mil when &,e tmb'alancing tab .ww. ocked. W i t h th e unbaiancfng

tab locked no 0verba;lanC'lng or tendency b w m d . rudder lock wasencountered.


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original tail. The horn-balanced ruader and extended. tailconfigurat ions would have similar f o r c e c h a r a c t e r i s t i c s e x c e p ta t high speeds, where th e extended t a i l would h v e samewhat smallerf o r c e s A t h igh alt itu de , he change in *rim force with speed f o rth e horn-balanced rudder appeared to Be lees than t h a t of theextended tail 88 shown i n figure 16. The p i l o t had the samed i f f i c u l t y holding c o n ~ % ; f m s teady throughout the run a t higha l t i t u d e as he d id a t low a l t i t u d e , thus causing t h e s c a t t e r i nthe data f o r t h e holm-balanced rudder: The d i f f i c u l t y i n main-t a i n ing steady conditions a t [email protected] waa attributad t o th e lowr u d d e r - f i x e d d i r e c t i m a l s t a b i l i t y of the a i rp l ane . Th e change i nrudder posi t ion throughout the dive, f o r low and high a l t i t u d e , 1sapproximately the a m , aa shown by f i g u r e s 17 and 16 .

I n order t o determine th e hinge-moment characteristics of t h ehorn-balanced rudder, rudder kicks wero made i n which th e p i l o tabrup tly deflecte d and held the rudder. These te s te were made a ta l t i t u d e s of 10,000 and 25,'OOO f e e t end at speeds of ,150,. 30, and.350 miles pe r hour. The variatfon of th e rudder hhge-mcmentcoeff 'fcient w i t h de f l ec t i on d$/d@ w a a d e t e r n b e d fraan the rudderf o r c e n i t i a ll y r e q u i r e d o d e f l e c t the rudde r. Th6 ,va r i s t i on ofrudder hinge-moment c o e f f i c i e n t wlth a n g l e of a t t a c k wasdetermined frdm %he change in rudder force as t h e s i d e e l i $ angleincreased.. ~ h e s e alues of dChld.8 and -dCb/dct a r e presented int a b l e II. From the ca l cu l a t ed ~ K l u e ~ , t ma y be seea -&at d%/dct

, for the .horn-bqlanced' middsr' m a approximately zero. The *balancingt a b appewed to Increaee the va lu e of dCh/dG ,frosn about -0 .OO7to -0 oog. '

Lateral o a c f l l a t i m s w e r e made a t high and l o w altitude bydeflect ing he rudder a t a r ap id rate and r e l e a s i n g i t . These t e s t aw e r e made a t altitudes of 10,000 and 25,OOO f e e t an d a t s p e e bof 130, 150, 230, and 350 milee per hour. The recorda showed. .thatt h e o s c i l l a t i o n e damped s a t i s f a c t o r i l y i n all xuna except thoee at130 miles pe r hour. A t ime history of a mical o s c i l l a t i o n i sshown in f i g u r e 17. The rudder re turned rapidly t o i t s trim positionwhen r e l ea sed and remained there during the o s c i l l a t i a n a . Anundamped lateral oeci l la t fon occurred a t an f n d i c a b d a i r s p e e d of130 miles pe r hour a t 25,000 f e e t a l t i t u d e . Figures 18 an d 19 showtime h i s t o r i e s of the undampea o s c i l l a t i o n s . The undamped lateralo s c i l l a t i o n was accompanied by a spiral divergence and an increasein the indicated ai rs pe ed' . When th e speed increased th e oacfllationsdamped rapidly. There was no 'tendency for a snaking o e c i l l a t i m , 5nwhich the ruddkr motion minf 'orces he mot im of t he a i rp l ane . Therudder pos i t ion record showed that th e ruclder remalned essentiallyf i m d during the o a c i l l a t i m , s o t h a t the l a ck of w i n g cannot bea t t r i b u t e d t o t h e c h a r a c t e r i s t i c s , of th e horn-balarlced rudder.

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XACA RMNo. L6J25 - 7

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This tspe of o s c i l l a t l a , wbich has been observed an o the r high-powered single-engine airplane, enVolves a caiiblnatian of lateraland longitudinal o s c i l l a t i o n s , and is bel ieved to be c a w e d by thegyroscopic effect of the prape l l e r. The pilot d i d no t cans ide rt h i s undamped o s c i l l a t i a n jio be objectLonable became it w a s eaei lycon t ro l l ed .

The pi lots considered th e cantzol f a m e ~ W a c t e r i s t i c s fth e horn-balanced rudder to be a8 good a8 those of t h e extarfed

tail ccerPiguration an d an improvemnt over the origlnal tail. Theyobjected t o the &L#iculty 3n keeping the directional con t ro l steadyduring the dives at high speeds.

A n i nves t i ga t i on was mado of the d i r e c t i o n a l e t a b i l i t y of aP-51D-20-NA a i rp l ane wtth a horn-balanced rudder. The results ofthese t es t s wore crslrparod with t h o s e of previoue t s s t a of th eairplane W f t h o r i g i n a l production tail ana x i t h an extended tat1 .The following conclusims were obtained f r a this inves t iga t fon:

1. Th e d i r e c t i o n a l s t a b i l i t y of th e airplane rudder f r e e 88i nd i ca t ed by the v a r i a t i o n of rudder force with s i d e s l i p anglewas g r a a t e r w i t h a horn-balanced rudder than tha t with th e orfginalproduct ion t a i l con f igu ra ti on and approzimatelg equal to th e valueobtained w i t h t h e extended- tsil con f igma t i an . n o rudder lock

was e n c o m b r o ddth

th e horn-balanced rudder.

3 . The change i n trim force with speed f 01.. the horn-balancedrudder WELB l e s s than that produced by the orfginal-tail conf igura t ionand approx3mately the same a~ that of the oxtonded-tall configuratfon,which i s cmeidered acceptable.


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8

4. The horn-balanced rudder did not cause any tendency f o ra snaking o s c i l l a t i o n .

Langley Memorial Aeronautical LaboratorgMatiaaal Advisory Camittee for Aeronautics

Langley Fie ld , Va.

Aeronautical Ehgineer

1. Skoog, Richard B., ma"Nissen, J m e s M. : A F l i g h t Investigationof th e D i r e c t i m a l S t a b i l i t y a n d . Control Chmacteriskice of

a P-5lD Airplane ~ L t h inor Modificatime t o t h e . F i n an dRudder. NACA MR Axmy A i r Forcea , Juna 6, 1944.2. Williams, W a l t e r C ., and Hoover,. H e r b e r t H. : Flight MeaEjuremm.I;8

, . of th e Directicrnsl S - b i l i t y and Control of a P-5lD-5-NA Air-.plane (AAF No. 44-13297) with a High-Aspect-Ratio VorticalTail. RACA ME3 n o . L305b, Army A i r .Force8 , 945

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e . e. e .e.. . NACA Uvl No. L6J25 . . - - . .. Fig. 1

NATIONAL ADVISORYCOMMITTEEFOR AERONAUTICS

Figure 1. - Three view lay-out of the P-51D-20-NA irplane withhorn balanced rudder.

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E

Wgure 2.- Side view of the P-61D-20-NA AAFNo. 44-83826) withthe horn balanced rudder.

H

N

. . . . . . .... .


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Fi@;ure 3.1 Comparison of a P-61D-6-NA irplane with an axtendedtail and P-6lD-BO-NA (AAF o. 44-63826) with a horn balancedrudder, -#umonvrm

L M U T RllDlllu -L uIo#RoIII" m o .


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Figure 4.3 Compa&ton of a P-51D-25-NT irplane with an originalproduction conftgurationand he P-51D-20-NA (AAF No. 44-63826)with a horn balanced rudder. U l P U L l W L D n m w n * l r m u r a w m o S

U Y c R "mswnx uclnolr-uruFI 1100.11.

. . .

H

tb

A C A Fi 6


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N A C A RM No. L6J25 . . Fig. 6

Figure 6." Steady sideslip characteristics at 10,000 eet altitude, climbing. . ".

condition Vi, = 103 miles per hour. P-51D-20-NA airplane with a h o r nbalanced rudder, original and extended tail configurations.

.meee NACA RM No. LsP.5 . . , .I - - - .. Fig. 7


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Figure '7.- Steady- sideslip characteristics at 10,000 eet altitude, climbingcondition Vi, = 2OO.miles per hour. P-51D-20-NA airplane with a

horn balanced rudder, original and extended tail configurations.

NACA RM N L0J25 Fi 8


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NACA RM No. L0J25 Fig. 8

figure 8. Steady sideslip characteristics at 10,000 ee t altitude, climbingcondition Vis = 35 0 m i l e s per hour. P-51D-2O-NA irplane with a o rnbalanced rudder, original and extended tail config'urations.

N A C A RM No. LSJ25 . Fig. 9


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g

Figure 9.- Steady sideslip characteristics at 25,000 feet altitude, limbingcondition Vi = -100 m i l e s p e r how.. P-51D-20-NA irplane wi th a orn

balanced rudder, and extended tail configuratims.

S

0 .0 . 0 .

0 .omom


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.0 ....... NACA RM No. LQJ25 Fig. 10

Figure 10.- Steady sideslip c haracteristics at 25,000 feet altitude, climbingcondition Vis = 250 miles per hour. P-51D-20-NA irplane with hornbalanced rudder and extended tail configuration.

...... ....... NACA R&l No. LSJZ5 Fig. 11


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......0 . .. 0.....0 0 .0 . 00 . .

.. 0

0 0 ...... .0 .

Figure 11.- Steady s i d e s l i p characteristics .at 25,000 feet altitude, climbingcondition Vis = 3 5 0 miles p e r hour. P-51D-20-NA airplane with a horn

balanced rudder and extexded tail.

N A C A R M No. L6J25 Fig. 12


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F i v e 12.- Steady s i d e s l i p characteristics of 10,000 f e e t altitude, clirnbmgrorpiition Vi, = 103 miles. per hour. P-51D-20-NA airplane wi th hclrn

balanced rudder with tab ocked.

a m . NACA RM No. L6J25a F i g . 13


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.a0 .

g

Figure 13.- Steady sideslip characteristics a t 10,000 feet altitude, c l i rnbhg -condition Vis = 200 m i l e s per hour. P-51D-20-NA airplane with a horn

balanced rudder, tab locked.

NACA RM No L6J25 Fig. 14


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NACA RM No. L6J25 Fig. 14

Figure 14.- Ste-agy sideslip characteristics at 10,000 feet altitude, climbingcondition Vis = 350 miles per hour. P-51D-20-NA airplane w i t h horn

balanced rudder, tab locked.

e 0 .0 . ee . 00.. 0

0e

e . NACA RM No L6J25 " "." . . .. . .

Fig 15


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e0 . e* .

.e..

e .0 0 .

e e. e

ee 0 .0

*..

0.

0 .

NACA RM No. L6J25- Fig. 15

Figure 15.- Rudder t r im force characteristics in diving through the speed rangefrom .14,000 to 8,000 feet altitude. P-51D-20-NA airplane with horn balanceJrudder, original and extended tail configuration.

N A C A RM No. L6J25 Fig. 16


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0 0 .0 . 0 .

0 0 .0 .

N A C A RM No. L6J25 Fig. 16

Figure 16.- Rudder trim force characteristics n a dive through the speed r afrom near 30,000 to 20,000 feet altitude. P-51D-ZO-NA airplane with a h o ~balanced rudder and extended tail configuration.

f Fig. 17


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fp.. . .

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Figure I f / . _ - .A ypical right rudder kick at 11,000 eet altitude, climbingcondition Vis = 150 m i l e s per hour. P-51D-ZO-NA irplane with

horn balanced rudder having the unbalancing tab locked.

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Figure 18.- Rudder ldck to left at 25,000 eet altitude, climbing condition Vis = 130 miles per hour.P-51D-20-NA irplane with horn balanced rudder.

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Figure 19.- Rudder kick to right at 25,000 feet altitude, climbing condition Vis 130 miles pe r hour.P-51D-20-NA airplane with h o r n balanced rudder.

E%

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naca rm l6j25 rudder tests

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