Document
copy
O.I-W
ro . 788
DJ.AG D=:TER:i:;:lTAl'IO:, TS Of 'L'RE FO?I-ARD CO .5?OlJE ;J'l. ' OF A TRICYCLE LANDING G~A~ Ey ~u~ert r . Harmo~ La n~ley Mccorial AeroLautical Labcr~tor7
IL COpy
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Advj ry CorTIllit
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Decer.'!oer 1940 ~ATI O NAL AD VI SORY ~OUMI~TEE FOE A~ ROIAUTI CS TECHNICAL NO TS NO . 788 DR.\.G DET ?~ RrnNA'.L I " mrs OF TT-E FORWARD em. POHEIIT OF A TR ICY CLE LATIDI~G GE AR ~7 H ubert N . Ear~on SUt-mARY Wind - tunne l t s sts were perf or med to deter m ine t~e d r a~ of the front - whee l arran~ements of seve r a l types of tri cy - cle landin~ ~ea r . O ne wheel was tested in arran~emen t s to s i mulaie b oth non retratt ed and p art l y r et r acted types . The lan din~ ~ea rs we r e tested i n conjunct io n wi th ~ fuse l a~e, and the e~fe ct s o f whee l ax ten . ion and lon ~ i tud in a l loca - tion we r e dete r E i ned .
The d ra~ chan~ed very li tt le v it h e ither lon~itudin R I lo cat io n or whee l ex t ens ion for t h landin~ ~ea r w ith th e lo wes t d r a~ : a c o ~~:e t e l y fa i red l and i n~ ~ear of tb e wheel - spat, sin~le - strut " type . T he dra~ of t ho trous e r- type l and in~ ~ea r i nc r eased cons i der a bly , howeve r, w it h an in- cre ase in the wheel extens io n . T he wheel of the unfa i r ed retract ab le l and i n~ ~ " ea r uas at le as t on e - half retr ac t ed i nto the " fusele~e befo r e the d r a~ beceDe less than tha t of th o bes t n o nretra ct od land i n~ ~ea r . Th e dra~ pe r unit fro ntal area of t he landin~ ~e a r s o f t he presen t tests was ab o ut th e same "a s tha t found fo r s i D il a r l and i n~ ~ea rs in earl i e r tes ts .
I N TRODU ~ T IO N Sev e r a l yea r s a~ o tests of a la r ~e n umber o f conven - tional two -o o'Th ee l land i n~ :>; " ea rs alone and als o i n comb i nat io n ~ith fusela~e , w i n~s , and nace ll e we re mad e by the N AGA.
(S ee ref e r en ces 1 , 2 , and 3 . ) T hece tests cont r i ~ ut ed a con s i derab l e a E ou ~ t of ~as i c i nfornat io n about t~e d r a~ of l and i n~ ~ea r s . T he d r a~ of the fixed and t ~e pa rtly r e - tracted forward co ~p o nen t of t he tric y cl e l and i n~ ~ea r c ould n ot be p re d i c t ed w it h certainty f ro m t he p r ev iou s t ost s because t h es o te sts did n ot i nclude l a~d i n~ ~ea r G th a t were l o cated at t he forwa r d end of t he ~use l u~e .
~A CA Tec~nid~l rote ITo . 7 38 The test s herein r epo rt ed we re n~de to dete r mi ne t h e dr a~ of nose - whee l . l~ndin~- ~ ear arrah~~rnen ts and p o ss i ble v a riatio :.'1s pecul i a r · to tricy clo landir.'!,; sea rs . T he la: di1: ."; ~ea r 8 te sted were re st rict ed t o n f~w ~a~tilev G r ty pe s f 0 un C'. t 0 "'::l e "; 0 0 d' i-n t !'_ e 0 a r I i 0 r t est s . i1 0 s to"!: t: '1 e I'l W ere t es t e d i n four lon~ i tud i na l pocitions .
A ?PARAs:'US The tes ts ~e r e ~ade i n t ~e ? ACA 2G - !oo t wi;~ t~nne l .
(S ee referen c e 4 . ) The - etu rn passa~es of t h'e tunne l ' _a y e bee~ . sli>htly a lt ere~ and a n ew s ix-el ement ba l an c~ has b een i ns ta ll ed s i nce r efe r en c e 4 was written .
The fusel a~e to ~hich th e :and i L~ ~ears were fitted is h o ~vn su.:? p orted on the balance i n fi, c ;ure ::. . T~e forr;r a rd hal"!: of the fase l ~e i s app ro ximately ell i ptical in cross s ec~ io n ; t~e nose and the win d shield ap ] ro~i =~ te the ~hape of the nose and the w in ds~ie l d on a no~ern tr3~sp ort fuse - l a~e .
The :andi n ~ ~ears t es ted ~ay be cl as8ed as n on retract - ed and par tl y retract ed types . ~he whee l u sed !or al l t ests i s a ---- - scnle :: lOdel o"!: a nominal 47 - in ,h nooth co :: tour 2 c 72 wh ee l . The unfaired w~eel and f or k are shown i n , fi~ u re 2 .
F i ~u r e 3 shows the landin~ ~ea r c,es i ~nated st r ut - fai cd l a ndin~ ~ea r. A strea~l i ne fairi n~ of Na vy I st r ut sect io n i s sl i pp e ~ ov e r the round strut . F i ~ures 4 ani 5 r ep resent c o ~p let e fa i r i n ~s es i ~na t ed I a~d II , wh i ch a r e the wheel - spat , s i n.r;le - stru t t~Tpe aE (l the t ro use r t; r pe t T.'e8peC - tiv ely .
Co mple t e fa iri n, I I i s 0 tained b7 slip~i~ ~ t~ e la r ~e streamline cylin~ ri cal fa iri ~ ~ do'~ o v er the str, t and t h e whee l t o the max i mum se c tion o f th e wheo l fairin~ , ITh i ch it fit s snu~ l y o ~he pa rtly r et r act0d lardin~ ~en r R teste(l i n - clu ~ed an unfa ir ed landin~ ~ear ~lo 2 e ani ret ~ acted into th e st r ea mli no fairin~ , bo t h uith a ~ d wi~hout t~e fai rin~ c ap . T he faiTin~ iA ~hown i n f i ~ure 6 .
l'T A CA Te chn~ c ['. l .:1 0 t e N'b .· 7 ' ~ 8 1,;E~ ;:rODS All the la~d i ~~ ~ea r s were tested ' i ~ co~~uLcti o n w it h the fusela~e , wh ic h was s e t at z e ro p it c~ . Fi ~u r e 7 i s a com p osit e sketch s~ow i n~ pa rt of th e ou tl i ne of the w heel i ~ Q~ ch y osit i on te s ted . The l o n~itud i L~l l o c~t io nn ~ r c a ll e d :9 os i tions A, E , 8 , an ... : D a~d L1. 8 r .s.. di a i loc at io !: alon~ a~~ of these l i nes is ~ i ven as aC8 rt ai~ exte~s io n in ~hee l dia6 e te r s m eas~ r ed f r om the o u t e r cost , u~ee l sur - f a ce. Fi~ures 8 to 32 show the va rious a rra n~ecients . t~c modif ic at ion~ ~ and the dra ~ r esu l ts .
Dr a ~ and dynaD ic pressure were ceasu r ed for eve r y ar - r a:!.",:: c[') en t .
P REC I SIO N Based o~ t he che ck of z ero r ead i n.e;s a~d on renea t t es ts , ' the drD,~ i s be li e v e d ~o b~ accu::-at e ".;0 wi thin ± 1) . 5 pound . The r e l at iv e p r ec i~ion of ·t he tes t 's Dade ciose to - ~et~e r i n a s e ri es , i n ~h i ch t~ 8 f ill e t· ~a~ t~e o:r:ly ch~:r:",::e , i s ~ ith few exception s bel i e v ed to be · wi th i n · ± O. 2 ~ ound • . ' RESUL~S A )TD DISC'JSsrOI'r Al l d r a~ v a lues presen te d in .t his repot ere ta ken from fa ir ed curves of d r a~ p lot ted a .e; a i :r:s t dy:r:ami c p re~ su r e · .
Th e most " useful of the res u lts ~ iv en . in f i ~~r es ~ to 32 a r e sucmar i zed i n tab l e s I and II . P l ot s of dr a.e; asains t Thee l extensi on fo r the va ri ous . type s of ~ea r a r e sho~n i n f i ~ure 33 . ?io;ures 34 and. 35 s how the va ri ati on o f d ra I!; w it h . the lon~ i tud in ~l loc at io n . T~ese three f i~ ures' p re sent the chi ef trends and the 106al devi~ t io ns ~ro~ t h e~ .
~he n o ~ retr a ct ed l and in s ~ca rs i n o rd e r of de cr eas i n~ d r a-; a re : unfa ire d. l a n d. i' ~':; "' ;ea r , st r ut - fa ir ed land i n?, ~ea r , co mp l e tely fa ir ed Inndin~ ~ea r I= . and co mp letely f a ir ed l ~nd i n ~ ~en r I . O ne ex c ep t io n to this ord e r i s f o und i n p osi t io n ~, w~e r e t~o conpletely fa ir ed l~~d i n~ . ~ea r II at lese th an 1 . :;" (; d i ar::e t o r ex te ns io 'n i s l o ,, 'e r in ·dra . <!, t h[1.n tho cor.:plete l ~T fc-. ir cd I nnd i r..<; ";ca r I nt · t~l ' e so,cie e xtonci '· o ~!. ..
l~ A CA r.l e c !L'1 :;. c a ll ; 0 t e II o . 7 a 8
ca p off , the unfa ir od l and i n~ ~ea r nlone , and t~e land i n~ ~e a r i n ct r e : :1T:ll inc f a iri n-,; w it : . th o c al? on .
T~e d r a~ of th e unfa ir ed landi n~ ~o~ r i n tho strean - li ne f a {ri n~ wi . th the . c a~ on i s D uch lo ~~ ~ ' t~an t~ n t of ~ny of the n o n r otr~c t ed l ~ n d i n~ ~c~rs oxtenje~ ·n o re th an l . 2~ whoel d i nnc t e rs , but th o ~~fni r ed l~nd i n~ ~enr alone nust b e retract ed nl~ost 0 . 5 d i nneto r be~ore it s d ra ~ is ro .uc ed to that bf th o be st n onr et~actod l ~ ~ d i n~ ~oa r .
There i s n ~en e r a l ~ r end of i nc r eased d~ a~ w ith an i n - cr ea sed ex t ens io n , b ut t~ e d r ~~ of t~e co mple t e l y f a ir ~d l a nd i n~ ~ea r I re ma i ns sustnntially con s t a nt u it h an i n - c r e a se i n the ex t ensi o n . T he unfa ir ed ID.ndin~ ~ea r and the completely faired l ~_d i n~ ~ea r II show t~e ~r ca te s t i n - cr ease s wi th ex t ens io n .
Th e d r a~ of ea ch l ancin~ ~ea r e it ho r does n ot ch an~e or ini t i a lly increnses a s t ~e land i n ~ ~ea r i s m ov ed to a mor e r ea ri 'l a rd p osi "'.; io n . Of th o 13.2l ·•• i n ., " ;ea r s teste d i n th e m ost r eaTi 7a r d :tJ ositi on D, o n1;. .. t he u nfaired l[l,r. ' d i n~ ~ear had a lo wo r d rn ~th~n t ho ' sarno l nnd i ~~ ~oa r i n th e ne:~t forl7 a r d IJos i t ion C . Of t he " _o n r e:' ~ ['_ ct od lan d, i 'n ~ ,;; e:;1Ts, t h o unf ir e"- l and i no; .o;ec,r 1..Ld th o st r ut - fai eel l ::t n t't - i n~ ~e ar shoTIed th e ~ r ea t eB t chan~o i n d r a ~ u i th lo n~ i t u D d in ~ l ~ o cition . T~ o ~a rtly r et ract od land i n ~ ea r s s ho wed pract i c~lly no c~~ n .e with lo n~ i t u~ i nal ~cs i ticn .
Fill e t c~ an,c s on t~e c on~ l et0ly faircd lan di n ~ ~ea r I ~ad o n ly a sma ll e ff ec t . ? i 1let chan~es on the qom~lete ly fa ired la4di n~ ~ea r II c~u sed consi de r a ble ch ~ n~e in d r a ~ , but t he va r i a tion rr i t l1 .f ille t 's iz e \T a s no t re ~u l n. r : ' Tn e d r a~ ~ e r un it fro nta l ar ea o f the complete ly fa ire d l an di n ~ ~ea r s I n nd II was nb o t ~~e S~ Ee as that : o und fo r the si n i la r Innd i n~ ~ears B an d A , r esp ect iv ely , of ref - e r en ce 2 .
COH C~ U ~ I O~ .1S T he d r ~~ ch an~ ed v e r y l i ttle l7it h e i t he r 1 0~~ it ud i nR I loc a tio n o r whee l e xten s i o n ~or t:::'e ' lano .i n o; ::;ea r n it h t~le lowes t d r~~ : a c cmp letely fa ir ed - an d i n~ o;ea r of t he w~ee l sp at , s in ~ le - strut t ype . ~he dra ~ 0_ t~e t r ouse r - ty ~e I nnd i n~ .o; e a r inc re sed con s i de r a~ l y , ~o~e v e r, I! i t~ an i n - c r C:lse i n the 'v!1ee l , exto:r:.sion . Tl1 e ' \ 'i~1 ee l of th e unfaircd etractable l and in, ~ea r w~s a t least on c - n~ l ~ r etracted NACA Technical ~ot8 No . 7 88 5 into the fusel~~e bofore the dra~ oec0~e loss t han that of the best nonrotracte ' l an~ in ~ ~ea r . The dra~ per un~t frontal area Qf the landin~ ~ears of th e present t e sts IT~S about tho same as that fou nd for similar landi~~ ~ea rs in earlier t os ts .
Lan,ley UeMorial Aero naut ic a l Laboratory.
rational A dv i sory Com~itt 8c for Ae ron aut ics, Lan~le y Fiold , V " October 10 , 19 40 .
REFERENCES 1 • Herrnste i ~, William il ., Jr., and Bier~ann, David : The Dra~ of Airplane ~~oe l s, {heel Fairin ~s, and L aL din~ Goars - I. Rop . No . 485 , N ACA , 1 934 .
2 . B ior M~nn , David , and Her r ns tein, ~illi an H . , Jr . : The Dr a~ of Air p la~o ~h oG ls, Wh eel Fairin ~s , and Land - in~ Gears . II - ~onretractable an Pa rtly Retrac t- ablo L~ndin~ Gears . Re p . No . ~1 8 , NACA , 193 5 .
3 . Horrnstoin , William H . , Jr., and Di ermann, David : The Dra~ of Air p la~e Who e l s, Wheel F~irin~s , an d Landin~ Gears - III . Ee p . o . 522, ~ ~CA. 1935 .
4 . ~eick, Frod E ., an d W oo~ , Don a l d E .: The Trrenty - Foot Pro pe ller Rose~ rch Tunnel of t .0 ~at ional A visory Co mm ittee for A eron~ut i cs . 3 cp . ilo . 300 , NACA, 1 928 .
J
NACA T ec hnica l N ote N o. 788 6 TABLE I Drag at 100 mph of N ottretracted L and in g Gear a nd Whee l Arrangecents [Drag values gi ven are for optimu m fillets. Fo r fillet dimensions used and for values ob tained w i th fillet arrangements w ith higher d rag, see fi gs . 8 to 28, inclusive.]
Whee l Fairin~ and extenston referonce ( di an . ) 2 . 00 Unfaired 1.50 (fi~. 2 ) 1.13 1.06 2 . 02 5 . 4 4 . 4 Strut 2 . 01 8 . 3 fa iri n~ 1.52 5 . 2 (fi~ . 3) 1 . 50 7 . 5 3 . 9 --------- --- f--- -- ----- 2 . 00 I 1 . 9 2 . 0 2 . 5 4 . 0 Conplete 2 . 5 3 . 8 1.50 1. 5 fairin:e; I, wheel - spa t 1. 50 1.7
Rnd strut j 1 . 25
2 . 0 type 1 .1 6 2 . 6 (fi~. 4) 1.11 ---------- --- -------- ---------- --------- - ---- ---_ . ----- ---- Conplcte 2 . 00 5 . 2 5 . 2 7 . 5 fairin~ II 1. 50 - 4 . 9 4 . 8 4 . 6 tr ouse r- 2 .1 type 1. 0 6
(fi~. 5) 1. 02 I - . 4 I
J
-------- - ------------1------- - --- -- ---- -- ----------------- a Wheel clearance incre ased b y t ri r.c i n~ of~ 1 i nch of fairin~ .
TIA CA Tec~nic a 1 TIote No . 7 88 T il. :S LE II Dra~ ~t 1 00 Eph of P ~ rtly 3etracted L ~nd in ~ -G ear and ~~eel Arra nsensnts (Dr a~ values ~ iven ~re fo r optiDUD fillets . For f il le t d i- nens io ns , see ::~ i) s_ 29 to ~2, i nclusiY8;
--- ------- - -r------ ---- -- 1 -------- ----- - ---- - -- - -------- - - -- - ----- - -
I n I" - 'b I - Q~ , L
I ~h eel !----- - ------:--------T---- -- -·-T- -- ------ --
F a irin ~ extension I I : I :?art1v
I I, "- and : P Os itio~;? os i t ion ! p os iti OL r etr~cted
re fe r en ce (d i an . ) i :3 I C I D in to t i p
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Str ea~ li ne I i I
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cap off . 50 I 5 . 2 ! 4 . 9
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