Report presenting a study of static wind-tunnel data on the effects of external stores like tanks, torpedoes, bombs, and radar domes on the stability of military airplanes. The results are focused on longitudinal and lateral stability. Static longitudinal stability is affected at various Mach numbers, but the data was not sufficient to estimate the effect on the lateral stability

Silvers, H. Norman

Vogler, Raymond D.

UNT Digital Library

.i Copy No. Q \ - " -i, r I iLj ... No. L6m8 t I U S  " NACA. RESEARCH MEMORANDUM RESUME OF W I N D - m L  DATA ON TRE EFFECT OF EXTERNAL STORES ON STABILITY OF Langley Memorial Aeronautical Laboratory Langley  Field, Va. r .- _I. " - b  NATIONAL ADVISORY" COMMITTEE FOR AERONAUTICS 'I By H. N o m  Silvers and Raymond D. VoqLer A study ha3 been %de of s t a t i c  wfnd-+mne1 dhta on the effects of external stores (tanks, torpedoes, bombs, and radar dams) on the Rtabili ty of l.tKLitary airplanee A smmry, in tabular form, 02 the available data ie presented. The data obtained indfcate that at khch n W e r s  below 0.4 the effects  of external  stores on a t e t i c  longitudinal etabil i ty were sma l l  but r a y  not be neglfgible. Although Ckta were meager f o r  Bkch nmbers above 0.4, the results indiceted that wlng-tip t a n k s  - which w6"e w e l l  faired t o  the wLng contour cawed reaeonably small changes i n  s"&tic longitudinal s t ab i l i t y .  The availabls data were ineufficient t o  estimate the geneml effects of ex t s r r a l  stores on l a t e ra l  s t ab i l i t y .  For one mcdel., however, the adverse e f fec t  of stores  on directional s t ab i l i t y ,  althou# smll, WELS of the order of magitude of the d i r e c t j o m l   s t a b i l i t y  of a fi#ter airphne conaidezed acceptable for milrtsry service. l imitations of space inside current long-range, heavily armed, kish-speed airplenes k v e  resulted in the practice of Fnstalling part  of the auxiliary equipment OA the exterror of the airplane. External ins ta l la t ion  of auxiliary equigmmt facilitates maintsnance a d  results in  a more flexible arrangerLent than interrfi l  installatfan of equipment. Such instal la t ions have. i n  c e r t e l n  caees,, adversely altered the aercdynmc charzcteriotice of  the aiiTl%ne. In an effort t o  overcme d i f f i cu l t i e s  arising in i'?-ight becauae of these external installations,  the KACA has undertakm a research prospan t o  de temtne  the effects  of external stores ( t a i h ,  torpedoes, bombs, and radar dones) on t he  aerod-c chamcteristicfi of airplanes. A br ie f  sumnary of the verious data obtained in s t a t i c  wind-tunnel teste a t  the Lmqley Meuoriel Aeronmtical f;sboratorg mid the h a  Aeronautical Laborator2 an the. effsc-b of  external stores on a t a b i l i t y  is pmsented herein.  The results ere taeei? upon static w"rnd-tumel t e a t s  of vwious service and rcsecrch airplans mcldels. c;han;2e In lateral stability p a r m a t a r ;  positive when external s t , G r s  increasea effective di!ledral l i f t  coefficient wing mean aeroQzexnLc chord (M .A .C . } V!ch nuollber (Vo/a,) f'rge-stress velocity, feet per secard velocity of sound in free strean, f ee t  per secmd Subscripts : * partial derivative of c o e r f i c i ~ t  w i t h  r e s p e e t  to Faw 0 free stream . NACA RM No. ~6~108 The analysie is based upon results crf xind-.t;unr-el tests presented in references 1 ad 2 and upon other &te. obtained at the Langley and -6 Uborator'ies a-6 represents t%e peater pe3.t of the data on t h e  effect cf exteml etores an s k b l i i t y  obtaired by the NACA t o  dete This &yais is confined to wind-tunnel data obtained frcm t ea t s  of nodela wfth progellers e i ther  removsd or windmilling ar-d w i t h  tZ;e flaps undeflected. The results are  presented as a c r e m a t s  of np, %, C n q .  end Gzv These fncrements were determfnsd, at e . q  pzrticuLar l i f t  coefficient, by subtracting tihe value obta ixd  withoat ike external store f r o m  the value obta,ined w i t h  t&e Store. The results of this a~ialysis axe Eummarized in t a b l a 1  a d  11- The r e su l t s  greeentei! Fn table 1 ara based upon datb. obtsined at Mach nwibers below 0.4 and thoee in table 11, upon d k t a  above M = 0.4. Such a divfsion ~ e e m 8  appropriate, because the data taken s p c i f 5 c a l l y  t o  determine compressibility efTects b e 5 3  a t  about M = 0.4. M.so included in  these tables are yertinent geonetric character is t ics  of the instal la t ions.  Elevak-r-fixe3 neutral points cver a l i f  t-coef - f ic ien t  r w e  f'ronr CT = 0.1 to C, = 1.0 were detel-mined by methods similar t o  those of r e f e r a c e  3 -  The r w e  of b"p ebown in tablea I and I1 is dete-ed by the mximum decrease or increase fn stability due t o  extern& stores. The average drag incrementa are presented for the r a g e  of lfft coefffcient Prcm CL = 0 to CL = 0 - 3 .  The average  increments (A+, ACD, LX!~:~, and presented in tables I and I1 were obtalne3 by a graphfcal 'method in which a man value of the fncremental coefficients was determined throu&out the l i f t  rage. This Il?e"%hod was -sed since data that are WlrelTable becawe of p&rtieL sbllln+3 of' the mdel  at high lift coefficients affect these mean values only sli&tly. Tbis methDd fa therefore believed to ~$ve a c l e a e r  general conception of the effects  of extern1 stores on stabi l i ty  thar dzes ccnsideration 02 the decrezse or increase in s tzb i l i ty .  d d ponnitc3inal st2billtS. - The resu l t s  shown in  table I indicate that at Mach nuinbers below 0.4 the ef fec t  of external store8 on a t a t i c  longitudinal stability, thowh mall, m y  n o t  be negligible. Only three of the installations showed an average change in stabi l i ty  t 4 MACA P!, No. ~ 6 ~ 0 8  greater than the axpected accmacy (t1.5percent M.A.C.) of  neutral-  point determination Althoush data for Mach numbers above 0 .4  a r e  meager (table 111, the results indicated that uin-,-tip tanks tha t  were well faired to tho  wing contour caused reescnabla arm11 chaqes  in stat ic  longi tudinal  s tabi l i ty .  A very appreciable Etabillzing e f fec t  was experienced e. t  higher Mach numbers, howsver, when two W-pound  bombs vere attached with drop hooks and sway braces to  the  undersurface of the wiw. This  change in s t ab i l i t y  i e  probably associated with the l a r g e  increase in drag due to the bomb inste.llation8 with an increase in Mach number. Pressure distributions taken a t  a low Mach number indicate Ut  the c r i t i c a l  Mach nlniber of such installations may be as low as 0.6. Lateral stability.- Insufficient data are avaflable a t  present to ectimate the General. effects  of external stores cn lateral s t a b i l i t y  a t  Mach numbers below 0 . k .  No data a t  M&ch numker8 Rbovs 0.4 a r e  available. It should be noted. however,thet the value of rlc of 0.00030 contributed by the wing tanks of one 91 model (table i> is of the order of rtiagnitude of t h e  t o t a l  C n\f, of a fighter airplane considered acceptable for m i l i t m y  eervics. Such an instal la t ion on a i a  fighter airplane would actually cause direc: tional i n s b b i l i t y  . CONCLUSION3 Anelysis o f  a collectian of data from s t a t i c  w.tnd-twae1 tests on t h e  effecte of external stores (tanks. torpedoes bombs, and radar domes) on t h e  e tab i l i ty  of airpiem -el9 Lxdicated The f o l l o ~ n g  conclQsions: 3 .  The aveilable h t a  were insuff ic ient  to  estimate the general effecte of extema.: stores on l a t e r a l  s t a b i l i t y .  For one mcdel, however, t h e  ai(v8z-w effect of e t o ~ e s  on directionel s - k b i l i t y ,  Elthough emall, waa of the order of DE.@ tude of the Birectional 8 5 . Langley Memrial Aeronautical Laboratory National Advisor3 C a m i t t e e  fc r  Aeronautics LanE;ley Field., Va . 2. Baneon, Frederick H., Jr. : The Effect of a W€q-Tip-l4crwLted Fuel Tank on the Aerodpmic Chz?zacteristica of e, High-Speed Bomber Wing. RAGA ACR No. 5806, 1345. 3 .  Schuldenfrei, Marvin: Some motes on the Determination of the Stick-fixed Neutral Point  from Wind-IllwLnel a t a .  XACA RB KO 3120, 1943. C NACA RM No. L6K08 6 """"_ """"" ____ -3.b to 1.0 -2.0 to 2.0 -1.5 to 2.3 -.7 to 3-5 -3.5 to 1.0 tc . -8 -1.5 to 1.5 -3.0 to o -2.0 to .8 -1.7 to 1.3 -1.0 to 1.0 -1.0 to 1.0 -1.4 to 1.6 -.9 to 1.8 "8 to 1.1 -2.0 to " 5  -2.2 to 1.0 -5.5 to -1.: "1-5 to - .$ -1.0 to 1.0 -2.0 to 1.0 """- -0.5 to 2.0 -1.0 to " 5  0 to -5 -1.0 to 0 -1.7 to 1.7 -10 to .2 0 to 1.0 -1.0 tu 1.5 -0.k 0 to 1.5 -1.5 to 2.0 -3.8 to 2.0 -1.0 tu 1.7 - .3 to 2.5 d"p (psh U.A.C. -0-4 .7 .1 1.6 -1.5 .2 -2 -1.0 .8 -.l "2 -3 .1 .3 0 -1.0 -1-8 -3.0 -1.2 "3 -.8 ."-" -5 "7 "2 -.2 .2 - .2 -3  -.4 .7 -1.2 .S -.1 - 3  .r I """ 1 6 -""_ 275 1 """ m o.ooolo + + """- .OOol2 1 """ """ T =E I"" 1. -IF I"" ' + I  +7 1 lo "" -"_" 1 """ i5 ""- - Io 1 I lo ""_" - . m 3 s  + -.oMx)l + """_ -G 3 -.a0025 -.ooop .lh ZT -32 +. "" - 1 """ """ * ""_" - 4  -30 .30 1 "I""" -.ooo8o .aoQzo + & "- .l5 "Oaaog . 2 m  """ ""_ .2m """ = -2373 I-/T "I"_ """ T Itam 'Ra, eal, 0- 1 I8 1.34 1.06 1.13 .47 73.63 -2.0 to 4.5 .6 4.5 tu 4.0 .Si9 -4.0 t o o  .e5 -1.0 t~ 3.0 .@ 0 to 2.3 .a 1.0 to 2.5 .m -1.0 to 3.0 .n -1.0 to 3.0 . 7 5  " 5  to 2.3 -70 -5.5 k 3.0 .65 -4.0 to 1.5 .m -.6 b .a .m 4.7 to 1.5 .mi -1.0 fo 2.0 , .7$0 -5.0 b 2.0 .& -1.0 to 3.0 .Bo -1.3 to 1.5 .8s -2.5 tO -3  *.&I -.8 fa 2.3 .y -.5 ia 4.0 - .sff -.9 bo -.l .a -.Is to -.l .6s -1.3 to .3  .m -1.2 ta - .3  ,725 0 to 3.7 .m -.3 to .4 .70 .a .9 to .1 0.3 .e5 -.l fo 3.5 .70 .5 to l0.0 .m -.1 to u.3 .eo - . 3  to la.7 iverage psmsnt U.A.C.) 9 - 0 .7 .a .3  1.8 . 3  '3 -1.0 2.0 1.0 0 -.3 -.3 1.3 0 .a -.a .2 3.0 -.4 -.3 - .a - .6 .1 1.8 . 3  . 3  .8 b.7 4.5 8.5 -. . . . . . .  . . . . . . . . . . - . . . .  L 

NACA Research Memorandums

https://digital.library.unt.edu/ark:/67531/metadc58013/m2/1/high_res_d/19930085616.pdf

NACA Research Memorandums

Abstract

Similar works

Full text

Available Versions

UNT Digital Library