h)hChi'?-'^'> '^ NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS WARTIME REPORT ORIGlNALLy ISSUED January 19'* 3 as Advance Ccoaf Identlal Report THE EFFECT CK STABIUTr /JID CCRTROL OF A PUSHES PBOPELLER BEHIND CCNVMTICHAL TAIL SDEFACES AS DETERM3HED BY TESTS OF A POWERED MODEL IS THE FREE-FLI&BT TCHinEL By John P. Canpbell and Thomas A. HoUln^orth Langley Memccrlal Aeronautical Lalxxratory Langley Field, 7a. ffxex WASHINGTON NACA WARTIME REPORTS are reprints of papers originaUy issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were pre- viously held under a security status but are now unclassified. Some of these reports were not tech- nically edited. All have been reproduced without change in order to expedite general distribution. L - 220 Digitized by tlie Internet Arcliive in 2011 witli funding from University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation http://www.archive.org/details/effectonstabilitOOIang 1^3 C- "i ITATIO^AL ADVI30HY COMKITTSS 103. AEHOITAUTICS AJVAIICL CO':j ;..3:-I?IAL REPORT TEE SFJSCT Or! STABILITY AND COl^TSOL 0? A PUSHEH PP.0P3LLEP. BEHIND CONVZIITIONAL TAIL SUHJ.XZS ..S DETEP.MIITED 3Y TESTS 0? ^. P0V7LP.ED i-iCDEL liJ '^V.?. JRVZ-PLI ^HT TUNir^L Sy John P. Campbell and Tnonias A. Hoi 1 ingwor th SUMMARY Tlie effects on stability' and control of a pusher pro- peller behind conventional horizontal and vertical tail surfaces have been determined in the IIACA free-flij^ht t\ir.- nel by tests of a l/lO-scalo model of r>,n NACA subner ged- enr.ine pusher airplane desie;r!. The inve s t i :^,at ion consisted of flight and balance testa r.t vii.dniilling and hi.'^h-power conditiona '-ith a partial-span Zap extensible flap extended and retracted. The effects of changes in -"-ert ical-tail area, horizontal-tail incidence, and center-of-gr ivity location v;ore also determined. The ta?ts showed that, '•■ith ? pusher propeller located behind tho tail surfjces, pc-.-er causod onl:'' minor chances in stability ind control, Tho v i..dmill ing propcllor provided slight incroesos in longitudinal -'nd directional stability. Application cf po'.;er only slightly affected the longitudinal stability, increased the direction?! stability, ziid. necesssi- tsted a small amount of aileron trim. The dihedral effect, stalling behavior, and rudder trim --.'ere not i=ffected by po'-'er . This particular pusher design -'ith the propeller behind the tail surfaces is considered very promising as a means of eliminating the undesirabla slipstream ef: propall.^rs. ic t s t ract or Il'TRODUCTIOl The trend toward more powerful en--;ines in s ingle-en^^ine military airplanus has c'^used the propel ler-<^ 1 ips t ream effects on stability and control to become iucreasingly important. Bocan.se those slipstream effects are, on the '-'hole con- sidered undesiratle, means are teing sou.^ht to eliminate thain. One apparent solution to the problem is the use of pusher propellers. Various designs to p'jrmit the use of pusher propellers have Deen proposed, such as the tail- less and tailfirst airplanes. The IIACA has recently sug- gested a suhmerged-engiae pusher design v/ith the propeller directl:/ behind conventional horizontal and vertical tail surfaces. A l/lO-scale powerjid model of this desi^jn has been tested in the IT^iCA free-flight tunnel to determine the effect of sv.ch a propeller arrangement on stability and control characteristics. During the investigation, a special effort v/a'? plso r.:ado to observe any changes in stability and control that night have been caused by tho short tail len^'th inherent in the design. APPA3ATUS AMD MjITEODS Wind Tunnel The investigation '--as carried out in the i*AGA free- flight tunnel described in reference 1. Photographs of the test section of tho tunnel show models b^..ing tested in flight in figure 1 and on the balance in figure 2. In the flight tests, tho model flies freely in the tun- nel under tho remote control of a pilot seated at the bottom ana roa,r of the tunnel. An operator at the side of the tun- nel adjiists the airspeed, tunnel angle, and power to the motor in the model to correspond to the desired flight con- ditions. After the lateral and longitudinal trim of the model h-s been adjusted for the p-'rticular conditions, the stability of the model in uncontrolled flight is observed and tho effectiveness of the controls is determined. In order to supplement the pilot's observations, moving-picture records of flights -?re taken by tnree cameras mounted at the top, side, and rear of the tunnel. The balance tests werQ run on the free-flight tunnel six-copiponent balance. The balance rotates i.;ith the model in yaw so that all forces and morasnts are measured with respect to tho stability axes. Model The l/lO-scalc model of thi ITACA 3Ub::iex'?:ei-Gnc;inc pushar airplane dcsi'^u used in bhe tssts v;aa constructnd and preparod for the t-sting ty the ilACA. A threo-vievj -lrawin,£^ of the nodel in pres.uated as fi<^uro 3 and photo- graphs of che model aro shovr in figures 4 and 5. The dimansion-il eharac t or i s t ic s cf the a.irplanG as scaled up from the ::iodel values are ^iven ii: talDle I. In addition to airpl;,no (tn. ils 1 installed on t Only the upper ruddar , the vertical tail^ mo and 2 of fig. o), a (tail 3) '".MS in3ta.ll.3d on t ho modol for soiai vertical tail '-/as provided 't i t h specified for the larger vertical tail r soma of the tosts. of the tosts. a mova'Dlo A sijiiplo wire landing T^ear '-'as installed on the model as shov/n in fi^ur.^ 3 to provide sufficient /ground angle for take-off anrl tc aLsorb shooh in landings. Tl'ie wei.jht of the nodel after final preparation and balancing was ■^bo-at 5.80 pounds, v/hich corr esi^onJcd to 5800 pounds for the airplane, 'Jho center of gravity of the raoael ''as .adjusted to 34.2 porcent of the mean aero- dynamic chord. The inomonts of in.-rtia cf the modul coi- re- sponded to those of typical T.odern fighter airplanes as in- die ".ted. by the r-tios of ■.vin-\- spar, to r.adii of gyration shov;n in table I. Z 1 e c t r 1? a gn e t s ■•' e r e installed in the ..-■ c. e 1 to provide abrupt deflections of the ailerons, rudder, s.nd elevator, The ailerons vrere deflected vrith an eq^ual up-and-down move- ment vrrying from ±13° to ±18°, P.udder deflections varying from ±10° to ±30- v/ero used in conjunction ■•;:th the ailerons to provide proper control c : ■.-..'.inat ion, For longitudinal control abrupt elevator deflections of ±3^ or ±3° were used. The model w.-;s powered a direct-current, controllable- speed electric motor rated l/S hor sepo-./er at 15,000 rpn and geered ■■.'itn ratio Ox 3.54:1 to a pusher propeller. '^he motor w.?s placed for"-.'ard of the v-'ins; .and was connected to the propeller by a 5/ 16- inch-diar.ot er , hollow, aluminum drive shaft about 13 inches long. An adjt;s table-pit ch , model. For all ti :ller v/ a 3 used on the m angle at 0.75 radius was set r,t 34° power at maximum efficiency with the d of 5000 rpm. f c - b 1 a d e , 11 - i n c h w a pro p e "■ '' ^ '' pov.'er tests, the blade order to absorb full sired propoller speed in •e s u Coiivl i t ions The power charac t e i'i o t i c s of t'. ■fa ox unit det- :irei 07 Prony "brnke modol motor and ke t :■ s t s and t he gear char- acteristics of the ^-ircpelicr ••ith v\rious p.!r:0\i.nts of j.dtch were ascertained at dynamic pressures of 0, 1,90, and 4.09 pounds pTr squp.re foot. These tests indicated that a hlade rngle of 24 at 0,76 raii'as would r.ost ne-,rly satisfy the required conditions. For each of the flight and b.alance tests the po'-fer sup'oliel tc the model was adjusted to the desired condition 07 varvin^' the in'Diit volta?;e. The flight te^ro? covered a. ran-je of airspeeds from 25 to 50 ;niles per hour, v:hich corresponded to 80 to 160 miles per hour for 'tiie airplane represented. I'he power was varied frou viindmill in,^^ to 0.335 "brake horsepower, which was tne maximum obtaina/Dle ■'^rc.:ii the motor used in the nodel. The thrust developed in the flight tests was determined from the difference hetv/een the fli§,ht-path angle, or tunnel angle, with. po<;er on and ^'"^ onr.T lift coefficient. • ac anaie v/ith propeller off 8.t the same Tr. ' ' ' hif;h-po';or condition in the fli.'^ht tests corresponded tc about b5G hrako hor sepo'^or for th; a i r p 1 an c , Most sure of 4. velocity conditions h a p e d. n t wore run a in order t hy extend the p w e r horsepower hy vrrying coof f ic ier. h r s e p >/ e r coof fie i ,n hors opowr r to the p :. r of a,n ciirp a i r p 1 :- n o w tions of t efficiency f the b a 1 f ! n c o tests 09 pounds per souare f about 40 miles p-^r and to a test ?.e3'"nol he mean c li o ;c d of 0.58 t a dynamic pressure: represent gr.;ater a the power ran:-:;e of th to the model -..'as adju for the airplane. '■} the V 1 u a g e t c g i v t Tq at each lift c (and then the thru. it t was cor!puted by nul (1100 bhp) by a prop ticular lift coeffici lane with a speed ran ere used in making th hrust coefficient, to with lift coefficien were run b.% f oot , which hoar under s ds number. of c foot. The cf 1,90 poun i r p 1 " w e n o r £ £ tests. ? 3 t e d to c r r i, i u p 'f e r ad t h o proper v e f f i c i e n t , c e f f i a i a n t tiplyin;; the eller effici ent. Propel ge E irailavT t cse computat rque coeffic t are shov.-n a dyn am i c pre s- Gorresponds to a ta.nda.rd sea.-level about 209,000 hirh-po\jer tests ds per square foot epower and there- r ?ach balance tet-, espond to 1100 brake la lance t est , '^ a iJ^iii.\jL uO 1100 br; justment was i!iade alues of thrust The desired thrust ) for each lift rated airplane ency corresponding Ier efficiencies that of this ions. The varia- ient , and propeller in figure 6, SYMBOLS m lift coefficient (L/iS) drag coefficient (d/o.S) lateral- force co efficient (Y/qS) .Vc'.win.'- m orient \ y av; i n ,3- n m e a t c o f f i c i f ; u t cits ; r oil iiir-raO'iisnt cooff iciont ("rollirg; moment) ^ qbS ^ pitchiap-raoment coefficient (pitching uoment \ qcS L D Y 1 c S b C ^P a lilt , pound ;^ drag, pounds later.'l fore.;, pounds dynemic prossure, pounds par square foot (spV^) average chord, fjot v/iiig area, square feat wing 3pan , feet rc'tc of change of roll ia,<;-mojnent coefficient v/ith siderlip, jjer radian r ,,tc o:l ch".n;;y of irrvriiij^-ao-aijnt coefficient 'dth sido-slip, per radian angle of sideslip, r ■^, d i an s angle of ya'-;, degrees angle of attack of fu:.ela=:e reference lino, degree: thrust coefficient pV^D^y p V D 5. thrust 5 po-ands air density, slugs par caoic foot a i rn p c G d , feet ]p e r second propellor dia.neter, feet toraue :;oe.f f iciont f ^ — ] torq^ue, pcund-faet ria;Iit aileron deflaction, degrees S .-^ elevator deflection vith respect to stabilizer chord, deere es rolling velocity, radians per second helix an-Tle generated by win^ tip in roll, radians P pb 2Y i^ an.v-le of stabilizer C, 'P setting, degrees k) r p £ 1 1 e r efficiency rate of change of r o lling-iTjonent coefficient v/ith the hclii: angle ^!i— 2V T3STS A^'JD EZSUI.TS Ihe stn,ljility and control characteristics of t, he model were investigated at the windniilling and high-po:ver conditions and with the propeller removed. Tests v/ero made I'ith the part ial-5pa,u Sap flap retracted and fully extended and with various combinnt i :^ns of the vertical tails shov;n in figure 3. A few pr el i'ninar;,'' tests were made to improve the longi- tudinal stability of the model with flaps down. During these tests the center of .-gravity v;a,s moved lor-'fard from 24.3 to 12.7 percent of the mean aerodynamic chord and the horizontal- tail incidence was changed from -.^o to Q° . Tuft tests vrere made to determ.ino the stalling characteristics of the wing and horizontal tail. • Flif^ht tejts. flip;at test. elevator de coef f ic isnt fiajj deflec feet ivenee s min'.^d by ao in tate tnun r e c !■ d s the ailsron man f r .;i these these tests s are pr flection s. The t i o n and of the ting the el I lii^h rolling euvei's w Daneuve r a r i3 pre I'ue loi;e:i t ud inal d.ata obtained in the ^nented in figure 7 in the form of s required for trim at different lift ciirv-3 3 of fif;ure 7 show the effect of power on longitudinal trii.'i. The ef- ai]. erons for lateral control v/as deter- deflections required for p,ood control ts and by measuriut'^ from moving-- picture velocities produced both in abrupt ith rudder fixed and in the recoveries s. The values of pb/^V obtained in sented in table II. Palance te^ts.- The result-i of the balance tests are gi von eff ec tics are r of po t r i Ti , r iat i locat tests shown of th g; i V e xi yav/in again slope f i-.?;ar i n f 3, i^u r .3 t s of p w e of the mod e plotted i v/er and fl The chan on of hori ion are sh made to d in firure e model as in figure g-moment , st anj^le o s ox the r es IP. and i. 8 to 11. r and flaps el . T'".e Ion n fijure 9 t ap deflect io res 1 n Ion .'j i zontal-tail own in f i f ur e 1 r m i n e the 11. The la affjcted by s I'J .-.■.ud 1^> and l.--,teral- f yaw at a 1 1 ling-mOrnun 1.3 are shov/n against 'no together v/ith neutral .sj)iral stability (E 1 r y stability ( R ■- G ) . Th control a ~ d e c ^ r ip i n o d by b a 15 in the ior.a of rolling-n: cients pl^tL^-d a, i; a i »i f^'- 1 ri^ih The Gurvos of figure 8 show the on the aerodynamic characteris- gitudinal data from this figure shov; more cloarly the effects n on longitudinal stability and tudinal stability caused by va- incidence c.nd c enter-of -gravity e 10. The results of balance ele'^ator effectiveness are teral-stability charact eristics power, flaps, and fin area are in the forni of rolling-moment, force coefficients plotted ift coefficient of 0.75. The t an-^ yawing-moment curves of in figure 14 on a plot of Cj approximate boundaries for - 0) and for neutral oscilla- e ei'f ec t ivene 3 -^ of tlie lateral lance terits is shown in figure oment and yaw ing-moment coeffi- t aileron c'e flection. mine t h -3 -i t £; 1 tal tail are presented in figure IS. ^^- The results of turt tejts made to deter- rv.v.g .• h^.r-'ac t er i s t ic s Oj.' \,he wing and horizon- Discussion preliminary Testa Because of the h, r i 2 ii b a 1 tail w a v. dence ox -5° to avoi trim with flaps ao''ai t i n of the rj a r t i a 1 - CO Tie statica. lly loa^ fli;-';hts w&re iiapossi gences in pitch that deflection. Hoving 24.2 to 19.7 percent the model longitudin 0,80 and good fli^'^ht control. At lower ]. fli/;:hts3 could he mad nate up-and-down ele f r in diverging. At the stability was no made even in this mo. short r i .-^ i n d e j: c e 'll i t span Z itudin b 1 e at c u 1 d. the c of th ally s s conl if t CO e n 1 y vat or lift c t suff n n e r . tail ally s 3 i ve h t h i ap fl ally any not n t e r e raea table d be eff ic b y c def le s f f i i c i e n len set ■up s t ap n.ns air be of n a at mad i e n ont ct i c is t t .-th of th at an an -elevator ail incid caused th table. S speed bee controlle gravity f er odynami lift coe e vrithout t s , h w c V inually a n s to p r n t s below permit e model, g 1 e of i travel ence , de e model ij. 3 t a i n 3 d au 3 e of d b;/ ele orward f c chord f f icient using e er , sus t pp lying event t h 0. 50 , m f 1 ifht s the nc i- f or flee- to b e - 1 V e r - vat or rem made s above levator a i n e d alter- e model 1' e V e r , to be tail the su-ff This on t nfif-';?: a 1 1 i trol e V i d as i The character of this instability suggested a form of stalling. 'v'hon the horiaonta,l tail was r,et at -5°, downv/ash at lov; an-^les of attach' was believed to be iciont to cause the lower sxirface of the tpil to stall, belief was substantiated by the behavior of the model he floor before take-off. The model often assumed a tive angle of attack before taking off anrl from this tule the nose could not be brou£_^ht up by elevator con- In these ca.,!es the lower sarfnce of the tail w a, : ently fully stalled instead of intermittently stalled t appeared to be in fj. ight. The tuf t e r i s t i c r. of I e h r i z ail s t a ; n t .'3 d i n ; a i 1 w a s of th i n g t pr ese the t of -4 tail f li,-h d i 1 1 c prove coef f and t s t a 1 1 i n t s at 1 n at an d Ion g i i c i e n t s t tesbn made to d.jter-^iine the stalling charac- the wing and of the upper and lower surfaces ontal tail proved that the assumptions regard- llJng were correct. T'le re-.uDts of these tests, figure 16, indicate that the lower surface of almost completely stalled at an angle of attack hat the outer portion was stalled at 0° . This g accounts for the difficulty encountered in ift coefficients belOv/ 0.80. The u.nstalled con- gles of attack of 4° and 6*^ explains the im- kudinal behaTior of the nodel at hi;;her lift It is realized that the tail stallin--:? of the airplane vo-ald ocsur Ft nuch higher negat''-ve angles of attack of the tail and tliat the moiel test results cannot be used quant i tr t ivel,v but ira>" be taken only as an indica- tion of an un :;at isf actory condition that would be eucoun-r tered by the airplane if too ^^reat a iie,<;ative tail inci- dence were used. Chan,-jing the horizontal- tail incidence to 0° elimi- nated tae tail stalling (fig. 16) and made the model lon- f-itudinallj' stable v;ith flaps iov:n at all lift coefficients vfith the 24.3 percent c enter-of-gravity location. The flight-test Icngitudinal-t r irj ci\rves of figure 7 indicate that the stability i/as slightly less for the flajjs-down condition than for the flaps-up condition. I\To difficulty was experienced in making ilirhts with flaps dov;n, however, and the ctrbility ■•;a,c; conciciersd entirely adequate. The results of balance tests (iit;^s. 3 and 10) show the chan/;es in stability with flap doflecticn. In fi^^'ure 10, the unstable pi tching-moment slope for the flr?.ps-down condition v.'ith the original tail incicence and c enter- cf- gravity position explains the ina.bility to obtain fli^vhts at this condition. The raarnor in which the forward shift in cent or-of- -gravity position increaced t'le stability is also shown in this fiture. As indicated by the fli_jht tests at this condition, the stability is positive at the high lift coefficients but only about neutral at lift coef- ficients belov 0.80. The pronounced stabilizing effect caused by the chanjje to Oo tail incidence is as evident in the results of balance t3sto (fig. 10) as in the fli|S^ht tests. Longitudinal Stability I n G r e a s i n -^ the static lon^'i and flaps -down c ures 7, R, and 9 data obtained in stability as ind to trim at diffe creased by power by power v/ith fl sented in figure results iii this stability v;ith p to have provided i t y for all c o r,. d the power caus tudinal stabil cndi t iona , as It appears the flight te icatad by the rent lift coef with flaps up aps down. Tho s 8 and 9 !\-t respect and an w c:i r . The win a s 1 i ^-ht incr i t i o n s . ■3d n 1 y a i t y for bo shov/n by t from the 1 sts (fig. elevator d f i c i e n t s 'i and very ba, lance t e fairly w w even s m d Ti i 1 1 i n g p a s e in 1 o L ~ht change in the flaps-up curves of fig- -itudina.l trim that the r tat ic .ections required slightly in- Lghtly decreased results pre- with the flight er changes in eller appears tudinal stabil- es t ell all r op n,-l 10 ATjpl icat i on of pov/er caused opposite changes in lon^-i- tudinr.l ti'iia for the flaps -up and f laps-d ovni conditions. The trim changes were apparent in the flight tests when successive flights vrere made at the windni 11 in.;; and hi ,-h~ power ccr.ditions v/ith a const^.nt elevator setting. Appli- cation of po'','er cauc-ed the trim airspeed to increase with flaps up and to decrease with flapa down. These trim changes r?,re shown by the curves of figures 7 and 9. The danpin^:^ of the phugoid oscillation was satisfac- torr/ for all power conditions and appeared to he sli^-htlj* "better r.t hi/;h power. Longi ti'.dinal Control The longitudinal control appeprel to oe good in all respects despite the short tail length of the modol and the nearness of the propeller to the horizontal tail. Abriipt elevator deflections of onlj ±2° or ±3° were re- quired to correct for longitudinal dis turhances and to maneuver the model in the tui-nel as desired. Sli:;htlv greater elevator deflections- hav'e "oeen required on most other models tested in the f re 3-f light tunnel. The eiovat or-t r i^ characteristics as indicated by the flight data in fi=;ure 7 appear to be A'ery good. Tria for the high-speed condition to the stall vras obtained without excessive elevator tra^'el 'ov.i a fairly large increase in elevator movement v/a:- required to produce the stall. These elevator characteristics are considered desirable. The balance-test resu.lts in figure 11 shov/ tha.t , with p vr e r on, the •.'■ a 1 u e s of m d5.-. were about -0.C13 with flaps up and -0.015 with flaps down. These values divided by dC„ rTQ. 2. for tne corr esjpond ing conditions give values of L 'L d.5, of 0.C84 with flaps up and 0.177 with flaps down. These values of d5. •hich are in fairly ^jood agreement with the flight-test results, indicate adeqtiate elevator effec- tiveness for the particular degrees of static stability dC A ii) afforded by the 24.2 percent cent er-of-gra^ity location. 11 S t a 1 -I i n j^ h ?:. r a 1 e r i 3 t i c s The "behavior oJ the model at the stall was not notiee- atly sff acted "by pov;or aiid vras considered satisfactory at all conditions of flaps aiid ^.'O'/er. V/ith the flaps up, the bohi^vior at the stall v;^s not cousistsnt. At tirajs a definite warnin^j of the stall was ohserved in the form of a slight pitching motion, hut at othoi' times the model would roll off to either side at the stall without warning;;. The stall was, however, gentle in all cases and caused no ;^reat difficulty. wer e a not dence tunne this f ect i tests for t dia^r tial- stall the h ty th and w warne Wh e.c ic d 1. &r ve s h3 am sp w or e as en the c e 1 1 e n eahle by a s E'.en adi;a 1 i u V. i h w n i ^:oc 3 s i 1. 1 i an Zap el3 he i 7, n t a tnft t nroba of the fla t. pi t c low -r i t less chiu 1 fi Stf 1 c^ t e fla fore 1 ta est s hly 3 ta p s '•' e r e Aniple ■'/ h i n £ mo droppin h the s of Fit up a T-ire 15 ling bo that t p and t the ai il at h '-.'as ac r 3 3 p n s 11. down, the st arning of the tion, and the 5 of tlie mode tall sufficir itude, the ai low win^;. Th provide a pi h.?vior with f hu up'OoT surf he portion of lerons. The i^-h angles of tually a form ible for thu alliuf: stall stall 1 to th ntly ad ler o.:s e r e s u 1 a u s i b 1 e laps do n.c :5 of the w i appar en attack of tai pit chin charac w as a f itself e floo vanced \i ere s ts of ■ sxpla v/n . T the la n g a h e t stal ■as in 1 buff g m 1 i ter is t ics forded by v/as evi- r of the to cause till ef- the tui't nation he stall r^e par- ad of it ling of dicated et ing ons that Lateral Stability E f f ''' c t of F AT =; r » - Power provided a noticeable increase in direct ioaal stability a.nd a sli<2;ht increase in dihedral effect. In the fli^^ht teats, these stability chani^es \iere evidenced by the saioother, steadier flights obtained v;ith po'ver 01. When, during a sijii;;le continuous flij?'ht, the po-./er was increased gradua.lly from vrindrjillinj; to high power, a definite stead;/-ing of the r.odsl, especially in 5''aw, could be observed. Thi3 effect of power, which was noted in fli^;hts with flaps either up or down, was consid- ered, beneficial in irnproving the flij;ht behavior of the model. The spiral sta,bility, which was satisfactory with power off, did not appear to be affected by power, V'ith the flaps up and only the upper vertical ta.il on, power definitely improved the oscillatory stability and reduced the adverse yav;inj caused by the ailerons. 12 The balance-test results in figures 1.?, 13, and 14 suostantiate the observat ions made in the i'lirht tests in regard to the effect of po'-rer on the lateral-stability characteristics of ths model. The 7/awing-iiioment curves of figure 12 have greater slopes with power on and, in addition, the curves are si; ra,ignt ened out b^ po'/er at the higher anles of yaw. This strai.^ht ening out v/ith pov/sr on suggests that the propeller vas acting in such a manner as to delay the stalling of the vertical tails. At the lov? angles of yav/ , however, the effoct of power in increasing the directional stability cannot be credited to the cliange in air flow over the tril surfaces be-iause, as shown in figurs 13, most of the increase was obtained with the tails renioved. I'either can the -najor portion of the increase in directiona.l stability with vjov/er on be attributed to the propeller normal force. The balance tests v;ith tails re- moved indicated a mach larger i/icrease in lateral force in changing froiT the propeller-of f to t ;io '"inimilling condition than in changing fro^n the '■■' indffiil ling to the high-pov/er con- dition. In this respect t h o tests agree v/ e 1 1 with propeller theory. On the other hand, ti^e iricrea^e in directional sta- bility (Cap) provided by the wiMdr i 11 ing ipropeller wao less than one-half as great as the 2-pn increase pirodiiced by the application of power. These results indicate that the inflov; to the po'-ered .^usher propeller might have pffected the air flov; over the fuselage in such a way as to reduce its unstable yav/ing m-oment without appreciably changing its side force. It is interesting to note in figures 13 and 14 tha.t , vjith nil tails removed, powc.r provided enough fin effect to bal- ance the unstable monient of the v: ing-e^nd-f us elage combina- tion tra thereby make the TiOdel lioutrally di rect ionally st able . The curves of fig--res 12 and 13 show the slight ir-crease ■in dihedral sffjct provided oy pc-'er. The increase a^OT^Oc'.rs to be substantially the same fdr flaps up or down and is aljiost negligible in either case. The summary of the balance results given in fi?:ure 14 indicates trie reasons for t''.e flight-test observations re- garding the- effects of power on spiral ar.d oscillatory sta- bility. Inasmuch as power increases both Cno ^■'^^- ""Ci-,, P P it causes a shift on the stability plot (5 to H or Z to ?) approximately parallel to the s.piral-s tabii i ty boundary and thereby affects the spiral st.-ibility very little. The im- provv^ment in oscillatory stability caused by power with flaps up o,nd only the uppsr vertic ■■■- ""= •'''' "-- th ^1 t f^. i 1 Tx ^ shift frOiTi CO ..„j i« conditiv:)!! I, is s h '■; n 3 ii d i t i n .?;r,iph— Dt near vv;ry g tnlDle ell up ancL only the uppsr v avzic-^. x zr.ii on ically in figure 14 by tha shift fTom th-3 osc illntory-s tability boundary, to away from th::it boundary .i.nd apparently r e g i r. . In general, the effects of pover on the lateral sta- bility of this model vere considerably less than the ef- fects of pov.'ar on the stability of conventional tractor models tested in th.^ free-fli|-ht tu-mel. The changes, moreover, v/ere in no ce.S'3 detrimental and v;ere in sone cases defiritely banoficial to the flight behavior of the model. In this respect, this p^'rticnlar pusher design appears to be completely Justified. Effect of flaps.- Iho res-ilts of balance tosts -.-iven in fi£;ur>:! 12 snov/ that flsp deflection cauccd a considerable reduction in dihedral eff.ict a?) expected but did not affect the r".ir."c t i onal stability. It appears from fijure 14 that this reduction in dihedral effect should havo caused the model to become spirpll:/ unstable. An anal y s i s of t h 3 P b/2 " Vil ucs in t r V G a, 1 s v i d 3nce of si if. ht sp iral i ustabili do-'! n . For t h flaps- d 0-1 :1 con d i t i n , the V a obt ained dur in,;;; re cove r i 3 fr m abr up t a i 1 wer e s 0i7iGv/ha t lower t h 3n t he valu3s obtai:ao maneuvers th ernsclves. J hi s r edticod aileron m ay be taken as an ind ic at ion .: f 3 p i r a 1 i n c cau s e the a i lercn roll in O* velocity was evid ty an unstab 1 e r 1 1 i n f in abr ■'i.pt maneuvers win g- level a ttitude an d op pos 3d by the sane rec V e r i e s , Inasmuch as t he var iat ion of t wit h f 1 ap s ti p v^as the re ver se of th Pt with mod el is, by the sane r e ;3 c oni n.3, Ju dged t for the flap s-up condi t i n o able II also ty i"ith flaps lues of pb/21'' ron maneuvers d durin,-; the effectiveness t ability, bc- e .a 1 1 J reinforced starting f r o .n a roll in. 2 during he pb/27 values flaps down, the be s p i r a 1 1 y stable The spiral instability '-rith flaps do;r_ '-ras apparently very sli:f:ht, as -ixo definite i.^dications of it could be noted in the uncont r olled-f 1 i ^nt tests. At any rate, the condition was certainly not obj ec t i ons-ble a.nd the flif:;nt behavior of the model v? i ■ flaps; dcv/n v/a.3 considered entirelj'' satisfactory, In regard to the question of 3pira.l stability, it should be pointed out that tests of several models in the free-flight tunnel nave shown that slight spiral ins tab il it:; is not objec- tionable. The rates of spiral diverirence with nioderate fin area and only slightly positive dihedral effect are ^^suL\ll3'■ 14 so small as to cause no difficulty in free-flight tunnel tests. The pronounced spiral ins talail i tj'' usuall;/ caused by negative dihedral effoct is, hov;ever, considered def- initely \iade 3 irable . :gffoct of vertica l-t ail are a.- In spite of the short tail len-j;th of the model, adequate directional stability was obtained v;ith relatively small vertical tails (tails 1 and 2 of fig. 3). For all conditions of power snd flaps, no objectionable adverse yawiu,'^ was noted when ailerons alone wove used for la.tera.1 control. The damping of the lateral oscillrtions v/as also l- at isf ac t ory . When the tail area vas increased 60 per.-:ent by replacing the upper tail with a. larger tail of the same aspect ratio (tail 3 of figs. 3 and 4), only a slight improvement in the fl;"i:ig characteristics -^'as noted. This improvement vras not considered sufficie.nt to Justify the increase in area. 'llhen the the lower tail t ional st abil i flaps up and 'i small upper to effect to keep V/hen the propo single tail '-'e effects of a 5. V of a i 1 r n con fixed, the mod a.n g 1 e , roll a. g The s t .bility off conditions tail with flap the flight beh much inproved t c c a.ti s e loss tail area i- a s , the m. j". e 1 re ty. In vrindmi i t h the a i 1 e r o i 1 alone did n the a.dve_"se y Her was remov re almost impo or 3 yawing, trol in flight el would at ti n i n s t the a i 1 e at both the pr was c n c i d r s up . ";.' i t h t h avio: the m and the advers of aileron con decreased 50 pe tainad a small 1 ling-power fli ns used alone f ot , however , pr aw i n g from b e c o e d sustained f 1 ssible because During a con tin 3 with propelle mes yaw adverse rons , a.nd drop p e 1 1 e r- v/ i ndm i 1 d unsat i sf act or fl.'.ps do'/n or d e 1 v; i t h the s e yawing was ne trol. rcent by removing aiaount of direc- ghts vrith the or control, the ovide enough fin mine excessive, ights '/ith the of the pronounced Uu-d. application r off and rudder 1 y to .a 1 a r g e to the floor, ling and propeller' y v/ith the single v; i t h p v.- e r on, ingle tail was ver great enough The balance test results in figures 13 and 14 sho'-r the increase in directional stability provided by the small ver- tical tails. Together the tails increased 0.075, which resulted in np '& by about value of about 0.055 for the complete airplane v-ith power off. .t Lateral Control The l;\teral control of the model was not noticeably affected oy power, exctpt that a slight amou.nt of pileron 15 trim '-'as required, to "Dplance propelldr torrue. For the hip;h- pov;er condition in the flii^ht tests, " total aileron deflec- tion of 5"^ rijht v/as required for literal iri.n. Po-ror appr.r- entl;" did not affect ths diraction'^1 trim, inasmiich as no chia.^ve in rudder setting was necessary in icoing from v.'ind- milling power to high po./or. The rudder control was not noticeably affected "by pov/or d.ispito the proximity of the propeller to the vertical trils. On t h c basi for sati sf ac tory cont r ol of t h e m fact , c n t; i d erah dur i Ht'r t he t e s t s flow n in . the fro hov/e ver, t ha t th cent of the •■/ i a p; aver age a i 1 e r n in t his area C V a i 1 e ron cont rol s 01 the abrnjfc aileron deflections required control in the flight tests, the lateral odel was considered entirely adequate. In ly smaller aileron deflections were needed than are required for the average model e-f light tunnel. It should be pointed out, e area o"' these plain ailerons is 8.8 per- arca, which is son:ev;hat greater th.i.n the a.rea of present-day airpla.nes. A reduction Id probably be made without rendering; the inaac quat e. Tiie proof of With the rudder fi required tial i:npr ailerons. durir-, re to slight inasmuch up condit figure If was prc^i ±1S|° tha rolling V i flcpS Uj.' the c r r c value? of iib/2'"' shown in tab the adequacy of the aileron co assumed tota,l aileron movement xed, the jjb/^T'" values are we value of 0.070. Flap deflect i ovemont in the rolling velocit The slight redxiction in aile cover ies v/ith flaps down, whic 3 p :: r r 1 i n ;7 1 a b i 1 i t y , w as not c as the pb/2V wa.s =?till great ion. It can be seen from the that a rolling-moment coeffic ded by the equal up-and-down a u s e a 1 n t s t d et 1 c i t i . ■1 val-i P is obtained by dividin: SDonding pb/,?7 value IC: Of this V (0.0-18 1 e II are ntrol of t of 45° rn 1 ]. above t on caused ius obtain ron effect h has been ensidered er than fo balance re ient of ab ilcron def orm. ine the .[-"'4 fjr th. further he model, d the he m. inimum a su.bstau- e d v; i t h the ivene s s att ribut ed serious r any flap- suits of out 0,026 lection of aileron e a odel ' ; i t h -Ut of 0^(0.026) by ). Abrupt rudder deflections varying from ±10^ to ±30° v.'ere required for good control c on rdin-^ t ion depending upon the particular flight condition. The larger rudder deflec- tions were used with the Ij.rger aileron d ef 1 .--.c ti ons at low airspeeds. Those rudder deflections were Dnly slightly larger than those required jn the average conventional trac- tor models tested in the froe-f light tunnel, even though only the upper tail of the model -^'as equipped with a rudder. 16 The short tail lenjth of this design does not aj^pear to necessitate large rudder areas or rudder deflection-.. In fact, smaller rudder areas and deflections might \ifell "be possible inasmir-ch as no rudder tri:Ti is required for high- po-'/er flight. V/ith the ailerons fired, the rudder provided a fair anount of lateral control vith the flaps up. Recovory from angles of canl: as high as 8° or 10'^ could te ace onipli shed v/ithcut excessive change in heading. V/ith the flaps do>rn, however, the rudder >ja.3 virtually ineffective in rolling the model aiid could not pic'': -up a low wing even at ver; an; small . es of bank COilOLuDIlIG- EE MAZES The effects of povrer on the stability and control characteristics of th3 pusher iriodjl with thu propeller be- hind the tail surfaces niny be siimnar i zed as fellows: lo Longitudinal stability and trim were only slightly affected by power. 2. power caused a substs.ntial increase in directional stability but did not apprecicbly change the effective dihe- dral. The stalling characteristics "ere not affected by power, 4, In poyer-on flights a snail amount of aileron triTi was re quired, but no rudder tri.T. was necessary. 5, The v/indmill ing propeller provided slight increases in longitudinal and directional stability. In spite of the short tail length that was necessary vrith this pusher-propeller arrangement, the genera,l flight behavior of the model v. as considered excellent. A hori- zontal tail only slightly larger than normal- provided sptis- factory longitudinal stability; ample directional str^bility and control v/ere afforded by vertical tails of normal size. These tests, therefore, indicated that the use of a short tail length did not materially increase the difficulty of obtaining good stability aiad control characteristics. 17 Cn the basis of the fre3-f light tunnel tests, it appears that the uncle siratl e effects of poiver on stability and control can be cl iTiinat sd by placing a pusher propeller behind conventional hori-jontal sind vertical tail surfaces. LanrL-ley Memorial Aeronautical Laboratory, National Advisory Ccmmittee for Aeronautics, Langley Pield, 7a. EEFSHEKCS 1. Shortal, Joseph A., and Osterhcut,. Clayton J.: Pre- liminary Stability and Control Tests in the IJAIIA Free-plight Wind Tunnel and Correlation v/ith Full- Scale plight Tests. -.N. llo. 810, ImACA, 1941. 18 TABLE I DIMENSIONAL CHASACTEEI ST ICS 07 NACA SUBMSHGED-SNGI^iS FuSHSH AIHPLAITE AS REPRSSS:?^^!, 3Y 1/10-SCALE luODEL TESTED IN ::ACA JREE-FLIC-HT TUSilSL Engine ; Eor sepo'.ver , rated IICO Propeller : rianeter.feet 9 Num'ber of t lades , 3 V/cight, pounds 5600 vr i n g : Area, sfiuare feet 225 Span, foet 39 Aspect ratio 6,73 Airfoil section - x.oot NACA 67,1-115 Dihedrel "brealc iTACA 67,1-116 Tip iJACA 57,1-115 Incidence - Eoot,de_3rees 3 Dihedral break, degrees 3 Tip, dev:;rees 1 Dihedral of outer panel, degroes 6 Sv/eepljack , 50 percent chcrl line, degrees .... Taper ratio 2.5:1 Mean aorodynamic chord - Length, inches 74.50 Location hack- cf leading edge of root chord, irches 12.75 Root chord, inches 100 Tip chord, inches 40 Wing loading, W/S, povrnd;: per square foot 35.7 Center of rravity: Back of leading edge of root chord, inches .... 30.80 Below reference- line, inches 0.70 Percent of mean aerodynamic chord 2-'',-.2 Ratio of v/ing span to radius of .gyration: b/k_^ , . . '. 7.4 3 h/kV ^T.7 9 ^'/kz ' • 5.13 19 TABLE I - (Contiiraed) DIMEHSIONAL CHA3AC ?^H 1ST IG 3 0? :TACA SUSMSPvCrED-SHG 111:3 PUSHEH AIRPLAIIE AS "'.EPHESEFTED BY 1/ 10- SCALE MODEL TESTED IN NAOA FHEE-EL IPrl-IT TUiuOL Flaps : Type - Zap ext-jusible, partial ^pan Span - Peet , Percent b Pcrcanbchoi'd , Aileron: Type - Plain Area Squr.re feet percent 3 , Span Pect Percent b Tail : H c r i 3 r. t .'• 1 - Area (incliiles fu:5ela;.'e) - Squiire I'eot percent 3 Center of gravity to elevator hin-e line, feet Incidence, de:;'reos Span, feet Elevator .-.rea, sq.nare fuet Above reference l^ne, inches Vertical (tails 1 and Z) - Total prea (uot iuciuding fur-elags) Sq.-'ia^e feet Perc.:nt S C-nter of .-^rpvity to rudder i* in :■::.; line, feet. Span (erch tail), feet Hudier area (tail 1), .-.j f.^^t 16,77 43.5 35, 20 8.8 15.6 4 54 24 13.5 13 16.2 13 16.15 7.2 13.72 l;.7 5 7.37 20 TAPL3 II AILEEOi*! EFiTSCTIVSrJESS OF NACA SUBHSEGSD-EI^GIICE PUSHSH MODEL TESTED Ul FHEE-FLI&HT TUNIEL Flap H o t r ci c 1 1;: d (Cl = 0.5) E X tended (Cl= 0.8) P^o/27 A-! 5 '■' tot a, 1 a i 1 1- n d e i' 1 e c t i n j 4 5° total ;o.lQron I d e f 1 c t ion ! (.b^^ Lovol flight I Rocovo-ry Level flight' ■Recoverj-1 (c) i (d) j (c) ■ (d) -J I 0.048 .0 67 0.052 .061 0.0 37 .121 i i 0.094 .110 a Deflention used in abrupt aileron maneuver". (Enual up-and-down deflection of ±12^"°.) Eudder fixed. Assumed inai:.imu;n aileron travel (±22^'"'). Values obtained bv direct extrapolation from values for 25° deflection. Values obtained in abrupt aileron maneuvers start in.?; from ^■;int-level attitude. Values obtained durin.;. recoveries from abrupt aileron mane avers . NACA Fig. 1 NAG A Fig. Z bD C •H ? o x: CO 1—1 QJ c c 3 «J ♦J , -C (U bo o ■-H c r— 1 cd <^ i-\ 1 n3 q; J3 (D u cd v-( c < o o < -a ■z. (U <-5 (-1 c o 3 o c E o •'^ .— 1 «J 0) u t3 0) O CO E ■fj CO OJ E-« (U S-i 3 bD NACA Fig. 3 NACA Fig. 4 Q) a OjrH cH •H a c6 t-i +^ •H CI) rH ^1 O 0) •H Xi +» a ^ :i (U p. > 0) fH C 0) •H fe faOO P! r-t 0) 1 rH -d rH 0) 0) boa fH CD 0) a XI -9 +^ •H CO » > fl o >iH f-t rH © ■K> rH p. OJ nJ P- t> C 0) •H H tlOO (U ■H bO t-t h Q> o oJ T) rH •H CO CO oJ-d C 1 a ^ C\3 o >. ^ rH 0) rH •H a > c! ■H i faO •H rH f-l 1 O 1 0) f-^ a .H Ee< NACA ig. \/00 ^ 90 ^ 80 ^ ^ TO 60 ^ 50 ^ 40 % ^ 30 20 \ g 10 ^ o JO .08 i^ OS I 8 %.02 O .8 ■KT .6 ^ 4- I .2 Airpioine Model n/ght Tests 1 1 1 1 , . , , , ,/^ — 1 — 1 f ' — - - - — . ^ 1 -^ --. -N N, t 1 1 1 1 1 —Model flight tests —t\4odel balance tests Airolane fiioo bhD ) / r / / / / /^ ^ y l-l ',■• J O Pi c o •y CD 'r. •r1 <+H -H O fH o fi o w R ill S-: •H PL. O r-1 o, rH tH ,C ,i,3 r-< •H ,o 'O O ^ lO n o fl in c\; ^1 •iH OJ • p. ti: « , I I i ! I i : I I ' O -4 ■I (.<, I §?p'"i ■otiooxjop ao'4-BAOxa: r-H -p 4^ to Ti 4J "M ^t • rj •P tie •!-= ■H •H rH r-l '^-l •H ,Q >j 1-1 tv ,0 o -!-:■ r.o Ti +j ('.; -P 'J •rl •d o 1 ' tn on o o ■S • i-H +J rH '(H f I J ■ rH C; -ci 1-^ o Vi P( CO %\ r— i - • ^■■i "J rH • ^H ,J rH fc, Pi f1 •H r-J r-l -p NACA Flaps Power Fig- 8 up propeller off down propeller off_ op raled down rolecl_ -4048 Angle of of look, (y: , deg /a /6 20 FiGUf$E 8.- Ef feci of power and flaps on aerodynam/c choraclenslics of N AC A submerged-cnaine pusher model as deterrnined by bob nee fests in tne NACA free-flighl tunnel, i ^o°- o^^ O'- ?ie. 9 o M 1 / > 6 / / // I -V- Xo 1—— ■-, u __, h ?-( -> o r--; id CL' fH r-: c-H :) ■;-. fH r-H H -1^ O O •' ■.' K (.: o f! Pi ch is Ph Ph » r! Ql o,, pi o 'H o r,-l -_|C\:. rH O I I I I I — o + X rj o. O o CO I "O '^TioToiijGoo q.-.i--^'.';oiiJ--.'uinoq.-c^ < +-•• '•> ^i •!i flL *,:-i -H rH fc ■»j O nj .w fH += cS .<1 Pi O -H r; CO •H -P in 03 4.-' (y -p T) n « d o M ;>, ctJ C? 4' rH •H .-5 M i-l ,Q •P •H d r^J >i o d .a • H -p o n rrf •iH o Cm rH PJ ',-1 Pj -H (U o •rl ^ CJ f-d I'D P -P -p -|J O 'H •H -d ■H 'lO n <.; CO o nJ rH rH r! .u o t) o to a p-l rt ^ rH O rH r-l ri O CJ tH o o rH a t^ fH 4--' o •H .-4 no J:. 'w • d !:i !-, Q. ty 'J «t-i i-1 o ■ rH nq 1 uo c.> -J i."- n +■' 1 • ^J rt 't.i n f) ^) ■J o ixO ■r) u O rH o •H fj Tl (H .■rt ,<^ t| 1 rJ •11 >•') o m • O o () p; "t r^ f 5 ■f T-i . -4 'H •H K-.» •fH O h-l tl-l -rr o CN/ • r-i w ■H C.J trt •H 1 W tH rH •H 'm n1 iH O -P O r-* -P U ~) O n o M Cii rH ■ri U rH !-l ni -J O r^ Ph s: (J O f4 'H :^ p^ O +:> r-j •t-i • • -P r-t ,H 1 o •H O Q ,<:5 d '(-■. fti g '^^ 4^ p) t'l to -P f-l •H u;,-i ( 'q-f-o-f^XTTooo q.'.:fraovi-r?utTpq.id; rH ':\ I o o 'H :^^\ '.j.i.'j.:i. ii'ic"; 11 i 1 1 i 1 1 1 1 1 i i 1 1 O O q 1 j ! 1 i 1 1 1 1 i i o CO tn r^ i r 1 ! t 1 1 b i 1 1 1 1 1 1 1 , 1 j 1 1 1 1 1 ; ; / C ^ ■+■ X o 11 1 / r- -1 -~ r ' ,1 1 1 1 f 4- o / J i 1 ) 1 " ' 1 1 1 i / 1 / / / 1 1 i 1 ' 1 1 ; / , / / 1 1 i ' 1 / 1 1 1 ----- M 5 r> 1 i 1 1 i 1 i 1 1 1 J 1 1 -|X - 1 1* 1 J 1 __J1 I r 1 ! ' ! / 1 / 1 A. 1 1 U 1 i I 1 i 1 i 1 1 1 1 L 1 CQ o o Fi a rH flS ^ . ,o t:! O ■H -P •d w flS r-H O 'd o • ^lO f} ° CO II d P. -t^ •H o ',■! - ■iH ^ to 'J hP . 1 i^ r-j o o 1 fl< *t Ti -p 'J Tj s-1 to o O U -tJ •H '.) fiS H ':^ •rt ." 'n d • «:H (0 ^^ J J O o ■tJ !^ -i^ o ■H U 4^ tH o O -Tj 'h O 'w -i! C !25 fH fi O -H -p !t (0 !> -P •: W r-H O W -'-■' t-. I o o •H "^0 'q.uotoijj:coc :v"i'^i20u-Sv.-fT-0';td. NAC« C? '^ F/aps Power up wlndm/l//ng rated windm/lling rated Fig. 12 a,deq a a ' o o -^O -/6 -^ /£ /6 £0 -8-4. O 4- a Aty/e of Yaw, ^, deg rtGUJPE 12- Effect of flop5 and power on latetol-sfability characterislics of NACA submerged-engine pusher moolel testeol in the NACA free -flight runnel. Vertical fails I anct £ on. CBolancp HafaJ NACA Vertical ta/f Power off propel fer off - off w/ndmill/ng - off rafed I i/vindmiliing /anc/i? windmilling - /and 2 rated Fie 'C '4^ O 4 3 /£ Angle cf tjaw, (/y. c/eg F/GukL I3~ Effect of vertical to:l area and pcyveron lateral-stotihty cf^,aract6ristic5 of NACA sutrrerged-engine pusher model ds determined IDL/ Oattnce tests in the NACA free-flight tunnei. Flaos retracted: oc=a°. NACA Test points 1 I Estimated /oo/nfs A B C Arrows show d/rect/on o/'sfab/llly D change caused by add/fjor? of E various facfors. F G Stability boandanes are H estimated for w/ndmillmg power I condition at C/f 0. 75 J K L Fig. 14 Flaps Po\ner \l2rtiCQl tail up propeller off none up windnnilhng ncne up rated none up yvindm/llina Ifupper) up yv/ndmillinQ land£ up rated /ana'£ down \A//ndmlll/nQ Iand2 down rated Jand2 up rated 1 doivn wino'm/lling 1 down rated / up propeller off / o .0/ .02 . .03 .04- -c .05 if Windmilling .^ propeller f__ ^ .06 ' oy .05 .09 ■^^ F/ouQE 14- Effect Of f /Op clef lection, power, and vertical -toil area on the lateral stability of the NACA submerged- engine pusher model tested in the free -flig/it tunnel. Cl--0-73. NACA Fig. 15 ^ ^ 8 r .06 04- .03 .Ol ^ O -.01 -oz .01 c -o/ O— be, dbg o r\ 1 5 /o X \ A \ \ \ '.^ i x-. \\ \ ~~-* ^\ \ s\ ^w \ ■ \ xN K \ ■k\ s. i \\ f\ N, \ ^ \ \ \ ■..\ N ) \ \r > < 1 i 1 1 ^ ■^ ^ fe^^^« V~~^ ,i •r^^^ ^ ^ s^ ) ^. ._.__= __. — =73 =-^ } -30 -£0 -/c o /o ^o 30 40 /Measure ^ \ /^/ght o Heron deflection, Sq^, deg ^ ^^'^^ ^^v F/ouj^E 15.- Aileron effectiveness of NACA submerged-engine pusher model as determined bu balance tests in the free ■ flight tunnel. Propeller windrnifling ; flops retracted. NACA k^^§ UNIVERSITY OF FLORIDA 3 1262 08106 525 1 "university of FLORIDA DOCUMENTS DEPARTMENT 120 MARSTON SCIENCE LIBRARY P.O. BOX 11 7011 GAINESVILLE. FL 32611-7011 USA