=.

=====ACR No. L5K05

NATIOt$AL ADVISORY COMMITTEE FOR AERONAUTICS

w’lu’’TIm luw(m’rORIGINALLY ISSUED

February1946 asAdmmce ConfidentialReportL5K05

DETERMINATIONOF THE STABllJ’I’YAND CONTROLCHARACTERISTICS

OF A STRAIGHT-WING,TAIL13SSFIGHTER-AIRJ?UNEMODEL IN

TEE LANGLEY

By CharlesL. Seacord,

FREE-FLIGHT TUNNEL

Jr. end HermanO. Ankenbruck

hngley MemorialAeronauticalLaboratory

-G. ,.–. .— .. . . . .

LangleyField, Va.

.’

,,.,., .”.’:,... -,,”, ,,. .

,,

: ‘<’ N ~ c A ~~~~;y.......,Z...,

LANGLEY MEIVIOW AERONAUTICAL 4

WASHINGTONLaboratoryLangleYFleldf‘a . “=

NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution ofadvance 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 - 199

..— ———

3 117601~~1.__—... —- - r3

llACAACR-Ffoc.L5K~ .: “ t . .- -m .:

IIATIC)HALJU)71S03Y .C01LIIITT3EEZFOR AZRCYAUTICS.“ .: ~..

. . .. . . . . . . . . . . .

. . . .. .. . . . .

ADVANC~ COITI~~IAL-%m~~”T” ~ ‘“”‘ ‘“ ~~

. . ..“

DETZRXTRATI ON OF ?TfiSTA91LITY A:;”COITTROL CEARACTERISTIC S

!&IHELANGLEY =-FLIGHT “TUNNEL,.

Charles L. Seacord; :“Jr. and Herman O. ~nkenbruck” “. .

SUMMARY ““.

An investigation to determine the stability andcontrol characteristics of a strai@t-wing, taillessfighter uode 1 Withl a pusher propeller desi~ned by theNACA has been made in the La~~le;’ free-flight t~tlel.The investigation ‘consisted principally of force andfli~ht tests of a pox~red dynamic model. The effectsof tail configuration, cer.ter-of-~avity location, and “power on the stability and control characteristics of themode1 were deterr~lined. Tests were also made in theLangiey 15-foot free-splnni.w- tunne1 to determine whetherthe model would trim at.ver~ high en~les of attack.

The results of the investigation may be summarizeda.sfollows: The general fli~ht characteristics of themodel were good and compared favorably with the flightcharacteristics of good conventional airplane modelspreviously tested in the Langley free-fllglht t~el. Asthe angle of attack was Increased, the lon@tudinalstability of the mcdel increased instead of decreasing asthat of tailless airplanes with swept-back wings usuallydoes. Power caused a slight reduction in the longi-tudinal stability measured at constant powsr. Thisreduction in stability, however, did not affect the longi-tudinal steadiness of the model in flight tests. Themodel did not show the tendency to tr$m at very highangles of attack (above the stall) that’has been a char-acteristic of some swept-back tailless airplanes. Thelateral fliCht ch@racteristlos of the model .with bothvertical tails installed were Good. The directlonal~ ..stability of the model was satisfactory and was improvedby the application of power. The effective dihedral wasdesirably small and was not appreciably affected by power.

t-m m..—— —

.,, . . .- ——— - -I

2

The controltud.inal and

surfaces of the modellateral control. .

INTRODUCTION

Previous investlfletions of the

NACA ACR NO, L5K05

provided adequate longi-

stakility and controlof ta!llesa a:rplanes with swee~back (references 1 to 4)have indicated that the sweepback is the cause of the poorlon~ltudinal stability and the loss of control near th6stall which e.reoften characteristic of such airplanes.Tn order to determine the effects on sta’bllity of elim-inating the sweepback, ‘a strai@lt-win&’, tailless fl@t6rairplane has been desi~ned by the NACA amd a model of thedesiqn has been tested in the Langley free-flight tunnel.

The present investigation Is one phase of the tailless-airplane research program being csmied out in the Langleyfree-fli@t tunznel to deternine the relative merits of thevarious t~es of’tailless aircraft and includes results ofboth force and flight tests cf a dynamic pof::eredmodel witha pusilerpropeller. Zecausc some tendencr has been notedfcr taillass airplanes to trim at very high angles of’attaclq+ 9~0,~brief tests wore”also m~de in the Langley15-foot free-spinni~- tunaei to investigate the trimcharacteristics of VIU r~odel at largo cngles of attack. “The force t~sts wera nade with the model equipped withtwo difforant sizes of vertical tail surface, with pro-pellers off and with propsllors on, tindwith power adjust~dto simulato that typical of modern fig??ter airplanes. Themodel was flown with twc different sizes of vertical tail,vith various center-of-~ravity locattor.s, and ‘:/ithvariousamounts of power.

CL (“7lift cceff?.ciemt ‘ ‘w

CD(+)

dra~ cceff’icient ‘qa

CmC.g.

pitchinz-moment coefficient about ~ormalcente7-cf-UmGvity locaticn. (M@)

la”teral-force coefficient ( )Lateral forceCy m

I “..—

..

NACA ACR NO ● L5K05 -“

C7. rolling-moment coefficient (i;qbs).....- “—

= ., . -.,.:.... . . . . . . . . . . . . . . .“,,..-+,- ...- - ,.-... .. ...-=,“., ---

Cn.-. .. —.- —’

L

M

P

yawing-moment coefficient (~~/tibS)““ - ,......-

.:,rolling moqent, foot-poiznds

pitching moment, foot-po&ds

yawing moment, foot-pounds

dynamic pressure, pounds per square foot ( $)*P

mass density of air, slugs per cubic foot

v

w

s

b

c

E

a

“CwTc

T

D

%

airspeed,

weight of

feet per second

airplane, pounds

wing area, square feet

whg 92an, feet

wing chord, inches

mean aerodynamic chord (hi.A.C. ), feet

angle of attack of fuselage reference line, degrees

angle of yaw, degrees (* = -P)

angle of sidesli.p,degrees

angle of roll, degrees

rate of cha~e of rolling-moment coefficient withangle of ;ideslip, pe; degree (de,/q

rate of change of ~awing-moment coefficientangle of sldeslip, “per degree (dC~d~]

thrust disk-lpading coefficient ~T/pi%)

tlmlst, pounds

propeller diameter, feet

right-aileron deflection, degrees

-

with

.,.

4 NACA AOR NO. L5K05

8e

kX

ky

kZ

The

d1:

F

elevator deflection, degrees

radius of gyration about X-axis .!

radius of gyration about Y-axis

radius of gyration about Z+xis

parts of the uodel are designated as follows:

wing

fuselage, including pilot?s enclosure and wirelanding gear

propeller

lower vertical tail

upper vertical tall

APPARATUS

hind Tunnels

!i??.einvesti~ation was carried o-~tin the Langleyfree-flight twqnel, which is equ?-pped for testing free-flyii~ dJ-i:fUtlfCP’iU<t)190A con~lete description of thsturme?.Qhrjits oper~ticn is given in reference ~. Forcer.easlrerc3nt.s WP;I=maG9 on the Lal~le;rfree-fli~t.-tunnelSix-cbrpo%r.t ~alance degcribed ir.reference 6~ Ths .forcas and com~n;s are rzeasurad on til.i~ balance ~iith

resgcct to sta-3!l!ty axes. ,Tha stability =9s of an air-plane sre defined as ar?orthogonal system of S.XOSinter-secting at the center cf’~~avity in which the Z-axis is inthe plans of s~.mzetryand perpendicular to the relativewind, the X-axis Is ir the ~lane cf s~ymetr~-and perpendi-cular to the Z-axi5, &nd tk.eY-axis 2s perpendicular to theplane of s~metr~-. A sketch shcwin~ the stablltty &~Gs ofan airplane is presented as fro-e 1. A.photograplh of thetest section of tha t~lnnelshowing the model being testedin flight is ~-esented as figure 20 The tests to deter-mine the trim ch~racteri3tics of the model at high anglesof attack were m.zde ir.the L&@ey 15-foot free-spinningtunnel, a description of which is given in raference 7.

Model . - .. “ .. ... . .., ... ..... ........... .,-,

..me. test ~odel” w’&s”““d&@”l@d”-aiid.“@nst~cts~. by.tiheNA.CAand cor~e.~p.ends.to s &-scale model of. a hypo-

thetical taill~ss “alrplahe+‘WI%- a 40-foot span. “It iSa hi~=wing de”sl~”With, the 50-percent-chord 11’na:stral@tand has a small fuselage; a pusher prope her, and conven-tional vertical tail’ surfaCeZ3.’ A p’awl~ anh ph~~tographsof the model are-[jivbrfa% ~i”&b.s. 3 to 6.. . . .,* -.*.. . .

“Lbngltudlnal Gohtrol I’oti”tl& mode1 was provided byelevators that extended. over -the inboard por~i’on of thewing, and lateral bontrol whs provided by bonventicmalaileron and rudder mirfaces. I?orpower-off (windmllling )tests, the.model”whs’fitted with”a f’cur-blade propellerthat was allowed tb Wihdmill fr~ely’. Fcr power-on tests,

the model wap equlpp~d with a ~-horsepower electric motor

drlvin~ an 11-lnch~dlameter thi?ee-blada propeller. Thethree-blade propeller was in~thlled in”plabe” of’the four-blade propeller because the characteristics of the motormade it possible to obtain higher thrusts with thisam angement.

;!l%e’mode~ w&& had a ~hode St..Genese 35 alrfoll

~ection (reflexed) because this a~ction has a high maximumlift coefficient at the 10VVReynolds numbers at which thetests were run.

.. .

The ph~slcal character istlstics of a full-scale air-plane based on scaled-up values (10:1) of the dimensionsof the model az-e:

-.Weight, pounds . ... . . . . . . . . . . . .“. . . 8030x ing .

Area, squarefe’et’ . .“. . . . . . . . . . . . 266.67Spn,feet. . . . . . ..b . . . . . . . . . . . 4:.:Asgectratio. .“. . . . . ; . . . . . . . . . .Sweepback of 50-percent-(?hord llne, degrees. . . . ‘oSweepback of 25-percent-chord llfie,degrees. . . 3.2Incidence, degrees.. . .“. “. . . . . . . . . . .m. 0Dtie~al angle of midtlilckness line, degrees . .“.Taper ratio. . . . . .“. . . . ~ . . . ... . . . 2::M.A.C., inches . . .. ... . . .. . . . .. .:. . . . 83.9Location of I!.A.C.behind L.S. of

root chord, tnches. . .. . . . . . “... . . . . 12.0Root chord, Inches . . . . . . .. . . , . . . . ... 107.8Tip CholVi, In.ekes. ... . . . . . . ., . . . . . 53D9

—m. —,,— —

‘6 ~:’” NACA AOR NO. L5K05

.

Wing loading, ‘#/S, pounds per squsre foot . “. ● . t 30Aileron“T~e.h...~....~ ti....i*~..*~.PlalnArea, percent whgarea d . . . ..og. .a. . .7Span, percent wi~ span ● . . . . ● ● 4 ● . . ● ● 45Chord, “percent wi@ chord . . . ● ● . . . ● ● ● . 20

ElevatorType:, . . ..~. .i . . ..a. oo. OPlain flap&rea~ percent wing area-t ● S.O s ~ * ● s ● ● ● s 7.7Span, pGrcentwhgs panO •04~acooooca 45Chord, ‘p~rcent wing chord ● . . . . . c . . . . . 15

Normal c.go locationBehlad L.E. of root chord, inches . 0 . . . . . 28,8Behind L.E. of root chord, percent M.A.C ● , . . ‘ 20.0Above thrust line, inches”~ . ● . . . . . . . . . 4;0Above thrust line, percent M.A.C. . . . . . . . . 4.8

. Ratios of radii of gyration to wing spankxfi, . . . . . .. h.. . . . ...6... 0;158ky/b . . . . . . . . . . . . . . . . ... ...0.133kZ@ . . . . . . . . . . . . . . . . . . . ...0.173

Vertical tatlsTotal area of each, percent wing area ● ● ● “~ ● “~ 3.0Rudder artia,percent total vsrtlcal-tall area . . 23Aspect ratio (each tail ) . . . . . . . . . . . 1.85Distance from e.g. to rudder hinge line,

percent wing span.... . . . . . . . . . . 24:2

TESTS

Fcrce Tests

?iost of.the for.cotests were .mde at a d@’Gmic yes-surs of 4.09 pounds ~er squsre foot, which correspondsto a test Re;ymolds nuniberof approximately 2)+0,000basedon the mean aerodynmtc chord -of”0.699 foot, The forcetests consi=ted of’angle-of-attack runs made to determinetha effects of power and vsrious modifications to tinemode 1 on lo~itudinal stabiIity and control ahd yEw runsmade to determine the lateral stability and contrGl char-actmlstics of the model in all conditions. A S_Sryof the farce -t~st conditions is civen in”table 1. Asshown In table 1, power-on force tests Were made to determinethe static longitudinal stability of the model opbratingwith power simulati~ zero thrust and 1200 brake horsepowerfor the hypothetical full-scale airplsnc. In the lateral-stability tests the model operated with power simulating

.

NACA ACR No. L5K!15 , .... “7. .. :.. -.’-:. .. . .,

zero thrust, 1200 br~o ho~sepqyqr, and,2QO0 brake,liorse-,.powe~...for ,~he...full-scals.,,~~,~l~neb.““ ;c “. . ~ ““-. >“

. . . .... . . .. . .......,. -Values of tl@ust coefficient re’qulred to “si~late

1200 and 2000 brake horsepower q~~r the;lift range of the.n@el .tes.tp.are ~shown ,l.n”:”~l~~7. .Thqse_.C@a. .-e based

‘“‘“on an “assumed pnopelkr e$fIcieDcy”for the full-scala“atipla& of 75- pe;aent +...a ~llng-per .~qtie foot. “ -+ .“.,, ...

.: .... . ....“

, :Fli@t. Teets..

Mdel. flitit teats ,weid made

~oading..of:30,pol+nds.*, .!

. . ,..” . ,,

. . . .;, ...”

.’(”.“ ,.

8“” . ..’ . .. .

to determine effectsof lift coeffi;terit~ “center-of-~ qvity :loca~ion, vertical-tall area, and pow~r..o~ the.sta~tlity and control ,char-acteristics of tilemodel. In the power-off conditIon,flights ‘wdre made over a“zmn~e of lift coefficients from.0.32 to 0.95 for center. of-~avity locations rangingbetween 15 and 23 percent H.A.C. ~ost fli@t t6sts weremade with the mode1 equipped with both upper and lower“vertical.tails, but a few tests were mqde with the mxlel“equipped wtth the uiipertail only. Power~on-fl~ght testswere madg fbr a lift-coefficient r8J~~~ with.the normalcenter-of-gravity locat.ton ‘(2O ~erce.ntM.A.C.). Th& highestpower simulated in flight was 1200 brake horsepower.

,.

.- ~ree-to-ll!r.@trTp$ts. . “ ‘ “ ..

In l%e free-to-trim tests the model was supportedin the air stream of tke”Langley 15-foot free-spinningtunnel on t~~estand.shown.in figure.8~ Tilemodel was ~eeto rotate in pitch.about its”center of graVity and hada possible travel of about 200°. The mode Z was restrained

“-”uhtilthe atrs~eed “had been adjustsd ati”was then releaaedto trim. The model was released at angles of attack from0° to & 90° with the-elevators set.”to.trti the mbdel at anangle of attack of 8°. . .

,.. . . .

RESULTS. AND DISCUSSION

“”made

.

Longi$uditil’ St.ibil’_& “’“ ...-J. ,.... .

. .

Power-off force tests .-”The results of force teststo dect-erminethe .longitudinal stability ‘characteristics. ..

,- -.. .

i“

8 NACA ACR NO. L5K05

of the model with power off are presented in figure 90The effects of the various component psYts of the modelon the stability are also sh~ in this figure.

The data of figure 9 show that the modal was longi- -tudlnally stable up to the stall. This characteristicis desirable and is not usually possessed by tal.llessdesigns incorporating sweepback. The .stabilXty of themodel increased with increasing lift coefficient; “thestatic margin, as indicated by the value of -d~/dCL,v&ied from about 0.02 at low lift coefficients to about0,07 at hi~h lift coefficients with the normal center-of-gravity location (2o percent K.A.c.). Reference 8 showsthat tb.ischange in the slope of the pitching-momentcurve is characteristic of a high-wing arrangement on arqund Jfuselage and Indicatgs that the pitching-momentcurve could grobably be stral@tened by lowering the wingto a high m.idwlng position. .

The data of figure-9 show that adding the fusela eto the wing caused a reduction in static-margin &%n%%)of about 0.01. .l?hedata also show, however, tha thestabillzl~- effect of the windmlllhg pushm propel~. “counteracted. the destabilizing fuselage effect, so that”the,stability of the complete madel was similar to.that -.. .of t-newing alone.

Power-off fl..,- In power-off fllghb testswith the center of gravity at 20 percent M.A.C., thelongitudinal stability oftho model -was satisfactory atilift coefficients fron”O.50 to the stall, at whtih-thestatfc -~-g:n was .0.059 A* lift coefficients less tlum.0,50, however, the lo~itudinal “rLotimnOf ths.model wasunstead~ tizdfrequent ,elevator”control was required tokeep the model flyi~. This unsteadiness was attributedto the small static mrgin (abont 0.02 or 0.03) atlowLift coefficients previously-~ndicatetiby the force tests. -

When the static margin was incre~ed by O.W-by movingthe center of gravity ahead to 18 percent H.A.C., steadyflights were .obtalned over the retire lift range frti--alift coefficient of 0.32 to the stall (flights cauld notbe mmle at lift coefflciants louer than O*32 because .of

“ tunnel a:rspeed limitations)...

Decreasing the static mrgln by shiftl~ t%e center“ofgravity to 22 percent H.A.C. caused the longitud~.

.:

flight behavior of the model to become. completely unsatisf-actory at lift coefficients less than 0.50 and only fair-ly satlsfac-tor.y..at..liftcoeff-l,c@n,tsgreater than 0.50.In some flights made at.ltft coeffici~ntd”ab.ovw 0:50 ml-tha static margin of about 0.422or ,0.03,.the.”modelwas. veryunsteady and difficult bo contr.o$and the longitudinalcharacteristics were very slmtlar to those obtqined “in thefli@t tests made at lift coefficients below Q;50 jmd withthe center of gravity at 20 percent M.A.C.

~evlois. tests in the L&#l&y free”=fli&~””tunhsl(reference 9 ) have shown that “conventl cmal models hadlongitudinal steadiness characteristics which wereessentially the same as t~Lo8e of the straight-wing, ,“.tailless model witln corresponding values of static.margin.In this respect the results of the present investigationare In agreement with the results of reference 9, whichshowed that variaticn of danpi.ng 4n pitch has little effecton lon~itudinal steadiness as long as the static marsin issatisfactory.

Power-on force tes~s.- For purposes of discussion,static margin has been assumed equal to -d~dCL. Thisassumption should be nearly true in the case of the modeltested because the model has no horizontal tail andbecause the wing is not in the slipstream. The force-bestdata of figure 10 show that power caused a reduction Instatic margin which, though appreciable (0..03or O.Cl!+),was not so ~eat as the reduction often caused by poweron conventional single-en~ine airplanes with tractorpropellers (reference 10). At 1200 brake horsepower withthe center of ~avlty at 20 percent M.A.C. the model hada static margin of only about.0.01 over most of’the llftrange. .

The results of calculations made to detemlne thecause of the decrease in stability with application of .power sre presented in flm~me 11 in the form of incre-mental pitching moments provided by the propeller normalforce and propeller thrust (figs. n(a). and (b)). Thecombined calculated effects of propeller forces sre alsocompared (fig. 11(c)) with the measured power effectstaken from the data of figure 10. The calculations shqwthat, although the normal force of tohepusher propeller”provided a sli@t st@iliz5.ng effect;” the propeller thrustprovided a much greater destabilizing effect. “Fi~e 11shows that the measured destabillz”lng effect of power wasabout twice the calculated effect of direct propeller

—.

10 ~“ NACA ACR NO. L5K05

““-”forces...‘fi~ additional unstable maments may have been‘- pr+uced’by the inflow ”eftec.tsover the.wing and the

~= .portlotiof the fuselage. we data of’figure12“show: that””.ifmthp center of gravity of the model weheshifted vertically downward from 0*048 M.A.C. above thetlmmti line to 0.011 M.A.C. below the thrust line, powerwould not affect the stamtlclongitudinal stability of“the model. ‘, “

.. .. .

power-on flight tests.- Although the force-testrestilts lcated a decrease in lo~itudinal stability toa static margin of 0.01 as the power was” increased fromzero thrust to 1200 brake horsepo;ver, the lo~itudinalsteadiness in flight tests of the model was not a~preciablychanged by” power application. Fli@ts made with powersimulating 1200 brake horsepower were as steady as fllghtsmade wl.t~ zero”thrust. These results tJnusappear todisagree.with the results of the power-off fllght tests,In which a reduction of the govier-off static -gin frbm0.05 to 0.02 caus~d the longitudinal steadiness of themodel to become definitely worse.

.,

An ”expl”an~atlon@f tl~isa~pare~t”discrepancy Is thatin the ~owe=-on force te~ts the thrust was varied withmqqle of attack to represent constant-power fli@ atdifferent ainspeeds - that is, Tc was varied with CL

and thus with airspeed, as shown ?.nfiStie 7 - whereasin the power-on fll@t tests the airspeed did not varyimmediately with a~le-of-attack chan~es - that is, Tcand airspeed rbmained constant when the ~~odelpitched upor downC If the thrust co~fflcient Tc instead of thepower had b~en”kept const”ant in the force tests, therewould- likely havs been llttle or no chanCe in stahllltyfrom the zero-thrust to the power-on conditions. The “assumption is here made that curves of pitching-momentcoefficient against lift coefficient at constant thrustcoefficient would b.avo remained ~srallel for any valueof thrust coefficient; that l?,

~*~T=~”(%)T< AnyvalueSince longitudinalcstsadiness 1S largely dependent on therapid pitchin~ motions or short-period oscillations. thatcause no appreciable change in airspeed, the steadinessappears to be affected principally by stability changesthat occur at conditions of constant thrust coefficientand”constant airspeed and vary.little by changes that occurat conditions of constant power and varying airspeed.

~“

----

NACA ACR NO. L5K05 11

Longitudinal Contmol.. -----““~e+loW-it~l~lticon~rol.data,.obtained illthe..fp~o?..

tests are shown in figure 10. These data indicate thatwith the normal center-of-gravity locatlon the model couldbe trimmed from zero lift coefficient to maxlnnun lift “coeffic~ent with a total elevator movemnt of’about 20°0

‘ The elevator effectiveness did not change noticeably whenpoWer was applied, which indicated that there was littleeffect of induced flow over the elevators. Fll@t testsshowed that the elevator was powerful enough to trim themodel over the entire flight range with the center ofgravity at 18 percent M.A.C.

Trti at Hi@ An~les of Attnck

In the free-to-tr?.m tasts In tlie Langley 15-foot free-s-phnirq tumnel, the mndel -.q]onbel~- released in the up-ri~?ht or inverted ncsition !at s.mles of attack of’900on--900) as.3umod ~;m.efllatel~the ;~lethe elevators had keen set, 8°. Undsrthe modei show tll.~taficncy to trLm atattack that b.asI>oer,exhibitud by scmede9igm.

of attack for whichno conditions didI+@ angles ofswept-back tailless

Lateral Stablli.ty

Force tests.- The results of tests made to determinethe lateral stability slia-a~teristlcs of’the model arepresented in figures 13 and l!+. These results aresl~~~ized in fi~e 15 in tEe form oi’a sta-uility chartthat is a plot of the directional-stabiilty parameter Cn

Pagainst the effective-dlkedral p=ameter CZP.

The data of fi~m?es 13 and 15 show the effect of thevarious component parts of ths ma%el on lateral stability.The wing-fuselage cowhinatioilhad slight directional .instability but was made slightly stable by the additionof the pusher propeller. Addition of the vertical tailsIncreased the directional stability with propellerwindmilling to a value of Cn

Pof about 0,0007. The

effective dihedral was small for all conditions, about 2°for the wing-fuselage combination and about 1° fm thecomplete model,

a— .—— .-

K ~“ “N&CA ACR No. L5K05

The force-test data of figures ~ and 15 show anoticeable increase in directional stabtlity with appli-cation of power. Increasi~ the power from Idllng to2000 brake horsepower increased the directional stabilityby approximately 65 Fsrcent, The data of figure fl)alsoshow that applying power with the vertical tails off didnot increase the directional stability appreciably. TheIncrsase In directional stability at high power with tailson appears to be caused primarily by tuneInflow effectsupon the vertical tails rather t’hanfrom action of thedirect propeller forces. The effective dihedral was appar-ently not affected by an increase In power. (See figs. ~and 15. )

Flight tests.- The lateral flight characteristics ofthe model with both ve:-tlcaltails installed were Good forpowers ranging from zero thrust to 1200 brake horsepower.The directional stability aqpeared to he satisfactory inflights at zero thrust and improved with the applicationof power. ‘.~aes~.alleffective dihedral sb.ownby the forcetests was noted in the flights by the absence of any appre-ciable rolllng mottons Y-hen tl~em~del was disturbed In yawand by the nogli~ible efl”ects on mleron control of theadverse yawing producad in rolling maneuvers. This smalleffective dihedral was considered a desirable characteristicfor a t~.illess design because of tbs relatively low direc-timal stal~ility of this type of airplane.

In fliShts with the lower tail removed, the lateralfll@t characteristics were not so good as those with bothtails installed. The adverse ya-:~ingdue to aileron controlwas greater and tb.eyawing ~Iotions of the model damped outmore slowly after disturbances Iil yaw. The lateral flightcharacteristics were considered not quite satisfactory witht~.istail config-uation.

Lateral Control

The fo~ce-test data showing the aileron effectivenesssre presented in fig’~-e 16. These data show that theailerons were effective at all ar@es of attack up to thestall (approxo 120).

In the flight tests adequate lateral control wasobtained by using abrupt aileron deflections of + 15°.Rudder deflections of+ 3.2°used in conjunction with the

I

..NACA4dR “tie”.“L5K05 ~~ 13

aileron control were ustilly” sufficient to balanoe out theadverse yawing moments caused by aileron deflection androlling v~,loc.~t.yo. . ..’..“”.... ......... .... . .

... ..: ... .,. .. .. . . .. . .., .. . . ..” . .

COfJCLtiIb~ “ “.. .:.. . . . . ... ,. . .

...’.. . . . .

~ilzen~sult~ of:t9&s In the “Lar@ey free-flighttdel of a straight-wl.pg,.tailless.fighter.model witha PW$~*. ~o’peller. fi$ ~. a~=ize.d aa foll~s: ...... .“.,..... . .... ~~”~e ~eneral f~l@t” characteristics of the model

.w”erego-odand compared favorably wit~ the flight character-istics of good conventional airplane models previouslytested in the Langley free-f~ight. tunnel. . - ‘“.. .

. . . 2“e As the a~le” of at-tackwas :nmeased, the”longt-“ .tufllnalstabilit$ of the.model iqcreased Instead-of

decreasing as that-of tailless airplanes with swept-back●wings usually does... ...

..”. . 3. Power caused a slight reduction In the longitudinaletabillty measured at.”constant Rower. This reduction instabil~tiy,”however; did not a~fect the longitudinal stead-iness of the mcdel in fll@t tests. .

...4. me model did “not show tinetendency to trim at very

high an~les of attack (cibovethe stall) that has been acharacteristic of some swept-back ta~lless airplanes.

5. The lateral flight characteristics of the model.with both vertical tails installed were good. ‘I% direc-tional stability of the model was satisfactory and wasimproved,by the application of power. The effec~lve Idlhedral~was desidabl~ smdll and.waa not appreciablyaffected by power. ..

.,..- :6. The control” sur~ace.s of the model provided ade-q~~atelo~itudinal aridlateral control.

. .. .. :..

L~ley” MemmialA erogautlcal Laboratory”Nat”$onhl”Advisory Committee for Aeronautics

.Lan@ey Field, Vs.. .# .1,.

IA__ - —. . A. .— — — — —— . — .. .

.- . .

4 {~1 ‘ NACA A(X NO. L5K05

REF2XUINCES...:. “., .“

.“1. Stab%lity Research Division: An Interim Report on-

the Stability and Control of Tailless Airplanes.NACA ACR No. L@lZ19,.1944,”.

2. Jones, Robert T.: Notes on the Stability and Controlof’Tailless Airplanes; NACA .TN NO. 837, 19~,

3. Campbell, John P., and Seacord,.C&rles L., Jr. :Determination of the Stability and Control Character-istics of a ‘Tailless A1l-Wing Airplane Model.with

.., Sweepback in the Langley l?&ee-Fli@t Tunnel. XACAACR ~JO.L5A13, 1945 ●

4. Trouncer, J., ‘and Wright~ D. F~: Wind Tunnel Tests-. on the.Effect of Variable Incidence Tips and,Tip

Slats on Tailless Gilders. TN No. Aero 496, Rzitish ..R.A.E., Augc 1944.

5. Shortal, Joseph A., and Osterhout, Clayton J.:*... . .l%eliminsry Stability and Control Tests in the NACA -Free-Fll@t ‘;ilndT~el and Correlation with Full-

. Scale Flight Tests. NACA TN ~{0.810, 194~o

6. Shortal, Joseph A., “and Draper, JohnV/.: P&ee-Fllght-. . Tunnel Investigation of the Effect of the I?uselage

Length and the Aspect Ratio and Size of the VerticalTail on Lateral Stabiltty and Control. NACA ARRj;O.3D17, 1943.

7. Zimmrman, C. H.: Preliminary T6sts”ln the NACA.

F&eo-Sphn@:iVind Tunnel. lMCA Rep; l?o.557, 1936.

%. House, Rufus C)., ~nd Wallace, Arthur R. : Kind-TunnelInvestigation of Effect of Interference on Lateral-Stability Characteristics of Four NACA 23012 ‘Nhgs,an Elliptical and a Circulsr Fuselage, and’Vertical??Ins. FACA Rep. Xo. 705, .lp41.

9. Campbell, John P., and Paulson, John W.: The Effectsof Static Margin and Rotational Dampl~ in Pitch onthe”Longltudhal Stability characteristics of anAirplane as Determined by Tests of a Model in theNACA Free-Flight Tunnel. NACA ARR KO. L@02, 1944.

. .

l?ACAACR NO s L5K05 ~ 15

. .

10. white, Maurice D.: Effect of Power on the Sticlc--,. .Fixed.i?eutralPoints of.Sev.~yal.9ingle-Engti~..

Monoplanes as D6terrninqd in Flight, NACA CB .No; T&ol, 194.46

—..-

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liATIOIML ADV120EYCOMUITX’REFOR AERONAUTICS

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COMMITTEE FOR AERONAUTICS

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COMMITTEE FOR AERONAUTICS

figwe 12 .– Compvison of }& effects of per& /Wo center-of- 9zwI& /bCdlO~S. DWk2 fromiest. of s+ralgh+ -wing, tai//ess+he Lo@ey A@e -7W9M Ame/./ocd/on, 0.20 ziv./4.c,

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COMMITTEE FC# AERONAUTICS

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.,.,.

;

NATiONAL ADVISORY

COMMITTEE FOR AERONAUTICS

Seacord, C. L. Ankenbruck, H.

AUTHOR(S)

DIVISION: Aerodynamics (2) SECTION: Stability and Control (1) CROSS REFERENCES: Airplanes, Tailless - Aerodynamics (06725); Airplanes, Tailless - Stability and control (067£6)

£W0° 6619 0~RlG. AGENCY NUMBER

ACR-L5K05

FORG'N. TTIU:

Determination of the stability and control characteristics of a straight-Ting, tailless fighter-airplane model in the Langley free-flight tunnel

ORIGINATING AGENCY: Rational Advisory Committee for Aeronautics, Washington, TRANSLATION:

!). C.

FEATURES photos, table, dlagrs, graphs

COUNTRY VI 3.

IU.US.

17 flBSTOAOT

Tail configuration, center of gravity location, and power effects on stability and control characteristics of subject model were investigated. Results shewed that general flight characteristics were comparable to those attained by good conventional designs. Longitudinal stability increased with angle of attack and decreased slightly with power application. Model did not show trim tendency, a characteristic of swept-haek tailless airplanes, at high angles of attack. Lateral and directional stabilities were good. Effective dihedral was low.

N0TE: lvfSiington0rDC08ie8 °f thiS r8P°rt mu8t be addressed to: N.A.C.A.,

£\ra 'O'ECHNJCAL ONOEX VWHGHT FIELD. OHIO, USAAFT^ -y T.2, KQ* AIR MATERIEL COMMAND WMI twa a t=a