Experimental determination of the effect of negative dihedral on lateral stability and control characteristics at high l...


Material Information

Experimental determination of the effect of negative dihedral on lateral stability and control characteristics at high lift coefficients
Alternate Title:
NACA wartime reports
Physical Description:
16, 8 p. : ill. ; 28 cm.
McKinney, Marion O
Langley Aeronautical Laboratory
United States -- National Advisory Committee for Aeronautics
Langley Memorial Aeronautical Laboratory
Place of Publication:
Langley Field, VA
Publication Date:


Subjects / Keywords:
Airplanes -- Wings -- Testing   ( lcsh )
Aerodynamics -- Research   ( lcsh )
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )


Summary: The effects of negative dihedral on lateral stability and control characteristics at high lift coefficients have been determined by flight tests of a model in the Langley free-flight tunnel. The geometric dihedral angle of the model wing was varied from 0° to -20° and the vertical-tail area, from 0 to 35 percent of the wing area. The model was flown with various combinations of dihedral angle and vertical-tail area at lift coefficients of 1.0, 1.4, and 1.8. As the effective dihedral was decreased from 0° to -15°, the model became increasingly difficult to fly. With an effective dihedral of -15° the flying characteristics were considered to be dangerous because, when there was only a slight lag in the application of corrective control following a disturbance, the unstable moments resulting from spiral instability became sufficiently large to overpower the moments of the controls so that return to straight flight was impossible. Inasmuch as full-scale airplanes because of their greater size will diverge at a slower rate than free-flight models, the amount of negative effective dihedral that would constitute a dangerous condition is expected to be greater for full-scale airplanes.
Includes bibliographic references (p. 15).
Statement of Responsibility:
Marion O. McKinney, Jr.
General Note:
"Report no. L-54."
General Note:
"Originally issued January 1946 as Advance Restricted Report L5J02."
General Note:
"Report date January 1946."
General Note:
"NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were previously held under a security status but are now unclassified. Some of these reports were not technically edited. All have been reproduced without change in order to expedite general distribution."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 003614488
oclc - 71261163
sobekcm - AA00006246_00001
System ID:

Full Text

hIcA L E{L{_

ARP. No. L5J02


January 1946 as
Advance Restricted Report L5J02

By Marion 0. McKinney, Jr.

Langley Memorial Aeronautical
Langley Field, Va.



NACA WARTIME REPORTS are reprints of papers originally 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 54


Digitized by the Internet Archive
in 2011 with funding from
University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation

hlip: www.archive.org delails/experimentaldete001ang



." 1.T .. .L .. 7._L--T

E"FE i '. -TAL DEETE;" vACA i",, T:-. EE7T OF




PT- "..r'i::i C .c 1in e-1c Jr.

SL i,.!., A-:Y

The e effectss of r.Ce.tive h.iei-i.-.i c.i ce.-i s t ability
andi control chlr-scL :;ist Lcs at hir!. liit co3'_ icie-.ts nh ve
been deTrer.miner oy fli.t tests o' a :.oi. i'- t. L L.ngley
frce-flizht tunnel. Tje iecmetr-ic :'.ine aii :.lni .e of the
model 'vin w.s v-r-,ed fr-.cr, 0 to -_i0 --id t ~ ver'jc .1l-
tail ar. from 0 to 5 :,-erc f t.e ,n-, ar-e The
model was flI n ,':ith v --icus c, .bi.. ,ticII- c :-.ih3d;---l ngle
and varic sl- ci s.re- t ift' co-' ic; it of 1.0, 1.4,
and I.- .

A0 the '..ti-- e -..e.. ll:'3 w..s cr .-Le.d f rom _'
to -150, the r-c- i bee :.e incres r eifficit to fln .
*ith an effective dih-.eirs! of -l.o th- -ix'ir ch ?o,-.te,--
ist~ics icare co,-sia 1a-:' to bte i.1.. "-- -' s bec "'h n t'i re
-"a on1 p s i-I r. i.l in the )p lic: = io~ f c. orr-c.r .Ctire
contr:.! ll'c o i, di- 'brice, t"e uns .ta le ror-ts
ress.ul t-in fror, 3:.ir.l Insta-liity c-1-c..... "--ufficiently l.9gi-E
to ov c : v -w r the ::'.Itmiern c of the I o= -trC,: 1i so ci---.t r tir-nl
to str i .h- ft h ir, :-' osible. In--s crn s fu'll-e.le
ir-. lane because ,: t' he r ,r-e e-' size '.ill d ivear e -t

tive tet:e e t... An
condi ion is epect- tt be ..e -. ,f r. fu l.-s.ale air-

Iic c P? t ci" ect i s2; c tilltT redCcea -he

b evioo. In the hreat;ve effect~ e-d ahedral range,
incre.;:- C in the lift coeI''i ci ent fro; 1..0 t 1. 3 had a.
s1. Ihtl v detrimren.al effect on to5 -enerail fight 'e'hvior
of the riimodel at any Tjivyn value of effective dihedra'l and
direct ionsl stability.

2 NACA ARR No. L5J02


Tests of modern nrilitsry airplanes have indicated
that large changes in dihedral effect may occur over the
speed range of sn airplane operating under high-power
conditions. This chsr.ce in dihedral effect may cause an
airplane that has a normal amount of positive effective
dihedral in the high-speed condition to have large nega-
tive effective dihedral in the flaps-down, low-speed,
high-power condition (weve-off, landin-approach, or take-
off condition).

Previous tests (reference 1) have indicated that
slightly negative dihedral effect is not objectionable
and that spirsi stability is not imoortsnt. It was
desired to extend the previous work to .iI--:.r lift coef-
ficients and to determine hew much negative dihedral could
be tolerated without excessive detrimental effects on
flying characteristics. Flight tests of a model with
variable dihedrsl Asve therefore been conducted in the
Lanfl-- free-flight tunnel in order to determine experi-
mentally the effects of various amounts of negative
dihedral on the lateral stability and control character-
istics of an airplane at hign lift coefficients. The
results of this investigation are presented herein.
These results ere part of more comprehensive investigation
being imde to determine the effects of large variations
of dihedral angle, vertical-tail area, and lift coefficient
on the lateral stability characteristics of an airpicne.

The :resent investigation consisted in power-off
flight tests of a model on vnic.I th-e geometric dihedral
angle wvas varied from G0 to -200 for vertical-tail aress
from 0 to 55 percent of the wing area and for lift coef-
ficients of 1.0, 1.1', and 1.8. Sufficient combinations
of dihedral an-le and teil area were tested at each ,f
the three lift coefficients to determine the effect of
dihedral, tail area, and lift coefficient on the lateral
stability and control characteristics over the range of
the variables. The results of the flight tests of the
model are -resented in the form of qualitative ratings of
the general flight behavior of. the model for each test

iACA ARR IT.:: L., 2'

ii :r 9:.? o' :c -i. 1, 1 S "

Si'"(i. s re qu-t t

St ve-t u caI-raii -r9e., squ-.e .f~l-et

b wil-r s.:.-r., .-. ot

V r'i'=-- 'ea:: v c.1cci Y, f:-.t i' s -: r:c
1 t

T ti; t. to I. : tc onc-- .1 ..', t forl. E ira-l
K:vs.2EIn:1. '>72>7::i.tt 1 .n. Zl.iIC t
,.i- i.e in.: r- ": L 9 c.ub. ^ ..t ...,

k.C- ra Pius ,' ': : iCo1 of v.,.:n:'x' a: .: t lor.:itjin' -- .C ,
"X c' e t

7 r.: iL'. c L i.,- -t'io :'r i m:-o i ;bcut -'e.rri',A .,:' feet

R R.:*i. cth's di'sc ; iPn 1t

D 0cf,3 fie :,ft in s rabi itvr c 9uso ic e :, t i: iv-n i
rsfier'ence 2

E co, -'c ci,-.t: t.- tai it- q,, rtic tq..,ti, -i:,4, ,i-:ern in
re f-3 .. -r=- c. 2

N r,:-tz ci" sr?'ilit7 q4.,.:- ric eqi.r*t In

r .';in' enr," .l P:- '.-i .:,cit -, r -'.. 1 't, 2 :- ,c .:.:,:J.

o rmas; -nsit-, of -:.; '. 1, ",r ."Jic fctt

2 len 1- ,: li',sli' -r'-- ... vi j. a i'.-
s ,:., .2 ie :1

p r l, i i" ; t: l.. -L .' : 0 i :- _t. :-:r : : ,:,. ,d

T f i i;ht-'e', ._.n l :, d -,' ,-s

r :C.:.s ric ( ilIt s. Perl- :'i' : 3;:-t.ic s-; 3z linl',
de r s


I[ airplane reletive-density factor (--b)
; m \
T time-conversion factor
CL lift coefficient -
/Lateral force
Cy lateral-force coefficient (\
(Rolling moment\
CL rolling-moment coefficient Roling morent-
(Yawing moment"
C, yawing-moment coefficient YaingqS on
n \ qSb

CyP rate of change of lateral-force coefficient with
angle of sideslip, per radian (0Cy/Bp)

CL rate of change of rolling-moment coefficient with
angle of sideslip, per degree except where
otherwise specified ( CL /p)

CnR rate of change of yawing-moment coefficient with
angle of sideslip, per degree except where
.otherwise specify ied (CCn 6P)

CL rate of change of rolling-moment coefficient with
p /C6c
rolling-angular-velocity factor ]

Cn rate of change of yawing-moment coefficient with
p i CDCn\,
rolling-angular-velocity factor i -

CLr rate of change of rolling-moment coefficient with

yawing-angular-velocity factor ( -r\

Cnr rate of change of yawing-moment coefficient with

yawing-angular-velocity factor b

liADA AT; !'o. LJOCi2

TiV in-I'es- ti -- ti oi .'i ca.eied c.t in tie L naL iey,-
fr3e i- t 'uinel, 't,: ciL 3 Uc,-. -:, f. D':,' tei- ill f'lee-
fl-i-r.:i -'r.:ric 91:11. .rode Ls. A c c r :'. : e L e It e c ti
Co the rel c.i its u 'k e i i i .e 5.
Force te ts rc t .;. .it:" rt-e st sr.ic I :-sl s:'bility
deriv ti .' Ie s rv e r.-.':e 0.1 L :: I,-:. 1 1 -.f 1 t-tUr. n
six-conaronent te -.tic -desc- "i d n -.r i '-cnc: L. his
balance rot e:es._ v.it.h the rc el :., mo tc-.-t Cll f o'ce
end m.o...ents s-e .- ure i ." th r'e u ct t t-e t bi-i Ity
axes. The still -; sx en or: .: l ; t C f
axes ir.-.'lt f its :C :'i.'in t t:' cent r_, E't.'it-. in wiic:
tihe Z-a--is i in t'l- p : e o ; ,:-;:"s cr. ,i-r-; d :e Sin: uculer
to ththe: X- :: l. i:, tle h ..,r.do o'
s,_..rttr t nd -6,e n :li.c.alr" to the L-ax--: .d t1 s 1-91is
is :cr-"enL i culiar -o th ;:] J-. : ci .- tt ".

T'-' c "':tc ul -e" oni fre:--rii:ht-t in.-;el tdtlS is a
"flicke.: (2 l -on cr rPu l- -':) '- : -.. L -ur n 9 r one
sarticulpr fl'f ht the r..tr:1l clei ect io:ns in the full-on
position -s ?P ccrn t -nt fn. cn c r.mo'r-A.t ok con'itri, : 1 li-d
to t-h r,;:cis1 is r; L2ulat d b, the loer.c rie th- c on-
trols are held on r-et._r th-rn hr the c.ontrcl dfleie tions

A tIree-vie'w .dr'awnin cf .:3 ruel .Use:, i r the :e;zs
i shown rs 'i.' Liu- 1 Sna "-C:Co -P [" tehe .:0' c.i G-re
presented -"icu-es to L. Fi.'.:'; 5 is A'cto.r;.. h of
the o:1el, it-h a ._-7 t,: r:tic i.ed- l -'t --zl o, ,? -15e, fl-'ing
in the test secti:; cf the ton-el Al:tho:u.ih .he m: i-
use. in the tests .'-s no. c-- .-:~c e :..:del cr an p ''-n .cuc.l r
alr- i ,,e, ic ae .-:e.,:i.?tc; c-:e. te .: ---sc-le .i"odel

of nry curr-en: firlhter ;rpl .ne.

For- r tests the ;i.c el v e; eq l :r oji w..ith e cd-cle::
flo ar"etr.g-er-enn Consi ::znc of' -p 'e..t-ci.crd .icuble
slottedd ., b:..ce. id ve 0 :. .:,cr-t of' tie seri-
scn-?. snd a '-pe rcent-c.o r-d. b _t` ., :2 :-:t fi. ,: locat.ed
c t- r.d ovar .r -2 c.n: cE the s -:is i. The front end
rear :.-oit io' cf ie drble .... tt, Le v.re dfic'cted c 0
and 700, res':-ective y, with respect to th. ali'foil chord.
The- balanced s lit ris: V'es defl rcted LLG-.

The effective .,ied:rel :'s c.ir-.ed by altarin" the
c:.orr:etric di.edr-l r.:1l- c"' t in ou geo rn- c lly

6 NACA ARR No. L5J02

similar vertical tails and two end-pl'iate vertical tails
were used on the model to produce changes in directional
stability. (See fig. 1.)

The model relative-density factor and radii of
gyration varied slightly during the test program between
the follc.ing limits:

S . .. 8.10 to 8.92
S. . . .161 to 0.181

S . . 0.241 to 0.290

The data Dresented in references 1, 5, and 6 indicate
that changes of weight and moment of inertia of the megni-
tudes involved in the present investigation would make no
pronounced difference in the stability or flying character-
istics of the model.


Scope of Tests

Flight tests of the model were made at lift coef-
ficients of 1.0, 1.4, and 1.8 with the following combi-
nations of dihedral angle and vertical-tail area:

------------ -?------ `-'- -~~--------.-~ -`-~ -'--~-~` "
VVertical-tail area Geometric dihedral
vertical VerSit/iS angle
tail (deg)

Off 0 -5, -10, -20

1 .03 0, -5, -10, -15, -20

2 .05 0, -5, -io

S.10 0, -5

4 .15 0, -5, -io, -15, -20

4, 5, 6 i 35 (total) I -5, -0o, -15, -20

PAC-' A-R !. LE'J'2 1

The :.ri- c "- C -.. cr- --' -j. :g to th'e vP .iou

", -' --

-:;r t' : ::. ; te e n i..:i. .. ,- l- :, *,: t t ,i:!'- t e hat

th. \- : j o. i-:" ,- : C j ci t -ri -. '1Y-2. .,' JT V
1- -
ti. -

(2":c bic 'p 9ip':1 .. Ft.- t ,e. '2 r : .:,=, n "' -1.,e 1 9 -i -i S ir..o-2
witri~n t-_- r'.nc e ,o v-'. .:s .:. -.' l -- tU ..: t t.-: .

-. tt i2 -

ThE r:o el. '.t fl tn s:" : ercjh r c7rdic i':, 0,' t e
of sile:-ors -kicne ^r.. ?P ler-':'r ci : l o C it.nl hti : *:Je .. The
r d e i.[ E'K :.'e sel- .:.t i -'', .:1 ... r 't 'n
c' .f'i t le.-: -. ti- .-: .i t nie r- ... ,.:, n i- i'n :e ta-s
,n:.'min J .e t.' .ci :on ifle Jion :-n. r:i.i2..:. FOt re.st:
irn .i-12 t>. .: :J ( 'Clt 1 -*2 c :l. T t a-. IS, left

t'5 sets tes- ccndi ion. For tre :-i-o: 2: 'ti .:n tt-:
aiierc z, 'V e ri-, .. i'c. oT-..:S : : i'ni:in t- t' e
a ver-se ,-winr I'J. tc le :-nI d let'- : i n. c E .f. i lit
0- f.5_ r e..,D .....

9n" c io t-'cl ?C c -i T ri ic- .:.' tl ;ic -i vb.e'-; not-d by
t'vn :c i: e fr.,::. v-s' 1 i os r:, -" t-,' r J., mri on -"i:tur- .s
ws-el- ,.-s,.:,,= c,:" ec CTi,-. -"li>.:-t in ,crd-= ..c. s ..,: l, 1 .. i=nt t;', -

.ie ".,i :,1 t b.. ilit'- ,:,f t.i-,a ,,,lel ,.' -3 ie;'r.,,iied b.,
4 I it

th'" ,; iloLt. '. ,:1 Li": ri :te .t wni c'i : ti_ ".:.t.:e _, : :.crtrols
f ::ed., ridss ip-eed ,nd r--ci fr-c:n i:el i :.. .
Incr.c'- asc; r'-ate ci' ri l .ii ,,:' .-,.. in-. ra si. e: 1 ii^ juied
as c ir:-:l s-.,iiLty.

v', e ;... c i 1 t -. .- t ".i :1- a : ti t "i: t Li

were jud, -. h :, t,-i ii..:L fr1' ^i: th- .= -.:1 !:.. i:,._ ,:,-' t e.... i t e .
Osc ll7t n._- 0:, e : ..e -' 1" C, ~it' ,-,-,, The- .. l l
could nL,.':e be lilc.e :i tc Il, ,; itn c,. nt:I s Ic .: --,.ed 'or
suit ic iCL nt t i:.e .0 ilow n.e : u- c ::srt ,"' .9-e iod a :i 1 ':' Z
fr.:: t rc.:tionr-'ict're r-eco d .


Flight-behavior ratings based on the pilct's opinion
of the general stability end control characteristics of
the model were recorded for each test condition. Each
racing was based on a number of separate flights. Although
t e accuracy of these ratings depended upon the pilot's
ability to recognize unsatisfactory conditions, it is
believed that the ratings give a qualitative indication
of the effect of change of the variables involved.


Boundaries for neutral spiral stability (E = 0),
neutral oscillatory stability (R = 0), and neutral
directional stability (D = 0) were calculated over the
test range by means of the stability equations of refer-
ence 2 and are shown in figure 6. Lines of constant
damping of the spiral mode were also calculated for the
model by determining the root cf the sltbility quartic -
that woula give the desired value of damioing by bhe
formula (from reference 2)

= -0.093T

and by determining various values of C- and C, that

would give this root k froi substitution of the root in
the stability quertic. The calculated lines of constant
d-:.:>ing are shown in figure d.

Values of the static-leteral-stability derivative Cy
used in the calculations were obtained from force tests
of the model. The value of the rotary derivative Cnr
was obtained from free-oscillation tests of the model b:,
the method described in reference 7. The other rotary
derivatives CLp, Cnp, and Cr were esti-ated from
the charts of reference 8 and the formulas of reference 9.
The values of the mass characteristics m, ky, and kZ
were measured for the model. Values of the stability
derivatives used in the calculations are given in table I.

iTA%, A T r '.. IrO02


T'he v9ri: ti:n o:,f Srl. clve -' i1.;-ir a .:e r! te- Cl
aodJ : irecr ic.nai-9 t- li -t. p .' ,ete were cbtai ned

in th e: Isent ir- 's i :-i'n by chLi ,n the eoe ric
di'.e.r l n-- n le 1 n .nd ert ical-'1 il ar he fl i-
char; cLLt- :L :- -'ev r, nd o: h'e 'I "SiL.s Col the
stability dc riv= ti ': n.t o n the iet-. .; L:. .c t.ey
v.ere ct -.e ; e:ie th2 "' i:" char:-ct Z.:- ticr oC t of L
r.iodel FP:-, be p-: lii-. tc c':r:d l'on.s cz. v .-.-orf,
ta',:E-Of I F and lo.'ir -s ,oi'cO h in W'h. ic .E '.' e
ef -fective a-e- I 2: n r...,,-e "-, Ld 1ne h_ icn ro',.er_ eCnd

high lift coe-liciu-.t.

The pr-inci'sl rcs..lcs of the & -es-ent in" s-ti z-ti'on
eae riven in ri.r-a r in tii- fir:u. of rs':-- of the
gener l .li h se. s:-:ircr. .A l li 'i" r trr.s n'ot 1.
narenthes es 'e-r.e c". :31 i tDtfi I- ,L :n relisction
of 50'; tlose it. a.r. t.i s .'ere o t" ine ie ;wi':l tctrl
aiileror. lefle=ci cn of '- Tfe W i.W. value of )p/'2V
corre.s;on-,aing to rthe sil:-: deslec tons cf a0e and 50
we6r determined to be bo,,t uI.j. -nd C.12, re-rc.ctiveliy,
fro:; rcll-offr : at a .e e rietr-c ,diai l. '' n--: ofa 0-', vith
the verticr l lsil -1 in -I = 0.1, an wit:- ccor -insted
rudder. It "Rgs, o irha': r.t necss_ -:r-, to u.3 rn l e lron
deflection of 0o -. sli th.. test : oints t .:ich this
incrc Ersd tr-vel e as usei. ,"' r. i s .-- C d n nec sar7
to uze S,0 ta'.l -a 't~l a cent in cc rc :inre-i of A._idr l
angsi-e end vertic sjl-1 .CAe 7 t a litt C.o-Ci ic n.I of 1. ',
the-s seie t~'':e a r I t c c
the sries t'a:-:'i ': e x L- laoer 1i ft coe fficients.

Effect, 1f Ll ed.G-1

Alt:nough the .,udel .r: cb :-rv:d to -e si--ally
unstdcl for -lI c.nt i D tes~- i, LA 'i t. : .tca cf
fi.j re 3 'jhoo th t ve' r. oc tisf? to,- f ii:-its ';e'e o' t ined
Ft pos i''i vvl,..e. of ef'f ctivs Li::.,rsl. Ths r-ata of
szizsl! diverr-:ence for t.:e conl ti:.i'ns c_ ,j',si tiv3e ffe~ active
aihedral '.,4ss c,-se rve=a to? e s.,~ 0 5s--d t. cntCrols-fi:.'ed
latse l '1cTlion :oss ch:=rszer-i zed y .z? sl.' y aentzl roil-
off 5nI side slin fo1-r: t'-L stSCdj SL-.e. Th& si.-cE'Tencd
ccula be cont'rolledI r'e:.J-ly by occsszcr:el Fr-)iicetio.n of
a total aileron deflection f 3C0. Under these conditions,
the r:,od l ..- a\. :IS .:,; to Il '. s if I t h s beSn spii: lly


stable and in the normal gusty air of the tunnel did not
seem to require more frequent control than in a spirally
stable condition.

At smell values cf negative effective dihedral,
flight characteristics were not much different from those
at small values of positive effective dihedrel end the
slowi spiral divergences were readily controlled by appli-
cation of the aileron and rudder controls. The rate of
spiral divergence, however, was found to become increas-
ingly rani with increasing negative effective dihedral
until, at en effective dihedral of about -150, the diver-
gence was quite violent. As in the case of small positive
effective dihedral, the motions were characterized by a
roll-off and sideslip from steady flight. As the negative
effective dihedral ':as increased, the rate of the diver-
gence increased until, for the condit ions ,ving the
lare-r negative dihedral angles, the motion a-peared to
be ss rapid as 3 fast aileron roll. As the negative
effective die dral was increased, the controls had to be
applied sooner after- the divergence was noticed because,
when there was only a sli._ht lag in the application of
corrective control following a disturbance, the unstable
moments resulting from spiral instability became suffi-
ciently large to overpowerv 'the moments of the controls
so that return to straight flight was impossible.

It was found impossible to fly the model with negative
effective dihedral angle~ greater than about -100
(C73 = 0.002) with a total aileron deflection of 30.
The rate of spiral divergence apparently had become great
eno-gh by the time the nilot applied cocosite control to
make recovery impossible. The rate of divergence was
observed to be retarded with aileron application, but the
model continued to diverge.

In order to obtain data for the whole test range,
the total eileron deflection was increased from 30 to 500
for all test conditions having a value of Cip>0.002.
It was therefore possible to control the spiral divergence
over the coiolete range of n-egtive dihedral angles.
Flight unaer conditions of C P0.002 was difficult,

however, because flying the modeel required constant
attention to the controls. The largest negative effective
dihedral n;_les (CLp = 0.005) see~ated to be the mlaximumn
for vhich the model could bo flown with a total aileron

'ACA AR ?,o. LcJu2

deflection of co-', 1inC:1:'I'.h s: e--en sli c -i delays in
e- "inr -_ 3te.:-.1 conri : -. i :~ilow,0d. t'. !'.odj. l to continue
to diver.ce. I-,',- c-zsh-:e.7 the ref'c.re .cicurord .du.inw tLhe
test', .t v iaues of C; of eoi '.C .

Thle craer '-. fll.ht-eL.evi- r-tlr rn. f -iie ,i 'ue e
given l whien the r :i:. s cc.:.i: r. ,r d ith tn i c-l :orns
in the n :'. i r '-.r' r i r'ic-..t .:.-.' t I-,ht p 1le -con .
The 'iV:htS t 9 : -.: .-:e st,... i, L. u ...n- c1h 9.i6r.:,nS
lone f'o. c ::\-trol .:. even .:.. r-o -- rg r- .-..'-.e.-- ?,r-ntcr.i
ir,'Tro.'ed :h.e 1- n c. r-r '" ^ter. t ic'. .t I i,: dl.5l t-iiecugnoh .ut
the ine t.ve di:. -- 1 l .- .. l --
C.. rj. ".*,:. ::, J .rE..e t i i.i

beca u 3 3-r si i i'" -. i i .- ,, t ..-- .n: -c
thre j.i .'. -:- :.e j-_: --. e.d '.' .. .1 i-' ; -~- nce

y i .; a, i ci'i-d i ze ~ tihe .:_illr c: iiL-e '.;:rnc :ecn
be i:-: ovec. ,T, -i .e ;:.. c ije o- t e f i : S
1-- ._ i.' .,
caused b' : inC .z.fi .o-t ::, -i:n -. ccj t ticon-
ab-l to th. .e-:li -t,.-nr l l s. .1 i o ice
r u. er '.i i It -' .L .c d ci -, Ii ; LCe e tic.I'] s l to
th3 "ilo: r .E i i.A,.tLch it i i r-i i'-iL t l
roticn sn,. vi'O ,. eim-: 9 l.,.:., 'L :4,.' tit J '_" I., e c 1il _
mome 1nt, th : lot' s cti n 'C .c.'b : b -; s
coor'Inse :t.er e n cl L t-h n I to
thin: to -r l.- i'; rui' r c< :-. t to t> ci1 A 'il' b
i t. ho'';.eve be t'r: irn to a.p1:,- o 1"i :..e. t.A .i L -on
control .-n r0-in- pn -irpl n- in c :c. _o: th .t are
kno'jn tc -ive nL Et--.'s di.ed.a l c a n .i iu c tarin
so"rI i. :nro'.'1 n t in tn control -e': l' r r '- -7.

'T,-. r ,eve- f-, L : -'o, -nd il''. in. c..r,', c conditions
r-e belie-ved to be d, n er,: ous '-'.- ie ...-. t :t h v l oi'e
rneabtiv effect ti. di:.s.,eil 1 bectise, ''. he- th,:e co:" iti Ons
Sre e~~r o nte2r;.:, t-ere e is. or.- 5 1i.-ite e titude in which
to c.- 1.-i zorrCctivE cn:rol. To fl-, v ith {: riTch- ne: eti ve
ef'f-.ti .ii-; tr-si .9 e, nrta r_--d in tihe -.esent te s
sno. ..: r.,- C -, 'l -e i -. si -.2 f -e a l-0_ :-.. e ns -,,.er--
',ui s- t ,z" e :. '9 th- .c l e -" S V efu l Itt -i..:n
is civen to cont roi -r.1 th. si.-: l-ie. To f :- air.:I, nes
vich -,_e.=.ter nr -.La i,.-e ef_-l'ct-,-? .i:i.,dral sci.s th-_n i e-re
.enc u.uit r :._-,, in ti_-e re a- r-.t w3ts .-:.,il t :, ... o -. sl ':', if.as:iuch
as the ra e :s os I je fri: i?"' .r. 1- l :S [D
ti:.'?s a: s. Cs t I:. :. The :..Dcel, \,,'., ,e :' is ti scale
of the iocl I as 10, i,., c. l infc rr.-t ir. is. available,
ho.-ev.'er, coC:,-.35--r i L. the r- e cl-'tive n! ct ion t i.. ani '-The

12 NACA ARR No. L5J02

tire to deflect the controls for free-flight-tunnel and
airplane pilots. Inasmach as there has been no correlation
of the boundaries of the region in which flight is pos-
sible in the Lnangley free-flight tunnel with time to damp,
extension of the results to more negative dihedral angles
has not been attempted.

Effect of Directional Stsbility

Increasing the directional stability Cn, improved

the general flight behavior of the model over the range
of dihedral angles and lift coefficients tested, as shown
in figure 8.

The tests showed that for the range of positive
effective dihedral engles tested adequate directional
stability was m nre desirable th.n the slightly lower rate
of spiral divergence associated with lower directional
stability, because excessive yawing was encountered with
low directional stability. The rates of spiral divergence
encountered in the positive dihedral range were, as
previously discussed, quite slow even with a high degree
of directional stability.

When the effective dihedral was negative, however,
increasing the directional stability was observed to cause
a slight reduction of the rate of spiral divergence. This
reduction is in agreement with the calculations of the
spiral stability, as shown by the increase in time for the
motion to increase to double aeilplitude as C increases.

An analysis of the general flight-behavior ratings and
the calculated lines of constant damping of the spiral
divergence indicates that ths general flight behavior
within the negative effective-dihedral range is primarily
influenced by the spiral stability.

The motions of the model with a. geometric dihedral
angle of -200, with tails off, and at lift coefficients
of 1.L and 1.8 appeared to be directional divergences.
Immediately after taking off, the model commenced a diver-
gence in yaw th:t wavs followed by rapid rolling in the
opposite direction caused by the negative dihedral. No
recoveries from the initial divergence could. be obtained.

I'A'A AR !co. L'JO? 1

Effe-t :: Lift Icc Lfficnt

T-.e .ti1 .t r tios .c f fi ..:,.ie s o'w that incr:3- in
the l ifC c eff'-ci nt f'romr 1.0 cc 1. ; it con, stat '., LOes
t r,
of C, ndi C :r U sli.f lv. :.eri.miint-l -:] feet ..n

eff ct '..'. -dih-.or 1 r nr Thi :.-It er. t efi c i"-
teiie'.ed to. be c u e by e i crr re in- the 'e f s.:i.al
divo.r; nc ind ic ted b t.. c cu i lines c' c on! nt
mcl i -n hiw n ir vi,-*,.t s ID.

C : ICLUSi ,

Th-r c f ol lo'.tr ::c i .cl ..i2or '..; f-l 1 :.:,r : 're ? i tht-
tunrn l r-crts to i ; ...it-r thi e -f e c.t c' .-'. t J il .dr
on the l-ce -,l st :. -,ty contr' o c2", :: *, l: tics o a
free-fl vin;.- nc_.i:i .:..xo ei at 'ii 11: t c e:l'if iirnts:

1. Ac tre eF c tive j.ihe..-l wc. .de-crea-2 L fEr- C'.
to -1o0, te mfri l ec. E 1 ; ,r:cel. I c .; :i If ii t t c. i'ly.
7litk l n ,effect-"e l -e eL -i ti 1 -:'. c
istfic ere -cons i ed to be d. n s ) Z. i"n thi-ere
wv s ci-ly o sli -h t 1i-7 in the n :,--ic.r .: or cofr:- ci e
control : :. i ..' r. .: i -: t'e .: z ':. .l : nts

L 4 c
resaitin f or. z'-ir-_ inr. at it7 b 29u., ...ffi
lar.e to c '. : t rc.r r..: th- : .-r Is o t st
return to stre iht "l hi :t ..rs .:..C c-. I, -i ,0c" Es
fuil- ,cale sit-o..ne-s bec--.. e of th. r -:c.-:e.r.- s L.e v'il!
dIi'er: t a si. p rrite :rhn 'r' :.-' -: -tu nel .'::.' i ,
the :cAI.t cf nu g ti.'e ef'ecti.;,: 1 di. I ... 'al : C' ,.a,.lI
co.stitunce 9 .c ,c .,.0,s : ,,. ::iti :-. i- 2 .h 1 to r1. [. cet?2r
f'cr "i.ll-scei-3 sir.c i--' s.

2. f it snl tic,: t: r'd.cL i.ai: t._3 fi' .jt ,f .1 -in
ovrg tl r.- -n ol Ji.e l- 1 t ,i. L .1 t .
, ir-ecti.n, al i stsbi lit:.. ., -, "cl. t..-L ': ,.* .. r. ..... :. i sta-
C" l it .' 1 ,r ,.:.- T 'i-.e -' e" .- a -. .. t,
ir,.s :i :- S i :9 s '- t f ,or '- .:._.,-. ":. ;' '. '.:iv
dime.ris. 1 n;. 1 T ,= i-. t re-: l t ....: .- 3 -,., ,i;"-. ion -i
st bili t '."' -- '. .: li :. :.'...-:; :' -- n .ai i -ll f: t
bsh 3 cr- :--er te -ant i-. i .. :-. el r- ; .

5. I- th .-_,- ve f'ecti,-'..-:l.. ,-: r '--e, increasing
the lift oef ici-cnt fro..:i 1.0 t 1.c; ,hs c sl ightlv

14 ACA ARR Nc. L5J02

detrimental effect upon the general flight behavior of
the model st any given value of effective ihedrsl and
directional stability.

Langley ".-olial AeronauticaJ Labo-atory
Ystional Advisory Conmittee for Aeron.utics
Langley Field, Va.

NACA ARR fo. L5J02

L-. .. 1'

1. C n.1be .I, Jc-r i-., sij. S ?'.rl, C':ir cE L., Jr.: The
L ::t I' i,:- Dist:-ibutl.A on Lr!: Lst -:. .3L .bi. lit
nI A- r r J s;
n.i,-. Co.. "' l ._ Z-,? L-.iS cL 3 C f en A r- 1.e t '

'Tu -.: t. .-.C.; ,,.-, .1 2 ;. -

2. 'i ,r," -r.., Cher. s 1 ; : An Ar-: .i.'si-,_ -, L-ter1 S1 e',ility
in Fco:r-C'Zf' 'li'inc vit'U Ch-Ltz for U-- in DeSli n.
Ct R -.. :;,. 5C 19 7.

'. Sho t .-.-t.n .J. : PrA-
l i i,'. ":- S ts. : -1t .n'! C',i',t e l, T ._ in t:-.3 ,;;,,.CA
F ree-? 11-'l t 'Vir:: Ti .r.1 r-.i CT,_re. 1,'.. rich Full-

. Shol'r' -, ,Jo. -"-_ "., '.i1 ',?. "- .Tc',n .'.' : "Pre -r' .:ht-
Ti'.- el In'. ? t- '.:. e ,. e:-.t c: t.e P i.:.. 1? ,
L.Cf it A

L n1 t :... t c. c S"L clf the. ?r tiC f c
-. .
-- -t I' t.u- 1 1 tAT.L

5. C..r.b, 11, 1 otri ., n S= 3C: ra, Cil-_ t L. Jr'.: Effect
o:' ',in- Lc?J r n, al itt.ncu :: L-ter.l Sttli"ty
nA C.nL l : :. -*. r i "C c_ n .- .- :lane r sl i Leta r-
:." .: 'j '-r Test C: r. I ...1-: i I LI,,- p'e c..-1 -". h.r "T'u. i," l1
.:A .. A ?-: FZS, C1 4 .

6. 3r- ti L. .1'., .I" Pu : --- t.. j.: I.i:L L teral S .--
oilitT o-" '.: ;_' Lo,.:it e -' .v ;: I :. s. -. ;. :'". : 1,- ,.0,
br-1tis.-. A. ., I., ,..

7 ,-. C i\, ,x .' n _n- c i,:L .-.: icr-.] C.: E:: ..- ::ental
Deat-_'*..i'-,.. i: -n ..; t!:_. fT .'".i, : n.. ..-n D .-- ,to : : ..n.

T e., 1 a ri- : .,: .i .-,i0...e :.. ')e 1. .... .tu;F. 1 -. :72 :,
.Lr .1
e 's n, ,ir 1n J n's, -. Lrt .. : 't. ec r tic
nS'A," li ,- nd C:;nt'.: l Ci i:' s c e cf .- i'. tir ith

'=. .? :..,ounLr o ? ': r s. d '" i t. !!AC R i.
::o b G'- ;.

.. B.br,, .ii' .. J." iffc of e.. PPe e',-It- ,'r, AirL-lane
D'si-n Tr'ecndc n Requlrerencs for L- te1 Sta ilit;y.
.'Ai *T- i l1., l 1 l.



Values were arbitrarily assigned to Cnp, the
CZ was used as the dependent variable. p =
P /. -. -

KZ/D = U.2o j

8.12; kx/b

Cy Cnp C p Cnp C r Cnr Y
(1) (1) (deg)

CL = 1.0
-0.102 0 -0.49 -0.060 0.246 -0.040 -11.6
-.11 .005 -.49 -.058 .248 -.048 -1.6
-.12 .010 -.49 -.056 .250 -.055 -11.6
-.166 .025 -.49 -.050 255 -.078 -11.6
-.230 .050 -.49 -.o4o 265 -.115 -11.6
-.29J .075 -.49 -.031 24 -.155 -11.6
.100 -.49 -.021 4 -.190 -11.6
.150 -.49 -.002 .303 -.265 -11.6
-.614 .200 -.49 .015 .320 -4 -11.6
-.742 250 -.49 .02 .337 .41 -11.6
-.70 .300 -.49 .o8 353 -.491 -11.6

CL = 1.4
.o.108 0 -0.49 -0.066 0.340 -o.o040 -11.6
-.121 .005 -.49 -.08 .542 -.048 -11.6
-.135 .010 -.49 -.0 .343 -.055 -11.6
-.175 .025 -49 -.080 .347 -.07 -11.6
-.42 .050 -.49 -.073 5354 -.115 -11.6
-.308 .075 -.49 -.067 .3o0 -.153 -11.6
-.375 .100 -.49 -.060 .567 -.190 -11.
-.508 .150 -.49 -.07 .380 -.265 -11.6
-.642 .200 -.49 -.05~ .92 -.340 -11.6
-.775 .250 -.49 -.025 .402 -.415 -11.6
-.909 .300 -.49 -.015 .412 -.491 -11.6

CL = 1.8
-0o14 o -0.49 -0.114 0.436 -o.04o -15.5
-.128 .005 --49 -.115 .436 -.048 -15.5
-12 .010 -.49 -.112 .437 -.055 -15.5
-184 .025 -.49 -.110 .439 -.078 -15.5
-.254 .050 -.49 -.106 .443 -.115 -13.5
-.322 .075 -.49 -.105 .446 -.153 -13.5
-.592 .100 -.49 -.099 .450 -.190 -13.5
- 532 .150 -.49 -.092 .457 -.265 -15.5
-.670 .200 -.49 -.085 .465 -.340 -15.5
-.810 .250 -.49 -.082 .468 -.413 -15.5
-.958 -.00 -.49 -.078 .471 -.491 -15.5

p is measured in radians.


= 0.165;


Figure I. Three-view sketch of model tested In Loangle
free-l./ght funnel showing range of dihedral adjustment
and alternate vertlcal-foil arrangements.

Fig. 1

NACA ARR No. L5J02 Fig. 2










NACA ARR No. L5j02 Fig. 3







NACA ARR No. L5J02 Fig, 4














NACA ARR No. L5J02 Fig. 5















Fig. 6

Esp Ja/ 'pU 'jppulaodv c///q/it-/^u/o)//a


tq 9 //.
. / /---
b .0c6 -- ^ y -
S Te ro //. ,

C LAmrp/ane A

-.0 -.002 O .002 .04
Ef chve -cd/edra/ ,/cr-- C per "9


iure 7 .- a/es o/ C arz' Ca/ for Avo
-m o h--orver4 oar---s -s
Gcrnaed wvh A /rpb/xae tes/ad
compared wi/7h the rag tested.

Fig. 7

NACA ARR No. L5J02 Fig. 8


-- --

a_ )

r )

"IQ 4
IQ n


S5 ic
^-- -- i 4

fSgp PJY I co ^

Q 1/

3 1262 08104 9644

PO. BOX 117011