Wind-tunnel investigation of control-surface characteristics

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Material Information

Title:
Wind-tunnel investigation of control-surface characteristics XIX - a double flap with an overhang and an internal aerodynamic balance
Alternate Title:
NACA wartime reports
Physical Description:
16, 35 p. : ; 28 cm.
Language:
English
Creator:
Liddell, Robert B
Langley Aeronautical Laboratory
United States -- National Advisory Committee for Aeronautics
Publisher:
Langley Memorial Aeronautical Laboratory
Place of Publication:
Langley Field, VA
Publication Date:

Subjects

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

Notes

Summary:
Summary: Wind-tunnel tests have been made in two-dimensional flow to investigate the aerodynamic characteristics of a double flap with an internal and an overhang balance. Three sizes of each type of balance were tested with three relative rates of deflection of the two flaps. An NACA 66-009 airfoil having a 0.30-airfoil-chord straight-contour forward flap and a 0.20-airfoil-chord straight-contour rearward flap was used. The test results indicated that a balanced double flap produced the same lift as a single plain flap of the same chord and also produced highly balanced hinge moments. High lifts and low hinge moments were obtained with a double-flap arrangement if either an overhang or an internal balance having a chord 50 percent of the flap chord was incorporated on the forward flap. The overhang-balance flap showed a lower value of the hinge-moment gradient due to flap deflection than the internally balanced flap.
Statement of Responsibility:
by Robert B. Liddell.
General Note:
"Report no. L-215."
General Note:
"Originally issued October 1944 as Advance Restricted Report L4F23."
General Note:
"Report date June 1944."
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 - 003593991
oclc - 70900971
System ID:
AA00009413:00001

Full Text
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NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS





WARTIME IRE PORT
ORIGINALLY ISSUED
June 1944 as
Advance Confidential Report L4F23

WIHD-TBHUL INVESTIGATION CF CO01ROL-SURFACE CHARACTERISTICS
XII A DOUBLE FLAP WITH AN OVERHAfG AND
AS InTERNAL AERODYNAMIC BALANCE
By Robert B. Liddell

Langley Memorial Aeronautical Laboratory
Langley Field, Va.






N .AC .. .


WASHINGTON

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 T15


DOCUMENTS DEPARTMENT








































Digitized by Ihe Inleinei Archive
in 2011 wilh funding Irom
University ol Florida, George A. Smathers Libraries wilh support Irom LYRASIS and the Sloan Foundation































hltp: www.archive.org details windlunnelinvlang




C T' -A /



'A,? A.,R No. Ll'F_25

TN'.TT ADV RY COqMM\IT0TFE ..O. AERONAUTI CS


ADYV/rE CO i E" T r i .t .- EPOET

Y'T' '-; V,,L IT! ESTIc.-. lON OF C.': A '.-STRF.'.. CHA.AC:'. .-mSTE'"

XIX A T .'L? FT .P ""'. A"' C~"T A' :. -

A! T ....:,-.J ALT.P::Y, .... TC L'..L. ::'

3 T bert .. Li. el


s. .:. .' .


1--r;i-tunnel tests have been made in two-dimersional
flow to in'esti ate the aerc ;-- characteristics of
a double '-lap with an internal and an ove F'er. o.lance.
Three sizes of ecch type of balance were tested v.ith
three rel-tive rates of deflection of the two fl...s.
An 'TACA 66-00c' airfoil having a 0.0-airfoil-c'r..
strai ht-conto forT:,rd Anl o? rf .2O-adrfoil-chard
s t r- .ni p t ior. t D ', i

Th- e"st r ults r'.. ....t.d t.. ... a b .'i ci- l
flt o prroi -ced the s a e 1'ft .. *: s 'r"e .' in f-ri. c '
th e s e. e '}t o r .' .rJ" a.' '.? ,: *-o',_c ..-" ." ',; ," i. -5
r "'l :ntF. _'l i 'ts r l 1 l" -I : r en1t, v.wer a,.ta i'cd
', it i a L :..ie- -'i a r..-,: -,-.t "f .t-er o'.e in-'n or
an [: 'tern-ri ha1 r. ? -e ::. ;iz c er 'ert 'i t"e
fla1 ch r v s ir.te.-:-.cr tet 0.1 t1" fr .ard L'-l :. rr"..
ove h .g-baln,;e la- sh.-.* '_nv. r l1;:- .of t -.-: "_:" n--
,-u." : t "'.rA "le:-t, d,. .o f I -... .e'i' tio t- a t:i 1 r ter-:;-
ally ':,.-. irm edc --1&^.





Previous wor. (- referei-?e 1 ".- ':hov'n tL.at .--r-eater
lifts with ligh1 ter Tortrol fi re .-iould ce 'ttL -,'.i y:
the use o r :laL,-fl:i srai1-c.' ord s'-,trol s..r f ..es
deflected to a lar.: ir,.1le than wj 1"'re-chor.d control
surfaces with a srsller ..e. 1.ctlor. range. The r-s. lt-
of reference 1 also shr.ved t.st two s all-,hord flaps
deflected s-'ultanr.eousl, in the s-a.Te direction '.iould be a







2 COITIDE'TTAL NACA AC2 !1o. LFr23


c :,m' :intion tht '7 1:1:1 zive even better lift and hinge-
mor,-.nt ch:-,racteris:t.cs. iomzr rietho-d f inrcor:.,oratinr
I:-oC'fylnaflic balance r.:ust be found. however, since tne
-.n,- 'n-;ennt forces of the plain fCla._s Tire muc.1 too'
1--.r- for those fl'Lps to :e used c :'bi '-SPeed airplanes.

SJc'.ible fi o :'.-ith v Prio,,s arn'!:untF of either over-
.;n,: or internal baicnce and with -!; fertnt r--tes cf
d0c flcticn of tL.e t,.'c- fl--? '.a l.-:n t -ed to fin.
out vh:e ther th?. hin:c rnmorn..ts co.ul '. .. -v c ,-c d r.d tie
lift characteristin-;, cf a l.'in '.n .Eta&ine A. dcuble-
fla->n rr' rei .--,nt .v. '/ r.-. sotmee '.' Lzrcer '-.crds t.an those
uc-ed in rr-Ifer ncs 1 '.-s s-le:tc:. in "r e to c -t in
rrea ter lift, eC -t l.v 1 t 1-r a.n-" s n f atLus.:1 : with
11f 3 defl 'o tions -'f -cosi .t ..





'he- co&ffici nts &nrd ': F'Trrals u sed in this oa-er
.are define: as- 1 li. c :

c airfoil section lift coefficient (i/q,)

co airfoil sccti-n profile-,.c' zr efficient (d.,'qc)

cm airfoil section oitchin--!:ment coefficient
m /q e-
Ce section hinm:.e-rcment coefficient a'crut forvard-
1 "a Is) -ivcc ";cint ? sh wn- in fi,:-re 1




Cy s':cticn ':.ne-n-crpment co.:fficiert &sout rearward-
2 fla 'jivet 'ocint ', sh :r.n in fi-ur-: 1





e control-stic!: (0or ords.l) hi nn .-mnent Ccoeffi-
"cs ient (I's/Qei2) *


CO NFTDE TI AL









T'ACA ACR TTo. Li;722


where

t airfoil section lift

airfoil section .:-.:ofile ('.

m airfoi3 section oitc:'.n-- moment abcut quarter-
chord ooint of sirfoil

hI forward-fl- section ri" oent a "'t ?P
h t
hs control-stick (or "ei" ) .- C orent bI :


C chord of basic a~fcil '.:th th fl-, :' neutral

cI forwar-''-flap c!.. with rearward flap neutral

C2 rearwarc'-flap c'.:..





c, "L.cr, f i El nc -

a er.j 'le f att S.ck f'.r airfoil. 7f infi.nite Lt ',: .t t


61 f.orwar',;'-fl.- .'-e lect'.in w.*ith re.:-",ct t.: sirfcil,


P,0 rearvI:Prr.-fl 7'e0fle2 t i.:n ', th reZ ,ect tc f ,or srJ
-f .1 e


^' rc r..-av rc-f'_n.; .cfl cc tl,' v t.) r3s::ect to ai'rfcil ,
de.-rees 's e ; F re' Irre.-' to t. "t,- L



C (-. a L



fi61 ^
\ t


CO IF! I.'TT AT.L


CO1')I TDF 'T! AL









COTI' TD 'TTAr., .A'A AC5 71 LL,.72


c, --

,












1 Ce


r"0p cc.w.-arison, ar.r-le of Rtt-ck< -Inc: a fl -.o '-efl action of 0- sr.d tj.s-refore
a .ply to crnl, a very lir.ite-' .crti r of thc data.


APPA..ATU, !r'D-L \'"D TESTS


The tests were r ide in the :'1 C 4- b-- 6-fcot ve-rtical
tunnel (reference 2) rnonifi'c' as :'sc'isscd in refePence 5.
The 2-fcot-c`orad U', -oct- rnin ',o.el -s r'-ie cf ]ami-
nated mahogsrny, ezceot for t'-he front flA '*::.ic- w.as steel.
The airfcil confersdn n the LAr. '-00 ar'il "--centour
forwvarI, cf the forv-ord-flac 1 lrne uris and to a str3ight-
line contour 'ehinc ti' hintLe x: Is. The model jwas f'ro-
ir'.ed with a C 0.50c forward fluy an' a ,.20c rears--.v d' fla,.
7Fiuurn 1 s'"o's the o th:.d usec- t 0 'onrni-t the fl a -s to
each other ann( to the a:'rf lil ''-. re-, rwar.i fl sn was
connected to the '"crw'.r' fla. bTy rechan.s.i that allowed
the reer''ard f'l 9 to :lefle:t one tv.'o, or three tines
As fast as the f.r' :-.rd fla that !s, d(21 /d1 c', als
either 1, 2. or Z. "he for',r..d flan *.vs orovi.red with
thr-e interchnnfea le ','lunt-ncFe ','vrrnn bnlanc.s and
three intcrc'ranrehle intcrbAl balances having chords 25,
IO, arnd 50 percentt of the fcrward-flan chord. The
arranaf,.-ents testc and 'rtin.nt mcdel dimensions are
shown in fi.rure 2.
CO rT .'IDETI AL









I7ACA ACR 'o. LLF25 COlRITDEr'TIAL


The d u"-l.e-f].. rran,- r'ent te---d is in rerl'ity a
fls ".ith a lsr-.'< _iL e f.: t. t "'e tab c jul, c ,C.:'
1 ir.:e.i t t -the .'.'U i ". .tn :. si '- le crc r.k c :.r r-:-
t ?n. "h r.or.'l :.:as 3 i1c'e -.' th the l-n!; 'st i'- 'n
"n i fi-.re 1., h..a, ev r, rn n" :,"li '," r.-,t o---o t;':'i
i C-
r.n t -ie model ..id tI.ct t. rc"dynp.:riz3 c x.C tc ir t i 3.
-re the same as fcr 0.cc fl it,- ..Gc ..iin:
ta '.e :' .r".a c'.--fi: d l U f c t..-, .-an1 t'-e :' ote of
-efl ec^c ,. .. tr.e ch...:.icA.'. pc i ..r .. t e r .' ** s r-'.':.? I.I.* .' .', r
'7crv. -ai frlan c* .'. b-r -,.-aii a'..; C ic, lly. I an'.:
ay are *:s in,: ic te. ir -'i re ,






O :. co.: C ;.
:.8 y cos 2


The depE.rt.ire of r-earw'-r .-fl. .i:'lec ticn an." of rate
0o rear-Terd-fila) Jefle.ct ion e'rn ] inejritt' 1. h :-c.rware-
f SapI dcs le ic't &r c'icul --tr-c ..or, e u tio s (1) ar.J
(2), i inifec.te'd in f'i ure f:,r c_ 2Cn 1 in:..k.c ro r- -
ncnt tcstei. It m'.. be r'ctd t'.t linca r .te r f
re-arwA.rd-fl p de .ec ti .- a cn h.:-ncr ccr, ta.,t v.'t.e
of d5)/d51 throuLr7ho, t the deflection rr:-.e wis

obtainca only vwin 1 t. t, is, ''rt.en "- =- v-. I

msay alsc be noted that = 2-, 2or --= 2 and
c.c-t 1
that 5: = S for -- = 2,


The airfoil mc.el l v -.en countedtd in the tunnel cor-
pletely spanned the t-st- secti.on. "ith this type cf
installation, t".'o-:. r. n ioial flo., is -n:.w-.roxir-ato.d anj
section char "cter.stic' of tiPe model can be determineJ.
'he t.sts were made at a ivn&r-.ic pressure of 1 acunds
per square foot, v-hich cc.rretpor.',s to an air velocity
of about 71 miles r.er hour cf str.:;carJ sea-level condi-
tions. The test Peyrolds number was appro71-
mately 1,310,000. (ETffoctivc- Peynolds number = T'est

CONFIDENTIALT








NACA ACR No. LLF25


Reynolds number > Turbulen-e factor. The turbulence fac-
tor for thie NACA Li- by 6-foot vertical tunnel is ].Q3.)
With the internally balanced arrangements, the gap
between tne forward flap and the cover plates was .00c50.
The gap between the rec-rward flap and the cover plates on
the forward flap varied with flap defiectlor.. in all cases,
for both internal and overhang balances, the gaps at the
nose of the balance ni-L th- forward flap 9an the gap between
the for-vard and rear,:,ard flaps were sealed with thin sheet
rubber.
An exl:ermTncntal3- determined tunnel corre-'tion was
apolIed to the lift. 'The pmgle of attack ar.d hinge moments
were corrected for strea..ml:rie curvature of the flap that
is nduce-I ty the tunnel walls. Th' r: thl useI to deter-
mine- these corrections.is siriar t. h.- theoretical
snaly.ris of referen.: t. Values of crc.s: a:- subject to
an undeterrindr t,_.nncil :'orrc t Io. The .-ats w. re corrected
as follo,-s;
0.'65 --0.007 i2T7 ,0

a =0 a,T + 0.21 -ql + 'c 7)

Ch = chm + 0.075CzTF
where ch denotes any hinge-monent coefficient, cZrp
is the tunnel ift coefficient produced oy deflection of
the flap (arbitrarily taken at aOT = -8 ), the subscript T
denotes a value fr'm the tunnel, and K and F are con-
stants that are functions of balance arrangerr:ents and are
given in the following table:


d/d K ., o.o0 0.50

1 -0.68 o.ocO 0.007 o.o06
2 -.72 ----- .009 .ooS

5 -.76 ----- .011

RESULTS
Lift and hinge-moment chara'.terlstics are presented
in figures h to 15 for each of the arrangements of
"91WI DE TI AL


COTFIDEITTALT,








COi'rTDE T'TIAL


S1- 9";EC double flap testd.-. Pitchiug-moment character-
istics are -!so presented in some of these fi .r-s for
the b>.].-e arr ,ev--.tts h=i."n lift ,,. ,'.:.>e-moment
*:1.r .2teristics trst were considered. reasonably satis-
factc '.o

'r-.e effectivenesss -nq hi .." -rom ent parameters in
table I are based on total I I.: r election. The '.;"n
moments, as means .r'e about the f rvard-fl:- pivot
'.cr:. transferred to th-- rearward-flao pivot f2. '.-:F
.in ..e-ro~ent and el f'ectiveness arraters thus are compar-
sLue- for the various *-.., .-ments tested, re; lesses of
r1.: relative rate of de election between the for-.. r I .--
re .r.,v:,rl fl':. .

DTS1JC? .TjYT

Lift

The slooes of the ] ft cu-rves are in i -nt with
h: ensuredd from preio '.. tests of the .'."A 66-1~ C air-
'"-.il fre fer. e 5). At la:-- itive fl:- deflections
I-,r r e .'- .- s.Hive rn.les of ettac~ 07 becomes ve:"
.reat regr''ess of balance type, size, or relative rates
o1f efictI. : of the two flaps. cT i effect is character-
isti f s; 01-b rrd 'ps. The 3h'... .: of some of the
lift -.rve? at h '.. flap deflections are s' -lar to those
'f r'feren- 5. h:- over.b- .a balance would protrude well
into t !.C s r' i 9 ,1 '..f1'.,1 9ni t' ,I1 -


''..' i l t ef ect v ne s vrr *: oe :- *'-i t ".th
l;-.;r 'ace in ^-/dig i] or all t:-- ? e.-." 1--^ .. :.f lu.i' n,.-.
te'terd i to 1'~ I The d,_Ir. er_ .' n f. i cct liv n;':.? -
'.coi.aunted f r by the iCt ti-t the fr". ,,r< fi.p hji -2
greater eff ."tiveress than ti-. rn:..r-v- rd fl a
d "'d n re. ,-1 f ] z t i or. .*.l. e -. r'.. --A c S
d$ 'I 5 .n-reas3 s th for,:.-.rd- .l., d>fPc tio ie .r*-iscs
for s given total ,feflectin 'Th :''re f c.*LIv
flc:: thus um-",*-s ,- m re sl.. ly ard thIL 1 2.3 elf" tiv fl r
--'-?.'ec fst-r. Th : i f : c v.' n ss s f th-: 'toi t, tirn,
shou h! r cefr-e 0 .r -' .

're- de; r.e se in a,,. ', t j r.-re a e In d,...'.. 1:
learly ,v- d r-r.t in fig ir' i,, v, '- -,ows a rricil tirn
li t co f f t f tent a- iln t tot.-l fT .1 e.ct i.i_ :t t' :r ed
fr mcr fI ur" ThJe st Ilar. t" o"_ t, ~ '.,o sh..... .. -
vure 16 ir..-'1 t..tes that th-.- lift t z se ri I. le-fl .:, ,.-
binations is r,-'-r' nea- a fu'r.,t'.on -f tL'.' totsl l oa.
C'V.T ID.E'T. .L


C' .F .CR T. LTL. 25








'ACA ACR I:o. L h23


deflection than of' either -f the separate flay deflections.
For coi--articcr., the 1'I t coeff:ic-rnt .-f the 0'.201? double
;.L:?i i'lsp reported -In refere-rce 1 has been lootedd in
figure 16. Even though a different airfoil sect,-'. was
a-e ? .ller-chr 'dci fl.i-s ..ri-duce less lift th .an the ln.rge-
, cr .I for .n -i ti';. flat; 'flec:ti-,'. at zer' .ni
ne native ean.:les cf att.,?k" nn at f itude r- t il f,-r a
ho-ri.zontl t9il. Th s.all-h:-'rd Is h:.:'ever, .rodu.ces
even .re-ter lift? than the i r-e--ch.rd fla. t hinh
positive anles of ,ttc1- o atit t re usuall-y 'ritical
f -r a rudd-?r. iure l. ind caSt-9 that tt-,e floo 'with an
in'ternli balance and the floa; vi th 2n overhnA:i balance
n.',e sa out th. sqmr.e li.'.t at t e s' -re fl.-.p deflection and.
at a = slthoa-u -. fltp -'-.th ov'--rhun., balance shows
.'u t r. ; re t r 1 ift. D& ata f' r the C',. "l1 il
flp of rtef ren=,- e n are ; .lso res' n t.ezd 1.n fi ure lo and
th of hesii Dit of the lift ,h-ar-cte ristics a.id t:h se of
the 0C.,3-c Aouble flap should be rtoted.

ilI rIe 'omrent

The hinve-rm.ent ceffl'ients .of the arrcine rents
of balanced double flap tested show.,d little change with
ang-le of rcttactck in the r-egion of low an-le of attack
(figs. L. to 1)"'. T'Ie curves ere t--pical. of r-oat lo'.,-drag
airfoils tested at low scale, ho.'E er, :'n th-it the-
r.fpi.-ly become increase.. ly nonl!'necar b -vond a = 6.
A nrec:ative value for c' is inhicateo for ell of the
arrangements except the 0.5 overhan' balance with
d62
-- = 1, for which ch- was about zero (table I). The

fle.ps w'.th a O.1Oc, or a C.5OcI overhang balance tended
to have a more positive value of ch than the flaps
-.2,a
with an internal balance of equal chord. The value of
ch2 becomes zero and sometimes positive at flap deflec-
tions other than 0 for most of the arrangements tested.

At large positive flap deflections and large negative
angles of attack, the hing.e-moment coefficients change
rapidly from a large negative value to almost zero at
large negative lifts. This rapid change in hinge-moment
coefficient occurs in the snkme lift range and at the
same large flap deflection for Which the slope of theliftcurve


CO IH' DENTIAL


COC FFI DE ITI AL










"'.Ci. ATC NT. TL4F2' Corn'FTEI'TTAL 9


becomes excessively steep. This r'. id chan e of the
-.i',.-moment coefficient ri ht cause reversal of control-
-.Jrface force but, in --.:- case, the force r:"uired to
return tie control surfrce to neutral should be relatively
.. i -

Of ',.e arran-i:r.enrts tested, the double flao with
eit!er a O..c1 internal or a C.c-'- overl..i- balance has
values of c. low encu'- to warrant its consideration

for an sirplane tail control .,rface. T-e overh.anr
balae.ce had a lower value of c, than the internal

balance. -: value remains fairly constant up to large
fla-. deflections for t- r.:ore usable arr.r: -. rts.

Th:. balanced dcule flap and the linked-balance
fl-ip are shown sche~rtically in fi2're 17, which indi-
cates that a linked-balance a'r.n-1orent ... be con-
sidereJ a b.'.c- i double fl -.. .av.; coincident forward
an.: r;a r.-"* -.I ss. thei equations (see fl 17)



1 1




IRi r 2, C r '1
+ --
11

it is thr' o.oi. ibl' to cm-sa'r t,- 1, i ;11:e. -balr.ce f'l '
an-, bala:ice i ,iou:ble fl :: cn t!he Scuis of rate iof flap
aeflecticn L61,./ 0,.

The vsriaticn c.f t-he hini e-; ,;ier.t :-,: --.eters ,"ith
rate of flra' deflection Is s O-. in fi .ire 1. .A1co
-included for conar c.or are the c-'rves fcr a i'.c fla'f
wit'- a O.-COc 1 1"...... cverhan. lance (refer..'Ice 1). 1An
ex.rina.Lticn of fir"- 1, i in.ic 't-s tlat *.-, va -ie

very little v.ith the- ra.e cf refl. icn .r.. cc. ,

is affected to a rc- ste:-r e:.t- :-t. For t.- particular
arirangemeinrt re ste, th'e parai-.tcrr for uc'e baloar.cri


COF i DF!TT TAL








'ACA ACR IPo. L:PF23


COYF IDE TI AL


d.ju'.le f'lap ar;e smnl'Ir t'han those for ti.e fla,- with the
linl:e, overh:r1g b'on fEr.cT .

The stic] hinrc-,,mrnt ,cefficients for the balanced
.o."hle fl' ..r' t.h a 0.5, bal arce r.c. shovn In fli2 re 1':
a: a fLun'tion of '11it cor .ffi-i ent at three qrgles cf
asttc-k. The ch arac fters ics c.f th- 1. inked-belar ce flap
(refer'eie 5. a .fc flaC h:vn: cc nv'ent ional overhang
bl..rnce / reerence ( ', and a '.i3l dzcuhle i].a.in fls:-
(refernce I are 'is3 "nsl 'c'.i in "I.fure 1r for cr"'-
aS '.,c. The control stiC: .'-r .assned to be l i'nitc d to
a nri,, iru. e "Lec tion c -" '. '-e to tal 21 o deflection
w.s sO..oYim-: elvy 5c, r all ofi' the prr.nr er.,--nts except
the .".ou'c ppla'n flae for wh'-h it was 1- 1m lmiti.ng
the tc(L fl.tr.o r'eIfl ..ction as .Lncic trc-J, the curves are
nearly equal ,ith rsesoe?. to x.:--. 1w 1 lift. Thl curves
of figure 19 therefore tel:e into account the r.echanical
ad'antaLe of the system, arnd -ytrspoolstlin to s hi her
lift coefficient '.iwld n: t be vali- unl,-.s the sloue is
increased. The c-.irve fro' the oou ile plain flap, popsented
in fire 1'( ), ',w ta'.:er. dt I.'eCtly '"rc:i re .rcnce 1 for
d .5
1 and the h in-.ner -r,.--,ent co,- '-f 'riie nt r 'vre' based on
du
a cO.*'j fl ap. Pec-.use-. t-. -r. i-rtnulrr !,jble. lain rlan
had a total flap dcflecticn ,-" 6.b', 5 h'.er lift cref-
ficlent *:s o')tained at -to i-c even th,.,u-h the floa
ch'r.'l vwas some that -.hcert,-.

Ca,.s'._nr th,: r-&.v..rd fl-q to :,'e inrcre singly
faster than the forv.er,1 f]ao 'rne- in-rreeed the
sticlk hin-Er-miment cceffi? e.t ic. .y .rticul.r value
of lift :cefricient. '1.e rne rsc '"'.s truF with regard
to the d'o'tl nlain fla3 i'eortcd li ref.-rence 1. This
a oaar.ent 'liscrer, c-, n'l mir r be r. ltir. d in the follcv.wing
manner- The decre -se in tin,--: r.a:'nt ".lt-. incr-as, in
the value eof dt2//1i for the cle.)_e ulair. fity is
indicative of 7-n iine easi nrl. bettr- cF r1mr- for the air-
foil. ny incorporatir-.: a L'alance ti-.t is attached to
th. forward flap, however, the for--:aro flp '.roulcd move
rare slowly as the r. te of flaet defl action d,2/d 1
increasci and therefore the bt.lance vculd th less effec-
tive for the same total flep deflection. Th- curves of
fig.uro 1Q(b) indicate thrt*sthn: link1 t-balsInce flap has
ri-hecr hinFe mnorcnts and ] owe- maximum lift than the


COF Fr DE'TI AL









I'..CA .,CR No. LLF-25


'1 rienc,. d,.jl, & flir -:th .. r r:'-u this : cd-
T
r- s ".:, i r .ci: :- ts' :o e".-' .? t s!.rt,- t .s .-e 2 '-
1 .. s. .i E '"- c -.' .. -p' -.. .: : .. .,. rt:.;* 9 -* '.en 1 T.
.' r 1 V i ; .t L v i 5 -" c c ."-. -I]. ,-:'

71.'s f i? t '. 11- t be e ',: '_ C.... i'- .e 'al a 1 -'re
',. ti, air, the zinc I. :- -- 2'. ::r '.e r.-: t ..,-- h i.c -: s.. t ,
ar'.- & s. ll 1? :a --- [-. :- i C1 :C i F r.e-
q',ert l-. la. r s.-? atl -'r,. r-0' :', tr t.be ,.la~n' double
fi t" an V ir t":-, Ir.'.-i-." 1. .,, .- .ri i, E .
result h '-er, .:r.' ..t .. .r. a l ad: r,r c.:, wi ;tI
a eTh.ord 1 -t .'- : .,:. :.* .... r Ft o'F ,*i -'.C.ap chor.d,
'-.e '." '-- -':- .r ts ir : e .' r' ::.i i ".te t.en the
lif -.t u. r t..: t ".'.. 1- .t t-: Ie'.vat. Thr

data in :c '..e t .. : :.r te .. *: -'0 .'lc .' l :e t'he'
o;-tim m f: r the t '" r.:.t er :P rr, r r" .-_ :51 .r very
larc.e c .r r,'. .,-. :t- r- t:..- t ., c', ." u in te-2ts
r3r.or-ted 'r' r. i .:,.. ': -" till iri t-r'" i;'ate.
'":1tT' a" noe r no '. e .I T .' il '-' n :" : ', tc n ct,-r-
.in.e t : c':: c it.n .c.rC fc r- a "ar:e 7 "s'..r. tr a 3e:
''tl.er tF sts a r':ccC r r.. to '-..c ide the c: tO neces-
s:.y .'for fi- t-,e .c : rI .ur' u ] .c,'r's snIi Sef' ti.n
r-ates The O1.r-vet cf a ccn'..r't n: i c/ ran- bal-t:ce
t-,a t would r- v.'el1 Yhsl r.cec' at s l fl'rp je 'ect,._ rs are
shc'v" for 2."nprn i scr:. :. f:icr= l' T-pe = c. .ta e n f a
oCUtlls-21a3 'Lrra-:;n.n" are et. :."t.

F'l p c cill' t': '.'-noted fcr t ? ar.i'?r-,,en 1.:s f'
'?bal s.'.eo d.1c' ,1 f'l p &.a ..,-r t .n of th.e **-...e tc st. -...
Ai:1 r'njeS i.n ".'i h t.'is .s i]Is_ ..-. o t're '"Ia *:ccurr.e
are sho.n b'r desnia ? i :~e i- .' th- ir. c-!.crn.-: cur ve oe
fi 2'ure3 i te 15, *im cccillatior. v'.? similar to -that


Drt
rep'c ted in ref ererce -..




Increm.Tent : siro'il section prof'le-drag enefficient
caused by flan d.flecttn .tai.-. totnl fla. deflection
at a, = 0 is prezetee ia-. fi, :re 2') for d e fr ran e-
nents tested. ?or n?.l t.t. l [Iin n lec tins (.n-r- f20
the type of L-lanc. :-d lit le c f'ct on t.n- roafile-draq
co, effi ient for. ll srr. -.g r nts c-stEr.. At: lar-'-e t.D t9 1
flan deflection-, ho-.'e,-o r, the :fl p viTh an ,'.-:a ri .
balance had mr.or :ra. ~'r.n .it-h n;-, internal lan ne. .
h-his result seems reasonable 7- c:-use an cver.hn,-. balance


COITFI DETTTI IAL


CO'T DLEI 'TT .L









NACA. !.CR 1N L4!'23


t r ini c' 'r- l ti .' s. .-;',nirat -r, -it hij.-n d elections
"*it, 9. *"cOs,_-,,l; ncni" l :a! .n irrea?:. in -r .,,. ,..t hrr.ie ;l-.n.
'" fie?,t'cns, the ri- ar '.lcrea :-s *.. r n -' crc vse ir.


-Th increrment cC c -rfo l" e t on iro'f .le e-ta-
"cc ff'0.e.ril CtallS*' b,' R. l .cn iL a'lic, '."m s. Las
f"rcr.lion of rect..-p 1 t n,:ffi .r t in. fiinre 21 in
vl.ich r 'i j'rs r0o ,"r,] 'j h-.. e 1 ee ? c rc.o' ,ed .r:d r, ..:' otted.
T-,.e relative rosit or of t}'.r intc rn.al- balance curves
m.r-e an i, r_.i, t i.on cf 'f,' n ti'.'urt seoura t iLn occurring
r.,r t} d"t:, .-,le -f a C-,tr; in.t c..- --. The upocr surface is
riot orol-en by t'-e cr.trusion o. a balar.ce that ;.vnld
preci.:'itate -ecarnti,.-n, L- .:- thi c2ss.- vit'> -rn ov,-rhran;
c:,I nc-".. It is *ov:..en t'tr. in tie i-- i,., f A n'.]-er lift,
t! e rce..l tant c- ;.'. r f t'-. r irf 1] ".:r d J-,.'d5 1 s
'ncr. in: *: te:,-dc. r. rn cz Fa ire.-si rr r-;- ra i r.t .-- v r the
a rfoll ',hi,. indr.tces l]_atcr a"- ii les pron-. .rced separ.a-
ton than w! re. the flo s mcr c t t .c s-ne ro.te-. ..'c m-
,.ari Json c"cf t-:. dr.e 1r.t" ..gains lift for tn- si.crt-
.]-r d :.,-ubl,. 1:.-i fl- of '- f-:'..r -1 nrd ..ic- lonr er-
chcrd intern-l ly bal.aicee' d lle i -.) :; t;' presrrit
re" :ort Ir. j r-te. t:at the rI r. e-or-:r, .? ": fic:le-.t
f t' an" .n.r ".Icul ]. lit i: c ''e ,? ..-i t ',a~s reac-p c- [L o-r.e-
what hi. h-:-r fcr te dou,. le-f'!.r- arran: :-m t wi th t-'-
shor t chrr;.


P tcht -ir I oF : :. .t

rThe pitch in-r:c-nr:' it curv.es .'.re llnPar for sn-.all
fl op collections hi:t chanc-a ra-.r ;,- th 9n;le of attack
at larc- fla n 1 orctirm.rs. The rari-d dec re:ase in pitching-
noine'nt coef ic er.t at neEc t 5 ve an !-E- s of at.ck "ar. larre
positi'.'e flan d-?flect :,rr tn th-3 Fs-e regain ir n which
values of hir,e moment -id lift nr,-e._ re a. 1-'2l v is char-
acteristic cf s.all-clh-.rd flps. "i tchin.ng-:crr.ent para-
meters, measured fro". the dta. .:,, figures ;, to 1 and
from some data not shown ir. these figr7.es, are riven in
table I. thesee values are an in-ication of the locations
of the centers of lift caused by ar.,1l cf attack c.nd bj
f an deflection.


CO TI0 DE TT J.


CON JFiDENTI.L










NIAC. ACR Yo. 1,4 25 3


CONCLUSIONS


The results of tests of an ":.-'"A 66-009 airfoil with
a 0.30-airfoil-chorcd strai:ght-contour double flap haviri,;
an overhren: and an internal balance of various chords and
several rates of deflection for the two flaps indicated
the followin- conclusions:

1. T':-e balanced .-cuble flap produced lifts about
enual to a single plain flao of the same chord and at
the same time pro.,,ce.- closely balanced hi,-"e moments.

2. Hi- lifts and low bi.n.:e moments were obtained
with a double-fl'-, arv:r,~nmcnt if either an cverhango or
an internal balance !hiving a chord 50 percent of the flao
chord was incp.:,rated on the forward fla-.. The data
slso indicated t.-.t, for the arrnnc-eients tse'ed, the
forward and re i--ard 1f ',)s sh..'l' de iect ,t so,.,t the
same relative r cL-.

The r.ai iv r t f e-le tio:- cof' the t'.c flaos
had a larc-ce efrf:ct on t..-e I.in.-e :mc-.,et-.t duc to fl.ap deflec-
tion arri a -mall efL'-:-ct on thI 5r-. r.c..:-e t du' to a rle.
of attack.

IL The flap ha.'vin i on ove:.rhang. ':al dance sho Ve a
lo'-.-r vali ce of the h'.n --. icr.e .-t r 'a* .. t du to fla
cdeflection t'.-ern the irterinol ly ~ l acce-i fla .
5. The r,3pld change in '"i.ge-m:ment coeff'cient at
larre fla' deflections and anri.es cf attack of opposite
sign rnmay cause reversal of contrc1-surface force : however,
a relti',ely srmll force should be requir-d to return the
control surface to neutral.

t. dcbnble-fla- arrangement incorooratirLg an
aerodynamic balance is a very p-ror!isin.. arranjr.ent.
Inasru.'ch as this double ilap is merely a large lea:ling
tab, its inr.orpcraticn .n the tail 74f an airnlpne should
not present any pa.-ticularl7 ,W"ffieult probletr. There


'0FFITTD'T TTIAL


COF I DFiFTIAL










NACA ACR ITo. L4F25


are rot enc',Fph data available, however, to determine the
optimuin chord for a large lea:'.in: tab and further tests
are necessary to find the ontimum flap chordr and r.:eflec-
tion rates.


Lrnngley ;:e-rlal Aercnautical Laocratory,
utional A.dvisory CcnrLTitteL for Aeronautics,
Langley Field, Vs.


CONFIDENTIAL


C00FIDE'TI AL









NACA .LC? No. I,.F25


REFERFI'CES


1. Sears, Richard I., arnd Purser, Fa'~l E.: 7Yind-Tir.nnr-l
Investigation of Control-Surface J'`.iracter'stics.
XIV A.CA 0009 Airfoil with a 2-rc -cr.t-Ch.rd
Douuble Plain Flap. !i.'CA AT'F :o. ="', 1943.

2. V:enzir--', Carl J., and Harris, S7":-.s A.: The
verticall 'irinc T-Inrtl of the :..tio:,nal Ac'-isory
Conrrimittee for Aeronautics. NACA "e. No. 587,
1'751.

5. Se-..s, Richa'rd I., and Fo-._rl, F. P o, Jr.: lind-
unre.el Investi-;t:"on cr' Control-Surf'ice Chars-cter-
istics. II A T:r.-? Aerocd-r.-"ic -i..ne of
Various !Uos3, E'r-.sies with a 30-P"cent-C1.c:r Flap
on an TACA 0CC:' Airfoil. ".C' .-~ Aug. 19C.

41. Swanson, Robert S., and "-ll, Thomas A.: Jet-
Bc' C ',rr- CrrC-ections for et,'ection-ln.r:e I,'c1els



5. Sears, r ichar .:c li(cl obert '. '"end-
Lurnel Inve0 cat.on : f C.,nt-rol-Surfsc,- Ch7aracter-
istics. X'"III A Lin-ecd "erhanL AerodJ nar'lic
7alar.ce. '7.A ACF ;;o. L 2', 1A C.

6. Gill's, Clarnene: L., nd Loc Tinnel Inrve tija icn 1 c Cc:inrcl -Sui face Charac tr-
istics. XIII ario. F1ao ("'erL-.ar s T.:ed v.'ith
a C-?Percen.t-Ch r .. Fla-' on 'r: ;ACA C-L', .airfoil.
T..CUA -ACC :co. 3520, 1D L .


CONFIDE N.TI:


CO?:FIDDE"'TI L








"ACA ACT? o. LL-F2)~


TA LE I

I[V'COPhiATION CO]C0G\;iI::G A5F%,n TEMIJTS OF


B..Lr;UC ), OULE :L.- TEJT'ED


N.-.TIO::AL LDVISZORY
CO"'I TTEE FOR LEROI:t.UTICS


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CONFIDENTIAL "a
(a) Internal balances. NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS.
/Igure 2.-Arrangements of bh/anced dou/le-flap
model tested. /VACA 4-00? airfoil hayin9 a
0.30c double flop.


CONFIDENTIAL


Fig. 2a






NACA ACR No. L4F23


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(b) Overharn ba/laces.


figure 2 Concluded.


NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS.


CONFIDENTIAL


Fig. 2b







NACA ACR No. L4F23


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CONFIDENTIAL







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;' NATIONAL ADVISORY
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