Pepoon, Philip W

English

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ARB No. 3E20 
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS 
111~1)() 
ORIGINALLY ISSUED 
May 1943 as 
Advance Restricted Report 3E20 
FREE- SPTImJNG-rruNNEL TESTS OF A MODEL OF 
A CANARD AIRPLANE 
By Philip W. Pepoon 
Langl ey Memorial Aeronautical Laboratory 
Langley Fiel d, Va. 
f' .Ill' RTY CC JET PROPULSION LABORATORY LIBRARY 
CALIFORN IA INSTITUTE OF TECMNOLOGY 
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-
mcally edited. All have been reproduced without change in order to expedite general distribution. 
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lLATIONAL ADV I SOR Y COMMITTEE FOR AERONAUTICS 
ADV_LICE RESTRICTED REPGRT 
ii'REE-SPINNING- TU1Bl'EL TEf;TS OF A HODEL OF 
A CANARD AIRPL ANE 
By Philip W. Pepoor. 
A series of tests taS ~ade in t~e TIA CA 15-foot free-
spinninG tunnel to s tudy the sp i n ch~rac t eristics of a 
1/24- scnle mocl el of a h~7pothetical cE.n3.rd airplane, ... rhi~h 
was designed to be the same size and to ~ave the same gen-
eral aerody~am ic ch a r acter istics as a Boeing B- 247 air-
plane . The mod el had a sino le fin and rudder at the rear 
of the :"ll.selnge . 
The model spun nornally and had excellent rec overy 
characteristics . 1 oder a te vari ations in maSs distribution , 
cent er-o f-g~av it y location , or changes in horizontal or 
vertical control surfaces had only moderate effects upon 
the r ecovery char a cteristics of the model . A fe, spins 
we re very oscillatory . 
IHTR02)UOT IOH 
The win~ lo nding and the power of present-d~y air-
p l a ne s a re co~stant ly increasin~. As a result, the slip-
stream p ro duces uncertain t y in ana generally has adverse 
effects on the stabi li ty and the control characteristics . 
With a view toward overco~ing these difficulties, some 
designers are rec ons i d e ring the possibilities of the 
canard airplane . Becau~e data on the 8pinning c~aracter­
istics of this type of airplane are l ack ing , tests were 
c on du ct ed in the NAOA I5-foot free-s pinnin " tunnel to de-
t e r mine the spin ~nd re c overy characterist ics of a canard 
airpl ane , ~rig inally de~i7nod for tes ts in the ~ACA gust 
tunnel ( reference 1) , of the saLO size and "ith the Same 
general aerodynamic ctar a c~ eristics a s a ~oo in g B- 247 air-
p l ano . 
The mode l was tested no t only at an estimated normal 
lo ading condition but a lso with the c en t er of g avity moved 
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forward a nd rearward , with the lo ad in g increased and de-
creased a lon ~ tho fuselage and alon g tho win g s, and with 
the aro ~s of t he horizontal and vertical control surfaces 
incroased a nd ~ccreasod . Invertod s p ins were test ed for 
only the norma l loadin g condition. 
SYlv1BOLS 
z/c r:J. tio of distance between center of g r av ity and 
centor line of fuselage to mean g eo me tric chord 
x/c r a tio of dist a nce of center of g r a vit y from leading 
edge of mean geometric chord to mean g eometric 
ch ord 
IX, 17 , a nd IZ 
Y , and 
moments of inerti a abo~t body axe s 
Z , respectively 
x, 
b \..ring s pan 
a a cute angle between thrust axis and vertical , degrees 
( approx. equal to abso l ut e 7s1ue of a n gle 
of at tack a t plane o f symmetry) 
a~g le b etween Span a~ is and horizont8l , degrees 
(whe ther i nne r wing ti p is up or down is indi- -
c a ted on ch a rts a s U or D , res pe ctively) 
V full- scale true r a te of de s cent, fe et pe r second 
o resultant angular velocit y , r ad ians per second 
: Ib r a dius of sp in of airplane center of Gr av ity divided 
by span 
angle of sideslip , degrees ( ~osi tive is inwa rd in 
spins to p ilo t t e righ t) 
AIJPARATU[l AND HODEL 
T~J. e tests were made i. the HACA 1;5-foot free- spinning 
t unnel in the manner descr ibed in reference 2 . 
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~~e ~odel used in the present tests ~as a 1/24-scale 
model of 11 hypothetical c anard airplane hnvi~g the general 
character~stics given in the following table: 
Wei€;ht , 1 b . 
Wing S::?an , ft ' 
Over- all length , ft 
Gross wing area , Sq ft 
Wing loading , I b/sq ft 
Vling sectiO!l . 
Wing illean geometr i c chord , ft 
Ratio of vertical tail leI gt: ( distance froLl 
c . g . to ru(1c1er hinge axis) to wing span . . 
Ratio of h~rlzontal tail length (d~stance from 
c . g . to elovator hinge axis) to,·lng span ' 
Stabilizer aroa, sq ft 
Total a rea of elevators , sq ft 
Fin ar e a , s q f t 
Rudder 2-rea , Sq ft 
14 , 600 
74 
66 
836 
17.5 
• ~;ACA 0015 
11. 3 
. 0 . 425 
0 . 249 
135.9 
47 . 5 
28.8 
30 . 7 
Tho model , which hetd been prev iously useCl. for th~ gust-
tunnel tests reported. :i.n ref e rence l, "!aG constrJ.cted 
p r inc i:.' :11 1 :y 0 f b a 1 s a \.! 0 0 c1 . ':!: h e f usc 1 a. ; 0 was 1... 0 11 Oli an 0. 
the wi~cs were of spar and rib construction ~overed with 
tissue paper . Because this model was representative of 
tho c3n ~rd type of airplane and did not represent any par-
ticul~r air~letn e, engil e nacelles Gnd other ~rotuberan cos 
were not inst~lled . Lead weights were suit~bly disposed 
to give the proper total weight and maSS distribution . 
For the sl)inning tests, the l.o del Fas mod ified by the ad-
dit i on of Dovable control surfacas and by the installation 
of a re~ote-control ~echanisrn to Dove the ru~der for re-
coyer;? tes'~s . 
Ph oto~r ap~ s of the mod~l are shown in figure 1 . Fig-
ure 2 gives a three- view drawin g . The original and the 
modified t~il sQrfaces are shown in fig~re 3 . 
T EST C OnD I ~ I 0:::) S 
The Tll 0 (1 e 1 ','I aGO a 11 a 8 t 0 C. tor 811 r e :..~ e c1 t the nor III all 0 D. d-
ing o~ the ~~pothetic~ l airyJ,ane nt an equivalent spin 
alt i tude of 7200 feet and corresponded to the following 
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full- sc'J.lo Df).S8 distribution \lith 1,and ing ge1.l' retracted : 
Weight , 
x/C 
z/c . , 
:ib 
I X , s 1 u §,;- f t <3 
I y, G J. u g- f t 2 
17. Sl~l ~~-ft 8 • 
,-, ' -
14,600 
O. 35 : Lh e ad. 0 f 1 . E . 0 f 1: . G . C • 
0 . 024 below cen~er line of fuselage 
33 , 500 
58 , 200 
8 7, 300 
TilE) follo 1;·ing ty})ico,l ;- ;J.ximum control defle ctions 
were uso~ for these teste : 
.Rndcler 
Ji]levatoi.'s 
Ailero:1.s 
RESULTS 
. 
25° up ~nd 35 0 down 
30 0 u) und 20° down 
T~e re~ults of the tests are pr esented in chnrts 1 
and 2 . ~~"le s°,jeo.d:,r-spin rar ,::.netel's presented i _ Lle charts 
we~e determined b? the DethodG describe d in reference 2 
~nd ~~ve been converted to corresponding fQll- s c~le values . 
The da'c.:. pj.' esented are for ' erect and inverted spins to the 
pilot ' s right . Control positionR indicated in the charts 
a ::-e fO:j: ti:.e st.e3.u;r sfin prior to recovery attempts . It€!-
cover" \"I .J. S att em~~)tecl , 2.n ever~- C'1.8e , by reYersing the 
ruduer ra~idly from full with t o full against the sp in. 
~ecovery is Le asured by the number of turns the s p in-
ning illodel ~akes from the ti~e th~ ru1der is Doved until 
t. e pin rotation CB'3.Ses . 
D IS CUSS I OH 
fIQ!:.gQ,1._1.9.,§:.9:i.~,g . - The effect of vQ,rious contro l p osi-
tio~s upon the spin nnd recovory charucteristics of the 
model Hiti1 normal lo ao.ing is shovTl in chart 1 . Quantita-
tive results ~ere not obtained for the spin with ailerons 
neutral ancL sti c l: b:lc~: ( elovators do\·m) because the l;lOde l 
wandered about exces8~vely . Data were obtained for a il er -
ons with t_e spin (right aiJeron up in a r"eht spin) and 
also for aile r ons agaiLst the spin . These spins were quite 
oscillatory ~nd recoveries were rupid a lt hough the spins 
oj er e ;.'" ° t s t e ep • 
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When the stick was ~orward (elev a torn up), t he spins 
were steeper b~t recoveries wer e slightly slower than for 
stick neutral or b a ck . 
Flacing th e ai lerons f ull wit h the sp i n resulted in 
f a irl y flat oscillatory spins when the stick was neutrn l 
or b2,C~: and in a steep s p in when the stick vIaS forwa rd . 
RG~nrdlcss of elevato r or ailer on position, the 
s p ins obtained were oscill at ory and reco veri es were rapid. 
The effectiveness of the rudder over the r ange of atti-
tud es covered is p robably a r esu l t of the fact that the 
rudder ~as not shielded by the tail plane as might occur 
for a conventional design . In gene r al , the recoveries 
made b~T r udcler reversa l wLen the sti e l: \'f<),S bac~: reJuJ.ted 
in stalled glides ; whe re as recoveries m~de b~ rudder re-
ve r sal dhen the stick waS forifurd resulted in dives . 
Ali~E.~Qi~-.1..22.d i Qg~ • - E 0 d e r a t e for e-an d - aft v a i a t ion s 
in the center-of-gravity location of tho model amounting 
to 5 ~ercent of the mean geometric chord had but snaIl ef-
fect UpO.1 t'le spin and reco'very char::.cteristics of the 
mocleJ. . i'Then ';;he center of grnvity \"!i'""S [.loved forward , tho 
spins were slightly stee~or and l ess osci ll ~tory than for 
the normnl center-of- grnvity location . 
Extending or retracting maSS a l ong the fuse l aee 
(changing 1y and 1Z by 15 pe rc ent of Iy) or oxtend-
ing or retracting mass ~long the wings (chan~ing IX and 
1Z b7 26 percent of IX) had but small effect on the spin 
and recovery characteristics . 
070r the range of loaQin., conditions tested , spins 
obtained ""ith the sti c ~ for':lD.rd showed hibher values of 
angul::'.r velocity [2 [tnd of Ob/2V th:>.n spins idth sticl;: 
back . 
Effects 
order to detormine whether the spin char~cteristics were 
criti cnlly dopcndant on tho size of the tail surfuces , 
te sts ~ere mad e 1ith the vertical- tail hcig~t co~stant 
and vlit''l (1) fin [trea increaced an'd cle(;reasecl 40 perce:Qt , 
( 2 ) rudder ~rea increaGe~ and decreased 40 gercent , and 
(3) fin and rudde a r ea sim~l taneous l y increased and de-
creased 40 percent . A similar series of chnnres was made 
in the hor izo ntal surfaces with the sp an co nstant . ( See 
fig . 3 . ) 
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The effects of these changes were not very marked. 
There V&~ SOBe tendency for increased r udder area to giv~ 
slightly f l atter spins but faster recoveries ~nd for de-
creased rudder area to have the opposite effect . Decreas-
ing the size of the hor i zonta l t a il plane tended to make 
the spins steeper and. the recoveries slo l'rer ; in creasing 
the size of t~e horizontal tail p l ane had the opposite 
effect . 
lE.~~£!~~_~.~~~~ '- The noelel ,'lould not spin inverted 
unless the ailerons were with the spin (stick and rudder 
controls cro ssed in the stead~ spin) or unless the ai ler-
ons we re neutral and the st ick forward . Recovery by 
rudder reversal was r a~id fro~ a ll spins obta:ned . The 
re sults are p resented in chart 2 . 
CONCLUDING REMARES 
§l'om the 'cests of '1 1!24- scale model of :.t hypothet i-
c 1 can ;~rd airplane , "hich hac1 a sincle fin and rudder at 
the rear of the fuselage and a tail length illGaRured from 
the centel" of g r a7 it y to the hip..c3e line that vinS conpara-
ble to that of convontional airpla~es , the following con-
clusions have been ~rawn : 
1 . ~ he s}in chnracteristics were genorally sioilar 
to those for conventional a irplanes . 
2 . AlthouGh spins for SODe te s t conditions !<lere fairly 
flat , r GCOve:C;'T by rudder revers al IV ,s rar id in every case . 
The effectiveness of the rudder was apparentl~ due to the 
fact that , for this desien , the rudder is not shielded b~ 
the tail pla:'le . 
3 . j'i ocLe::.' D. te changes in maSs distribut i on and tail 
size difi not seri ous l y alter the spin characteristics . 
4 . ~he node l Buun inv erted for only a few control 
positions . 
It should be re a liz ed that t~ere hRve been other 
p rojec teo. arrangements for c anard airplanes , S01:'e __ aving 
four engines ~ith a lar ge increase in weight along the 
.... lings anc sO :"1 e having - ertical tail su r faces ;,10untec:' on 
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th e wing tips , The spin characteristics of these types 
you l d be expectel to d i ffer froM the characteristics of 
the design studied in the present investigation . 
Lang1 eJ" i'ienorj.a l Aerenall.tical L:1.boratory , 
N~tional Ad7is or y Com~ittee ~or Aeronautics , 
Langley Fi e 1~ , Va . 
REJi'ER]H! CES 
7 
1 . Do~ely , Philip , Pio~ce , ~aro1d B ., and Pe poon , Philip W.: 
iioasurements and Analysis of the i:otion of D. Canard 
Airplg,ne :iodel in Gusts . ::: J . j,'Jo . 758 , NACA, 1940 . 
2 . Zim~er rna~ , C. H.: Preli~inary 
:'r e e-S p inn i)_g '1:1 ind TU!1n e 1. 
Tests in 
Rep . ,-.:; o . 
'che lILA . C. A. 
557, ~~CA, 1936 . 
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CHART 1 
EFFECT OF CONTROLS ON SPIN AND RgCOVERY CHARA~TERISTICS OF :4 -SCALE MODEL OF CANARD AIRPLANE - ERECT SPINS TO PILOT 'S RI GHT 
[Nor mal loading ; re cove r y by rapi d full rudder reversal ; recovery a t tempted from, 
and s teady- spi n data presented f or , rudder-wi t h sp i ns] 
of spin to teet 
~ 
Too os ill pi tch c t a tory in 
o test 
C ompl etely. 
~ 
AILERONS AG-AINST 
-20 
o to 8U 
. 24 -1-13 
} 
. 4 i 
C ---
~~r o  
t:J1'Q 
en 
ttl 
~ ~l 
o to ID 
1 , 1 
AILERONS 
Range ot va l ue s 
during spi n 
~. 
38 to 57 
127 
! 
a ~ 
v ~ 
'l\lmS tor Recovery 
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~ 
I» 
a 
I» 
a 
b' 
e; 
... 
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CHART 2 
EFFECT OF CONTROLS ON SPIN AND RECOVERY CHARACTERISTICS OF ~-SCALE MODEL OF CANARD AIRPLANE - INVERTED SPINS TO PILOT 'S RIGHT 
[Normal loading; recovery by rapid full rudder reversal; recovery attempted from, 
and steady-spin data presented for, rudder-with spin~ 
Too wandering to 
t~~ 
:2 
~ ;; 
rzl IJ 11lr&. 
NO 
NO 
~w~ ~~ 
CIllO 
-\----
NO 
NO 
-~-
NO means model would not spin. 
40 to 50 17D to 26D 
+1 
4 _~ STICK AND RUDD--
CONTl\OLS CROSSED IN 
STEAD'.! SFIN) 
---
a: ~ 
V ~ 
'l\lms for recov61'1 
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a 
! 
~ 
(a) Three-quarter front view 
(b) Side view 
Figure 1.- Model of hypothetical canard airplane. 1/24 scale. 
l-2.22 
z 
~ 
o 
~ 
~ 
~. 
~ 
~ 
~ 
~ 
a. • 
M 0 
• 0 o ,~ I to) '" , I .., 
I 
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,."J \ ~ 
18.5" 
rlgtlrt!l Z. - TlJree wewJ or model of IJypolhef/C'Q'/ con~rcl · 
. I I OlrplO'~ ;!'I- sco/s. 
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-_._--- -- -- - - -- ---
--- ---- .............. 
~\ 
- ---- --- - ----- ----
--- ---- ---~ ~/ 
Z 
l> 
(> 
P 
././ AREA 
/" INCREA 5 ED 
/" - - 40 PERCENT 
./ 
./ CONTROL 
/" ~RIG/NAL 
./' SURFACES 
/ _____ AREA DECREASED 
-10) HORIZONTAL 40 PERCENT 
TAIL . 
/7. / 
/. / 
/ / 
/ / 
/ / 
/ / 
.... , 
, 
\ 
\ 
\ 
\ 
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\ 
~ 
~ 
\ 
\ 
\ 
/ ;' 
/ / 
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--
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(0) VERTICAL TAIL. 
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Figure J - Orlg/nol ond mod;fied 1011 .5y/rroce05 
te05led on .e~ scale model of co nord olrplo/le. 
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Free-spinning-tunnel Tests of a Model of a Canard Airplane

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