Free-flight tests in the transonic and supersonic speed ranges utilizing rocket-propelled models have been made on two pairs of 1/9-scale Convair YF-102 airplane wings with elevons to investigate the possibility of flutter . These wings had modified 60 deg delta plan forms with the trailing edge swept forward 5 deg. The aspect ratio of two exposed wing panels was 2.19 and the wings had NACA 0004-65 (modified) airfoil sections. The model wings and elevons were dynamic-scale models at sea level of the full-scale wings at 20,000 feet. The first set of wings developed elevon buzz near a Mach number of 1 during both power-on and coasting flight at amplitudes of equal to or greater than +/-4 deg.. The second set of wings did not develop the elevon buzz experienced by the first set but, as the model reached the maximum speed of the test (Mach number 1.93), one or both of the wings suddenly failed, possibly as a result of aerodynamic heating or high stresses imposed on the wings at separation from the booster. No flutter was experienced during either flight

O'Kelly, Burke R.

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NACA RM S ~ 5 4 ~ 2 2  
NATIONAL ADVISORY COMMITTEF: FOR AERONAUTICS 
RESEARCH MEMORANDUM 
f o r  the 
U. S. Air Force 
FREE-FLIGHT TESTS OF 119-SCALE CONVAIR YF-102 AIRPLANE 
WJBGS AT TRANSONIC AND SUPERSONIC SPEEDS TO 
INVESTIGATE TKE POSSIBILITY OF FLUT'I'ER 
By Burke R. O'Kelly 
Free-flight t e s t s  i n  the transonic and supersonic speed ranges u t i -  
l i z ing  rocket-propelled models have been made on two pa i rs  of 119-scale 
Convair YF-102 airplane wings with elevons t o  investigate the poss ib i l i ty  
of f l u t t e r .  These wings had modified 60' del-ba plan forms with the 
t r a i l i n g  edge swept forward 5'. The aspect r a t i o  of two exposed wing 
panels w a s  2.19 and the wings had NACA 0004-65 (modified) a i r f o i l  sections. 
The model wings and elevons were dynamic-scale models a t  sea l eve l  of the 
ful l -scale  wings a t  20,000 fee t .  
The f i r s t  s e t  of wings developed elevon buzz near a Mach number of 1 
during both parer-on and coasting f l i g h t  a t  amplitudes of equal t o  or  
greater than fbO. The second s e t  of wings did not develop the elevon 
buzz experienced by the f i r s t  s e t  but, as  the model reached the maximum 
speed of the t e s t  (Mach number 1.93), one or both of the wings suddenly 
fai led,  possibly as  a r e su l t  of aerodynamic heating or high s t resses  
imposed on the wings a t  separation from the booster. No f l u t t e r  w a s  
experienced during e i ther  f l i g h t .  
INTRODUCTION 
A t  the request of the Air Force, f r ee  -f l i g h t  rocket-propelled-model 
t e s t s  a t  transonic and supersonic speeds have been conducted by the 
Langley Laboratory t o  investigate the poss ib i l i ty  of f l u t t e r  of 119-scale 
Convair YF-102 airplane wings, This paper presents the r e su l t s  of the 
f i r s t  two t e s t s  of a ser ies .  The t e s t  wings were dynamic models of the 
ful l -scale  wing and were equipped with spring-restrained elevons. The 
model wings, tes ted  near sea level ,  simulated the ful l -scale  wings a t  
20,000 fee t .  The f i r s t  model was tes ted  t o  a maximum Mach number of 1.31 
t o  investigate the poss ib i l i ty  of f l u t t e r  i n  the transonic and low super- 
sonic speed range. The second model was tes ted  t o  a Mach number of 1.93 
t o  explore the  poss ib i l i ty  of f l u t t e r  a t  higher supersonic speeds. 
Restriction/Classification 
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Restriction/Classification Cancelled
CONFIDENTIAL NACA RM ~ ~ 5 4 ~ 2  
SYMBOLS 
aspect r a t i o  of two exposed wing panels 
model normal accelerometer reading 
frequency, cps 
Mach number 
area of 'two exposed wing panels, sq f t  
time from launching, sec 
velocity, fps  
elevon deflection, deg 
atmospheric density, slugs/cu f t  
MODELS AND INSTRUMENTATION 
Models 
The t e s t  vehicle used i n  this investigation was a cyl indrical  body 
with a parabolic nose. The t e s t  wings were mounted i n  an aluminum-alloy 
casting which was a s t ruc tura l  par t  of the body. A n  oversize s l o t  i n  
each side of the casting received the undersize root attachment of each 
wing and bol t s  were ins ta l led  t o  hold the wing i n  place. A thermosetting 
polyester r e s in  was used t o  f i l l  the spaces between the root attachment 
and the w a l l s  of the s l o t .  Past experience has shown t h a t  this procedure 
r e su l t s  i n  a mounting which has more than adequate strength. Two ve r t i ca l  
f i n s  were attached t o  provide direct ional  s t a b i l i t y  and s t a b i l i t y  i n  
p i tch  was provided by the t e s t  wings. 
The lower speed model (M 5 1.3) contained a ?-inch cordite rocket 
motor which, a f t e r  model-booster separation, accelerated the model a t  
about 8g through the f l u t t e r  t e s t  range. The higher speed model (M <= 1-93)  
used a high-performance air-to-ground (WAG) rocket motor modified t o  
three-fourths of i t s  or iginal  length t o  accelerate the model through the 
f l u t t e r  t e s t  range a t  about 20g. The lower speed model used an HPAG 
rocket motor booster t o  accelerate the model t o  a Mach number of 0.76 and 
the higher speed model used a Deacon rocket motor booster which provided 
a Mach number of 1.27 a t  separation. 
CONFIDENTIAL 
NACA RM ~ ~ 5 4 ~ 2 2  CONFIDENTIAL 3 
The general layout of the models i s  shown i n  figure 1 and a photo- 
graph of one of the models is  shown as figure 2(a).  A photograph of the 
higher speed model with i t s  booster on the launcher is  shown as f igure 2(b).  
Weight and balance data f o r  the models a re  presented i n  table  I. 
Test Wings 
Two pa i rs  of Convair YF-102 f l u t t e r  wings have been tested i n  t h i s  
investigation. The wings were 119-scale dynamic models of the ful l -scale  
wings and had modified de l ta  plan forms with the leading edge swept back 
60' and the t r a i l i n g  edge swept forward 5'. The wings had an aspect 
r a t i o  of 2-19 and NACA 0004-65 (modified) streamwise a i r f o i l  sections. 
A sketch of the wings giving pertinent dimensions i s  shown i n  figure 3(a).  
The wings were dynamically scaled models equivalent a t  sea l eve l  t o  
the ful l -scale  wings a t  20,000 f e e t .  Similarity requirements were based 
on unity r a t io s  of reduced frequency, mass ra t io ,  Mach number, and struc- 
t u r a l  damping. In order t o  meet these requirements, the model wing 
s t ructure was b u i l t  up of r ibs ,  spars, and skin. The s t ruc tura l  charac- 
t e r i s t i c s  of the t e s t  wing were scaled down from the prototype according 
t o  the r a t io s  l i s t e d  i n  table  11. The components of the t e s t  wings were 
bonded together with an adhesive because the usual method of fastening 
with r ive t s  was not feasible.  Two dummy spars were b u i l t  i n to  the model 
wings as a precaution against skin-panel f l u t t e r .  The s t ructure of the 
elevon, because of i t s  small s ize,  was not duplicated on the model. 
Instead the elevon was made of a balsa core having hardwood pads a t  the 
places of attachment and covered with a t h i n  (0.012 in . )  aluminum skin. 
Flexure pivots ( f i g .  4 ( a ) )  were used as the method of attachment rather  
than hinges because of the poss ib i l i ty  of binding i n  the hinges. Leaf 
springs attached between the elevons and the wings simulated the tors ional  
s t i f fness  of the elevon actuator and were designed t o  provide the scaled 
rotat ional  frequency of 243 cps. In order t h a t  the mass d is t r ibut ion  of 
the model and ful l -scale  wings would be comparable, lead weights of the 
proper mount were fastened i n  the w i n g s  i n  the proper places. A photo- 
graph of the wing s t ructure with the skin and elevon removed showing the 
r ibs ,  spars, weights, and flexure pivots is shown i n  figure 4(b). 
Prior t o  the f l i g h t  t e s t s ,  the models were vibrated i n  the labora- 
tory and the natural  frequencies and node l ines  of the wings were recorded 
and are  shown i n  figure 5 .  Each model was suspended by shock cord a t  i t s  
center of gravity where it was vibrated by an electrodynamic shaker. 
Although the wings were fabricated al ike,  the wing frequencies and node 
l i n e  locations varied widely between models 1 and 2. The natural  rota-  
t i ona l  frequency of the elevons could not be found, even though there 
were node l i n e s  close t o  the elevon hinge l i n e  a t  240 cycles per second 
on model1 and a t  222 and 236 cycles per second on model 2. Camparisons 
of the scaled measured frequencies of the ful l -scale  wings with the 
CONFIDENTIAL 
CONFIDENTIAL NACA RM SL54L22 
measured frequencies of the scaled wings mounted on the models is  shown 
i n  table  111. Frequencies and node l ines  f o r  the ful l -scale  wings may 
be seen i n  reference 1. 
Structural  influence coeff ic ients  f o r  one s e t  of the wings were 
measured by Convair and are  given i n  reference 2. These influence 
coeff ic ients  were normalized, averaged, and corrected f o r  f l e x i b i l i t y  
of the root attachment by Convair. Calculated influence coefficients 
f o r  the ful l -scale  wing were scaled t o  model values and, when compared 
with values obtained from the model, were considered t o  be i n  reasonable 
agreement. 
Instrumentation 
The models were equipped with telemeters which gave continuous 
records of the quant i t ies  t o  be measured. These quantit ies f o r  both mod- ' 
e l s  were normal acceleration of each wing provided by vibrometers 
in s t a l l ed  as shown i n  figure 3 ,  normal acceleration near the model center 
of gravity, and t o t a l  pressure. Also measured were deflection of the 
right-wing elevon f o r  model 1 and deflection of the left-wing elevon f o r  
model 2. 
The vibrometer i s  an accelerometer designed t o  give a t rue  repr\e- 
sentation of frequency. No reliance can be placed on the values of accel- 
erat ion from the vibrometers. Atmospheric conditions prevailing at the 
t h e s  of the model f l i g h t s  were obtained from radiosondes. Each radio- 
sonde was tracked during i t s  ascent by radar t o  determine the wind veloc- 
i t y .  Two radar s e t s  tracked the models during t h e i r  f l igh ts ;  one t o  give 
the re la t ive  velocity of the models with respect t o  a ground reference 
point and the other t o  give t h e i r  positions i n  space. The models were 
tracked by motion-picture cameras t o  give photographic records of the 
f l igh t s .  They were launched a t  the Langley Pi lo t less  Aircraft  Research 
Stat ion a t  Wallops Island, Va. 
FLIGHT TEST RESULTS 
Time h is tor ies  of the f l i g h t s  showing Mach number, velocity, and 
atmospheric density are shown i n  figure 6. Portions of the telemeter 
records a re  reproduced i n  figure 7 and portions of the data reduced from 
the telemeter records are  shown i n  figure 8. 
Model 1 
Figures 7(a)  and 8(a)  show vibrations of the elevons beginning a t  
M = 1.05 (V = 1160 f e e t  per second) having deflections with limits of 5' 
CONFIDENTIAL 
NACA RM SL54L22 CONFIDENTIAL 5 
and i n  excess of -2.T0 a t  frequencies between 200 and 243 cycles per sec- 
ond. This vibration began t o  drive the wings and fuselage a t  the same 
frequency as the elevons . The vibrations stopped a t  M = 1.22 
(V = 1335 f e e t  per second). After the model reached maximum velocity 
(M = 1.31, V = 1440 f e e t  per second) and was decelerating, the elevon 
vibrations began again a t  M = 1.08 (V = 1174 fee t  per second) having 
deflections with l imi ts  of nearly 60 and i n  excess of -2.7' a t  frequencies 
between 213 and 182 cycles per second. The w i n g s  began t o  vibrate almost 
immediately a t  the same frequency as  the elevons and the model s ta r ted  t o  
vibrate short ly thereafter.  The open portions i n  the envelope of the 
elevon position (6) curve of figure 8(a)  indicate tha t  the deflections 
read from the telemeter record were beyond the instrument calibration 
range. The magnitude of tha t  portion of the envelope which i s  shown is 
i n  er ror  t o  some extent owing t o  the attenuation i n  the instrumentation 
and no attempt should be made t o  establ ish a mean l ine .  The vibrations 
stopped a t  M = 0.96 (V = lo50 f e e t  per second). Normal loads on the 
model did not exceed the range of 3g t o  -2g during the vibrations. It 
is of in t e res t  t o  note tha t  the elevons of the full-scale airplane buzzed 
a t  a Mach nmber s l ight ly  higher than 1 and at  amplitudes of about f 0.3'. 
Model 2 
Figure 8(b) shows tha t  a t  about 1.8 seconds (M = 0.70, V = 780 f e e t  
per second) the model-booster combination began experiencing a steady 
increase i n  normal acceleration and tha t  6 was increasing positively.  
A t  about 2.25 seconds (M = 0.92, V = 1030 f e e t  per second), 6 began t o  
increase i n  the negative direction. A s  the Mach number increased t o  the 
maximum before booster separation (M = 1.26, V = 1411 f e e t  per second), 
6 reached -0.7' and the normal acceleration reached 8.4g which amounted 
t o  about 2420 pounds of l i f t  on the 288-pound combination. T h i s  load is 
about 940 pounds on the model alone. The design c r i t i c a l  loading f o r  the 
model was 1144 pounds (l0.25g) based on calculations using a symmetrical 
s tep  gust of 30 f e e t  per second. The load encountered by the model, 
therefore, was 82.2 percent of t h i s  c r i t i c a l  load. The model pitched 
rather  severely a f t e r  booster separation but damped rapidly. During sls- 
ta iner  burning the model osc i l la ted  about a trlm l ine  of about -0.4g with 
amplitudes of f0,8g. As the model reached maximum velocity (M = 1.93, 
V = 2145 f e e t  per second), the l e f t  wing suddenly f a i l ed  (f ig.  7(c)  ), 
the model became unstable, and.thus the useful portion of the f l i g h t  w a s  
ended. The vibrometer t races throughout the f l i g h t  were similar i n  
appearance t o  the traces shown i n  figure 7(c)  before the f a i lu re  of the 
wings. 
It i s  possible tha t  this fa i lu re  might be the r e su l t  of the struc- 
ture  of the wing having changed because of e i ther  the near design c r i t i -  
c a l  loads experienced at  booster separation or  as a resu l t  of softening 
of the adhesive bond due t o  high temperatures on the wing or f o r  both 
6 COKFIDENTIAL NACA RM S ~ 5 4 ~ 2 2  
reasons. The temperature a t  a locus of points 6 /inches back of the 
leading edge was calculated t o  be about 2600 F a t  6.7 seconds a f t e r  
launching based on the f l i g h t  path t h a t  the model traversed. Owing t o  
these conditions, fur ther  f l u t t e r  t e s t s  on these wings a t  higher Mach 
numbers w i l l  be necessary. 
CONCLUDING REMARKS 
There was no indication of wing f l u t t e r  during the t e s t s  up t o  a 
Mach number of 1.31 f o r  one model and a Mach number of 1.93 fo r  the 
other. Although no wing f l u t t e r  occurred during e i the r  f l i gh t ,  elevon 
vibrations o r  buzz occurred on the f irst  model a t  frequencies of from 
182 t o  243 cycles per second having deflections with limits of 6O and 
i n  excess of -2.7' over Mach number ranges of 1.03 t o  1.22 during accel- 
erat ing f l i g h t  and 1.08 t o  0.96 during coasting f l igh t .  
Two possible explanations f o r  the f a i lu re  which occurred on the 
wings of the second model are weakening of the wings from the high loads 
imposed a t  booster separation and softening of the adhesive bond a t  the 
temperatures encountered by the model so t h a t  the wings were weakened 
or both. 
Langley Aeronautical Laboratory, 
National Advisory Committee f o r  Aeronautics, 
Langley Field, Va., December 8, 19 
Aeronautical Research s c i e n t i s t  
cia.  
Joseph A. Shortal  
ess  Aircraft  Research Division 
Sam 
REFERENCES 
1. Dublin, Me, and Morgan, H.: Results of Ground Vibration Tests on the 
YF-102 Airplane. Rep. No. ZU-8-011 (Contract A F ~ ~ ( ~ c o )  -5942), Con- 
solidated Vultee Aircraft  Corp., Nov. 2, 1933. 
2. Wolf e , J. J., and Camp, R. G. : 1/9 Scale F lu t te r  Model Proof and 
Influence Coefficients Tests. Rep. No. 7839, Consolidated Vultee 
Aircraft  Corp., Apr, 30, 1954, 
NACA REI S ~ 5 4 ~ 2 2  CONFIDENTIAL 
TABU3 I . . WEIGBT AND BALANCE M A  OF MODELS 
Model 1 
Weight with fuel. l b  . . . . . . . . . . . . . . .  159 0 
Weight without fuel. l b  . . . . . . . . . . . . .  132.75 
Wing loading with fuel. lb/sq f t  . . . . . . . . .  28.3 
Wing loading without fuel. lb/sq f t  . . . . . . .  23.6 
Center-of-gravity s ta t ion  with fuel. i n  . . . . .  52.41 
Center-of-gravity s ta t ion  without fuel. i n  . . . .  50.88 
Weight of each wing panel. l b  . . . . . . . . . .  12.75 
Model 2 
CONFIDENTIAL 
TABU I1 . . SIMILARITY REQUrtiEMENTS 
NACA RM ~ ~ 5 4 ~ 2 2  
Quantity Model value I Full-scale vdue 
. . . . . . . . . . . . .  Strouhal number. bf/v 
. . . . . . . . . . . . .  Density ratio. pb3/m 
. . . . . . . . . . . . . . . .  Mach number. V/V, 
. . . . . . .  Structural damping coefficient. g 
. . . . . . . . . . . . . . . . . . .  Length. b 
Mass.m . . . . . . . . . . . . . . . . . . . .  
Mass moment of inertia. Ip 
. . . . . . . . . . . . . . . . .  Frequency. f 
. . . . . . . . . . . . .  Bending stiffness. EI 
. . . . . . . . . . . .  Torsional stiffness. GJ 
. . . . . . . . . . .  Skin or web thickness. t 
. . . . . . . . . . . .  Stagnation pressure. q 
Stress due to aerodynamic force. aa . . . . . .  
Stress due to inertia force. ai . . . . . . . .  
Deflection due to unit load. 6 . . . . . . . .  
Deflection due to comparable loads. A . . . . 
Elevon spring constant. k . . . . . . . . . . .  
1 
4.1 
119 
11333 
NACA RM SL54~22 CONFIDENTIAL 
TABU 111. - COMPARISON OF SCALLED-FLEG-SCU-WING FFZQUENCBS 
WITH MODEL-WING FFZQUENCIES 
C - 
Symmetrical 
mode 
1 
2 
3 
4 
5 
6 
7 
8 
Model 1 
frequency, cps 
81 
104 
118 
144 
205 
223 
240 
320 
9.72 ful l -scale  
frequency, cps 
96 
165 
202 
232 
282 
382 
I 
Model 2 
frequency, cps 
76 
100 
108 
124 
168 
222 
236 
298 
NACA RM
 S
~54L22 
CONFIDENTIAL 
EsACA R
M
 S
~
54~
22. 
CONFIDENTIAL 
CONFIDENTIAL 
(b)  Moael 2 and booster on launcher. L-85012 
Figure 2.- Concluded. 
CONFIDENTIAL 
MACA R
M
 S
~
5
4
~
2
2
 
CONFIDENTIAL 
Ma hogany mounting pad P 1 ( I  per pivot.) 7 Aluminum skin 52 m 
L-.l 
This surface screwed, 
(a) Elevon and flexure pivot details.  
Figure 4. - Wing and elevon structure. 
C ONFIDENT IA
L 
NACA RM
 
~
~
5
4
~
2
2
 
CONE' IDEW
I'IAL 
NACA R
M
 S
~
'j4~22 
CONFIDENTIAL 
Time,t, sec 
( a )  Model 1. 
Figure 6. - Time his tor ies  showing Mach number, velocity, and atmospheric 
dens i t y  . 
NACA RM S ~ 9 ~ 2 2  CONFIDENTIAL 
Time, t,,sec 
(b)  Model 2. 
Figure 6. - Concluded. 
C om IDENT IAL 
NACA RM ~ ~ 9 L 2 2  
- 
~~ . . - 
.............................................................................................................................................................................. 
.............................................................................................................................................................. 
. 1 -  4.8 -- Time from launching, sec. 0.0isec. 4 ~ 0 . 1 0 s e c . ~  6.0 6.5 
(a) Model 1, accelerating. 
10.2 11.0 
M-1.08 
/ Vibrometer, left wing M=I.OI 
Total pressure, ,r Vihrorneter, right wing i 
(b ) Model 1, coasting. 
Figure 7.- Portions of telemeter records. 
CONFIDENTIAL 
NACA RM S ~ f S 4 ~ 2 2  
Maximum velocity-. 
9 
Normal accelerometer 
Vibrometer, right wing 
Vibrometer, left wing 
Maximum velocity 
M.1.93 
I 0.01 sec. 0.lOsec. Vibrometer, right wing 
'&-- L A -  - -  - 1 
--------------- --------. 
( c )  Model 2. 
Figure 7. - Conc.luded. 
CONFIDENTIAL 

NACA RM ~ ~ 9 ~ 2 2  CONFIDENTIAL 
Time,t, sec 
(b ) Model 2. 
Figure 8. - Concluded. 
CONFIDENTIAL 
Restriction/Classification Cancelled
Restriction/Classification Cancelled


Free-Flight Tests of 1/9-Scale Convair YF-102 Airplane Wings at Transonic and Supersonic Speeds to Investigate the Possibility of Flutter

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