-CONFIDENTIAL Copy RM L52K13b

NACA

RESEARCH MEMORANDUM

FLIGHT MEASUREMENTS OF THE STABILITY CHARACTERISTICS

OF THE BELL X-5 RESEARCH AIRPLANE IN

SIDESLIPS AT 590 SWEEPBACK

By Joan M. Childs

Langley Aeronautical Laboratory Langley Field, Va. JcLPtS5'1

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DirEt FERWR 21., 196

CLASSIFIED DOCUMENT

Defense of the United States within the meaning , the transmission or revelation of which in any

NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

WASHINGTON February 11, 1953

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Declassified

https://ntrs.nasa.gov/search.jsp?R=19930087404 2019-12-27T02:02:56+00:00Z

NACA RN L52K13b

NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

RESEARCH MEMORANDUM

FLIGHT MEASUREMENTS OF THE STABILITY CHARACTERISTICS

OF THE BELL X-5 RESEARCH AIRPLANE IN

SIDESLIPS AT 590 SWEEPBACK

By Joan M. Childs

SUMMARY

Flight measurements of the stability characteristics of the Bell X-5 research airplane at 590 sweepback were made in steady sideslips at Mach numbers from 0.62 to 0.97 at altitudes ranging between 35,000 and 40,000 feet. The results showed that the apparent directional stability was positive and increased at Mach numbers above 0.90. The apparent effective dihedral was positive and high, increasing at Mach numbers above 0.75. The cross-wind force coefficient per degree of sideslip was positive and increased rapidly at Mach numbers above 0.94.

INTRODUCTION

The Bell X-5 airplane was procured by the U. S. Air Force for research, in the transonic speed range, with an airplane having extreme amounts of sweepback but using variable sweep angle so that the landing would not be a problem. The acceptance tests of the airplane were con-ducted by the manufacturer (Bell Aircraft Corp.). Results from these tests were reported in references 1 and 2. One of the two airplanes was assigned to the NACA High-Speed Flight Research Station at Edwards Air Force Base, Calif., for detailed measurements of the aerodynamic characteristics. The NACA tests to date have been concerned with char-acteristics with the wings swept back to 59 0 which is the extreme case for the airplane. This paper presents results of measurements of the lateral and directional stability in sideslips performed as part of the stability and control program for the airplane.

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2 CONFIDENTIAL NACA RM. L52K13b

SYMBOLS

U

M Mach number

sideslip angle, deg

br rudder deflection, deg

baT total aileron deflection, deg

angle of bank, deg

d5r/d43 apparent directional stability parameter, slope of variation of rudder deflection with sideslip angle

da 2/d3 apparent effective dihedral parameter, slope of variation of total aileron deflection with sideslip angle

dq/d13 variation of angle of bank with sideslip angle

CNA airplane normal-force coefficient

Cy lateral-force coefficient per degree of sideslip

hPpressure altitude, ft

The Bell X-5 airplane is a single-place fighter-type airplane powered by an Allison J-3 5-A-17 turbojet engine. It is designed for research in the transonic speed range and incorporates a wing having flight-variable sweepback between 20 0 and 59°. Figure 1 is a photograph of the airplane and figure 2 is a three-view drawing of the airplane with 590 sweephack. Table I contains the airplane physical character- istics. Reference 1 gives a complete description of the airplane and its wing sweep angle and longitudinal translation characteristics. The friction in the control systems as measured on the ground under no load is shown in figure 3.

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INSTRUMENTATION

NACA internal instruments, synchronized by a common timer, recorded the following quantities:

Airspeed and altitude Vertical, longitudinal, and transverse accelerations Sensitive longitudinal acceleration Rolling angular velocity Pitching angular velocity and acceleration Yawing angular velocity and acceleration Angle of sideslip and angle of attack Aileron, elevator, rudder, and stabilizer positions Wing sweep angle Elevator and aileron stick force Rudder pedal force

In reference 1 the airspeed system is discussed and the Mach number calibration accuracy as obtained from a radar-phototheodolite calibra-tion is given as ±0.01.

TESTS, RESULTS, AND DISCUSSION

The static lateral stability characteristics were measured in gradually increasing and decreasing sideslips at various speeds with the airplane in the clean configuration with 59 0 sweepback. These side-slips were performed by deflecting the rudder and using aileron and i vat or to mintc.in straight flig ht.. The Mach number range covered

was from 0.62 to 0.97 at altitudes ranging between 35,000 and 140,000 feet.

The results of these tests are presented in figure Ii. which shows aileron, rudder, and elevator positions and forces plotted as functions of the sideslip angle. There is discontinuity in elevator force and position in figure ll-(a) because the maneuver was done in two separate data runs. Angle of bank as calculated from the measured transverse acceleration is also shown. Most of the scatter of these data results from the almost continuous oscillatory motions of the airplane during the sideslip maneuvers. The apparent directional stability is indicated by variation of rudder position with sideslip angle, whereas the apparent effective dihedral is shown by the slope of aileron position as plotted against sideslip angle. The variation of'elevator position and force with sideslip angle indicates the pitching moment due to sideslip, whereas the angle of bank plotted against sideslip angle is indicative of the cross-wind force characteristics.

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The slopes dc)/d3, dEr/df3, and döa,2/d13 obtained from figure 4

are presented as functions of Mach number in figure 5. The apparent directional stability parameter dbr/d13 is positive and approximately constant at a value of 1.6 to a Mach number of about 0.92 where it starts to increase reaching a value of 2.6 at M = 0. 97 . The apparent effective dihedral parameter dEa,/d13 is high throughout the Mach number range

and constant at a value of 6.7 to M = 0. 75 where it starts to increase to a value of about. 13.5 at M = 0. 97 . These changes in dr/d13 and

of course, result both from changes in control effectiveness

and from changes of effective dihedral and weathercock stability. The apparent effective dihedral is so high that at lower Mach numbers only about 50 of sideslip can be trimmed out while at the highest Mach numbers the available aileron is insufficient to trim more than about 2.50 of sideslip. In this condition the ailerons are easily overpowered by the rudder.

There was little change in elevator position throughout the test range indicating little or no change in pitching moment due to sideslip.

The cross-wind force is stable, requiring right bank for right side-slip. The parameter dc/d13 shows a gradual increase with Mach number to a value at M = 0.94 which is approximately double the value at M = 0.62. At Mach numbers greater than 0.911., dq)/do increases abruptly reaching a value approximately five times its low-speed value at M = 0.97. The coefficient Cy, as calculated by the relation -Cy, = CNA sin q, is

presented in figure 6 as a function of Mach number. The variation of CNA

with Mach number is also shown in this figure. The value of Cy remains

constant at about -0.0085 up to a Mach number of 0.94 where it increases to a value of approximately -0.0135 at a Mach number of 0.97. The varia-tion CY, with Mach number does not follow the d(p/do variation in

figure 5 because of the change of CNA with Mach number.

CONCLUSIONS

Flight measurements of the static lateral stability characteristics of the Bell X-5 research airplane at 59 0 sweepback in steady sideslips at Mach numbers of 0.62 to 0.97 at altitudes ranging between 35,000 and 1 0,000 feet give the following conclusions:

1. Throughout the Mach number range the apparent directional stability is positive. It is constant from a Mach number of 0.62 to 0.90 and increases to a value about 60 percent higher as the Mach number increases to 0.97.

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2. The apparent effective dihedral is positive and high, doubling in value between Mach numbers of 0.75 and 0.97. The dihedral is so high at the highest Mach number that the ailerons can only trim out about 2.50 of sideslip and can be easily overpowered by the rudder.

3. The cross-wind force coefficient per degree of sideslip Is stable and constant to a Mach number of 0.94, above which it increases rapidly to a Mach number of 0.97.

4. There is little or no change in pitching moment due to sideslip.

Langley Aeronautical Laboratory, National Advisory Committee for Aeronautics,

Langley Field, Va.

REFERENCES

1. Finch, Thomas W., and Briggs, Donald W.: Preliminary Results of Stability and Control Investigation of the Bell X-5 Research Airplane. NACA RN L52K18b, 1953.

2. Rogers, John T., and. Dunn, Angel H.: Preliminary Results of Horizontal Tail-Load Measurements of the Bell X-5 Research Airplane. NACA P.M L52Gi1 ; 1952.

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TABLE I-- PHYSICAL CHARACTERISTICS OF BELL X-5 AIRPLANE

Airplane: Weight, ib: Full fuel ......................... 9960 Lessfuel ......................... 7850

Power plant: Axial-flow turbojet engine .............. J-35--A-17 Guaranteed rated thrust at 7800 rpm and static sea-level conditions, lb ................ 900

Center-of-gravity position, percent M.A.C.: Fullfuel ......................... I.5.6 Less fuel .........................

Over-all height, ft ..................... 12.2 Over-all length, ft ..................... 33.6

Wing: Airfoil section (perpendicular to 38.02-percent-chord line):

Pivot point .................... NACA 64(10)AO11 Tip . . . . . . . . . . . . . . . . . . . . . . NACA 64(08)A008.28

Sweep angle at 0.25 chord, deg ................. 59 Area, sq ft ......................... 1811..3 Span, ft ............................ 20.0 Span between equivalent tips, ft ............... 19.2 Aspect ratio .......................... 2.16 Taper ratio ........................ o.io95 Mean aerodynamic chord, ft .................. 10.05 Location leading edge of mean aerodynamic chord,

fuselage station ...................... 100.2 Incidence root chord, deg .................... 0 Dihedral, deg .......................... 0 Geometric twist, deg ....................... o Wing flaps (split):

Area, sq ft ......................... 15.9 Span, parallel to hinge center line, ft ........... 6.53 Chord, parallel to line of symmetry at 200 sweepback, in.: Root ........................... 30.8 Tip ........................... 19.2

Travel, deg ......................... 60 Slats (leading edge divided):

Area, sq ft ......................... ]A.6 Span, parallel to leading edge, ft ............. 10.3 Chord, perpendicular to leading edge, in.: Root ........................... 11.1 Tip ........................... 6.6

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TABLE I .- PHYSICAL CHARACTERISTICS OF BELL X-5 AIRPLANE - Concluded

Travel, percent wing chord: Forward ........................... 10 Down ............................ 5

Aileron ( l1.5-percent internal-seal pressure balance): Area (each aileron behind hinge line), sq ft ....... . 3.62 Span parallel to hinge center line, ft ........... 5.15 Travel, deg ......................... ±15 Chord, percent wing chord .................. 19.7 Moment area rearward of hinge line (total), in. 3 ..... . 11.380

Horizontal tail: Airfoil section (parallel to fuselage center line) . . NACA 65A006 Area, sq ft .......................... 31.5 Span, ft ........................... 9.56 Aspect ratio ......................... 2.9 Sweep angle at 0.25 percent chord, deg ............ li.5 Mean aerodynamic chord, in ................. 11.2.8 Position of 0.25 M.A.C., fuselage station ......... . 355.6 Stabilizer travel, (power actuated), deg:

Leading edge up ....................... Leading edge down ....................... 7.5

Elevator (20.8-percent overhang balance, 31.5 percent span): Area rearward of hinge line, sq ft ............. 6.9 Travel from stabilizer, deg:

Up ............................. 25 Down ............................. 20

Chord, percent horizontal tail chord ............. 30 Moment area rearward of hinge hue (total in. 3 ....

Vertical tail: Airfoil section (parallel to rearward fuselage

center line) . . . . . . . . . . . . . . . . . . . . NACA 65Aoo6 Area, sq ft .......................... 29.5 Span, perpendicular to rearward fuselage center line, ft . 6.25 Aspect ratio ......................... 1.32 Sweep angle of leading edge, deg ............... 11.3 Fin: Area, sq ft ......................... 211.8

Rudder (23.1-percent overhang balance, 26.3 percent span): Area rearward of hinge line, sq ft ............. 11.7 Span, ft Travel, deg ........................ ±35 Chord, percent horizontal tail chord ............. 22.7 Moment area rearward of hinge line, in. 3 ......... . 3585

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z1

I

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2.

00

NACA RM L52IC13b CONFIDENTIAL

StQt ion to 0

'S

Figure 2.- Three-view drawing of Bell X-5 research airplane at 59 0 sweepback.

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40 -

30 - --- -

20----

I:30 - -

scale

Left aileron position, deg

Ir

Off scalet 10—__

__ Rudder position, deg

60 ---

50-- -

40----

• 30 -- -

°- 20------- - .010--- -

0 - - —

D --- _

• 20-----

- 30— --

40----

50 30 20 10 0 10 20 30

Down Elevator position, deg lip Left Ririhf

Figure 3.- Forces required to deflect controls on the ground under no load.

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- 10

C o

I-

2 5 a,

o 0

CP C 5 4 _j

10

0-5-210 a_ cc

o 4- .00

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0a,

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NACA IM L52K13b CONFIDENTIAL 11

30

25

4-.0

0.21

15

10

5

0

5

10

'5

a _j 20

25

o Rudder =Now <> Elevator MEME m

01 a,

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U, C 0 4-U)

a

2

4 2 0 2 4 Left Right

Sideslip angle, $, deg

(a) M = 0.62; h 40,0OO feet.

Figure ii. .- Sideslip characteristics of Bell X-5 research airplane.

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Left Right • Sideslip . angle, $,deg

(b) vI= 0.70; h 0,000 feet.

- -. Figure ii. . - Continued.

10

CP C; o 5

0

C 5

10

.0 = 20

a) a. .0 .2'

or 1 0 e

0 2 C

2 o > -. = -w o <0

20

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20

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No w M mmus or

MENEM

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a) -o

4- -o I.-4) -j

12 CONFIDENTIAL NACA RM L52K13b

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Vej

2 0 2 4 Left Right Sideslip angle, ,8, deg

(c) M = 0.76; Ii 40,000 feet.

Figure 4.- Continued.

4.-C 0

II-

c—I

5

10

.20

lo 12 0

0

'°:

: o2 15

0

j

cr

5

0 0.

5 . C C c&b0

IS

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100

50

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100

c Rudder ME U _____ MMMIENEru ___

um u-UI

MENNo 1M1

1*.ME

NACA RM L52K13b CONFIDENTIAL 13

C0TFITIAL

ro:

Left Right Sideslip angle,$,deg

(d) N = 0.81; 39,000 feet.

Figure ii. . - Continued.

C 0

4-.

MM 5

.T-e-

: 410

30

20

5 U I.-

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0

o 4- o '

10 0. Q 1t

Ui 20

30

25

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5

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20

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m MEN no

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No MEN U-.....

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14 CONFIDENTIAL NACA RN L52}3b

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.x_ C •

o.v 0...

C 4 _J

.0

a-

.0

10- 0 '4-

.2 5

- .0 (I)

C 0

0 =

w

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2 4-C o C4..

ow ci

IC

5

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cr

0 '4- D o D

100

50

0

50

100

NACA RM L52K13b CONFIDENTIAL 15

o Aileron

I

Left IRight

Sideslip angle, $, deg

(e) M = 0.85; h 40,000 feet.

Figure Ii. . - Continued.

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150

•ff% I'.JJ 4- C .0 Cl -

50e

:o:1

100 —J

o Aileron

C•Elevator MENEM"0,0110 MOMMENUME MENEM.-MAME pi•su_

Now

MAMA*;*,

ME[MAMEME EMONAME Mlroolmmm ML

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1.0I.

-C a --

l.-0 o-a -- 4-.

*- C 5

10

30 4.-

.0 -

o=

a.-cr 0

00

o o U)

C

0 o 0..

<20

30

25

20

4-

iE

2 5 0 U) 0 Q.

5 C4 10

C.,

15

20

Left Right Sideslip angle,$,deg

(f) M = 0.89; h z 140,000 feet.

Figure L- Continued.

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F

Left Right Sideslip angle, $, deg

(g) M = 0.91; h 36,OOO feet.

Figure 4.-. Continued.

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- 4-

I0 110 iia

30

25

20

15

D CC 10

U,

0

0 0 CL

0 10

8520

254

MEE NONE

o Aileron

,0 Elevator

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150

100CP

50

50 M

100 _j

ISO

NACA RM L52IC13b CONFIDENTIAL 17

• to 4--

C 0

CP 0 1- Q 00

C _J

tO

30 I-

.0 0)

0

C

tO

-J2o

30

25

20

15

10 0

5 C 0

0

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'5

20

25

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18 CONFIDENTIAL NACA RM L52KL3b

IN (s) 0

ov

150

100CP

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.2 0

50 -0

100a)

—J

150

0 Elevator

I.I1I..-.

U...,-'

EL

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Left Right Sideslip angle, 0, deg

(h) M = 0.94; b 110,000 feet.

Figure Ii. .- Continued.

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4-.0 DI cr

-Q

0 U

.2 U,

4-'ø.. 0

—J

i•U4

MEN

NACA EM L52K13b CONFIDENTIAL 19

4- to -C -

a0 U, o -a

- tO

50

40

30

cr 20

ar 10

- 10

20

—j30

40

25

20

•- 15 -C

10 -a5 C

0

0 U, 0 CL

- 5 2C4 10 o00

15

20

254

a--Q

0 2 .2 0 4-a

-C U,

(i) M = 0.96; h z 37,000 feet.

Figure 4. Continued.

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a- a a

I. 0 0 C.) C)

I.. o o

I.-

C o 4.. 0

0

w.0 U)

a-

w

60

5C

40

30

20

10

0

I i

20

204.--C

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IA 0

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204

00

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00

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20 CONFIDEWPIAL NCA RM L52K13b

10 4-

.c C 5 .0

CP

-e- 4 .-

0Allemn

U!1IiiUS

OEMF1aI •U.rIUIIM No - - ME

Left Right Sideslip angle, $,deg

(j) M = 0.96; li 35,000 feet.

Figure Continued.

MACA RM L521<13b CONFIDENTIAL 21

10 C 2 5

•1-0

-JIn

a-.

i.2 C

.2 2 2

I&l

a-

50

40

30

20

10

0

10

4- 20 I.-0

-J 30

40

50

201I-

I - .5a 1 5

10

ci• .-

20

254

ce 0 Aileron o Rudder 0 Elevator

•uui•u

MEN uuwa••u I

-I 0 -

0 z 4 Left Right

Sideslip angle, $ ,deg

4-

cc 0

0 -C)

0

0 .5 .5

4-'I-0 -J

(k) M = 0. 97; h 36,000 feet.

Figure 4. - Concluded.

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8

QX an

100

6

12

Q.

a

4

0 .7 .8 .9 10

Mach number, M

Figure 5.- Variations of dçd43, d5r/d.13, and da,1/d13 with M as

measured in steady sideslips with Bell X-5 research airplane. h = 35,000 to 1 0,00O feet.

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MACA RM L52K1b 23

.6

.4

z 0.2

0

.04

>.02

.7 .8 .9 10

Mach number, M

Fire 6.- Variations of C and Cy with M as measured in steady A sideslips with Bell X-5 research airplane. lip = 35,000 to 40,000 feet.

NACA-Langley - 2-11-53 - 325

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