AILERON LOADS

Requirements

FAR 23.455(1) requires the calculation of loads on the 
aileron for neutral position during symmetrical flight conditions 
and FAR 23.455(2) for deflected positions during unsynunetrical 
flight conditions.

Symmetrical conditions are always less than unsynunetrical 
flight conditions at the same speed. For symmetrical conditions, 
the aileron average pressure is about 16 percent of the average 
wing pressure. The deflected surface pressure is made up of that 
pressure plus the pressure due to aileron deflection. Yet the 
regulations permit a rational analysis for the deflected aileron 
(unsynunetrical conditions) which ignores the undeflected pressure 
as being insignificant. Therefore the symmetrical conditions are 
not critical.

FAR 23.455(a)(2)(i) requires the calculation of loads on the 
aileron for sudden maximum displacement of the aileron control at 
V^. Suitable allowance may be made for control system deflections 
(stretch for cables, compression for push-pull tubes).

FAR 23.455(a)(2)(ii) requires the calculation of loads on 
the aileron for sufficient deflection of the aileron control at 
VQ to produce a rate of roll not less than obtained in FAR 
23.455(a)(2)(i).

FAR 23.455(a)(2)(iii) requires the calculation of loads on 
the aileron for sufficient deflection of the aileron control at 
Vp to produce a rate of roll not less one-third of that obtained 
in FAR 23.455(a)(2)(i).

The Computer Program

The program AILERON.BAS calculates the rational loads for 
deflected (unsynunetrical conditions) with the simple equation:

L(ail)SCL(ail)*Q*s(ail) 
Where C^/-ji\=.04*aileron deflection in degrees

(Ref CAM 3.222(c))

Q=dynamic pressure in pounds/square foot

S/^J\=area of aileron in square feet

This is easier and more accurate than the arbitrary method 
of Appendix B permitted by FAR 23.455(b).

The computer program uses the maximum deflection of the 
aileron without allowing for system deflections at V^. This is 
the practice in the industry and is especially reasonable when 
push pull rods or larger diameter cables are used to minimize

219

FAR 23 LOADS

system deflections.

The deflection at V^ is the deflection at V^ times V^/Vc. 
(Ref CAM 3.222(b)(3))

The deflection at Vp is .5 times the deflection at V^  times 
V^/Vp. (Ref CAM 3.222(b)(3))

220

AILERON LOADS

3 REM------------------------------------------------------------------

5 REM           HEADING AND COPYRIGHT 
7 REM-----------------------------------------------------------------

9 CLEAR:CLS

10 PRINT "PROGRAM TO CALCULATE AILERON LOADS --- AILERON.BAS VERSION 
1.0"

20 PRINT "COPYRIGHT (C) HAL C MCMASTER 1990"

21 REM---------------------------------------------------------------

22 REM          ROUTINE TO ENTER DATA

23 REM---------------------------------------------------------------

24 LPRINT CHR$(27)"1"CHR$(5): REM   TO SET LH MARGIN

25 LPRINT "AILERON LOADS" 
27 LPRINT: LPRINT "INPUT"

30 INPUT "     ENTER STRUCTURAL SPEEDS IN KNOTS VA, VC, VD ";VA,VC,VD 
35 LPRINT:LPRINT "VA = ";VA;" VC = ";VC;" VD = ";VD;" KNOTS"

40 INPUT "ENTER MAX DOWN AILERON DEFLECTION IN DEGREES ";ADEG:ADEG=ABS 
(ADEG)

41 INPUT "ENTER MAX UP AILERON DEFLECTION IN DEGREES ";AUPDEG:AUPDEG=-
ABS(AUPDEG)

45 LPRINT USING "MAX DOWN AILERON DEFLECTION = +##.# DEG ";ADEG

46 LPRINT USING "MAX UP AILERON DEFLECTION = +^#.# DEG ";AUPDEG

50 INPUT "ENTER AILERON AREA FWD OF HINGE LINE, SQUARE FEET ";SAFWD

51 INPUT "ENTER AILERON AREA AFT OF HINGE LINE, SQUARE FEET ";SAAFT

52 LPRINT "AILERON AREA FWD OF HINGE LINE = ";SAFWD;" SQ FT"

53 LPRINT "AILERON AREA AFT OF HINGE LINE = ";SAAFT;" SO FT"

54 SA=SAFWD+SAAFT

55 LPRINT "AILERON AREA = ";SA;" SQ FT"

56 CDEG=VA/VC*ADEG:CUPDEG=VA/VC*AUPDEG

57 REM---------------------------- -------- -------------------------

58 REM       ROUTINE TO CALCULATE AND PRINT AILERON LOADS

59 REM---------------------------------------------------------------

62 LPRINT: LPRINT "OUTPUT": LPRINT

64 LPRINT USING "AILERON DEFLECTIONS AT VA = ##.## DEG AND +#^.## DEG" 
;ADEG;AUPDEG

65 LPRINT USING "AILERON DEFLECTIONS AT VC = tt#.## DEG AND +##.## DEG"

;CDEG ;CUPDEG

70 DDEG=.5*VA/VD*ADEG:DUPDEG=.5*VA/VD*AUPDEG

75 LPRINT USING "AILERON DEFLECTIONS AT VC = ##.## DEG AND +#t.## DEG"

;DDEG ;DUPDEG

80 LA=.04*ADEG*SA*VA~2/295:LUPA=.04*AUPDEG*SA*VA~2/295

90 LC=.04*CDEG*SA*VC~2/295:LUPC=.04*CUPDEG*SA*VC~2/295

100 LD=.04*DDEG*SA*VD~2/295:LUPD=.04*DUPDEG*SA*VD"2/295

110 LAIL=LA:VAIL=VA

120 IF LAIL<LC THEN LAIL=LC:VAIL=VC

130 IF LAIL<LD AND LAIL<LC THEN LAIL=LD:VAIL=VD

140 LPRINT USING "CRITICAL LOAD FOR DOWN AILERON IS ####.## LBS AT ft##

150 LUPAIL=LUPA:VUPAIL=VA

160 IF LUPAIL>LUPC THEN LUPAIL=LUPC:VUPAIL=VC

170 IF LUPAIL>LUPD AND LUPAIL>LUPC THEN LUPAIL=LUPD:VUPAIL=VD

180 LPRINT USING "CRITICAL LOAD FOR UP AILERON IS +####.## LBS AT #^#.

# KNOTS";LUPAIL,VUPAIL

190 W=LAIL/(SAFWD+.5*SAAFT):WUP=LUPAIL/(SAFWD+.5*SAAFT)

191 LCHECK=W*SAFWD+.5*W*SAAFT

192 REM   LPRINT "LCHECK = ";LCHECK

221

FAR 23 LOADS

200 LPRINT "CHORDWISE DISTRIBUTION IS CONSTANT FROM LEADING EDGE TO 
HINGE LINE THEN"

210 LPRINT "THEN TAPERS TO NOTHING AT TRAILING EDGE." 
220 LPRINT USING "PRESSURE FWD OF HINGE LINE FOR DOWN AILERON IS 
+#.### LBS/SQ IN";W/144

230 LPRINT USING "PRESSURE FWD OF HINGE LINE FOR UP AILERON IS +ft.W 
LBS/SQ IN";WUP/144

235 CHECK2=W*SAFWD+.5*W*SAAFT

236 REM   LPRINT "CHECK2 = ";CHECK2 
240 END

222

