FLAP LOADS

Requ i rement s

FAR 23.457(a) requires the calculation of the critical loads
in  the flaps extended flight conditions with the  flaps  in  any
position.  The computer program FLAPLOAD.BAS calculates  all  the
critical  conditions on the flight flaps extended  envelope  only
for full deflection of flaps.

FAR23.457(b)  requires  that the effects  of  the  propeller
slipstream  for takeoff power be taken into account at  not  less
than  Vg where Vg is the computed stalling speed with  flaps  re-
tracted  at the design weight. For this investigation,  the  load
factor may be assumed  to be 1.0.

FAR23.345(C)(1) requires that,in designing the flaps,a head-
on  gust  having a velocity of 25 feet per  second (EAS)  be  ac-
counted for.

FAR23.345(C)(2)  requires that specified slipstream  effects
be accounted for in designing the flaps.

FAR  23.345(e) permits the critical loads of the  flaps  ex-
tended  envelope (FAR 23.345) and the requirements of FAR  23.457
may be complied with separately or in combination.

The Computer Program

The  computer program FLAPLOAD>BAS calculates  the  critical
flap loads on the flap extended envelope by calculating the  lift
on the flap due to wing angle of attack plus the lift on the flap
due  to  deflection of the flap. The equation used  is  developed
from figure 98 in Theory of Wing Stations By Abbott and  Doehenh-
off.

A  subroutine in the program calculates the  propeller  slip
stream at the flap based on momentum theory. Then the area of the
slip  stream is added to the  area of the fuselage  (or  nacelle)
from which a radius is derived.  The butt line of the engine plus
or  minus the radius determine the inboard and outboard edges  of
the slip stream.

The  computer program FLAPLOAD.BAS combines the  slipstream
effects  of  FAR  23.457(b) with the critical flap  load  of  FAR
23.457(A).  The  critical flap loads in the  slipstream  are  in-
creased  by the ratio of the dynamic pressure of the slip  stream
to that out of the slipstream.

The  computer program FLAPLOAD.BAS accounts for the 25  foot
per  second horizontal gust by increasing the critical flap  load
of FAR 23.457(a) by the ratio of dynamic pressure of the velocity
of  the airplane plus 25 feet per second to the dynamic  pressure

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