FAA Federal Aviation Regulations (FARS, 14 CFR)

(a) Each airplane must be designed to withstand loads on each lifting surface resulting from gusts specified in §23.333(c).

(b) The gust load for a canard or tandem wing configuration must be computed using a rational analysis, or may be computed in accordance with paragraph (c) of this section, provided that the resulting net loads are shown to be conservative with respect to the gust criteria of §23.333(c).

(c) In the absence of a more rational analysis, the gust load factors must be computed as follows -- $$

Where --

Kg=0.88μg/5.3+μg=gust alleviation factor;

μg=2(W/S)/ρ Cag=airplane mass ratio;

Ude=Derived gust velocities referred to in §23.333(c) (f.p.s.);

ρ=Density of air (slugs/cu.ft.);

W/S=Wing loading (p.s.f.) due to the applicable weight of the airplane in the particular load case.

W/S=Wing loading (p.s.f.);

C=Mean geometric chord (ft.);

g=Acceleration due to gravity (ft./sec. ²)

V=Airplane equivalent speed (knots); and

a=Slope of the airplane normal force coefficient curve CNA per radian if the gust loads are applied to the wings and horizontal tail surfaces simultaneously by a rational method. The wing lift curve slope CL per radian may be used when the gust load is applied to the wings only and the horizontal tail gust loads are treated as a separate condition.
 

[Amdt. 23-7, 34 FR 13088, Aug. 13, 1969, as amended by Amdt. 23-42, 56 FR 352, Jan. 3, 1991; Amdt. 23-48, 61 FR 5144, Feb. 9, 1996]