FAA Federal Aviation Regulations (FARS, 14 CFR)

(a) If a rear lift truss is used, it must be designed to withstand conditions of reversed airflow at a design speed of --

V=8.7 √(W/S) + 8.7 (knots), where W/S=wing loading at design maximum takeoff weight.

(b) Either aerodynamic data for the particular wing section used, or a value of CL equalling −0.8 with a chordwise distribution that is triangular between a peak at the trailing edge and zero at the leading edge, must be used.

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as amended by Amdt. 23-7, 34 FR 13089, Aug. 13, 1969; 34 FR 17509, Oct. 30, 1969; Amdt. 23-45, 58 FR 42160, Aug. 6, 1993; Amdt. 23-48, 61 FR 5145, Feb. 9, 1996]