Sec. 27.175 - Demonstration of static longitudinal stability.

(a) Climb. Static longitudinal stability must be shown in the climb condition at speeds from 0.85 VY to 1.2 VY, with --

(1) Critical weight;

(2) Critical center of gravity;

(3) Maximum continuous power;

(4) The landing gear retracted; and

(5) The rotorcraft trimmed at VY.

(b) Cruise. Static longitudinal stability must be shown in the cruise condition at speeds from 0.7 VH or 0.7 VNE, whichever is less, to 1.1 VH or 1.1 VNE, whichever is less, with --

(1) Critical weight;

(2) Critical center of gravity;

(3) Power for level flight at 0.9 VH or 0.9 VNE, whichever is less;

(4) The landing gear retracted; and

(5) The rotorcraft trimmed at 0.9 VH or 0.9 VNE, whichever is less.

(c) Autorotation. Static longitudinal stability must be shown in autorotation at airspeeds from 0.5 times the speed for minimum rate of descent to VNE, or to 1.1 VNE (power-off) if VNE (power-off) is established under 27.1505(c), and with --

(1) Critical weight;

(2) Critical center of gravity;

(3) Power off;

(4) The landing gear --

(i) Retracted; and

(ii) Extended; and

(5) The rotorcraft trimmed at appropriate speeds found necessary by the Administrator to demonstrate stability throughout the prescribed speed range.

(d) Hovering. For helicopters, the longitudinal cyclic control must operate with the sense and direction of motion prescribed in 27.173 between the maximum approved rearward speed and a forward speed of 17 knots with --

(1) Critical weight;

(2) Critical center of gravity;

(3) Power required to maintain an approximate constant height in ground effect;

(4) The landing gear extended; and

(5) The helicopter trimmed for hovering. (Secs. 313(a), 601, 603, 604, and 605 of the Federal Aviation Act of 1958 (49 U.S.C. 1354(a), 1421, 1423, 1424, and 1425); and sec. 6(c) of the Dept. of Transportation Act (49 U.S.C. 1655(c)))
 

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as amended by Amdt. 27-2, 33 FR 963, Jan. 26, 1968; Amdt. 27-11, 41 FR 55468, Dec. 20, 1976; Amdt. 27-14, 43 FR 2325, Jan. 16, 1978; Amdt. 27-21, 49 FR 44433, Nov. 6, 1984; Amdt. 27-34, 62 FR 46173, Aug. 29, 1997]