CFR > Title 14 - Aeronautics and Space > CHAPTER I—FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION > SUBCHAPTER C—AIRCRAFT (parts 21 to 50) > PART 27—AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT > SUBPART B—Flight (§27.21 to §27.251) > 27.175—Demonstration of static longitudinal stability.

27.175—Demonstration of static longitudinal stability.

(a) Climb. Static longitudinal stability must be shown in the climb condition at speeds from Vy − 10 kt to Vy 10 kt with—
(1) Critical weight;
(2) Critical center of gravity;
(3) Maximum continuous power;
(4) The landing gear retracted; and
(5) The rotorcraft trimmed at V Y.
(b) Cruise. Static longitudinal stability must be shown in the cruise condition at speeds from 0.8 V[=E T=8052]NE − 10 kt to 0.8 V[=E T=8052]NE 10 kt or, if V[=E T=8052]H is less than 0.8 V[=E T=8052]NE, from V[=E T=8052]H −10 kt to V[=E T=8052]H 10 kt, with—
(1) Critical weight;
(2) Critical center of gravity;
(3) Power for level flight at 0.8 V[=E T=8052]NE or V[=E T=8052]H, whichever is less;
(4) The landing gear retracted; and
(5) The rotorcraft trimmed at 0.8 V[=E T=8052]NE or V[=E T=8052]H, whichever is less.
(c) V [=E T=8052]NE. Static longitudinal stability must be shown at speeds from V[=E T=8052]NE − 20 kt to V[=E T=8052]NE with—
(1) Critical weight;
(2) Critical center of gravity;
(3) Power required for level flight at V[=E T=8052]NE −10 kt or maximum continuous power, whichever is less;
(4) The landing gear retracted; and
(5) The rotorcraft trimmed at V[=E T=8052]NE − 10 kt.
(d) Autorotation. Static longitudinal stability must be shown in autorotation at—
(1) Airspeeds from the minimum rate of descent airspeed−10 kt to the minimum rate of descent airspeed 10 kt, with—
(i) Critical weight;
(ii) Critical center of gravity;
(iii) The landing gear extended; and
(iv) The rotorcraft trimmed at the minimum rate of descent airspeed.
(2) Airspeeds from best angle-of-glide airspeed−10 kt to the best angle-of-glide airspeed 10 kt, with—
(i) Critical weight;
(ii) Critical center of gravity;
(iii) The landing gear retracted; and
(iv) The rotorcraft trimmed at the best angle-of-glide airspeed.

Code of Federal Regulations

(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) ))

Code of Federal Regulations

[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; Amdt. No. 27-44, 73 FR 10999, Feb. 29, 2008]