Never-exceed speed.

§ 27.1505 Never-exceed speed. (a) The never-exceed speed, V NE, must be established so that it is— (1) Not less than 40 knots (CAS); and (2) Not more than the lesser of— (i) 0.9 times the maximum forward speeds established under § 27.309; (ii) 0.9 times the maximum speed shown under §§ 27.251 and 27.629; or (iii) 0.9 times the maximum speed substantiated for advancing blade tip mach number effects. (b) V NE may vary with altitude, r.p.m., temperature, and weight, if— (1) No more than two of these variables (or no more than two instruments integrating more than one of these variables) are used at one time; and (2) The ranges of these variables (or of the indications on instruments integrating more than one of these variables) are large enough to allow an operationally practical and safe variation of V NE . (c) For helicopters, a stabilized power-off V NE denoted as V NE (power-off) may be established at a speed less than V NE established pursuant to paragraph (a) of this section, if the following conditions are met: (1) V NE (power-off) is not less than a speed midway between the power-on V NE and the speed used in meeting the requirements of— (i) § 27.65(b) for single engine helicopters; and (ii) § 27.67 for multiengine helicopters. (2) V NE (power-off) is— (i) A constant airspeed; (ii) A constant amount less than power-on V NE ; or (iii) A constant airspeed for a portion of the altitude range for which certification is requested, and a constant amount less than power-on V NE for the remainder of the altitude range. (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))) [Amdt. 27-2, 33 FR 964, Jan. 26, 1968, and Amdt. 27-14, 43 FR 2325, Jan. 16, 1978; Amdt. 27-21, 49 FR 44435, Nov. 6, 1984]