Section 27.1509 - Rotor speed(a)Maximum power-off (autorotation). The maximum power-off rotor speed must be established so that it does not exceed 95 percent of the lesser of- (1) The maximum design r.p.m. determined under § 27.309(b) ; and(2) The maximum r.p.m. shown during the type tests.(b)Minimum power off. The minimum power-off rotor speed must be established so that it is not less than 105 percent of the greater of-(1) The minimum shown during the type tests; and(2) The minimum determined by design substantiation.(c)Minimum power on. The minimum power-on rotor speed must be established so that it is-(1) Not less than the greater of-(i) The minimum shown during the type tests; and(ii) The minimum determined by design substantiation; and(2) Not more than a value determined under § 27.33(a)(1) and (b)(1) .