14 C.F.R. § 27.1509
(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—
(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—
(c) Minimum power on. The minimum power-on rotor speed must be established so that it is—
(1) Not less than the greater of—