14 CFR 25.33 - Propeller speed and pitch limits.
(a) The propeller speed and pitch must be limited to values that will ensure -
(1) Safe operation under normal operating conditions; and
(2) Compliance with the performance requirements of §§ 25.101 through 25.125.
(b) There must be a propeller speed limiting means at the governor. It must limit the maximum possible governed engine speed to a value not exceeding the maximum allowable r.p.m.
(c) The means used to limit the low pitch position of the propeller blades must be set so that the engine does not exceed 103 percent of the maximum allowable engine rpm or 99 percent of an approved maximum overspeed, whichever is greater, with -
(1) The propeller blades at the low pitch limit and governor inoperative;
(2) The airplane stationary under standard atmospheric conditions with no wind; and