Text in force at 23-63: from 23-48, effective 11 Mar 1996.
[(a) Each engine mount and its supporting structure must be designed for the gyroscopic, inertial, and aerodynamic loads that result, with the engine(s) and propeller(s), if applicable, at maximum continuous r.p.m., under either:
(1) The conditions prescribed in Sec. 23.351 and Sec. 23.423; or
(2) All possible combinations of the following--
(i) A yaw velocity of 2.5 radians per second;
(ii) A pitch velocity of 1.0 radian per second;
(iii) A normal load factor of 2.5; and
(iv) Maximum continuous thrust.
(b) For airplanes approved for aerobatic maneuvers, each engine mount and its supporting structure must meet the requirements of paragraph (a) of this section and be designed to withstand the load factors expected during combined maximum yaw and pitch velocities.
(c) For airplanes certificated in the commuter category, each engine mount and its supporting structure must meet the requirements of paragraph (a) of this section and the gust conditions specified in Sec. 23.341 of this part.]
61 FR 5145 · Source