Text in force at 25-153: from 25-40, effective 2 May 1977.
[No hazardous malfunction of an engine, an auxiliary power unit approved for use in flight, or any component or system associated with the powerplant or auxiliary power unit may occur when the airplane is operated at the negative accelerations within the flight envelopes prescribed in Sec. 25.333. This must be shown for the greatest duration expected for the acceleration.]
42 FR 15043 · Source