Text in force at 29-59: from 29-40, effective 10 Jun 1996.
[Compliance with the requirements of Sec. 29.65 and 29.67 must be shown at each weight, altitude, and temperature within the operational limits established for the rotorcraft and with the most unfavorable center of gravity for each configuration. Cowl flaps, or other means of controlling the engine-cooling air supply, will be in the position that provides adequate cooling at the temperatures and altitudes for which certification is requested.]
61 FR 21900 · Source