Text in force at CS29-12: from CS29-0, effective 14 Nov 2003.
For cooling fans t hat are a part of a powerplant installation the following apply:
(a) Category A. For cool ing fans i nstalled in Category A rotorcraft, it must be shown that a fan blade failure will n ot prevent continued safe flight either because of dam age caused by the failed blade or loss of cooling air.
(b) Category B. For cool ing fans i nstalled in Category B ro torcraft, th ere m ust b e m eans to protect the rotorcraft and al low a safe l anding if a fan blade fails. It must be shown that :
(1) The fan blade would be contained in the case of a failure;
(2) Each fan is located so that a fan blade failure will not jeopardise safety; or
(3) Each fan blade can withstand an ultimate lo ad o f 1 .5 tim es the centrifugal force expected in service, limited by either:
(i) The highest rot ational speeds achievable under uncontrolled conditions; or
(ii) An overspeed limiting device.
(c) Fatigue evaluation. Unless a fatigue evaluation under CS 29.571 i s conduct ed, i t m ust be shown that cooling fan blades are not operating at resonant conditions with in th e o perating lim its of the rotorcraft.
ED Decision 2003/016/RM · Source