(a) The special factors prescribed in Sec. Sec. 29.621 through 29.625 apply to each part of the structure whose strength is--
(1) Uncertain;
(2) Likely to deteriorate in service before normal replacement; or
(3) Subject to appreciable variability due to--
(i) Uncertainties in manufacturing processes; or
(ii) Uncertainties in inspection methods.
(b) For each part of the rotorcraft to which Sec. Sec. 29.621 through 29.625 apply, the factor of safety prescribed in Sec. 29.303 must be multiplied by a special factor equal to--
(1) The applicable special factors prescribed in Sec. Sec. 29.621 through 29.625; or
(2) Any other factor great enough to ensure that the probability of the part being understrength because of the uncertainties specified in paragraph (a) of this section is extremely remote.