70-12-04: Main Rotor Shaft Cracks

70-12-04 SIKORSKY ROTORCRAFT: Amdt. 39-997. Applies to S-55, S-55B, S-55C, and S-62A type helicopters certificated in all categories. Compliance required within the next 15 hours in service after the effective date of this AD, unless already accomplished. To prevent failure of the main rotor shaft due to fatigue cracks originating from surface conditions, accomplish the following: (a) Inspect main rotor shaft P/N S14-35-4308-1, -2, -3 or -4, for cracks and surface conditions in accordance with applicable Sikorsky Service Bulletin No. 55B35-3 or 62B35-10 dated 3 April 1970, or later FAA approved revision, or an equivalent inspection procedure approved by the Chief, Engineering and Manufacturing Branch, FAA Eastern Region. (b) Main rotor shafts exhibiting crack indications, or unreworkable surface conditions shall be retired from service prior to further flight and replaced with a shaft which has been inspected in accordance with paragraph (a). (c) Main rotor shafts found with reworkable surface conditions may be reworked in accordance with applicable Sikorsky Service Bulletin No. 55B35-3 or 62B35-10 dated 3 April 1970, or later FAA approved revision, or an equivalent rework procedure approved by the Chief, Engineering and Manufacturing Branch, FAA Eastern Region. Should the extent of rework necessitate removal of the shaft from the main gear box, then the replacement shaft must have been inspected in accordance with paragraph (a). (d) Upon request of the operator, an FAA maintenance inspector, subject to prior approval of the Chief, Engineering and Manufacturing Branch, FAA Eastern Region may adjust the compliance time specified in this AD if the request contains substantiating data to justify the increase for that operator. This amendment is effective June 17, 1970.