AD 67-29-06

67-29-06 SIKORSKY: Amdt. 39-502 Part 39 Federal Register November 2, 1967. Applies to all S-51 type Helicopters.

Compliance required as indicated unless already accomplished.

To preclude the possibility of loss of tail rotor power due to failure of sleeve and tube assembly, P/N S535180, accomplish the following:

(a) Immediately upon the effective date of this AD and every 50 aircraft hours' time in service thereafter, perform the following torsional check on sleeve and tube assembly P/N S535180 as follows:

1. Apply rotor brake.

2. Induce a torsional force in both clockwise and counter-clockwise directions to tail rotor drive shafting by hand applied light rotational pressure on tail rotor blades.

3. Inspect shaft ends for evidence of movement between end fittings, rivets and tube.

4. If evidence of movement is observed, replace sleeve and tube assembly P/N S535180 with like new or serviceable part.

(b) Following the effective date of this AD daily inspect sleeve and tube assembly P/N S535180 for loose rivets as evidenced by the presence of black fretting residue around rivet heads, or actual movement of the rivets, and the presence of cracks in the areas where the tube and sleeves (adapters) are joined. If cracks are found replace sleeve and tube assembly P/N S535180 with like new or serviceable part. Loose rivets may be replaced by removing the existing rivets, drilling No. 2 (.221) diameter and installing new rivets P/N MS20470-B7-9. Alternate oversize rivets P/N MS20470-B8-10 may be used if holes are drilled to No. F. (.257) diameter.

(c) Upon request, with substantiating data submitted through an FAA maintenance inspector, compliance times may be increased by the Chief, Engineering and Manufacturing Branch, FAA Eastern Region.

(Sikorsky Aircraft telegram to all operators dated September 5, 1967 covers this same subject.)

This amendment effective October 31, 1967.