AD 66-16-06

66-16-06 PRATT & WHITNEY: Amdt. 39-256 Part 39 Federal Register July 2, 1966. Applies to Models JT3C-7 and JT3C-12 Turbojet Engines.

Compliance required as indicated.

To prevent further failures of fourth stage compressor rotor disc spacer assemblies, accomplish the following:

(a) For fourth stage compressor rotor disc spacer assemblies, P/N 359413, with 1,000 or more hours' time in service since last overhaul, comply with (c) within the next 50 hours' time in service after the effective date of this AD, unless already accomplished within the last 575 hours' time in service, and thereafter at intervals not to exceed 625 hours' time in service from the last inspection until installation of assembly, P/N 429177.

(b) For fourth stage compressor rotor disc spacer assemblies, P/N 359413, with less than 1,000 hours' time in service since last overhaul, comply with (c) before the accumulation of 1,050 hours' time in service since last overhaul, unless already accomplished after the accumulation of 425 hours' time in service since last overhaul, and thereafter at intervals not to exceed 625 hours' time in service from the last inspection until installation of assembly, P/N 429177.

(c) Drill an inspection hole and install a plug in the compressor case and fourth stage vane and shroud assembly in accordance with Pratt & Whitney Aircraft letter dated April 15, 1966, and sketches PWA 15814 and SL61447. Using an American Cystoscope Makers Incorporated Model B-175-AS-15, B-110-AS-15 instrument (or FAA-approved equivalent) inserted through this hole, inspect the fourth stage compressor rotor disc spacer assembly for indication of cracks in visible areas of the spacer. If any indications of cracks are found, remove the engine before further flight, disassemble, and reinspect. If, after disassembly, no cracks are found, the engine may be returned to service. Replace any cracked spacer assemblies before further flight with an assembly of the same partnumber or P/N 429177.

NOTE: During the inspection required by (c), particular attention should be directed to the front and rear seal edges.

(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 repetitive inspection intervals specified in this AD to permit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for that operator.

This directive effective July 2, 1966.