AD 64-06-02

64-06-02 BOEING: Amdt 707 Part 507 Federal Register March 17, 1964. Applies to All Model 720 Series Aircraft with Pratt and Whitney JT3C-7 and JT3C-12 Turbojet Engines Installed.

Compliance required as indicated.

As the result of the failure of the second and third stage compressor rotor disc spacer assemblies, P/N's 359411 and 359412, respectively, and resultant serious engine damage together with possible aircraft damage, accomplish the following:

(a) For spacer assemblies previously inspected by the procedure described in (c), reinspect in accordance with (c) as follows:

(1) Inspect spacer assemblies having 200 or more hours' time in service since the last inspection within 50 hours' time in service after the effective date of this AD, and within each 250 hours' time in service thereafter.

(2) Inspect spacer assemblies having less than 200 hours' time in service since last inspection prior to the accumulation of 250 hours' time in service and within each 250 hours' time in service thereafter.

(b) For spacer assemblies not previously inspected by the procedure described in (c), inspect in accordance with (c) as follows:

(1) Inspect spacer assemblies with 950 or more hours' time in service since last overhaul within the next 50 hours' time in service after the effective date of this AD, and every 250 hours' time in service thereafter.

(2) Inspect spacer assemblies with less than 950 hours' time in service since last overhaul prior to the accumulation of 1,000 hours' time in service since last overhaul and every 250 hours' time in service from the last inspection.

(c) Incorporate an inspection hole and plug in the compressor case and second stage vane and shroud assembly and in the compressor case and third stage vane and shroud assembly in accordance with Pratt and Whitney Aircraft letter dated November 22, 1963, and its two enclosed sketches. Using an American Systoscope Markers Incorporated Model B-175-AS-15 or FAA approved equivalent viewing instrument inserted through these holes, inspect the second and third stage compressor rotor disc spacer assemblies for possible cracks in all the visible areas of each spacer. Give particular attention to the front and rear seal edges. If any cracks are found, remove the engine before further flight and disassemble for confirmation of the cracks. Replace any cracked spacer assemblies.

(d) When P/N's 420145 and 429175 second and third stage compressor rotor disc spacer assemblies, respectively, are incorporated, the inspections prescribed by this AD are no longer required.

(e) 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 such operator.

(Pratt and Whitney Aircraft telegraphic message dated November 20, 1963, to Eastern Air Lines and Pratt and Whitney Aircraft letter dated November 22, 1963, and enclosed two sketches to all operators of JT3C-7 turbojet engines cover the same subject.)

This supersedes AD 63-26-01.

This directive effective March 17, 1964.