64-11-04 PRATT & WHITNEY: Amdt. 734 Part 507 Federal Register May 23, 1964. Applies to All Models JT4A-3, -9 and -11 Turbojet Engines.
Compliance required as indicated.
To preclude front compressor failure as the result of front compressor rotor blade shift in front compressor rotor assemblies incorporating blade locks P/N's 429601, 310293, 429602, 310294, 429603, 310295, 429604, and 310296, accomplish the following:
(a) Front compressor rotor assemblies with 3,000 or more hours' time in service since last overhaul, which have not previously been inspected by the procedure described in (d) shall be inspected in accordance with (d) within the next 100 hours' time in service after the effective date of this AD and within every 500 hours' time in service thereafter.
(b) Front compressor rotor assemblies with less than 3,000 hours' time in service since last overhaul, which have not previously been inspected by the procedure described in (d) shall be inspected in accordance with (d) prior to the accumulation of 3,100 hours' time in service since last overhaul and within every 500 hours' time in service thereafter.
(c) Front compressor rotor assemblies previously inspected by the procedure described in (d) shall be reinspected in accordance with (d) within every 500 hours' time in service from the last inspection.
(d) By means of a boroscope or FAA-approved equivalent viewing instrument inserted through the existing inspection ports in the front compressor cases, inspect all front compressor blades in the fifth through eighth stages for blade axial displacement.
(1) If forward displacement is between 0.045 and 0.080 inch, or if aft displacement is between 0.040 and 0.080 inch, reinspect within every 125 hours' time in service thereafter all blades in the stage or stages exhibiting blade displacement. If the forward or aft displacement has progressed beyond the limits established by this subparagraph comply with either subparagraph(2) or (3) whichever is applicable.
(2) If forward or aft displacement is between 0.080 and 0.120 inch, within 25 hours' time in service remove the engine from service until the displaced blade condition is corrected.
(3) If forward or aft displacement is in excess of 0.120 inch, before further flight remove the engine from service until the displaced blade condition is corrected.
(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 & Whitney Aircraft telegraphic message dated March 4, 1964, to all operators of JT4A-3, -9 and -11 turbojet engines covers the same subject.)
This directive effective May 26, 1964.