74-15-05 PRATT & WHITNEY: Amendment 39-1898. Applies to all Pratt & Whitney Aircraft JT3D turbofan engines containing 14th stage compressor disc, P/N 657814.
Compliance required as indicated.
To ensure adequate life limit margin for 14th stage compressor discs, P/N 657814, the cyclic life limits on these discs have been reduced below the figures currently approved. Unless already accomplished, remove from service 14th stage compressor discs prior to exceeding the revised life limit listed below or within the next 25 cycles in service after the effective date of this airworthiness directive whichever comes later.
Engine Model
Previous Life Limit (Cycles)
Revised Life Limit (Cycles)
JT3D-1
19,000
10,000
JT3D-3B
15,000
8,000
JT3D-7
15,000
8,000
If a disc has been used in more than one engine model, the disc is limited to the lowest cycle life permitted for the engine models in which it has been exposed.
This amendment becomes effective July25, 1974.