73-16-05 PRATT & WHITNEY: Amdt. 39-1698. Applies to all Pratt and Whitney Aircraft JT9D turbofan engines containing fourth and fifth stage turbine discs, P/N 646304, 694804, 618305, and 705905.
Compliance required as indicated.
To prevent possible failure of fourth and fifth stage turbine discs, the life limits on these parts have been reduced below the figures currently approved. Unless already accomplished, remove from service fourth and fifth stage turbine discs prior to reaching 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.
Disc Part Number
Previous Life Limit Cycles
Revised Life Limit Cycles
646304
8000
4000
694804
8000
4000
618305
8000
4000
705905
8000
4000
(Upon submission of substantiating data through an FAA Maintenance Inspector, the Chief, Engineering and Manufacturing Branch, FAA, New England Region, may adjust the compliance time).
NOTE: (Pratt and Whitney Service Bulletin No. 3785 pertains to this subject).
This amendment becomes effective August 15, 1973.