AD 77-01-07

77-01-07 PRATT & WHITNEY AIRCRAFT: Amendment 39-2807. Applies to all Pratt & Whitney Aircraft JT9D-3A, -7, -7H, -7A, -7AH, -7F and -20 turbofan engines containing fifth stage turbine hubs, P/N 704705, 714905, 718905, 719205, and 726805.

Compliance required as indicated.

To prevent cracking and possible failure of fifth stage turbine hubs, the cyclic life limits on these parts have been reduced below the figures currently approved. Unless already accomplished, remove from service fifth stage turbine hubs prior to reaching the revised life limit listed below or within the next 25 cycles in service after the effective date of this AD, whichever is later.

Hub Part Number Previous Life Limit (Cycles) Revised Life Limit (Cycles) 704705 15,000 7,000 714905 15,000 6,000 718905 8,000 5,000 719205 8,000 5,000 726805 8,000 5,000

Upon request of the operator, an FAA maintenance inspector, subject to prior approval of the Chief, Engineering & Manufacturing Branch, New England Region, may adjust the 25 cycle compliance interval to permit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for that operator.

(NOTE: Pratt & Whitney Alert Service Bulletin No. 4671 pertains to this subject.)

This amendment becomes effective upon publication in the Federal Register.