Airworthiness Directive · Amendment 39-16995 · Pratt & Whitney (PW)Turbofan Engines
Pratt & Whitney (PW)Turbofan Engines
This AD applies to Pratt & Whitney JT9D-7R4G2 and -7R4H1 turbofan engines.
We are adopting a new airworthiness directive (AD) for PW JT9D-7R4G2 and -7R4H1 turbofan engines. This AD was prompted by the determination that a new lower life limit for high-pressure turbine (HPT) 1st stage air seals, part number (P/N) 735907, is necessary. This AD establishes a new lower life limit for HPT 1st stage air seals, P/N 735907, and requires removing them from service using a drawdown schedule. We are issuing this AD to prevent critical life-limited rotating engine part failure and damage to the airplane.
Remove HPT 1st stage air seals, P/N 735907, from service as follows:
(1) For air seals that have fewer than 6,500 CSN on the effective date of this AD, remove the air seals from service before exceeding 9,000 CSN.
(2) For air seals that have 6,500 CSN or more on the effective date of this AD, do the following:
(i) If the engine has a shop visit before the air seal exceeds 9,000 CSN, remove the air seal from service before exceeding 9,000 CSN.
(ii) If the engine does not have a shop visit before the air seal exceeds 9,000 CSN, remove the air seal from service at the next shop visit, not to exceed 2,500 cycles from the effective date of this AD or 15,000 CSN, whichever occurs first.
(1) After the effective date of this AD, do not install or reinstall into any engine any HPT 1st stage air seal, P/N 735907, removed from service in accordance with paragraph (f) of this AD.
(2) After the effective date of this AD, do not install or reinstall into any JT9D-7R4G2 or JT9D-7R4H1 engine any HPT 1st stage air seal, P/N 735907, that exceeds the new life limit of 9,000 CSN.
For the purposes of this AD, an engine shop visit is the induction of an engine into the shop after the effective date of this AD, where the separation of a major engine flange occurs, except that the following maintenance actions, or any combination thereof, are not considered engine shop visits:
(1) Introduction of an engine into a shop solely for removal of the compressor top or bottom case for airfoil maintenance or variable stator vane bushing replacement.
(2) Introduction of an engine into a shop solely for removal or replacement of the stage 1 fan disk.
(3) Introduction of an engine into a shop solely for replacement of the turbine rear frame.
(4) Introduction of an engine into a shop solely for replacement of the accessory gearbox or transfer gearbox, or both.
(5) Introduction of an engine into a shop solely for replacement of the fan containment case.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
