Airworthiness Directive · Amendment 39-11559 · General Electric Company GE90 Series Turbofan Engines
General Electric Company GE90 Series Turbofan Engines
General Electric Company (GE) GE90-90B, -85B, and -76B series turbofan engines, with fan mid shafts, part numbers (P/Ns) 1767M71G01, 1767M71G02, and 1767M75G02, installed. These engines are installed on but not limited to Boeing 777 series aircraft.
Note 1: This airworthiness directive (AD) applies to each engine identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For engines that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (c) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
This amendment adopts a new airworthiness directive (AD), applicable to certain General Electric Company (GE) GE90 series turbofan engines, that requires reducing the cyclic life limits for certain fan mid shafts with undesirable microstructure, and removing from service those mid fan shafts prior to exceeding the new limits and replacing with serviceable parts. This amendment is prompted by reports of magnetic particle inspections conducted by the manufacturer identifying segregation in the raw material, resulting in lower fatigue life properties. The actions specified by this AD are intended to prevent fan mid shaft failure, which could result in a total loss of thrust and inflight engine shutdown.
To prevent fan mid shaft failure, which could result in a total loss of thrust and inflight engine shutdown, accomplish the following:
(a) Remove from service fan mid shafts and replace with serviceable parts prior to the following new, lower cyclic life limits:
(1) For fan mid shafts, P/N 1767M71G01, installed on GE90-85B and -90B series engines, the new life limit is 4,200 cycles-since-new (CSN).
(2) For fan mid shafts, P/N 1767M71G02, installed on GE90-85B and -90B series engines, the new life limit is 4,200 CSN.
(3) For fan mid shafts, P/N 1767M75G02, installed on GE90-76B, -85B, and -90B series engines, the new life limit is 8,200 CSN.
(b) This AD establishes new life limits for fan mid shafts, P/N 1767M71G01, 1767M71G02, and 1767M75G02. Except as provided in paragraph (c) of this AD, no alternate life limits for these affected parts may be approved.
