Airworthiness Directive · Amendment 39-22386 · Turbine section
General Electric Company Turbofan Engines
This AD applies to General Electric Company (GE) GE90-76B, GE90-85B, GE90-90B, and GE90-94B model turbofan engines, excluding those engines with an installed full set of high-pressure turbine (HPT) stage 2 nozzles with part numbers 1847M47G23 and 1847M47G24.
The FAA is adopting a new airworthiness directive (AD) for certain General Electric Company (GE) GE90-76B, GE90-85B, GE90-90B, and GE90-94B model turbofan engines. This AD was prompted by a commanded in-flight shutdown (IFSD) due to cracking and rockback of the high- pressure turbine (HPT) stage 2 nozzles resulting in blade liberation, severe rotor imbalance, and liberation of the exhaust centerbody. This AD requires initial and repetitive borescope inspections (BSIs) of the forward platforms of the HPT stage 2 blades or the leading edges of the HPT stage 2 nozzles and, depending on the results of the inspections, removal and replacement of the HPT stage 2 nozzles with parts eligible for installation. As a mandatory terminating action to the repetitive BSIs of the forward platforms of the HPT stage 2 blades or the leading edges of the HPT stage 2 nozzles, this AD requires replacing the HPT stage 2 nozzles. The FAA is issuing this AD to address the unsafe condition on these products.
(1) Within the compliance times specified in paragraphs (g)(1)(i) and (ii) of this AD, perform an initial borescope inspection (BSI) of the forward platforms of the HPT stage 2 blades, or perform a 360 degree BSI of the leading edges of the HPT stage 2 nozzles (optional procedure) in accordance with the Accomplishment Instructions, paragraph 3.A.(3)(a) of GE GE90 SB 72-1166, Revision 3, dated February 14, 2019 (the SB):
(i) For engines with HPT stage 2 nozzles that have accumulated 22,000 or more flight hours since new or since last overhaul as of the effective date of this AD, perform the initial BSI before accumulating 250 flight cycles (FCs) after the effective date of this AD.
(ii) For engines with HPT stage 2 nozzles that have accumulated less than 22,000 flight hours since new or since last overhaul as of the effective date of this AD, perform the initial BSI before accumulating 22,000 flight hours since new or since last overhaul, or within 250 FCs after the effective date of this AD, whichever occurs later.
(2) Thereafter, at intervals not to exceed 100 FCs from performance of the last BSI of the forward platforms of the HPT stage 2 blades, or at intervals not to exceed 500 FCs from the last BSI of the leading edges of the HPT stage 2 nozzles, as applicable, perform a repetitive BSI of the forward platforms of the HPT stage 2 blades or the leading edges of the HPT stage 2 nozzles in accordance with the Accomplishment Instructions, paragraph 3.A.(3)(a) of the SB.
(3) If, during any inspection required by paragraphs (g)(1) or (g)(2) of this AD, rub marks, evidence of contact on the HPT stage 2 blade forward platform on three or more HPT stage 2 blades, or an unserviceable HPT stage 2 nozzle is found, before further flight, remove and replace the HPT stage 2 nozzles with parts eligible for installation.
Note 1 to paragraph (g)(3): Serviceability criteria can be found in the GE90 Boeing 777 Aircraft Maintenance Manual, 72-00-00, INSPECTION/CHECK, Subtask 72-00-00-220-074-G00.
As a mandatory terminating action to the repetitive inspections required by paragraph (g)(2) of this AD, at the next engine shop visit after reaching 22,000 flight hours since new or since last overhaul, replace the HPT stage 2 nozzles with parts eligible for installation.
(1) For the purpose of this AD, “parts eligible for installation” is a full set of HPT stage 2 nozzles with part numbers 1847M47G23 and 1847M47G24.
(2) For the purpose of this AD, an “overhaul” is the complete refurbishment of the HPT stage 2 nozzle segments.
(3) For the purpose of this AD, an “engine shop visit” is the induction of an engine into the shop for maintenance involving separation of pairs of major mating engine case flanges, except for the following situations, which do not constitute an engine shop visit:
(i) Separation of engine flanges solely for the purposes of transportation of the engine without subsequent maintenance; or
(ii) Separation of engine flanges solely for the purpose of replacing the fan or propulsor without subsequent maintenance.
