Airworthiness Directive · Amendment 39-17571 · General Electric Company Turbofan Engines
General Electric Company Turbofan Engines
This AD applies to General Electric Company (GE):
(1) GE90-76B, -85B, -90B, and -94B turbofan engines with stage 1 high-pressure turbine (HPT) stator shrouds, part number(P/N) 1847M52P14, installed.
(2) GE90-110B1 and -115B turbofan engines with stage 1 HPT stator shrouds,P/N 1847M52P16, installed.
We are adopting a new airworthiness directive (AD) for certain General Electric Company (GE) GE90-76B, -85B, -90B, -94B, -110B1, and - 115B turbofan engines. This AD was prompted by multiple reports of distress of certain stage 1 high-pressure turbine (HPT) stator shrouds due to accelerated corrosion and oxidation, including one engine in- flight shutdown (IFSD) caused by failure of the HPT stator shrouds. This AD requires initial and repetitive on-wing 360-degree borescope inspections (BSIs) for corrosion and oxidation of stage 1 HPT stator shrouds. If a shroud is found to be distressed, this AD requires reinspection at a reduced interval or removal from service before further flight. We are issuing this AD to prevent failure of stage 1 HPT stator shrouds, resulting in an IFSD of one or more engines, loss of thrust control, and damage to the airplane.
(1) Perform an initial on-wing borescope inspection (BSI) of the stage 1 HPT stator shrouds for corrosion and oxidation before accumulating 2,100 cycles since new, or within 100 cycles in service after the effective date of this AD, whichever occurs later.
(2) Thereafter, repeat the BSI of the stage 1 HPT stator shrouds every 250 cycles since last inspection or fewer, depending on the results of the inspection.
(3) For engines listed in paragraph (c)(1) of this AD:
(i) Perform a 360-degree BSI of the stage 1 HPT stator shrouds for corrosion and oxidation. Guidance for performing the BSI can be found in paragraph 3.A of the Accomplishment Instructions of GE Service Bulletin (SB) No. GE90 S/B 72-1076, dated November 19, 2012.
(ii) Refer to Figure 2 of GE SB No. GE90 S/B 72-1076, dated November 19, 2012, to determine the degree of shroud corrosion and oxidation.
(iii) Use paragraph 3.B. of the Accomplishment Instructions of GE SB No. GE90 S/B 72-1076, dated November 19, 2012, to determine the next inspection interval.
(4) For engines listed in paragraph (c)(2) of this AD:
(i) Perform a 360-degree BSI of the stage 1 HPT stator shrouds for corrosion and oxidation. Guidance for performing the BSI can be found in paragraph 3.A of the Accomplishment Instructions of GE SB No. SB 72-0528 R01, Revision 1, dated April 1, 2013, or GE GE90-100 SB No. SB 72-0528, dated November 15, 2012.
(ii) Refer to Figure 2 of GE SB No. SB 72-0528 R01, Revision 1, dated April 1, 2013, or GE GE90-100 SB No. SB 72-0528, dated November 15, 2012, to determine the degree of shroud corrosion and oxidation.
(iii) Use paragraph 3.B. of the Accomplishment Instructions of GE SB No. SB 72-0528 R01, Revision 1, dated April 1, 2013, or GE GE90-100 SB No. SB 72-0528, dated November 15, 2012, to determine the next inspection interval.
(5) Remove from service before further flight, any stage 1 HPT stator shroud found with any hole further than 0.35-inch from the shroud leading edge, and more than 0.25-inch in diameter, and that is more than 0.049 square inch in area.
