Airworthiness Directive · Amendment 39-18405 · General Electric Company Turbofan Engines
General Electric Company Turbofan Engines
This AD applies to all General Electric Company (GE) GEnx-1B54, -1B58, -1B64, -1B67, and -1B70 turbofan engine models with high-pressure turbine (HPT) rotor stage 1 blade, part number 2305M26P06, installed.
We are adopting a new airworthiness directive (AD) for all General Electric Company (GE) GEnx-1B54, -1B58, -1B64, -1B67, and -1B70 turbofan engine models. This AD was prompted by reports of two separate, single engine in-flight shutdowns (IFSDs) caused by high-pressure turbine (HPT) rotor stage 1 blade failure. This AD requires inspection and conditional removal of affected HPT rotor stage 1 blades. We are issuing this AD to prevent failure of the HPT rotor stage 1 blades, which could lead to failure of one or more engines, loss of thrust control, and damage to the airplane.
(1) Perform an initial borescope inspection (BSI) of the convex surface of the HPT rotor stage 1 blades for axial cracks from the platform to 30% span, within 1,000 blade cycles since new or 25 cycles after the effective date of this AD, whichever occurs later, and disposition as follows:
(i) If any axial crack with a length greater than or equal to 0.3 inch is found, or if any axial crack of any length turning in a radial direction is found, or if more than one axial crack of any length is found on one blade, remove the cracked blade from service before further flight.
(ii) If an axial crack is found with a length greater than or equal to 0.2 inch and less than 0.3 inch, remove the cracked blade from service within 10 blade cycles.
(iii) If an axial crack is found with a length greater than or equal to 0.1 inch and less than 0.2 inch, inspect the cracked blade within 50 blade cycles since last inspection (CSLI).
(iv) If an axial crack is found with a length less than 0.1 inch, inspect the cracked blade within 100 blade CSLI.
(v) If no cracks were found, perform a BSI of the blades within 125 blade CSLI.
(2) Thereafter, perform a repetitive BSI of the convex surface of the HPT rotor stage 1 blades for axial cracks from the platform to 30% span within 125 blade CSLI and disposition as specified in paragraphs (e)(1)(i) through (e)(1)(v) of this AD, or remove the blades from service.
For the purpose of this AD, a “blade cycle” is defined as the number of engine cycles that a set of rotor blades has accrued, regardless of the engine(s) in which they have operated.
