EASA AD US-2023-05-17
Engine - High Pressure Turbine Stage 2 Nozzles and Blades / Exhaust Centerbody - Inspection / Replacement
Summary
Airworthiness Directive 2023-05-17 is a final rule issued by the FAA addressing certain General Electric Company GE90-76B, GE90-85B, GE90-90B, and GE90-94B turbofan engines. It mandates inspections and replacement procedures for the high-pressure turbine (HPT) stage 2 nozzles and blades, as well as the exhaust centerbody, to prevent in-flight shutdowns caused by cracking and component liberation. This directive applies to engines installed on aircraft such as the Boeing 777-200ER.
What Changed
This new airworthiness directive introduces mandatory initial and repetitive borescope inspections of the HPT stage 2 blade forward platforms and nozzle leading edges. It requires removal and replacement of affected HPT stage 2 nozzles based on inspection results, with a mandatory terminating action to replace the nozzles to end repetitive inspections. The directive also clarifies acceptable methods for flight hour calculations and incorporates related service bulletins for compliance.
Why It Matters
This directive is critical for aviation professionals to prevent unsafe engine conditions that could lead to in-flight shutdowns and severe engine damage. Operators and maintenance organizations must ensure timely inspections and replacements to maintain engine airworthiness and avoid operational disruptions. Compliance with this AD helps mitigate risks of rotor imbalance and component liberation that threaten flight safety.
What To Do
Affected operators must perform initial borescope inspections before accumulating 22,000 flight hours since new or overhaul or within 250 flight cycles after May 10, 2023, whichever is later, followed by repetitive inspections as specified. If inspections reveal damage, the HPT stage 2 nozzles must be replaced with eligible parts. The mandatory terminating action requires replacing the HPT stage 2 nozzles to discontinue repetitive inspections by the compliance deadline.
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