EASA AD US-2021-03-02
Engine Fuel & Control - Hydromechanical Unit/Main Engine Control Idler Adapter on the Accessory Gearbox Assembly - Inspection / Replacement
Summary
Federal Aviation Administration Airworthiness Directive 2021-03-02 is a final rule addressing certain General Electric Company CF6-80C2 series turbofan engines. It mandates inspections and possible replacement of the hydromechanical unit/main engine control (HMU/MEC) idler adapter inserts on the accessory gearbox assembly to prevent significant fuel loss and in-flight engine shutdowns. The directive applies to multiple CF6-80C2 engine models with specific affected part numbers.
What Changed
This new airworthiness directive introduces initial and repetitive shim checks of the HMU/MEC idler adapter inserts, along with a terminating action involving a protrusion check and pull-out test. It updates applicability to include specific part numbers of affected adapters and allows credit for previous compliant actions performed under earlier service bulletins. The directive also clarifies marking requirements and terminates certain inspection requirements upon successful completion of the terminating action.
Why It Matters
This directive is critical for aviation professionals to prevent unsafe conditions caused by improperly installed or failing HMU/MEC idler adapter inserts, which have led to fuel loss and engine shutdowns. Operators and maintenance organizations must ensure compliance to maintain engine reliability and flight safety. The directive also provides clarity on inspection intervals and acceptable compliance methods, aiding in maintenance planning and regulatory adherence.
What To Do
Affected operators must perform initial shim checks within 1,200 flight hours after March 31, 2021, followed by repetitive inspections as specified. If shim checks fail, inserts must be replaced, and a terminating action involving protrusion and pull-out tests must be completed. Compliance includes marking the HMU/MEC idler adapter to indicate completion. Credit is allowed for prior actions performed under specified GE service bulletins.
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