Airworthiness Directive · Amendment 39-10033 · Bell Helicopter Textron, Inc. Model 412 and 412EP Helicopters
Bell Helicopter Textron, Inc. Model 412 and 412EP Helicopters
Model 412 and Model 412EP helicopters with main rotor mast (mast), part number (P/N) 412-040-101-105, -109, -117, - 121, -125, -127, or -129, and main rotor spline plate (spline plate) P/N 412-010-167-105 or P/N 412-010-177-101, -105, -109, -113, or - 117, installed, certificated in any category.
This amendment adopts a new airworthiness directive (AD), applicable to Bell Helicopter Textron, Inc. (BHTI) Model 412 and 412EP helicopters, that requires creation of a component history card or equivalent record using a Retirement Index Number (RIN) system; establishes a system for tracking increases to the accumulated RIN; and establishes a maximum accumulated RIN for certain main rotor masts (masts) and main rotor spline plates (spline plates). This amendment is prompted by fatigue analyses and tests that show certain masts and spline plates fail earlier than originally anticipated because of an unanticipated high number of takeoffs and external load lifts utilizing high power settings, in addition to the time-in-service (TIS) accrued under normal operating conditions. The actions specified by this AD are intended to prevent fatigue failure of the mast or spline plate, which could result in failure of the main rotor system and subsequent loss of control of the helicopter.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
