Airworthiness Directive · Amendment 39-13637 · Bell Helicopter Textron Canada Model 407 Helicopters
Bell Helicopter Textron Canada Model 407 Helicopters
Model 407 helicopters, with bearing, part number (P/N) 406-040-339-ALL, 407-340-339-101, 407-340-339-103, or 407-340- 339-107 installed on the oil cooler blower bearing assembly or segmented tail rotor drive shaft assembly, certificated in any category.
This amendment supersedes an existing airworthiness directive (AD) for Bell Helicopter Textron Canada (BHTC) Model 407 helicopters which requires a one-time replacement of certain oil cooler blower bearings. Also, the existing AD requires adding a limitation and caution to the rotorcraft flight manual (RFM) and inspecting, replacing, and lubricating certain bearings at specified intervals. This amendment adds certain segmented drive shaft bearings to the applicability and requires modifying the oil cooler blower inlet ducts and airflow shields and replacing certain bearings. Thereafter, this amendment requires removing the current temporary limitations and inserting revised limitations into the RFM. This amendment also requires revising the inspection and lubrication requirements. This amendment is prompted by several cases of bearing failure. The addition of certain segmented drive shaft bearings is due to two recent failures. The actions specified by this AD are intended to prevent failure of a bearing, loss of tail rotor drive, and a subsequent loss of directional 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.
