Airworthiness Directives; Eurocopter France Model AS350B, B1, B2, B3, BA, and EC130 B4 Helicopters

Résumé

We propose to adopt a new airworthiness directive (AD) for the specified Eurocopter France (ECF) helicopters. This proposed AD results from a mandatory continuing airworthiness information (MCAI) AD issued by the European Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Community. The superseding MCAI AD states that several engine flameouts have involved failure of the 41-tooth pinion in the engine accessory gearbox. Each affected helicopter had a starter-generator manufactured by one company. Investigation revealed the torque damping system of the starter- generator was inoperative due to incorrect adjustment and caused bending stresses on the 41-tooth pinion. Failure of the pinion causes the engine fuel pump to stop operating and results in an engine flameout. The EASA AD requires a new adjustment procedure to optimize the performance of the specified starter-generator damping assembly. These proposed AD actions are intended to prevent failure of a pinion and a fuel pump, engine flameout, and subsequent loss of control of the helicopter.