Airworthiness Directive · Amendment 39-13524 · Eurocopter France Model EC 155B Helicopters
Eurocopter France Model EC 155B Helicopters
Model EC 155B helicopters with an upgraded Quiet Fenestron tail rotor hub, part number (P/N) 365A33-3501-02, with tail rotor attachment bushing, P/N 365A33-3530-20, and tail rotor gearbox, P/N 365A33-6005-04 (without the reinforced control shaft, P/N 365A33-6161-21) or tail rotor gearbox, P/N 365A33-6005-06 (with reinforced control shaft, P/N 365A33-6214-20), installed, certificated in any category.
This amendment adopts a new airworthiness directive (AD) for the specified Eurocopter France (Eurocopter) model helicopters that requires installing a tail rotor blade (blade)-to-torsion bar attachment tuning weight assembly on each blade of the Quiet Fenestron tail rotor and replacing each blade attachment bushing. This amendment is prompted by the discovery of tail rotor induced vibrations during flight tests. The actions specified by this AD are intended to prevent vibration in the tail rotor and the pilot's anti-torque pedals, blade pitch control failure, and subsequent loss of control of the helicopter.
