The FAA is issuing an emergency airworthiness directive (EAD) No. 2012-21-51 - sent to owners and operators of Eurocopter France (Eurocopter) Model AS350B3 helicopters.
This EAD is prompted by premature failures of laminated half-bearings (bearings), three cases of vibrations originating from the tail rotor due to premature failure of bearings installed with certain tail rotor blades, and an accident. This EAD requires installing two placards and revising the Rotorcraft Flight Manual (RFM). This EAD also requires certain checks and inspecting and replacing, if necessary, all four bearings. Finally, this EAD requires a one-time removal and inspection of the bearings, and replacing the bearings if necessary.
These EAD actions are intended to prevent vibration due to a failed bearing, failure of the tail rotor, and subsequent loss of control of the helicopter.