Stems From Premature Failure Of Bearings In The Tail Rotor Assembly

The FAA has issued an Emergency AD (EAD) for certain Eurocopter Model AS350B3 helicopters. The 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.

EASA, which is the Technical Agent for the Member States of the European Union, has issued EASA AD No. 2012-0207-E, dated October 5, 2012, to correct this unsafe condition for certain Eurocopter Model AS350B3 helicopters.

The EAD requires the following:

• Before further flight, install two placards on the instrument panel.
• Before further flight, revise the RFM to reduce the VNE airspeed limit.
• Before further flight and thereafter after each flight, without exceeding 3 hours time-in-service between two checks, visually check all the visible faces of the bearings.
• An owner/operator (pilot) may perform the visual checks required by this EAD and must enter compliance into the helicopter maintenance records in accordance with 14 CFR §§ 43.9(a)(1)- (4) and 91.417(a)(2)(v). A pilot may perform this check because it involves only a visual check for separation, a crack, or an extrusion in the tail rotor blade and can be performed equally well by a pilot or a mechanic. This procedure is an exception to our standard maintenance regulations.
• If there is an extrusion on any bearing, before further flight, replace the four bearings with airworthy bearings.
• If there is a separation or a crack on the pressure side bearing, measure the separation or the crack. If the separation or crack is greater than 5 millimeters (.196 inches), before further flight, replace the four bearings with airworthy bearings.
• After the last flight of the day, perform a one-time inspection by removing the bearings and inspecting for a separation, a crack, or an extrusion. If there is a separation, crack, or extrusion, before further flight, replace the four bearings.

The FAA says it considers the EAD to be an interim action. The design approval holder is currently developing a modification that will address the unsafe condition identified in this EAD. Once this modification is developed, approved, and available, additional rulemaking may be considered.

This helicopter has been approved by the aviation authority of France and is approved for operation in the United States. Pursuant to our bilateral agreement with France, the EASA, its technical representative, has notified us of the unsafe condition described in the EASA AD. The FAA is issuing this EAD after the evaluation of all information provided by EASA, and making a determination that the unsafe condition exists and is likely to exist or develop on other helicopters of this same type design.

(AS350 B3 image from file)

FMI: www.faa.gov