Executive summary
At 1112 on Sunday 13 April 2008, ZK-IAV, a Eurocopter AS355 helicopter, departed from Wellington International Airport on a visual flight rules flight to Marlborough Sounds, with the pilot and one passenger on board.
Two minutes after departure, one of the 3 main rotor blade spherical thrust bearings attached to the rotor head failed. The failure caused a significant main rotor loss of balance and track, which resulted in severe vibration and limited the pilot’s ability to control the helicopter. Despite the vibration and limited control, the pilot completed a successful emergency landing in a nearby sports field with no injuries.
The bearing failed because of internal corrosion and de-bonding of its elastomer segment, which was probably a result of some undetected surface damage to the elastomer surface.
Safety issues identified included the old age of the bearings, the adequacy of inspections and the bearings continued use without a specified calendar life. Safety recommendations were made to the Director of Civil Aviation to address these safety issues.
Related Recommendations
The Spherical Thrust Bearings remained in service in an unserviceable state despite inspections by various engineers and the pilot over the preceeding 18 months. This may indicate that the documented inspection procedures for the bearings are not being followed correctly or that the procedures need to be examined for their adequacy.
With no calander life but an hour and on-condition limit on the bearings only, their service life limits may need to be examined in conjunction with the aircraft manufacturer to determine if they are satisfactory.