The UK’s Air Accidents Investigation Branch (AAIB) published a further “special bulletin” late last week in its investigation into the controlled ditching of a Bond-operated EC225 medium twin in May in the North Sea, confirming an earlier hint by Eurocopter that the emergency lubrication system gave the pilots a false failure warning.

According to the AAIB, the crew had received indications that both the primary and backup (emergency) gearbox lubrication systems had failed. The latter warning illuminated 32 seconds after the crew activated the emergency lubrication system, and AAIB investigators subsequently found no leak in the backup system.

Moreover, the back-up pump was operating normally from the time the system was activated until the aircraft ditched, the investigators determined. They also suggested that the bleed-air pressure sensor triggered the warning. The AAIB noted that, during development of the EC225, no test was performed on the complete backup system, either on a test rig or installed on the helicopter itself.

Yesterday a CHC-operated EC225 performed a controlled ditching in the North Sea. All 19 occupants were rescued safely. In the meantime, CHC, Bond Helicopters and Bristow have grounded the 29 EC225 and AS332 Super Pumas that transport workers to offshore North Sea oil platforms.