Probe into EC225 North Sea Ditching Centers on Gearbox

 - May 22, 2012, 3:59 PM

The EASA issued an emergency Airworthiness Directive for Eurocopter EC225 medium-twin helicopters, requiring operators to closely monitor vibrations. The emergency action stems from a May 10 incident involving an EC225 operated by Bond Offshore Helicopters, which safely ditched, with 14 on board, into the North Sea. Under the AD, those EC225s not equipped with vibration health monitoring are restricted to day VFR for flights over water.

The Bond EC225 investigation is focusing on the failures of two main gearbox lubrication systems–standard and back-up. According to the UK’s Air Accidents Investigation Branch (AAIB), the event began when the main gearbox oil pressure gauge indicated zero. The crew initiated a descent and then activated the emergency lubrication system. However, the warning light for this system, designed to allow 30 minutes of flight, quickly illuminated, prompting the pilots’ decision to ditch.

After the incident, Bond suspended EC225 and later AS332L2 Super Puma flights. The AAIB identified a “360-degree circumferential crack in the bevel gear vertical shaft in the main gearbox.” This caused disengagement of both mechanical (standard) oil pumps.

On May 15, Bond announced the resumption of all flights. This was the result of “a rigorous engineering analysis and safety risk assessment.” A Eurocopter spokesman noted that neither the AAIB nor the EASA had required any aircraft grounding.