The aircraft, with two crew and 12 passengers on board, ditched 25 miles east of Aberdeen on 10 May after a low oil pressure warning. A bulletin by the government’s Air Accident Investigation Branch has already revealed that its gearbox shaft was cracked.
The gearbox has been traced to a batch of only ten spare parts, one of which was supplied to Bond and used in the downed aircraft. The safety agency has now issued an alert to the operators of Super Puma EC225 helicopters supplied with one of a batch of parts for the main rotor drive bevel gear shaft.
The EASA airworthiness directive states: “The preliminary findings of the investigation have shown a full circumferential crack of the lower vertical shaft of the main gearbox bevel gear. As a result, the vertical shaft ceased to drive the main and backup oil pumps. Although the investigation is still in progress, at this early stage a manufacturing defect of the part must be considered.
“The investigation has also determined that prior to the flight during which the helicopter ditched, the Vibration Health Monitoring system installed on the helicopter had identified a rising trend in certain monitoring parameters associated with the MGB oil pump drive system.”
A spokesman for Bond said the EASA directive had been “implemented with immediate effect.” He added: “The directive applies to certain batches of a main gearbox part in the EC225, and requires regular monitoring of flight data and reporting to manufacturer Eurocopter.
“Bond Offshore Helicopters will be discussing flight scheduling arrangements with customers to avoid any potential disruption, and in accordance with the directive will continue to monitor developments.”
Helicopters operated by rival companies Bristow and CHC are unaffected.