Eurocopter chief executive Lutz Bertling has committed to returning the global EC225 fleet to unrestricted service by next February as operators continue to wait on firm information from the airframer on the cause of the 22 October ditching in the North Sea.
As in interim measure it has issued a revision of its emergency service bulletin, introducing new guidance for overwater flights of the type.
Bertling attended a 15 November meeting of the Helicopter Safety Steering Group in Aberdeen and expressed his "deep apologies" for the two ditchings and subsequent operational disruption.
He says a hypothesis for the root cause of the cracks on the main gear bevel shaft has been developed and Eurocopter will now attempt to prove this through a combination of ground and flight tests. It says it will take around three months to complete the testing and agree on corrective measures with the authorities.
"Therefore, a return to flight of the EC225 in full capacity and overwater is expected in February 2013. Eurocopter will of course make its best efforts to reduce this timeframe," it says.
Eurocopter followed up on the meeting with a revision to its emergency service bulletin covering the EC225 and AS332, and their military equivalents, on 22 November. It says that its studies suggest the cracks propagate in the shaft more slowly at lower engine power. Therefore, for aircraft "performing operations which do not enable an emergency landing on the ground within 10 minutes" it has reduced the maximum continuous power limit for the aircraft in level flight by 15% to 70%.
However, although the CHC Scotia-operated EC225 involved in the October ditching had developed a similar crack to that seen in an earlier incident this year, the service bulletin says it did not initiate from a hole drilled in a weld on the shaft, as was the case in the May ditching.
Additionally it has revised the thresholds used on the type's vibration monitoring system which provides an early warning that a crack is developing. And for those helicopters not fitted with that equipment, it says in-situ non-destructive testing of the integrity of the shafts is possible.
Although a ruling from the UK Civil Aviation Authority banning overwater flights covers only UK-based helicopters, both CHC Helicopter and Bristow Helicopter Services have grounded their EC225 fleets globally.