If you are in the oil and gas industry, air transport does not end with the airline flight to Aberdeen or Stavanger - there lies ahead a long helicopter flight over the grey and lethal waters of the North Sea to the oil platform, passengers and crew alike stuffed into survival suits.
Not surprising, therefore, that the oil and gas industry reacted strongly after the October 22 ditching in the North Sea of a Eurocopter EC225 operated by CHC Helicopters. Worldwide, almost every oil and gas operator suspended flights by both AS322L and EC225 Super Pumas, workhorses of the offshore market.
CHC AS322L2 (airliners.net photo via wikipedia)
All 19 passengers and crew were rescued and the aircraft recovered after the Oct 22 ditching, which the preliminary investigation says was caused by a loss of main-gearbox oil pressure almost identical to the May ditching in the North Sea of an EC225 operated by Bond Offshore Helicopters.
Inspection of the CHC aircraft revealed a crack that severed the bevel gear vertical shaft that drives the oil pumps for the main gearbox. It was failure of this shaft that caused the Bond ditching in May. Investigation of the Bond incident revealed a rising trend on two vibration parameters in the aircraft health and usage monitoring system (HUMS) data.
After the Bond incident, the European Aviation Safety Agency issued an airworthiness directive requiring operators of AS322s and EC225s to download and review the HUMS data at set intervals. The AD did not apply to the serial number of vertical shaft in the CHC EC225, but post-incident analysis shows a rising trend on the same two vibration parameters. On Oct 25, EASA expanded the AD’s applicability to all vertical shafts, regardless of serial number.
Operators began returning some AS322Ls to service today (Oct 26), but only those without the suspect vertical shaft. AS322Ls with the new-style shaft and the later EC225s are still grounded, except for some search-and-rescue flights, and could remain for for weeks, reports say.
Over the last couple of years, oil and gas companies and offshore operators have been striving to improve the industry's safety record, and the rapid worldwide response to the CHC ditching is an example of their determination. Better use of HUMS data is a key part of improving safety.
After the May ditching, Bond - which had an AS332L2 crash in the North Sea in April 2009 following a catastrophic main gearbox failure, killing all 16 on board - put in place a 100-day plan to improve safety. This includes additional barriers to prevent helicopters being cleared for flight when HUMS parameters have not exceeded alert thresholds, but are showing anomalous trends.