INVESTIGATORS probing two separate ditchings of Super Puma helicopters in the North Sea have called for tighter regulations around the technology used by rescuers to locate survivors in the event of an aircraft crash.
In May, all 14 passengers and crew members on a Super Puma were rescued after the craft came down off the coast of Aberdeen. It was on a scheduled flight from Aberdeen Airport to a platform in the North Sea.
The model was thrust into the spotlight again in October when a CHC-owned helicopter was forced to ditch while carrying an oil crew from Aberdeen to a rig 86 miles north-west of Shetland. The 17 passengers and two crew were rescued and escaped injury.
An earlier AAIB bulletin blamed a problem in the aircraft's gearbox for the crash.
Today, the AAIB report warns water flooding the cabin may have caused the CPI to cut-out in the May ditching, and that improvements were needed to ensure search parties could locate a helicopter and its passengers if ditchings occur in future.
CPI is a "primary location aid" which transmits a beacon signal that can be detected by satellites, pinpointing a stricken aircraft's location.
In the first crash, the AAIB reports that CPI – supposed to be water-activated – was not triggered, possibly due to electrical failures.
The report said: "Photographs show the water level in the cabin was above the level of the water activated switch. While further work is required to support any final conclusions, issues relating to the continuity of the helicopter wiring when submerged, the design of the water activated switch and the location of the water activated switch relative to the water level following the ditching are being investigated as possible causes for the non-deployment of the CPI."
In the case of the October Super Puma ditching, the CPI correctly emitted distress signals to rescuers but only after being switched on manually by the crew.
However, investigators said that, had the helicopter subsequently overturned and the CPI become submerged in water after already being activated manually, the beacon release unit would have been rendered redundant –although the pilots were not aware of this because it was not mentioned in the flight manual.
The report added: "This would greatly reduce the possibility of successful detection of the beacon transmission by satellites. As no information relating to this feature was included in the EC225 LP Flight Manual, the operators of [both helicopters] were not aware of this feature."
The AAIB recommends that the European Aviation Safety Agency and its US equivalent, the Federal Aviation Administration, require the manufacturers of aircrafts fitted with Type 15-503 CPI, or similar location technology, to review and amend flight manuals if necessary.
The AAIB is continuing to investigate gearbox malfunctions and will report back on its findings later this year.
Helen McArdle
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