The Air Accidents Investigation Branch today said pilot error was responsible for a fatal offshore helicopter crash, which left four people dead.
On August 23, 2013 at 5.17pm a Super Puma helicopter carrying 16 passengers and two crew crashed in the sea on its approach to land at Sumburgh Airport.
The report detailed a fatal 30 seconds lapse when both pilots failed to notice the helicopter’s descending airspeed until it was in a “critically low energy state”.
“In the latter stages of the approach there was a period of some 30 seconds when the flight instruments were not adequately monitored and the helicopter’s airspeed continued to reduce unchecked below
80 kt,” the AAIB report said.
The ‘Check Height’ audio alert sounded when the helicopter was 300ft from the sea’s surface.
Their last-ditch rescue attempts failed and the helicopter crashed shortly after.
The report read: “The helicopter’s flight instruments were not monitored effectively during the latter stages of the non-precision instrument approach. This allowed the helicopter to enter a critically low energy state, from which recovery was not possible.”
It added: “The commander attempted recovery action and ultimately applied maximum collective pitch, but evidence suggests that the helicopter had probably entered Vortex Ring State and the situation was unrecoverable
in the remaining height available.”
The report also explains how the four passengers died – one in the liferaft from a chronic heart condition, likely to have been exacerbated by the stress of the evacuation.
A second managed to escape from the cabin, but drowned, while a third suffered a head injury during impact.
The fourth passenger died as a result of being unable to escape from inside the helicopter. They had tried to use the emergency breathing system.
The flight had left the Borgsten Dolphin semi-submersible drilling platform in the North Sea and was on route to Sumburgh Airport for a refuelling stop when the tragedy unfolded.
The Air Accidents Investigation Branch (AAIB) identified a period of inattention to the flight instruments starting 30 to 40 seconds from impact, and the dynamic approach profile as the immediate causes.
The report also found that flight crew had obtained inaccurate meteorological forecast for Sumburgh, which indicated that the “weather conditions would be better than they actually were”.
The report read: “The flight crew did not obtain up to date weather reports for alternate airports during the final flight sector and did not have a well rehearsed plan for a diversion.
“The weather conditions at Scatsta, the nominated alternate airport, would probably have precluded making a successful approach, but the flight crew were not aware of this.”
The weather on the day dictated the final approach be made by sole reference to the helicopter’s instruments.
The report read: “Although the approach vertical profile was maintained initially, insufficient collective pitch control input was applied by the commander to maintain the approach profile and the target approach airspeed of 80 kt. This resulted in insufficient engine power being provided and the helicopter’s airspeed reduced continuously during the final approach.
“Control of the flightpath was lost and the helicopter continued to descend below the MDA. During the latter stages of the approach the helicopter’s airspeed had decreased below 35 kt and a high rate of descent had developed.”
“The commander’s attempt to recover the situation was unsuccessful and the helicopter struck the surface of the sea approximately 1.7 km west of Sumburgh Airport,” the report added.
“It rapidly filled with water and rolled inverted, but was kept afloat by the flotation bags which had deployed.”
The report highlighted a number of contributing factors, including the pilots’ failure to develop a shared, unambiguous understanding of how the approach was to be flown.
However, it said no evidence found a fault with the helicopter or that the helicopter had not been maintained or certified in accordance with industry regulations.
Duncan Trapp, vice president for safety and quality at CHC Helicopter, said: “CHC deeply regrets the tragic Sumburgh accident, and we continue to extend our sympathies to the survivors and to the loved ones of those who died.
“Our priority is always the safety of our passengers and crews and we would like to thank the Air Accidents Investigation Branch (AAIB) for its thorough investigation.
“Although the AAIB makes no recommendations specific to CHC, immediately after the accident, and in the time since, we put in place additional measures to further improve safety. Among those actions, we have enhanced crew monitoring procedures and supported the industry-wide deployment of improved emergency breathing systems and training for offshore passengers and crew.
“We continue to lead and contribute to industry-wide efforts to further improve the safety of offshore helicopter transportation, including as a founding member of HeliOffshore.”
HeliOffshore’s chief executive officer, Gretchen Haskins, added: “Our thoughts are with those who lost loved ones in this tragic accident.
“Any loss of life is one too many, and that is why stakeholders across the global offshore helicopter industry are collaborating to further enhance safety.
“HeliOffshore members are continuing to enhance safety performance; taking action to implement our ambitious safety plan, which is already making a difference at the frontline.”
Four people were killed when the Super Puma helicopter they were travelling in ditched in the sea around two miles south of Fitful Head, Shetland, on August 23 2013.
Duncan Munro, 46, from Bishop Auckland, Sarah Darnley, 45, from Elgin, Gary McCrossan, 59, from Inverness, and George Allison, 57, from Winchester, all lost their lives in the accident.
The Lerwick Royal National Lifeboat Institution lifeboat, the Sumburgh based Coastguard helicopter and an RAF helicopter from RAF Lossiemouth were sent to find the downed helicopter. Two helicopters from Bond Offshore Helicopters, the passenger ferry MS Hjaltland and a cargo ship, the MS Helliar also joined in the search. The helicopter was found;12 passengers and two crew were rescued and sent to Gilbert Bain Hospital in Lerwick, Shetland Islands.
A day after the accident CHC helicopter temporarily suspended all Super Puma L2 flights worldwide.