Within hours of the police helicopter crashing through the roof of Glasgow’s popular Clutha Vaults Bar at 10:22pm on Friday 29 November 2013, it became clear this was not a straightforward accident.
Why did the helicopter come down on a building although there was plenty of open space near it, including the river Clyde? Pilots directing a distressed aircraft avoid buildings in favour of open space for obvious reasons, not least the reduction in risk of injury to those on board. As it happened, all three crew in the helicopter died, and so did seven people in the bar.
Perhaps the pilot had no control for some reason, but early evidence suggested the Eurocopter EC-135, operated for the police by Bond Air Services, did not break up in the air nor shed critical components.
Now the Air Accident Investigation Branch has published its report. It reveals that the fuel system had been mismanaged and, as the helicopter flew west along the Clyde toward a landing at the Glasgow City Heliport, within 30 seconds of each other the two engines stopped.
The investigation determined that, upon losing power, the pilot’s physical reaction was more or less the opposite of what was required to put the aircraft into a successful autorotative descent to a forced landing. As a result the main rotor rapidly stopped turning and the aircraft dropped like a stone.
Also extensively examined by the AAIB was the fact that, about an hour into the flight, the main tank fuel feeder pumps were switched off. There was no evident reason for this to be done, but it was. Subsequently the pilot was provided with a succession of low fuel warnings, and acknowledged them by suppressing the alert chimes, but did nothing to correct the situation. All that would have been required was to switch the main tank fuel transfer pumps on, and the two small engine feeder tanks would immediately have been replenished.
The pilot’s regular communications with air traffic control were calm and measured throughout the sortie. The EC-135 had taken off from the Glasgow heliport, and the crew proceeded with a planned sequence of surveillance tasks in the region between Glasgow and Edinburgh, and it was on its return to land that the engine feeder tanks ran dry. There was no emergency call nor indication the crew faced any problems.
The AAIB’s report has a drier than usual style, reflecting its clear puzzlement as to why an experienced helicopter pilot with a good professional record would demonstrate such incompetence. Protocol would allow the AAIB to discuss possible reasons, but it has chosen not to do so.
A post-mortem examination of the crew demonstrated that they had no alcohol or drug traces in their blood. If the pilot was feeling unwell he didn’t say anything about it, but one wonders whether he was suffering some form of subtle incapacitation without realising it. The AAIB, however, has chosen not to pose that question in the report.
If the subtle incapacitation theory were true, a normal flight data recorder and cockpit voice recorder would not necessarily prove it. But a video recording of cockpit activity and of the instrument panel might record evidence suggesting it.