Later this year – or, given the glacial nature of such proceedings, next year – there must be a fatal accident inquiry into the Clutha Bar helicopter crash in Glasgow, which killed the pilot and two observers on board as well as seven people in the pub. 'Must' because in cases such as this, where some of the victims died in the course of their employment, a fatal accident inquiry is obligatory.

But will the outcome be any more conclusive than the much-criticised report of the Air Accidents Investigation Branch into this baffling tragedy? Will the new inquiry be able to answer perhaps the most tantalising of the many questions surrounding the events of 29 November 2013: why, with the aircraft in severe difficulties for some time before it plunged into the bar, there was no alert from the cockpit. A possible, wholly plausible, explanation now emerges for the absence of any signs of panic on board.

But first, let's remind ourselves what happened that night.

Fuel in the helicopter's main fuel tank was pumped by two transfer pumps into a supply tank, which was divided into two cells. Each cell fed its respective engine. During a painstaking examination of the tank, it was found that 76kg of fuel remained in the main tank, yet the supply tank at the point of impact was empty. The investigators 'deduced' – with the limited evidence at their disposal, they could do no more than deduce – that both fuel transfer pumps in the main tank had been selected OFF for 'a sustained period' before the accident, leaving the fuel in the main tank unusable. They were not at OFF for the entire journey, otherwise the helicopter would not have flown for as long as it did; they must have been switched to OFF in the latter stages of the journey.

The investigators believe that the LOW FUEL 1 and LOW FUEL 2 warning captions were then repeatedly triggered and displayed and that the pilot acknowledged them – it is not clear from the report what form this acknowledgement took – yet continued to fly in breach of protocols. They were unable to explain why a pilot rated 'above-average', with 5,500 hours of flying experience in military and civilian helicopters, who had seen operational service with the RAF in Afghanistan, Iraq and Northern Ireland, acted in the way he did.

Let's now set the pilot aside and think of the two police observers who accompanied him. When the warning captions were displayed, the observers should have seen them – especially as they were permanently illuminated towards the end of the flight. The report states at one point that they 'would' have seen them. but even if they had not, they would have heard the audible warning which accompanied them: an attention-seeking gong.

Despite the proliferation of warnings indicating fuel starvation, the report implicitly invites us to believe that two experienced observers were unconcerned. Each had a personal set of radio controls. Each had the ability to call base at any time. Neither did so. The flight continued with no word from the crew that there was anything amiss. At 10.19pm, when the pilot informed air traffic control that they had completed their mission and were returning to the police helipad, still there was no evidence of apprehension. On the contrary there was a routine feel to the communication. Yet, a mere three minutes later, all three crew members were fatally injured.

Why, given their awareness for 'a sustained period' that the flight was in difficulties, did the observers do nothing to alert ground staff? If we accept the report in its totality, we shall probably never know what the pilot was doing or thinking in the last half hour of his life. But the lack of response from the observers is, on the face of it, equally incomprehensible – until we look at the history of air accidents.

On the evening of 28 December 1978, a United Airlines flight was making an approach to Portland International Airport when the captain detected an abnormality in the landing gear. He decided to enter a holding pattern so that he could deal with the problem; and for an hour the captain concentrated on the faulty landing gear, impervious to the dwindling fuel supply. The first officer and the flight engineer dropped hints – but not wishing to challenge the authority of the captain they were no more than hints – about the possibility of fuel starvation. It was only when the engines started to flame out that the captain realised the gravity of the situation. The aircraft crash landed in a suburb of Portland, Oregon, six miles short of the runway, killing two of the crew members and eight passengers.

In an inquiry for the American equivalent of the Air Accidents Investigation Branch, an aviation psychologist, Dr Alan Diehl, realised that the Oregon crash bore disturbing similarities to several other major airline accidents, in both the United States and Europe, and that the common denominator was an extreme reluctance on the part of crew to question the decisions and actions of their captain.

Eleven years later, in July 1989, a more collaborative approach almost certainly saved many lives. Captain Al Haynes, pilot of a United Airlines flight which crashed in Iowa, said after the incident: 'Up until 1980, we kind of worked on the concept that the captain was THE authority on the aircraft. What he said, went. And we lost a few airplanes because of that. Sometimes the captain wasn't as smart as we thought he was. And we would listen to him, and do what he said, and we wouldn't know what he was talking about. [That night] we had 103 years of flying experience there in the cockpit, trying to get that airplane on the ground, not one minute of which we had actually practised, any one of us. So why would I know more about getting that airplane on the ground under those conditions than the other three? If we had not let everybody have their input, it's a cinch we wouldn't have made it'.

From the mid-1980s, in an attempt to minimise the potentially devastating effects of human error, airlines began to introduce a set of training procedures known as crew resource management (CRM). Although it respects the command hierarchy on board, CRM aims to foster a less authoritarian cockpit culture and to encourage others on board to question captains if they see them making mistakes.

But the history of air accidents since the mid-80s informs us that crew resource management, while admirable in theory, has not completely eliminated poor communication in the cockpit. The failure to observe CRM has been cited as one of the reasons for the disastrous fate of Air France flight 447 from Rio de Janeiro to Paris in June 2009, which plunged into the Atlantic with the loss of 228 lives. One analyst of the disaster wrote that 'the men utterly failed to engage in CRM. They failed, essentially, to co-operate'.

If even major airlines can still get it wrong, we are bound to wonder whether anyone on board the police helicopter which crashed into the Clutha Bar had ever been trained in crew resource management. As one aviation specialist told the Scottish Review: 'Clutha was a terrible tragedy and if, as seems likely, the fuel situation was critical, then it's the pilot's job to notice. Whether the police observers would have been sufficiently trained to monitor the pilot, I frankly doubt'.

Could this be the solution to the psychological riddle of the Glasgow helicopter crash – the utter silence of all those on board in the final stages of the flight? It is an important question worth exploring at the fatal accident inquiry.

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