Clutha crash: Police helicopter engines 'flamed out'
A police helicopter which crashed into a busy Glasgow pub killing 10 people suffered a double engine failure, air accident investigators have found.
The Air Accident Investigation Branch (AAIB) said both engines "flamed out" but its report does not pinpoint the cause. Some commentators have suggested a problem with the fuel supply.
The Eurocopter EC 135 came down on the Clutha Bar on Friday 29 November.
All three people on board and seven others in the pub were killed.
In its report, the AAIB said that its investigation into the crash was still ongoing.
Investigators said they were still trying to establish why both engines "flamed out" when there was 76kg of fuel remaining.
Examination of the engines showed "no evidence of foreign object damage or intake or exhaust blockage in either engine".
Also, the report said no faults were found with the transmission or rotor system, there was no evidence of structural failure or in-flight fire and no evidence of damage caused by bird strike or a foreign object hitting the aircraft in flight.
An examination of the fuel pump switches at the accident site showed that the No 1 and No 2 prime pump switches were set to the 'on' position but the fore and aft transfer pump switches were set to the 'off' position.
No CCTV recordings had been obtained which captured the end of the flight and the recorded radio transmissions did not contain any reference by the crew to difficulties with the aircraft.
The AAIB is also investigating why there was no Mayday call and why the aircraft was not able to make a controlled landing.
An initial report on the crash, which was released on 9 December, said there was "no evidence" of major engine or gearbox failure.
Although the aircraft did not have a black box data recorder, the AAIB investigation has been able to piece together elements of its last flight.
It established that the Police Scotland helicopter took off at 20:45 with 400kg of fuel on board.
It stayed over an area of Glasgow's south side for about 30 minutes before making a short 10 minute foray over Dalkeith in Midlothian, some 38 nautical miles away.
The helicopter was granted permission to re-enter Glasgow air space at 22:18 but radar contact was lost at 22:22.
The latest AAIB report states: "Recorded data indicates that, in the later stages of the flight, the right engine flamed out, and shortly after the left engine flamed out."
The report states that the rotor blades and tail rotor were not rotating at the time of impact.
However, it does not offer an explanation as to why both engines failed. It notes that there was no blockage on the fuel lines, both fuel pumps were in working condition and there was no leakage from the fuel tanks either before or after the accident occurred.
The report concluded: "The AAIB investigation continues to examine all the operational aspects of this accident and to conduct a detailed engineering investigation.
"In particular, the investigation will seek to determine why a situation arose that led to both the helicopter's engines flaming out when 76 kg of fuel remained in the fuel tank group, why no emergency radio transmission was received from the pilot and why, following the double engine failure, an autorotative descent and flare recovery was not achieved.
"The AAIB will report any significant developments as the investigation progresses."
Following publication of the report, Bond Air Services, which operated the helicopter for Police Scotland, said the development was the "another step" in "a long and complex investigation".
"While the investigation continues, we would urge against speculation," the company said.
"We owe it to the memories of those who died, those who were injured, and the families affected by this tragedy to help the investigation team answer as many questions as possible and discover exactly what happened.
"We continue to support the investigations and our thoughts remain with all those who have been touched by this tragedy.
"We also continue to work with Glasgow City Council and other parties to support bereaved families and the local community."
A spokesman for Airbus, which manufactured the helicopter, said: "Airbus Helicopters does not speculate on potential causes of any accident and continues to actively support the ongoing investigations of the AAIB."
The British Airline Pilots' Association said the AAIB report appeared to show a problem with the helicopter's fuel system.
In a statement, the group said: "We now know that the engines were not running at the time of the crash and it appears this was to do with the fuel system.
"However, pilots, like the AAIB, will not be satisfied until this is explored further and the exact reason for that failure is identified. The AAIB have our continued support in their work."
The helicopter crew who were killed in the Clutha bar crash were pilot David Traill, Pc Tony Collins and Pc Kirsty Nelis.
The seven customers in the Clutha who died were John McGarrigle, Mark O'Prey, Gary Arthur, Colin Gibson, Robert Jenkins, Samuel McGhee and Joe Cusker.
Jim Morris, a former RAF pilot and partner in Irwin Mitchell Solicitors, which is representing some bereaved families and survivors, said the focus of the AAIB report was "on the fuel system".
He said: "As there is no indication of problems with the engines, gearbox or flying controls, it appears that a serviceable aircraft crashed due to some form of fuel starvation, despite having 76kg of fuel in its tanks. This is something that should have never happened."
He said the AAIB would have had more information if the helicopter had been carrying flight data recording equipment.
Hannah Bennett, from Thompsons Solicitors, which is also representing some bereaved families and survivors, said the report offered "some clarity on what happened".
"It would appear there was a problem with the supply of fuel to the aircraft's engines but questions still remain as to why both engines failed while there was still a significant amount of fuel on board and why no emergency radio transmissions were sent by the pilot," she said.