The Glasgow pub helicopter tragedy which claimed 10 lives happened after both engines on the aircraft failed, an interim accident report has revealed.
And air accident investigators today admitted they still don't know what caused the helicopter to lose power and crash on to the roof of the Clutha Bar.
The accident happened on November 29 when the busy nightspot was packed with revellers.
A special bulletin from the Air Accidents Investigation Branch has revealed a series of alarms were triggered inside the cockpit minutes before the crash.
They included low fuel warnings for left and right fuel supply tanks triggered by thermal sensors in the tanks.
They are normally activated when there 32kg and 28kg of fuel left in the left and right tanks respectively.
The report also revealed that both helicopter engines stopped despite rigorous checks confirming there were no blockages between the engines and the fuel tanks.
It also said rotor blades should have automatically continued working during the emergency but instead they failed to "autorotate".
Investigators also uncovered a fault on the internal display panel but have not given details and are currently probing the fault. They have established the helicopter was using its reserve fuel supply but there should of been enough for it to return to its city base.
The report said: "In particular, the investigation will seek to determine why a situation arose that led to both the helicopter's engines flaming out when 76kg of fuel remained in the fuel tank group."
It will also try to find out 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 pilot who died was David Traill and his passengers were Pc Kirsty Nelis and Pc Tony Collins.
More than 100 people were in the popular city centre bar, near the River Clyde, at the time of the crash.
Those killed in the pub were John McGarrigle, 57, Mark O'Prey, 44, Gary Arthur, 48, Colin Gibson, 33, Robert Jenkins, 61, and Samuel McGhee, 56.
Customer Joe Cusker, 59, was pulled from the wreckage alive but died in hospital from his injuries almost two weeks later. In total, more than 30 people were taken to hospital after the crash.