Mystery still surrounds last month's crash-landing by a British Airways airliner at Heathrow after a preliminary inquiry found no cause for the accident and said no mechanical defects had been found in the Boeing 777's engines.
The report, by the Air Accidents Investigation Branch (AAIB), added that examination of the black box had confirmed there was nothing wrong with the airliner's major systems but that the jet's fuel supply was not shut off properly.
All 136 passengers and 16 crew on the BA flight from Beijing survived the crash-landing on 17 January. A few suffered minor injuries and one a broken leg.
The failure to cut the fuel supply could have had "serious consequences" had there been a fire, the AAIB found . The oversight "resulted in the loss of fuel from the aircraft", according to the report, but was not related to the crash-landing.
Evidence from the aircraft revealed "no evidence of a mechanical defect or ingestion of birds or ice".
The AAIB said there were "no anomalies in the major aircraft systems", adding: "The autopilot and the auto-throttle systems behaved correctly and the engine control systems were providing the correct commands prior to, during and after the reduction in thrust".
With the pilots unable to gain the required thrust as the Boeing approached Heathrow, the aircraft came down on grass and started to skid "some 1,000ft short of the paved runway surface and just inside the airfield boundary fence", the report said.
A significant amount of fuel escaped from the airliner on landing but did not catch fire, it added.
The AAIB – which has produced three initial reports into the incident – is now focusing on damage to the fuel pumps, as well as some small items of debris found in the fuel tanks.
The AAIB made a safety recommendation relating to the order in which crew should go through evacuation procedures. It has suggested that Boeing instructs airlines to ensure that the fuel valve is cut off before the fire handle is operated.
"We have already implemented these changes to reflect the latest advice," a BA spokesman said.
After the incident, passengers on Flight BA38 described the "desperate" scene as the aircraft landed, in effect, without power after "dropping" out of the sky. One of those on board, Paul Venter, said: "The wheels came out and went for touchdown and the next moment we just dropped. I could not tell you how far."
Another passenger, Neil Jones, said: "The aircraft was banking to the left and it was coming in very low over the surrounding houses. The aircraft was significantly lower than it would normally be. You could tell that the pilot was desperately trying to get the plane down. The pilot was struggling but I think he did a great job."Reuse content