An aeroplane maker has issued urgent guidance to pilots in the wake of an investigation that found a British Airways jet’s crash landing was probably caused by ice in its fuel system.
The previously-unknown problem was revealed in an Air Accidents Investigation Branch (AAIB) report into the incident at Heathrow Airport on January 17th.
Boeing has issued airlines with advice on how to fly the planes in such a way as to minimise the formation of ice in the fuel supply.
Boeing said the new operational procedures — including revising the speed and altitude of flights — would not be noticeable to passengers.
Regulators were urged to review the safety of all passenger aircraft after the investigation's findings.
It is likely that ice crystals built up inside the aircraft's fuel tanks as it flew at high altitudes and then blocked fuel flow to its engines as it descended to land, the inquiry found.
Disaster was narrowly averted when flight BA038 from Beijing to London came down 1,000ft short of the runway. The Boeing 777's Rolls-Royce Trent 800 engines failed to provide the required thrust as it approached Heathrow and it landed just inside the airfield's boundary fence.
One passenger suffered a broken leg and eight others received minor injuries after the jet skidded across the grass and onto the end of the runway.
Boeing said it was analysing its full range of aircraft to check whether ice build-up could affect them, while rival large passenger jet manufacturer Airbus said it was studying the new report.
BA said the report had no safety recommendations specific to it, but pledged to continue co-operating fully with the inquiry.
Rolls-Royce spokesman Neil Williams said: "While the investigation into this accident continues, it would be inappropriate to speculate on the exact cause and we continue to fully support the ongoing investigation."
The AAIB's final report into the incident will be published at a later date.
Aircraft are designed to cope with significant amounts of the ice crystals which form in fuel when they climb into sub-zero atmospheric conditions. But tests on a Trent 800 engine showed that restricting fuel flow to the high-pressure pump caused a similar effect to that recorded in the accident.
Investigators noted that the BA aircraft encountered very low temperatures en route from China to London, but comparison with 141,000 other Boeing 777 flights showed they were not unique.
But flight BA038 stood out for the length of time the fuel in the main tanks had stayed below 0C, as well as for its low fuel flow demands while cruising and high fuel flow demands in the final approach to Heathrow.
The AAIB report concluded: "The investigation has shown that the fuel flow to both engines was restricted — most probably due to ice within the fuel feed system.
"This ice is likely to have formed from water that occurred naturally in the fuel whilst the aircraft operated for a long period, with low fuel flows, in an unusually cold environment."
PA