09.02.10
The British Airways Boeing 777-200ER plane crash at Heathrow Airport on January 17 2008 was 'probably' caused by a build-up of ice in the fuel system, an official report released today says. The plane lost power to both engines due to restricted fuel flow, the Air Accidents Investigation Branch (AAIB) report said.
The report says that it is probable that ice formed within the fuel system from water that occurs naturally in fuel. When fuel temperatures were at a ‘sticky range’, ice crystals were likely to stick to their surroundings. The AAIB concluded that an engine component, called the fuel oil heat exchanger, was likely to stop working in a combination of soft ice and with a fuel temperature below -10C (14F).
The AAIB report said: ‘Certification requirements, with which the aircraft and engine fuel system had to comply, did not take account of this phenomenon as the risk was unrecognised at that time.’ The report adds that research in the 1950s identified the problem of ice formation in fuel systems from dissolved or trapped water, but did not identify that it was possible for accumulated ice to restrict fuel flow. There were also no published guidelines or tests on the susceptibility of a fuel system to ice.
Having lost power, the BA plane, arriving at Heathrow from Beijing, came down within the airfield boundary, but 330m (1,080ft) short of the runway, sliding 372m (1,220ft) before coming to rest. It avoided a more serious accident after the pilot executed a last-minute manoeuvre to clear antennas fringing the runway. BA Captain Peter Burkill altered the flap settings to reduce drag when the aircraft was only 240 feet above the ground, which delayed the impact for 50 meters (164 feet).
Had he not adjusted the flaps, the 777 would have plowed into a cluster of antennas that communicate with the instrument landing systems of aircraft before touchdown, the AAIB said, adding: ‘The effects of contact with the ILA antenna are unknown but such contact would probably have led to more substantial structural damage [to the plane].’
All 152 passengers were safely evacuated from the aircraft, with one passenger breaking a leg. The plane cracked a wing and its wheels were ripped off in the crash and was an insurance write off.
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