'Ice in fuel' caused BA Accident
17/09/2008
It is thought that the BA plane that crashed at Heathrow in January was brought down by ice in its fuel system. The Air Accident Investigation Branch believes the flow of fuel dropped causing the engines to lose power less than a minute before touchdown. Investigators say however they still do not know how the ice could have formed.
Water is naturally present in aviation fuel and the investigators believe there may have been as much as five litres within this aircraft's fuel load. But levels of water found in fuel recovered after the 17 January crash were very low for a Boeing 777.
The plane flew through unusually cold air over Siberia while en route from Beijing to Heathrow. The fuel temperature fell to -34C (-29F). But jet fuel should not freeze until it is at less than -57C (-70F), and the report says the temperatures involved were not "unique".
The investigation into the crash of flight BA38 continues with testing at Rolls-Royce in Derby, and Seattle in the US, the home of Boeing. Following Thursday's report, a spokesman for the US Federal Aviation Administration said it would be issuing an air-worthiness directive to US carriers operating Boeing 777 aircraft. This was likely to be about changes in procedures for pilots to follow in certain cold weather conditions as well as changes in certain fuel procedures on the ground.
Water in aviation fuel can be dissolved at the molecular level, or simply float as free water, suspended in the fuel. As the fuel gets colder tiny droplets can form and freeze. The problem facing investigators is why this might have happened on an apparently fully functioning aircraft. The report however makes three safety recommendations:
- that the US Federal Aviation Administration (FAA) and the European Aviation Safety Agency introduce interim measures to reduce the risk of ice forming on the Boeing 777 powered by Trent 800 engines
- the agencies should consider the implications for other aircraft types
- review the requirements for new engines
In response to the recommendations, the European Aviation Safety Agency said it had agreed with the FAA to "interim measures" for "mandatory aircraft level action", but gave no further details. It also said it would examine the other recommendations.
Flight BA 38 from Beijing was extensively damaged when it touched down on 17 January, landing short of the runway but staying largely intact. One person suffered a broken leg and others received minor injuries during the emergency evacuation.