A fuel leak from the British Airways (BA) Boeing 777-200 that crash-landed at Heathrow on 17 January ” which would have had ”serious consequences in the event of a fire during the evacuation” - could have been avoided.
The latest Air Accidents Investigation Branch (AAIB) report found that ” while this ”was not causal to the accident” - both engine spar valves (designed to shut off fuel supply in the event of a fire or accident) were open. A Boeing evacuation checklist shows the switches should be closed before fire handles are pulled to initiate the engines” fire extinguishers, but the pilots first pulled the handles, meaning the switches could not close, resulting in a dangerous fuel spillage on landing.
The report says BA”s checklist ” which required the commander to operate the fuel switches whilst the first officer operated the fire handles ”to reduce the time required to action the checklist” ” had received no technical objection from Boeing, but meant there was ”no measure in place to ensure the correct sequencing.”
A BA spokesman told ABTN: ”The flight crew followed the evacuation checklist which had received no technical objection from the manufacturer ” and this formed part of the operations manual which is accepted by safety regulator the CAA.”
It seems the aircraft”s system leaves potential room for error, and Boeing has already issued a recommendation for all 777 operators to splice together the two separate wires for the fuel control switches and the fire handles ”to avoid the need to sequence their operation.” US air safety regulator the Federal Aviation Administration has told all operators to implement this revised system by July 2010.
In the meantime, the AAIB has recommended to Boeing that it reminds all 777 operators of the precise emergency drill, and BA said it has ”already implemented the changes to reflect this updated procedure.”
The BA 777 landed short of London Heathrow”s runway 27L on Thursday 17 January, with all 136 passengers and 16 crew managing to evacuate with only minor injuries being suffered.
The AAIB report says that while the aircraft”s electric and electronic engine and fuel system controls were working perfectly, it found damage to the high-pressure fuel pumps on both engines.
”This could be indicative of either a restriction in the fuel supply to the pumps or excessive aeration of the fuel. The manufacturer assessed both pumps as still being capable of delivering full fuel flow.”
There were no signs of contamination or unusual levels of water content in the fuel.
Flight data recorder showed there ”were no anomalies in the major aircraft systems”and the engine control systems were providing the correct commands prior to, during, and after, the reduction in thrust.”
There was also no evidence of birdstrike or ice in the engines, and no indications of any pre-existing problems with any of the aircraft”s systems.
The report does point out that temperatures during the flight were ”unusually low compared to the average, but not exceptional”, and that the lowest recorded during the flight was -45”C (-113F). The freezing point for the aircraft”s fuel type is -47”C, but the minimum recorded fuel temperature inflight was -34”C.
The AAIB is now attempting to ”replicate the damage seen to the engine high pressure fuel pumps and to match this to the data recorded on the accident flight.”