LONDON // Ice in fuel lines probably caused a British Airways jet to lose power and make a jarring emergency landing in London in January, investigators said today. The Air Accident Investigation Branch (AAIB) said the problem was unprecedented on any large modern aircraft, and it urged US and European regulators to investigate what could be done to prevent a repeat. Nineteen people suffered minor injuries when the British Airways Boeing 777 made a crash landing 300 metres short of the runway on Jan 17.
Investigators from the AAIB said water, which is normally present in aircraft fuel, may have frozen because of unusually cold weather on a flight from Beijing to London. "Although the exact mechanism in which the ice has caused the restriction is still unknown in detail, it has been proven that ice could cause a restriction in the fuel feed system," the report said. "The risk of recurrence needs to be addressed in the short term while the investigation continues."
The report called for the Federal Aviation Administration and the European Aviation Safety Agency to work with Boeing and Rolls-Royce, maker of the plane's Trent 800 engines, to develop measures to reduce the risk of ice forming. The report also recommended that the regulators review certification requirements to insure that fuel systems can cope with the possible accumulation and sudden release of ice. Regulators, however, would be heading into unexplored territory.
"Extensive data analysis has revealed that not only has there never been a previous occurrence of this type on the Boeing 777, but also that this is the first known occurrence of this nature in any large modern transport aircraft," the AAIB said. The flight had been uneventful until its final approach into Heathrow. The problem developed when the plane was at a height of 220 metres, at which point power dropped in the right engine and, seven seconds later, in the left engine as well, the report said. That was consistent with a drop in the fuel flow, it said.
The Trent 800 engines have fuel oil heat exchangers that cool engine lubricating oil and warm fuel to prevent the formation of ice, the agency said. However, there are no regulatory requirements that address the possibility of a sudden release of ice in large quantities, which might disrupt fuel flow. "Water is always present, to some extent, in aircraft fuel systems and can be introduced during refuelling or by condensation from moist air which has entered the fuel tanks through the tank vent system," the report said.
Water can be dissolved in the fuel, particles can be suspended in the fuel or free water in the form of drops or puddles can be present. There was no evidence, the investigators said, that the amount of water in the British Airways plane's fuel was excessive. British Airways, which operates 15 Boeing 777s with the Trent engines, noted in a statement that this was not the final report, and that the AAIB had made no recommendations relating specifically to its fleet.
"We will work closely with the relevant regulatory authorities and will comply with any requirements issued to all operators of Boeing 777s powered by Rolls-Royce Trent 800 engines," British Airways said. *AP