Seattle – A second engine power loss on a Boeing 777 following one that caused a hard landing in London has resulted in a stronger recommendation from the manufacturer to avoid icing in fuel lines in extremely cold conditions.
The fuel temperature in more than 200 777s with Rolls-Royce Trent 800-series engines should not be allowed to remain at -10 degrees Celsius or colder in flight after two hours, one hour less than previously advised, Boeing Co. told customers in a notice issued Jan. 29.
After two hours, pilots are told to reduce altitude, which can result in slower air speeds and increased fuel consumption.
"It's not the greenest thing in the world, but it's the safest thing we can do right now,'' Boeing spokeswoman Liz Verdier told The Associated Press on Wednesday.
The new recommendation was first reported Wednesday by the Seattle Post-Intelligencer.
Flight International, a British magazine, has reported that Boeing engineers found a heat exchanger in the Trent series is inadequate to prevent moisture in the fuel from freezing, raising the risk of a blockage that can halt the flow of fuel to the engine.
The heat exchanger was discussed at length in an interim report by the British Air Accidents Investigation Branch, which reached no conclusions on the functioning or design of that apparatus.
No decision has been made on a mechanical fix or design change pending further investigation by the National Transportation Safety Board and British authorities, Verdier said.
Meanwhile, the Federal Aviation Administration likely will issue an airworthiness directive ordering operators of 777s with Trent 800-series engines to impose the two-hour rule immediately, Verdier said.
Trent 800-series engines were first installed on the two-engine planes about a decade ago and remain on about 30 per cent of the more than 700 777s in use worldwide, Verdier said. About 50 of the affected planes are flown by U.S. carriers, chiefly Delta and American Airlines.
Engines made by General Electric and Pratt & Whitney and are not thought to be susceptible to the ice problem. The newest models, the 777-300ER and 777-200LR, all have GE engines.
No 777 has been involved in a fatal crash since the plane first went into service in 1995, but British Airways had a close call on a flight from Beijing to London with 152 passengers and crew members on Jan. 17, 2008.
As the 777-200ER approached Heathrow Airport, both Trent 895 engines failed to respond to autopilot commands for thrust and the plane came down hard and short of the runway. More than a dozen people were injured, one seriously.
Investigators decided the cause was probably fuel line icing, and in September the FAA ordered a number of changes in preflight preparations by ground crews and precautionary action by pilots.
Pilots were told that after three hours with the fuel temperature at no more than -10 degrees, they should open the throttle to maximum thrust for 10 seconds to try to dislodge any ice in fuel lines and then descend to warmer air.
On Nov. 26, a Delta Airlines 777-200ER, also with Trent 895s, lost power in the right engine over Montana on a flight from Shanghai to Atlanta. Following the new procedure, the pilot descended 8,000 feet, to 31,000 feet, regained power in the right engine and landed in Atlanta without further incident.
Investigations into both episodes are continuing, but because of the similarities in the apparent cause the three-hour limit was reduced to two hours.
Peter C. Knudson, an NTSB spokesman in Washington, D.C., said late Wednesday he could not answer questions about those potential issues.
Boeing warns of ice problem in some 777 engines
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