Boeing warns of ice problem in 777 engines

A second engine power loss on a Boeing 777, following one that caused an emergency landing in London, 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 14 degrees Fahrenheit (minus 10 degrees Celsius) or colder in flight after two hours, one hour less than previously advised, Boeing told customers in a notice issued on January 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 said.

The new recommendation was first reported 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.

No decision has been made on a mechanical fix or design change pending further investigation by the National Transportation Safety Board and British authorities, Ms Verdier said.

“It’s still open,” she 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, she said.

Trent 800-series engines were first installed on the two-engine planes about a decade ago and remain on about 30% of the more than 700 777s in use worldwide. About 50 of the affected planes are flown by US 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 January 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 pre-flight preparations by ground crews and precautionary action by pilots.

Pilots were told that after three hours with the fuel temperature at no more than 14 degrees F (minus 10 C), 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 November 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 8,000ft (2,438m), to 31,000ft (9,448m), 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.

Ms Verdier said the British Airways case was the first apparent fuel line icing in a 777, adding that investigators have yet to determine whether ageing, maintenance or equipment design might have been involved.