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Boeing warns ice can 'starve' engines
Altitude linked to two 777 incidents
By JAMES WALLACE
P-I AEROSPACE REPORTER
A Delta Airlines 777-200ER was flying from Shanghai, China, to Atlanta in November when its right engine suddenly lost thrust while the plane was cruising at 39,000 feet over Montana.
The pilots followed flight manual procedures and descended to 31,000 feet, where the Rolls-Royce engine recovered and responded normally. The flight, with 15 crew members and 232 passengers, continued to Atlanta and landed safely.
That incident would likely not have gotten much attention had the same kind of Boeing jet, with Rolls-Royce engines, not lost all power in both engines just before landing at London's Heathrow earlier in the year. The British Airways 777 crash-landed short of the runway. Several passengers were injured, but none seriously.
Safety experts eventually decided that the British Airways jet, also on a flight from China, had flown through unusually cold weather at cruise altitude and ice apparently formed in part of the engine and blocked the fuel flow.
On Thursday, Boeing sent a notice to all operators of its 777s with Trent engines made by Rolls-Royce, advising them that it now believes the Delta and British Airways incidents appear to have been caused by the same thing -- ice blocking the fuel path.
A Boeing spokesman said Tuesday the "all operators" notice contains a series of precautionary measures that pilots should take during flight to lessen the chance ice could cause a sudden loss of engine power.
Eventually, the spokesman said, the Federal Aviation Administration can be expected to order a "permanent fix." That likely would mean a redesign of part of the Trent 777 engine.
The Boeing Co. would not release a copy of the letter it sent last week. A spokesman said it is not a public document. But the industry magazine Flight International obtained a copy and said the Boeing letter describes the Delta and British Airways incidents as likely being caused by "similar factors."
More than 700 Boeing 777s, a widebody jet that typically carries from 300 to 360 passengers, are in service with airlines around the world. About 30 percent have Trent engines.
General Electric and Pratt & Whitney also make engines for the 777, but those have a different design from the Trent engine from Rolls-Royce and are not thought to be susceptible to the ice problem. The newest 777s built by Boeing, the best-selling 777-300ER and the ultra-long-range 777-200LR, are powered only with GE engines.
In September, the FAA issued a formal airworthiness directive that required changes in the way ground crews prepare 777s with Trent engines and how pilots fly them in extreme cold weather in response to what investigators found in studying the British Airways crash in January. Shortly before the FAA issued its warning, Boeing had sent out an "all operators" notice with a series of recommendations developed to prevent a similar problem on its 777s with Trent engines.
Boeing recommended, for example, that pilots rev their engines when the fuel temperature falls to 14 degrees Fahrenheit. That would conceivably dislodge any ice that might be in the fuel line.
Another procedure Boeing recommended, and the FAA ordered, called for the crew to advance the engine throttles to maximum thrust for 10 seconds before descending on flights that have maintained the same altitude for at least three hours, if the fuel temperature is below 14 degrees.
Those procedures have been modified in the Boeing bulletin sent last week, following the Delta incident.
Boeing now recommends that pilots advance engine throttles to maximum thrust before descending on flights that have maintained the same altitude for two hours, not three.
And Boeing recommends that pilots, during the descent for landing, reduce engine power to full idle for at least 30 seconds. By reducing fuel flow, engine oil heat can melt any ice that may have accumulated.
The FAA, as it did in September, is likely to make Boeing's latest recommendations mandatory.
The 777 has never had a fatal crash since it entered service with United Airlines in 1995. But the Delta and British Airways incidents have given safety experts cause for concern, in large part because they are apparently dealing with a previously unknown phenomenon.
The British Airways crash occurred Jan. 17, 2008, as the 777-200ER, with 152 passengers and crew members, approached Heathrow after a flight from Beijing. Both engines failed to respond to autopilot commands for thrust as the plane approached the airport.
It turned into one of the most puzzling aviation accidents in modern times. The plane was badly damaged but mostly intact, so investigators had all the physical evidence in hand to look for clues. But one thing was missing -- the ice. The key piece of evidence had literally melted away.
Investigators now believe the problem is with the fuel-oil heat exchanger system on the Trent 777 engine.
Boeing engineers, according to Flight International, have determined by working in the laboratory that the heat generated by the Rolls-Royce fuel-oil heat exchanger is not adequate to prevent moisture in the fuel from freezing. When that happens, ice can form that blocks fuel to the exchanger, "starving the engines," according to the magazine.
Altitude linked to two 777 incidents
By JAMES WALLACE
P-I AEROSPACE REPORTER
A Delta Airlines 777-200ER was flying from Shanghai, China, to Atlanta in November when its right engine suddenly lost thrust while the plane was cruising at 39,000 feet over Montana.
The pilots followed flight manual procedures and descended to 31,000 feet, where the Rolls-Royce engine recovered and responded normally. The flight, with 15 crew members and 232 passengers, continued to Atlanta and landed safely.
That incident would likely not have gotten much attention had the same kind of Boeing jet, with Rolls-Royce engines, not lost all power in both engines just before landing at London's Heathrow earlier in the year. The British Airways 777 crash-landed short of the runway. Several passengers were injured, but none seriously.
Safety experts eventually decided that the British Airways jet, also on a flight from China, had flown through unusually cold weather at cruise altitude and ice apparently formed in part of the engine and blocked the fuel flow.
On Thursday, Boeing sent a notice to all operators of its 777s with Trent engines made by Rolls-Royce, advising them that it now believes the Delta and British Airways incidents appear to have been caused by the same thing -- ice blocking the fuel path.
A Boeing spokesman said Tuesday the "all operators" notice contains a series of precautionary measures that pilots should take during flight to lessen the chance ice could cause a sudden loss of engine power.
Eventually, the spokesman said, the Federal Aviation Administration can be expected to order a "permanent fix." That likely would mean a redesign of part of the Trent 777 engine.
The Boeing Co. would not release a copy of the letter it sent last week. A spokesman said it is not a public document. But the industry magazine Flight International obtained a copy and said the Boeing letter describes the Delta and British Airways incidents as likely being caused by "similar factors."
More than 700 Boeing 777s, a widebody jet that typically carries from 300 to 360 passengers, are in service with airlines around the world. About 30 percent have Trent engines.
General Electric and Pratt & Whitney also make engines for the 777, but those have a different design from the Trent engine from Rolls-Royce and are not thought to be susceptible to the ice problem. The newest 777s built by Boeing, the best-selling 777-300ER and the ultra-long-range 777-200LR, are powered only with GE engines.
In September, the FAA issued a formal airworthiness directive that required changes in the way ground crews prepare 777s with Trent engines and how pilots fly them in extreme cold weather in response to what investigators found in studying the British Airways crash in January. Shortly before the FAA issued its warning, Boeing had sent out an "all operators" notice with a series of recommendations developed to prevent a similar problem on its 777s with Trent engines.
Boeing recommended, for example, that pilots rev their engines when the fuel temperature falls to 14 degrees Fahrenheit. That would conceivably dislodge any ice that might be in the fuel line.
Another procedure Boeing recommended, and the FAA ordered, called for the crew to advance the engine throttles to maximum thrust for 10 seconds before descending on flights that have maintained the same altitude for at least three hours, if the fuel temperature is below 14 degrees.
Those procedures have been modified in the Boeing bulletin sent last week, following the Delta incident.
Boeing now recommends that pilots advance engine throttles to maximum thrust before descending on flights that have maintained the same altitude for two hours, not three.
And Boeing recommends that pilots, during the descent for landing, reduce engine power to full idle for at least 30 seconds. By reducing fuel flow, engine oil heat can melt any ice that may have accumulated.
The FAA, as it did in September, is likely to make Boeing's latest recommendations mandatory.
The 777 has never had a fatal crash since it entered service with United Airlines in 1995. But the Delta and British Airways incidents have given safety experts cause for concern, in large part because they are apparently dealing with a previously unknown phenomenon.
The British Airways crash occurred Jan. 17, 2008, as the 777-200ER, with 152 passengers and crew members, approached Heathrow after a flight from Beijing. Both engines failed to respond to autopilot commands for thrust as the plane approached the airport.
It turned into one of the most puzzling aviation accidents in modern times. The plane was badly damaged but mostly intact, so investigators had all the physical evidence in hand to look for clues. But one thing was missing -- the ice. The key piece of evidence had literally melted away.
Investigators now believe the problem is with the fuel-oil heat exchanger system on the Trent 777 engine.
Boeing engineers, according to Flight International, have determined by working in the laboratory that the heat generated by the Rolls-Royce fuel-oil heat exchanger is not adequate to prevent moisture in the fuel from freezing. When that happens, ice can form that blocks fuel to the exchanger, "starving the engines," according to the magazine.