Originally published on November 25, 2013
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Aircraft manufacturer Boeing has advised airlines about the risk of engine icing problems on its new 747-8 and 787 Dreamliner planes with engines made by General Electric (GE) and asked them to avoid flying near high-level thunderstorms.
The move comes after several incidents in the last six months involving 747-8s and one 787 when planes powered by GE's GEnx engines suffered temporary loss of thrust while flying at altitude.
According to Reuters, "the warning led Japan Airlines to pull 787 Dreamliners from two international routes. Other affected airlines include Lufthansa, United Airlines and Cathay Pacific Airlines.
"The problem was caused by a build-up of ice crystals, initially just behind the front fan, which ran through the engine, said a GE spokesman, adding that all of the aircraft landed at their planned destinations safely.
"Boeing on Friday issued a notice prohibiting the affected aircraft from flying at high attitude within 50 nautical miles of thunderstorms that may contain ice crystals.
At high altitudes, humid air exists in an ice state. The tiny ice crystals are invisible to pilots and go undetected by airplane equipment. Normally in such a cold environment, the ice particles would bounce off each other, lacking the necessary moisture to bond.
Inside the hot environment of a turbofan engine, however, the mini atmosphere is so altered as to support slight melting and bonding. Ice particles accumulate on stationary compressor blades. The build up can obstruct airflow or shatter off, damaging the internal compressor blades.
This animation shows the process of ice particle icing inside a plane's turbofan engine.
Japan Airlines said on Saturday it will replace Dreamliners on its Tokyo-Delhi and Tokyo-Singapore flights with other types of aircraft while also dropping a plan to use 787s for its Tokyo-Sydney route from December.
JAL will continue to fly 787s for other international routes, which are unlikely to be affected by cumulonimbus cloud for the time being, a company spokesman said.
GE and Boeing are working on software modifications to the engine control system, which they will hope will eliminate the problems.
