Boeing issues warning: Further icing problems with GE GenX engines on Boeing aircraft

GenX 2B GE

GenX 2B GE


Reuters: Boeing advised airlines on Friday about a risk of engine icing problems on its new 747-8 and 787 Dreamliner planes with engines made by General Electric, urging 15 carriers to avoid flying them near high-level thunderstorms. 

The move followed six incidents from April to November involving five 747-8s and one 787 when aircraft powered by GE’s GEnx engines suffered temporary loss of thrust while flying at high altitude. 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.

Icing problems with GE engines on Boeing’s Dreamliner has led to Japan Airlines pulling the Dreamliner from two international routes.

This comes on top of the icing problems noticed recently on the latest 747 cargo aircraft. A few weeks ago it was reported that a number of the latest long-haul Boeing 747 cargo aircraft fitted with the new GenX series of GE engines experienced engine icing problems when flying in particular cloud conditions at 41,000 feet:

Wall Street JournalIcing Hazards Surface on Boeing’s Newest 747 Jet

Years after aviation-safety experts thought they had eliminated the danger of airliner engines abruptly shutting down from internal ice accumulation, the same airborne hazard is showing up on a new generation of Boeing Co. jumbo jets.

The Chicago plane maker and General Electric Co., whose engines are installed on the biggest and newest Boeing 747 model, are now working together on fixes to prevent ice buildup that can prompt the giant airliner’s engines to temporarily malfunction or even stop working while cruising roughly 7 miles, or 41,000 feet, above the earth.

A GE spokesman said there are proposed software changes—which still need to be tested and then approved by the Federal Aviation Administration—designed to detect the presence of ice crystals in the atmosphere and eject the tiny particles before they form a coating deep inside engines that can melt or break into chunks.

… challenges with the GEnx-2B engines on extra-long 747 aircraft—known as 747-8s—highlight complex and nagging icing hazards that once again are forcing industry leaders and an international research team to scramble for answers. Before the partial government shutdown, according to industry officials, the FAA was moving toward mandating modifications to the 747-8’s computerized engine controls and making plans to warn pilots about susceptibility to internal engine icing while flying over storm-prone regions at roughly 40,000 feet.

Previously, experts believed such icing occurred primarily below 25,000 feet. ….

These cases of icing are different to those normally encountered and which are relatively well understood.

Aviation Week: 

….. The AirBridge Cargo event is the latest in a growing number of engine-icing incidents, which have triggered recent changes in international certification requirements. Unlike traditional engine icing, in which supercooled liquid droplets freeze on impact with exposed outer parts of the engine as the aircraft flies through clouds, engine core ice accretion involves a complex process where ice particles stick to a warm metal surface. These act as a heat sink until the metal surface temperature drops below freezing, thereby forming a location for ice and water (mixed-phase) accretion. The accumulated ice can either block flow into the core or shed into the downstream compressor stages and combustor, causing a surge, roll-back or other malfunction.

Until relatively recently, it was assumed that ice particles would bounce off structures and pass harmlessly through bypass ducts, or melt inside the engine. Now, there is evidence of an environment where a certain combination of water, ice and airflow is susceptible to accreting ice. Like many of the other known core icing events, the ABC 747-8F incident occurred near convective clouds. When incidents were first reported, investigators initially assumed supercooled liquid water, hail or rain were responsible because they had been lifted to high altitudes by updrafts. Yet most events have been recorded above 22,000 ft., which is considered the upper limit for clouds containing supercooled liquid water. ……

To find out exactly what is happening inside the convective systems that most frequently cause core icing, particularly in mid-latitude and tropical regions, an international team plans to conduct the High Ice Water Content (HIWC) test campaign in Darwin, Australia. The team includes NASA, FAA, Environment Canada, Transport Canada, Airbus, Boeing, the U.S. National Center for Atmospheric Research and the Australian Bureau of Meteorology. Also joining the effort will be the European Union’s High Altitude Ice Crystals (HAIC) project, which will be contributing a specially configured Falcon 20 research aircraft. ……

But now Boeing has warned all its clients who use aircraft with GE’s GenX engines not to fly them near certain kinds of storm clouds. And Japan Airlines whose Boeing 787 Dreamliners are powered by GenX engines has pulled the aircraft from two of its international routes:

Reuters: Japan Airlines (JAL)  said on Saturday it will pull Boeing 787 Dreamliners from two international routes after the U.S. aircraft maker notified it of icing problems in engines produced by General Electric .

Japanese carrier said Boeing notified airlines not to fly aircraft with GE’s GEnx Series engines near storm clouds following a recent incident in which a 747 aircraft experienced a loss of thrust after flying through anvil cloud.

As a result, JAL 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 and domestic routes, which are unlikely to be affected by cumulonimbus cloud for the time being.

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