An unusual rash of engine shutdowns since early December has temporarily stranded three of the normally reliable General Electric-powered Boeing 777-300ERs.

Although each incident involved a shutdown of the GE90-115B, GE’s investigation so far indicates the causes of each power loss appears to come from three different sources, says a company spokeswoman.

The incidents have forced two different Air France airliners to make emergency landings at alternate airports since 12 December. Similarly, on 1 February, a Singapore Airlines 777-300ER was forced to land at Frankfurt International Airport in Germany.

In the first incident, the Air France pilot crew noticed “excess vibrations” and powered down the engine, making an emergency landing in Rome. A visual inspection revealed excessive wear on a stage six low pressure turbine blade that “reduced contact pressure between blades on that disk,” the spokeswoman says.

On 25 January, a second Air France 777 diverted to Milan Malpensa airport after an inflight engine shutdown. The engine’s transfer gearbox broke out of its housing, causing the power loss.

Finally, the Singapore Airlines flight was disrupted by an undisclosed problem with the engine’s accessories gearbox. At press time, GE was not certain if the pilot commanded the engine to power-down, or if the engine failed in flight. GE is continuing to investigate the incident to uncover the root cause of the gearbox issue.

Both the transfer gearbox and the accessories gearbox are produced by the same supplier, Italy’s Avio. GE is “working with them to find out what the cause would be,” the spokesman says.

Both components have been installed on older-model aircraft equipped with GE90-94B engines, achieving an 11-year in-service record with no prior incidents before 25 January.

Air France was the launch customer for the GE90-115B-powered 777-300ERs, and therefore has the fleet’s oldest airframes and engines in service.

Source: FlightGlobal.com

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