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Tuesday, March 2, 2021

TRACKING WITH CLOSEUPS: In-depth Analysis of the United Airlines 1175 Fan Blade Failure

United Airlines flight 328 was not the first Boeing 777 to experience a catastrophic fan blade failure. On 2018-02-13, UAL 1175, also bound to Hawaii (from San Francisco) suffered a fan blade failure around a hour before arrival in Honolulu. As in the more recent event, the engine cowling was lost and resulted in increased drag on the aircraft. The U.S. National Transportation Safety Board has issued its final report on the incident and in this video Juan Browne examines it in depth, explaining the implications for two-engine operations over long ocean crossings (ETOPS).

The ETOPS flight rules assume an engine failure en route is benign and does not damage the aircraft structure or affect its aerodynamic performance. Both of these 777 incidents and the Southwest flight 1380 737 engine failure in April 2018, although considered “contained”, destroyed the engine cowling and added dramatically to drag on the aircraft. An airliner in such a configuration may not be able to maintain the altitude and speed prescribed by the ETOPS guidelines and, forced to fly at a lower altitude where fuel efficiency is less, might not have the fuel reserves expected to reach the closest alternate landing site or destination.

I've always thought the concept of flying over the Pacific Ocean on two engines a triumph of bean-counting over common sense.

Posted at March 2, 2021 12:27