Metal fatigue behind 777 engine failure

The jet engine fan blade that broke loose on a United Airlines plane on Saturday near Denver, triggering a massive failure leading to the grounding of dozens of Boeing Co. 777s, resulted from metal fatigue, according to National Transportation Safety Board chairman Robert Sumwalt. A preliminary examination of fragments found after the episode that sent metal chunks raining on a suburban neighbourhood suggested a crack that grew gradually over time prompted the failure, Sumwalt said on Monday night. “Our mission is to understand not only what happened but why it happened so that we can keep it from happening again,” he added. Boeing said all 128 of the 777s with Pratt & Whitney engines were grounded following Saturday’s emergency landing of United flight 328.