An inquiry into the crash-landing of Asiana Airlines flight 214, which killed three people and injured almost 200 at San Francisco airport last year, has blamed the complexity of the Boeing 777 cockpit controls.
American investigators said a series of mistakes made by the pilots also contributed to the accident.The flight crew committed "between 20 and 30 errors" during their final descent, according to the US National Transportation Safety Board report, quoted in The Independent.
Some of these came about because the pilots "over-relied on automated systems that they did not fully understand," according to the board chairman, Chris Hart.
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He suggested that safety systems fitted to the Boeing 777 had introduced new risks.
"In their efforts to compensate for the unreliability of human performance," he said, "the designers of automated control systems have unwittingly created opportunities for new error types that can be even more serious than those they were seeking to avoid."
The inquiry found that the pilots:
- set the autothrottle to idle: just before landing, the plane "climbed unexpectedly high". Captain Lee Kang Kuk changed the plane's autothrottle to idle, thinking the device would "continue automatically controlling speed", which it usually would have done
- turned off the autopilot: because Kuk turned off the autopilot at the same time, the auto-throttle "remained on hold at the last selected speed"
- imbalanced the flight systems: a training captain who was also in the cockpit then shut down a single key flight management system, while leaving another active; such programs are meant to be operated in tandem, and having one on and one off "compounded" the previous problems.
- failed to recognise and react to these errors: although "a third pilot...noticed the plane was descending too fast", he did not tell anyone; even when the pilots did realise what was happening, they failed "to start aborting the landing" until it was too late.
Boeing has rejected the committee's conclusions, pointing out that the aircraft has performed "over 55 million safe landings" and arguing that "the evidence collected during this investigation demonstrates that all of the airplane's systems performed as designed".
The Asiana Airlines crash was the first fatal accident involving a Boeing 777. Since then, a 777 operated by Malaysia Airlines has gone missing in mysterious circumstances and is presumed to have crashed into the Indian Ocean.
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