WASHINGTON - A mismanaged approach for landing in a highly automated cockpit was the probable cause of last July's crash of a South Korean airliner in San Francisco, US investigators said Tuesday.
Three young Chinese citizens died and 182 people suffered injuries when Asiana Flight 214 from Seoul clipped a sea wall with its landing gear, then crashed and burst into flames, in the first commercial airliner disaster in the United States since 2009.
"In this investigation, we have learned that pilots must understand and command automation, and not become over-reliant on it," said acting chairman Christopher Hart of the National Transportation Safety Board (NTSB).
"The pilot must always be the boss," added Hart, a licensed pilot himself, at the end of a day-long NTSB hearing that concluded the federal agency's probe into the July 6, 2013 disaster.
While the Boeing 777 was in the hands of "a seasoned flight crew with a good safety record, they misunderstood the automated systems at their command," Hart said.
The NTSB, which never explicitly assigns blame, refrained from explicitly accusing the Asiana crew of pilot error.
Instead, it cited a long and varied list of contributing factors, from the Boeing 777's automated throttle system to pilot fatigue and jet lag after an otherwise routine 10-1/2 hour trans-Pacific hop.
Autopilot switched off
Investigators testified that captain Lee Kang-Kuk, a seasoned Airbus A320 pilot transitioning to the bigger Boeing 777, cut the autopilot on final approach into San Francisco, where the instrument landing system was out of service on a clear sunny day.
Doing so put the auto-throttle on hold, meaning it would no longer automatically control airspeed, explained investigator-in-chief Bill English.
When the jet dipped below the correct glide path, Lee reacted by pulling the nose up - but the auto-throttle, still on hold, failed to deliver an expected burst of engine power that would have enabled the airliner to make the runway.
"The Boeing 777 is one of the more sophisticated and automated aircraft in service," Hart said.
"But the more complex automation becomes, the more challenging it is to ensure that pilots adequately understand it," he added.