The National Transportation Safety Board released its final conclusions about what caused the crash of Asiana Airlines Flight 214 in San Francisco last July, blaming the pilots for making a series of critical missteps related to the Boeing 777’s automated systems.
At a hearing in Washington, D.C., this morning, the NTSB highlighted one mistake in particular for setting up the conditions in the cockpit that led the airliner to lose speed and crash-land short of the runway. Investigators say the relatively inexperienced captain who was flying the visual approach to San Francisco’s Runway 27L, concerned about being too high and too fast when 5 nm from the runway, changed the autopilot mode, inadvertently causing the 777 to start a climb back to the selected go-around altitude of 3,000 feet.
Confused about what the autopilot was doing, the pilot switched it off and reduced power to idle, mistakenly assuming the autothrottles would come back to life once the target airspeed was reacquired. But instead, the pilot’s action put the autothrottles into “HOLD” mode, a state neither of the pilots noticed until the airplane descended well below glidepath and target approach speed.
The training captain in the right seat eventually called for a go around and advanced the throttles to full power, but by then it was too late. The tail of the 777 hit a seawall and broke off as the main fuselage careened down the runway, flipped over and caught fire, killing three passengers in the process.
“Automation has unquestionably made aviation safer and more efficient, but the more complex automation becomes the more challenging it is to ensure that the pilots adequately understand it,” NTSB acting chairman Christopher Hart said in his opening remarks. “In this instance, the flight crew over-relied on automated systems that they did not fully understand. As a result, they flew the aircraft too low and too slow and collided with the seawall at the end of the runway,” he said.
As a result of the investigation, the NTSB today made several safety recommendations regarding the Boeing 777’s autoflight system, the appropriate use of flight directors, and low-energy alerting systems. The NTSB also blamed pilot fatigue and poor cockpit resource management for the crash.
