A preliminary report by the US National Transportation and Safety Board (NTSB) into the July 6 2013 Asiana Flight 214 crash at San Francisco Airport has concluded that the flightcrew’s mismanagement of the approach and inadequate monitoring of airspeed were the primary causes of the crash.
The Boeing 777-200ER was on final approach to San Francisco and undershot the runway, striking the seawall and breaking up as it cartwheeled across the runway threshold. Three of the 291 passengers and crew died as a result of the crash, and 53 were seriously injured. The impact and a subsequent fire destroyed the aircraft.
The NTSB found that the flight crew mismanaged the initial approach and that the airplane was well above the desired glide-path as much as five nautical miles out from landing. In response to this, the pilot selected an incorrect autopilot mode and took other actions that resulted in the auto-throttle no longer controlling airspeed.
As a result, the 777 descended below the desired optimum glide-path and the crew failed to notice the airspeed dropping below the approach speed or respond to the increasingly unstable approach. A go-around manoeuvre was initiated when the 777 was well below the glide-path at 100 feet, but it was too late and the airplane struck the seawall.
“In this accident, the flight crew over-relied on automated systems without fully understanding how they interacted,” NTSB Acting Chairman Christopher A Hart said in a statement. “Automation has made aviation safer. But even in highly automated aircraft, the human must be the boss.”
The report also highlighted “complexities” in the 777’s automatic flight control system and in related training and documentation, and that the pilot had an “inaccurate understanding of how the autopilot flight director system and auto-throttle interacted to control airspeed.” It said a review of the design of the 777’s AFCS could “yield insights about how to improve the intuitiveness of the 777 and 787 flight crew interfaces as well as those incorporated into future designs.”
In a statement, Boeing said it, “…respectfully disagrees with the NTSB’s statement that the 777’s auto-flight system contributed to this accident, a finding that we do not believe is supported by the evidence,” adding that, “the 777 has an extraordinary record of safety – a record established over decades of safe operation. More specifically, the auto-flight system has been used successfully for over 200 million flight hours across several airplane models, and for more than 55 million safe landings.”
As a result of the accident, the NTSB has made recommendations to the US Federal Aviation Administration, to Asiana Airlines, to Boeing, to the Aircraft Rescue and Firefighting Working Group, and to the City of San Francisco, including the need for reinforced adherence to Asiana flight crew standard operating procedures, more opportunities for manual flying for Asiana pilots, a context-dependent low energy alerting system, and both certification design review and enhanced training on the Boeing 777 auto-flight system.
An NTSB animation of the final approach can be viewed here. The report summary can be viewed here.
