The U.S. National Transportation Safety Board has determined that Asiana Flight 214 crashed on July 6 last year at San Francisco International Airport because the pilots mismanaged the approach and inadequately monitored airspeed. Announcing the findings at a meeting on Tuesday in Washington, D.C., the Board also found that the complexities of the autothrottle and autopilot flight director systems and the crew’s misunderstanding of those systems contributed to the accident.
Three of the 291 passengers died after the Boeing 777-200ER struck the seawall at the threshold of Runway 28L at San Francisco International; 40 passengers, eight of the 12 flight attendants, and one of the four flight crewmembers sustained serious injuries. The other 248 passengers, four flight attendants and three flight crewmembers received minor injuries or escaped injury. The impact forces and a post-crash fire destroyed the airplane.
The NTSB determined that the flight crew mismanaged the initial approach and that the airplane flew well above the desired glidepath as it neared the runway. In response to the excessive altitude, the captain selected an inappropriate autopilot mode and “took other actions” that caused the autothrottle to relinquish its control of airspeed.
As the airplane descended below the desired glidepath, the crew did not notice the dwindling airspeed and they did not attempt to correct the unstable approach. The flight crew began a go-around maneuver when the airplane had descended below 100 feet. By that time they could not climb fast enough to avoid hitting the seawall.
“In this accident, the flight crew over-relied on automated systems without fully understanding how they interacted,” said NTSB acting chairman Christopher Hart. “Automation has made aviation safer. But even in highly automated aircraft, the human must be the boss.”
As a result of this accident investigation, the NTSB issued recommendations to the Federal Aviation Administration, Asiana Airlines, Boeing, the Aircraft Rescue and Firefighting Working Group and the city of San Francisco.
The recommendations include 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 autoflight system. The recommendations also address the need for improved emergency communications, and staffing requirements and training for aircraft rescue and firefighting personnel. One of the three deaths resulted from a rescue vehicle running over an injured passenger thrown from the wreckage.