Asiana airlines: secondary cause of San Francisco crash was bad software
WASHINGTON — While the world has been fixated on the disappearance of Malaysia Airlines Flight 370, the investigation in the crash of another Boeing 777, the Asiana flight into San Francisco last July, is plodding forward, and the Korean carrier is raising arguments that threaten to put another question mark over the jetliner.
Asiana’s crash, into the sea wall in front of a runway at San Francisco International Airport, was captured on video, with debris spread over a few hundred feet of runway.
Three people died and scores were injured, but most people walked away.
The prime cause was quickly clear; even Asiana faulted its crew for failing to notice that the airplane was flying far too slowly to stay in the air.
But it is also blaming “inconsistencies in the aircraft’s automation logic.”
The carrier said Monday in a filing with the National Transportation Safety Board that bad software design “led to the unexpected disabling of airspeed protection without adequate warning to the flight crew” and that a system to warn the crew of low airspeed did not sound soon enough.
The airline also said that the approach ordered by air traffic controllers “led to an excessive pilot workload during the final approach.”
Boeing has focused on the crew’s failure to maintain proper airspeed, which is expected to be listed by the NTSB as the probable cause of the crash.
Asiana’s filing is an effort by the airline to have the plane’s design characteristics listed among the contributing factors.
The board’s conclusions are not admissible in court, but its ranking of factors often influences how a carrier’s insurance company and the plane’s builder apportion the damage settlements or court judgments.
In the Asiana crash, the crew believed that an auto-throttle would manipulate the engines to keep the plane’s airspeed within the range needed for a safe landing, somewhat like the way the cruise control in a car will adjust the throttle to keep the speed constant.
It became obvious in the first few days after the crash that because of a quirk in two tightly linked systems, the autopilot and the auto-throttle, and because the crew had manually adjusted the throttles at one point, the auto-throttle had gone into “sleep” mode.
The Asiana pilots union, in a separate submission to the NTSB, said that pilots were not trained on this characteristic of the 777.