Asiana says jet partly to blame for SFO crash

The destroyed fuselage of Asiana Airlines Flight 214 is visible on the runway at San Francisco International Airport after it crashed on landing and burned on Saturday, July 6, 2013. Photo: Carlos Avila Gonzalez, The Chronicle

Asiana Airlines conceded Monday that its pilots were flying a Boeing 777 too slowly in the seconds before the plane crashed last year atSan Francisco International Airport, but said the aircraft's navigation equipment was partly to blame.

The South Korean airline said in a filing with the National Transportation Safety Board that the causes of the July 6 crash were "complex and interrelated." But it said the plane's navigation instruments had "led the crew to believe" the jet was maintaining enough speed for the aircraft to land safely.

Instead, the plane was flying too slowly as it came in for a landing and slammed into a seawall short of the runway. The crash left three young Chinese passengers dead, including one who apparently survived being ejected but was run over by two San Francisco fire rigs.

Boeing told federal investigators in a filing Monday that the plane's navigation equipment had been functioning normally and had not contributed to the crash. Boeing's chief engineer for air safety investigations, Michelle Bernson, blamed the crash on the "crew's failure to monitor and control airspeed, thrust level and glide path."

The federal safety board is investigating the cause of the crash and may issue safety recommendations. It hopes to complete its report before the crash's one-year anniversary.

In its filing, Asiana told investigators that something happened to the autopilot device when the plane was at 1,600 feet and headed to a safe landing. "For an unknown reason," the autopilot issued an order that commanded the plane to climb to 3,000 feet, the airline said.

Two of the three pilots in the cockpit said they did not remember pressing a button that would prompt the navigation computer to change the plane's approach, Asiana said.

In its filing with the safety board, Boeing said the third pilot in the cockpit said it was possible he had pushed the button. Boeing contends that the cockpit's voice recorder captured the sound of the button being pressed as the plane reached the 1,600-foot level.

Three seconds after the button was activated, the pilot flying the plane, Lee Kang Kuk, shut off the autopilot and told the crew he was going to land manually. He reduced the plane's speed to counteract the autopilot's commands to raise the plane's altitude, Asiana said.

When Lee shut off the autopilot, he expected the jet's auto-throttle device to maintain a safe speed, Asiana said. But the auto throttle "surprisingly" shut down in the process, and no alarm sounded right away in the cockpit, the airline said.

With its speed dropping, the aircraft descended too quickly and came up short of the runway. The warning alarm eventually went off, 11 seconds before impact, but that was too late for the pilots to pull the plane out of its descent, Asiana said.

The Federal Aviation Administration urged Boeing in 2010 to install software on its auto-throttle devices that would cause them to reactivate automatically in the event of a sudden loss of speed, but the manufacturer has not done so, Asiana said.

The agency made the recommendation after an incident on a newer model Boeing 787 in which a pilot discovered problems similar to those on the flight that crashed at SFO, Asiana's report said.

Boeing responded that the Asiana crew had ignored many obvious warning signs well before the cockpit alarm went off and should have been able to avoid a crash.

Jaxon Van Derbeken is a San Francisco Chronicle staff writer. E-mail:jvanderbeken@sfchronicle.com Twitter: @jvanderbeken

Source:

www.sfgate.com