Autothrottle a focus in San Francisco crash investigation

  • Posted: Wednesday, July 10, 2013 12:01 a.m.
The National Transportation Safety Board is now looking into the possibility that the Boeing 777's autothrottle, which the pilots of Asiana Flight 214 were relying on when it crashed upon landing Saturday, either was not set properly or malfunctioned.

SAN FRANCISCO — The pilots of Asiana Flight 214 airliner that crashed at San Francisco International Airport have told investigators that they were relying on automated cockpit equipment to control their speed, turning a focus of the accident investigation toward whether a mistake was made setting the autothrottle or if it malfunctioned.

One of the most puzzling aspects of the crash Saturday has been why the wide-body jet came in far too low and slow, clipping its landing gear and then its tail on a rocky seawall just short the runway.

The plane then careened before slamming to the ground, killing two of the 307 people aboard the Boeing 777 and injuring scores of others.

Among those injured were two flight attendants in the back of the plane, who survived despite being thrown onto the runway when the plane hit the seawall.

National Transportation Safety Board Chairwoman Deborah Hersman said Tuesday the training captain who was instructing the pilot flying the plane has told investigators he thought the autothrottle was programmed for a speed of 137 knots, the target speed the pilots had selected for how fast they wanted the plane to be flying when it crossed the runway threshold.

Instead, investigators said the plane reached speeds as low as 103 knots and was in danger of stalling because it was losing lift before it clipped the seawall.

The pilot told investigators he realized the autothrottle, similar to a cruise control, was not engaged just seconds before they hit.

Their last-second efforts to rev the plane back up and abort the landing failed, although numerous survivors report hearing the engines roar just before impact.

Asked if the autothrottle was malfunctioning, Hersman said that is something investigators are looking into as they examine hundreds of parameters of data downloaded from the plane's flight data recorders.

An overreliance on automated cockpit systems has figured in dozens of air crashes and incidents in recent years.

“Some people, if they believe the autothrottles are engaged and if they are used to flying with the autothrottle engaged, will not realize that the autothrottles are not engaged and will let the plane get pretty slow. That has come up before,” said John Cox, an aviation safety consultant and former Air Line Pilots Association accident investigator.

Hersman said the pilots told investigators they were relying on automated cockpit equipment to control their speed during final approach, but NTSB officials said it is still unknown whether a mistake was made in programming the autothrottle or if the equipment malfunctioned.

Hersman said the pilot at the controls was only about halfway through his training on the Boeing 777 and was landing that type of aircraft at the San Francisco airport for the first time. And the co-pilot was on his first trip as a flight instructor.

A final determination on the cause of the crash is months away, and Hersman cautioned against drawing any conclusions based on the information revealed so far.

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