'B777 has flaw in auto-throttle system'

Asiana Airlines Flight 214, a Boeing 777 product, lies at the San Francisco International Airport on July 6, after it crash-landed at the airport. Anthony Keyter, a retired Boeing senior instructor pilot, said that the aircraft model has a design flaw in its auto-throttle system. / AP-Yonhap

By Kim Jae-won

Anthony Keyter

A retired senior Boeing instructor pilot said Friday that the American company’s aircraft B777 has a design flaw in its speed control system, suggesting that Asiana Airlines flight 214 may have avoided its crash at the San Francisco International Airport on July 6, if the system worked properly.

The crash-landing claimed the lives of three Chinese schoolgirls and injured more than 180 passengers and crew members.

The functioning of the auto-throttle became a hot issue during the investigations of the U.S. National Transportation Safety Board (NTSB) because the federal agency said that the plane was too slow as it approached the airport’s runway.

“There is an inconsistent functioning of auto-throttle and stall protection systems in the Boeing 777 aircraft. This weak point has been discussed with grave concern among some B777 pilots,” said Anthony Keyter in a statement.

Keyter, who lives in the U.S., said the flaw becomes evident when an aircraft is descending in autoflight in the “flight level change” mode, as Asiana 214 was likely to have done during its wide base leg turn and final approach to landing.

If the autopilot is then disconnected, and if the auto-throttles are left “armed,” the thrust would hold in idle power and would not automatically increase to pursue the target airspeed, he said.

The former Boeing instructor pilot added that if a decrease in speed was not noticed and corrected manually by the pilot, it would continue to bleed off to the point of “stick shaker,” as was the case with Asiana 214.

Representatives of Boeing Korea were not available for comments.

Keyter said that the auto-throttle is one of the most important devices in the cockpit because pilots rely on the system as a “last resort” back-up to keep their aircraft safe under all circumstances.

“The design flaw in the auto-throttle can thus be considered a contributing factor to the causes of the accident,” he said.

He said that the American aircraft manufacturer should address the problems through changes to flight procedures, or an express note in the manual.