SOUTH SAN FRANCISCO — Investigators are trying to understand whether automated cockpit equipment Asiana flight 214's pilots said they were relying on to control the airliner's speed may have contributed to the plane's dangerously low and slow approach just before it crashed.
New details in the accident investigation that were revealed Tuesday by National Transportation Safety Board Chairman Deborah Hersman were not conclusive about the cause of Saturday's crash. But they raised potential areas of focus: Was there a mistake made in setting the automatic speed control, did it malfunction or were the pilots not fully aware of what the plane was doing?
One of the most puzzling aspects of the crash has been why the wide-body Boeing 777 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 crash killed two of the 307 people and injured scores of others, most not seriously.
Among those injured were two flight attendants in the back of the plane who survived despite being thrown onto the runway when the plane slammed into the seawall and the tail broke off.
The autothrottle was set for 157 mph and the pilots assumed it was controlling the plane's airspeed, Hersman said. However, the autothrottle was only "armed" or ready for activation, she said.
Hersman said the pilot at the controls, identified by Korean authorities as Lee Gang-guk, was only about halfway through his training on the Boeing 777 and it was his first time landing that type of aircraft at the San Francisco airport. And the co-pilot, identified as Lee Jeong-Min, was on his first trip as a flight instructor.
Two of the four pilots were questioned Monday and the other two and air traffic controllers were interviewed Tuesday, according to the Ministry of Land, Infrastructure and Transport officials in South Korea. The ministry hadn't requested any criminal investigation because a probe is underway to determine the cause of the crash.
In the 777, turning the autothrottle on is a two-step process — first it is armed then it is engaged, Boeing pilots said.
Choi Jeong-ho, a senior official at South Korea's Ministry of Land, Infrastructure and Transport, said investigators confirmed the auto throttle was in an armed position, and an exact analysis on whether the automatic throttle system worked will be possible after an analysis on the plane's black box.
Hersman didn't say whether the Asiana's autothrottle was engaged.
Bob Coffman, an American Airlines captain who has flown 777s, said the only way he could think of for the Asiana plane to slow as quickly as the NTSB has described would be if the autothrottle had somehow shifted into the idle mode.
"There is no way to get from a normal airspeed and normal position at 500 feet to an abnormally slow airspeed at 300 feet unless there wasn't enough thrust either deliberately or inadvertently," he said.
Only moments before the crash did the training captain realize the autothrottle wasn't controlling the plane's speed, Hersman said.
"This is one of the two hallmarks of complexity and challenge in the industry right now," said Doug Moss, an Airbus A320 a pilot for a major U.S. airline and an aviation safety consultant in Torrance, Calif. "It's automation confusion because from what Deborah Hersman said, it appears very likely the pilots were confused as to what autothrottle and pitch mode the airplane was in. It's very likely they believed the autothrottles were on when in fact they were only armed."