SOUTH SAN FRANCISCO, Calif. — The pilots of Asiana Flight 214 relied on automated equipment to control the jetliner’s speed as they landed at San Francisco airport, but realized too late they were flying too low and too slowly before the aircraft crash landed, investigators said Tuesday.
The new details 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 more puzzling aspects of the crash has been why the wide-body Boeing 777 jet came in far too low and slowly, 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.
National Transportation Safety Board Chairwoman Deborah Hersman said the training captain who was instructing the pilot flying the aircraft told investigators he thought the autothrottle, similar to a car’s cruise control, was programed for a speed of 137 knots, the target speed they 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 hit the seawall.
The pilot told investigators he realized the autothrottle was not engaged just seconds before the aircraft hit. Their last second efforts to rev the plane back up and abort the landing failed, although numerous survivors reported hearing the engines roar just before impact.
“We just seemed to be flying in way too low. Last couple seconds before it happened the engines really revved into high gear. Just waaah! Like the captain was saying ‘oh no, we gotta get out of here.’ And then, boom! The back end just lifted up, just really jolted everybody in their seats,” said crash survivor Elliot Stone.
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 consult 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. Also, 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 available information.
More than 180 people aboard the plane went to hospitals with injuries. But remarkably, more than a third didn’t even require hospitalization.
The passengers included 141 Chinese, 77 South Koreans, 64 Americans, three Canadians, three Indians, a Japanese, a Vietnamese and one person from France.
South Korea officials said 39 people remained hospitalized in seven hospitals in San Francisco.
The flight originated in Shanghai, China, and stopped in Seoul, South Korea, before making the 11-hour trip to San Francisco.