SAN FRANCISCO (AP) — Asiana Airlines acknowledged in documents released Monday that its pilots failed to correct their fatally slow approach to a landing at San Francisco International Airport but also blamed the maker of the jet, saying it did not automatically maintain a safe speed.
U.S. accident investigators made public a filing in which the South Korea-based airline asserted that the Boeing 777 had major design flaws that led the pilots to believe it would keep flying at the proper speed and that failed to warn the cockpit crew in time when it did not.
Boeing Co. countered in its own filing with the National Transportation Safety Board that the airplane performed as expected, and the pilots were to blame for the July 6 crash because they stuck with a troubled landing.
The plane slammed into a seawall at the beginning of a runway during its final approach. The impact ripped off its back and scattered pieces of the jet as it spun and skidded to a stop.
In all, 304 of the 307 people aboard survived. Coroner's officials concluded that one of three teens who died, Ye Meng Yuan, was run over and killed by a rescue vehicle as she lay on the tarmac.
Asiana acknowledged in its NTSB filing that the crew failed to monitor air speed in the moments before the crash and should have aborted the landing for another go around.
"The probable cause of this accident was the flight crew's failure to monitor and maintain a minimum safe airspeed during a final approach," Asiana conceded.
However, Asiana argued that the pilots and co-pilot reasonably believed the automatic throttle would keep the plane going fast enough to reach the runway — when in fact the auto throttle was effectively shut off after the pilot idled it to correct an unexplained climb earlier in the landing.
The airline said the plane should have been designed so the auto throttle would maintain the proper speed after the pilot put it in "hold mode."
Instead, the auto throttle did not indicate that the plane had stopped maintaining the set air speed, and an alert sounded too late for the pilots to avoid the crash, Asiana said. The airline added that U.S. and European aviation officials have warned Boeing about the issue, but it has not been changed.
In most other planes, idling the auto throttle would not disengage it for the rest of a flight, aviation safety consultant John Cox said.
Cox, president and CEO of Safety Operating Systems and a former airline pilot and accident investigator, likened it to the cruise control in a car. If a driver sets it for 55 mph (88.5 kph) and then accelerates to pass a car, the driver would expect the cruise control to re-engage when the speed slows to 55 mph (88.5 kph) again.
"The flight crew had an expectation that the auto throttle system was going to do certain things that it did not do," Cox said. "Although they were trained about it, it was not overly intuitive."
Asiana wrote that the pilot flying the plane, Lee Kang Kuk, had been trained to recognize the throttle issue with a 777. The most recent training was three months before the accident, and the instructor specifically used a landing at San Francisco airport as an example.
"This lesson was explained on two occasions by two different instructor pilots," Asiana wrote. Lee "attended the lectures, asked questions specifically about this feature of the automation, and discussed the 'anomaly' with his fellow trainee captains after class."
The NTSB previously said the pilots showed signs of confusion about the 777's elaborate computer systems. The agency has not determined an exact cause of the crash.
Lee was an experienced pilot with Asiana but was a trainee captain in the 777, with less than 45 hours in the jet. He has told transportation safety board investigators that he did not immediately move to perform an emergency "go around" because he felt only the instructor pilot had that authority.
Asiana wrote to the NTSB that under its company policy, "any pilot can and should call for a go-around — without penalty — whenever confronted with a potential safety issue."
Boeing told the NTSB the airplane and all its systems were functioning as expected.
"Boeing believes that the evidence supports the following conclusion: This accident occurred due to the flight crew's failure to monitor and control airspeed, thrust level and glide path on short final approach," the airplane manufacturer said.
Asiana and Boeing have been sued in U.S. courts over the crash.
Attorney Michael Verna, who represents several clients seeking damages from Asiana, said the airline documents released Monday amounted to a probable cause statement that he would use when his cases go before a federal judge in Oakland.
"Had the pilots monitored the instruments," Verna said, "we wouldn't have had the accident."
Pritchard reported from Los Angeles.
Contact Justin Pritchard at https://twitter.com/lalanewsman