WASHINGTON — The fatal crash of Asiana Airlines Flight 214 was caused by the pilots mismanaging the descent toward San Francisco's airport and not aborting the landing to try again, the National Transportation Safety Board said Tuesday.
Contributing factors included the complexities of the Boeing 777's autothrottle, which were inadequately described in the manufacturer's documents, along with inadequate pilot training and monitoring, the board said.
The board agreed to the cause and contributing factors by a series of 4-0 votes. To avoid future crashes. the board agreed to recommendations including enhancing training for the autothrottle and requiring pilots to land flights manually more often to remain familiar with it.
"Our goal in this investigation is to help prevent similar accidents in the future," said Christopher Hart, acting chairman of NTSB. "In this instance, the flight crew over-relied on automated systems that they did not understand."
The crash July 6, 2013, killed three people and injured 187, out of 307 aboard the flight from Seoul. The plane was flying lower and slower than intended when it slammed into the seawall at the end of the runway, spun around and burst into flames.
While Asiana acknowledged the pilots were flying too slow and too low, there is a dispute between the airline and Boeing about why that happened.
Asiana cited "inconsistencies" with the autothrottle that led pilots to believe it would maintain the plane's speed after some adjustments in the autopilot, when in fact the engines were idling in "hold" mode.
But Boeing said the plane was functioning as expected and "did not contribute to the accident," and that the pilots should have aborted the landing when they realized things were awry and tried again.
Miles Kotay, a Boeing spokesman, said after the board's recommendations that the 777 has an extraordinary record of safety and that the auto-flight system has been used successfully for 200 million flight hours. The company is carefully reviewing the recommendations.
"However, it is important that any recommendation concerning changes to the airplane's design be reviewed with great care and with due consideration for the potential unintended consequences of any change," Kotay said.
The hold mode is widely used in Boeing wide-body planes. But board members offered different perspectives on the pilot's confusion dealing with the wakeup feature that was introduced about 18 years in the 777.
Robert Sumwalt, a board member who previously was a 24-year airline pilot, said confusion about the autothrottle was widespread in the industry and not well known. He said the pilots were experienced, but expected the autothrottle to work differently than it did.
The flying pilot, Lee Kang Kuk, was landing for the first time at San Francisco and he had spent just 43 hours flying the 777, although he had clocked 9,684 hours on a variety of other jets. Another pilot serving as an instructor on the flight, Lee Jung Min, had spent 3,208 hours flying 777s out of 12,307 total flying hours.
"I personally don't believe this is a case of crew competency," Sumwalt said. "It was not just this pilot who misunderstood. I think this problem is a lot more widespread than we may have thought."
The disputed hold mode for the autothrottle was common among Boeing wide-body planes for decades.
"This particular feature, if you will, has been on Boeing airplanes for 30-some years," Board member Earl Weener said.
Capt. Roger Cox, the investigator who studied operations in the crash, said the Asiana pilot was surprised by the throttle not waking up.
"He used the word 'astonished,'" Cox said.
But Cox said the hold mode was displayed on control panel in front of the pilots. And he said the flying pilot should have called out that he was flying manually, but he didn't.
"You have to look at them," Cox said. "There are plenty of cues in front of you telling you what you've done, but you have to look at them."
Six people – two passengers and four flight attendants – were ejected from the plane as it broke apart.
The two passengers, who hadn't been wearing seatbelts, died. But investigators found they likely would have survived if they had worn their seatbelts.
"Seatbelts save lives and protect people in all modes of transportation," said board member Mark Rosekind.
The third dead passenger was struck by a door that detached when the plane struck the ground.
The board commended the fire department for having 23 staffers on duty rather than the minimum required three workers, that allowed rescue workers to remove five injured passengers as the plane became engulfed in fire.
But one of the fatalities, 16-year-old Ye Meng Yuan, was run over by a fire truck after being thrown from the plane. The board recommended the fire department develop policies to avoid injuring passengers.
Two of the plane's emergency slides deployed into the cabin, complicating the evacuation. But investigators found that the crash put two to four times more pressure on the slides than are required for certification.