The complex automation system on Boeing Co.’s 777 should be reviewed and improved, according to U.S. accident investigators, who concluded it contributed to pilot confusion on the Asiana Airlines Inc. flight that crashed last year.
Training by Asiana and Boeing’s documentation on the plane “inadequately described” the automatic throttle system, the National Transportation Safety Board found yesterday. While the auto-throttle almost always prevents a plane from getting too slow, the pilots didn’t realize they’d placed it on “hold.”
The action, which stops short of calling for a redesign, is a blow to the image of one of Boeing’s most successful aircraft. Until the July 6 accident in San Francisco, the 777 had never had a fatal crash since its introduction in 1995.
The confusing automation and inadequate training combined with pilot fatigue all contributed to the plane striking a seawall as it tried to land. The pilots mismanaged their approach to the airport, failed to notice the deteriorating speed and lights near the runway showing they were too low, and then didn’t abort the touchdown, which they were trained to do, according to the NTSB.
“I think the expectation of this pilot was that the auto-throttle was going to take care of him,” NTSB board member Robert Sumwalt said during the hearing to determine the cause of the crash, which killed three teenage girls.
While the NTSB voted down a motion to recommend changing Boeing’s auto-throttle design, it said the Federal Aviation Administration should study whether such changes are needed. If all the same errors had occurred and the speed protection had worked, it would have added thrust 20 seconds before the crash and potentially averted disaster, the NTSB said.
“We have learned that pilots must understand and command automation, and not become over-reliant on it,” acting agency Chairman Christopher Hart said in a press conference after the hearing. “The pilot must always be the boss.”
The findings brought to a close an investigation into the accident that triggered questions about South Korea’s pilot training and one of Boeing’s most popular jetliners. The crash was the first in the U.S. with passenger fatalities since 2009.
Boeing “respectfully disagrees” with the NTSB’s findings on its cockpit automation, spokesman Doug Alder said in an e-mailed statement. “We note that the 777 has an extraordinary record of safety,” the Chicago-based company said.
Seoul-based Asiana said it agreed with the NTSB’s findings in an e-mailed statement. The airline has already made NTSB-recommended changes to its training, it said.
The airline’s shares declined 0.5 percent to 4,575 won as of 1:40 p.m. in Seoul trading, extending the drop this year to 7.3 percent.
The Boeing 777-200ER struck a seawall after the pilots allowed the jetliner to get almost 40 miles (64 kilometers) per hour slower than intended as they neared the runway. By a series of actions -- including adjusting the autopilot and manually reducing power -- the plane shut off its speed protection. Within seconds, it began slowing without pilots realizing it, according to the investigation.
The two pilots also didn’t communicate as they each made changes to the cockpit automation, the board found.
Pilot fatigue on the Seoul-to-San Francisco flight also played a role. The crew on the airline was landing in San Francisco at 3:30 a.m. South Korea time, which probably hurt their performance, the NTSB said.
The tired pilots made a series of “cascading errors” that began miles away from the airport, Roger Cox, an NTSB investigator, said at the hearing.
An underlying reason for the accident was that Captain Lee Kang Kuk, a veteran of the airline who was being trained on the Boeing 777 wide-body, didn’t realize he had disabled the speed protection system, according to the NTSB.
Lee told investigators after the crash he thought “the auto-throttle should have come out of the idle position to prevent the airplane going below the minimum speed” for landing, the NTSB said.
Another Asiana captain, Lee Jung Min, who was making his first flight as instructor pilot, was seated in the co-pilot’s seat. He would have reactivated the speed protections had he flicked one switch on the final descent. He told investigators afterward he recalled making the change, but the plane’s data recorder showed otherwise, according to the NTSB.
Sumwalt, the NTSB board member and a former pilot, said he spoke to a senior airline training pilot after the accident to determine whether average flight crews understood how the 777’s speed protection worked.
“He said, ‘To be honest with you, I don’t think it was widely known at all,’” Sumwalt said. “I think that the problem was a lot more widespread than we may have thought.”
At the same time, the cockpit display showed that the plane’s air-speed protections had been disabled and the pilots should have seen that, Cox said.
“There are plenty of cues in front of you telling you what you have done, but you have to look at them,” he said.
The FAA is “confident” the plane’s throttle system is safe, it said in an e-mailed statement. While it supports reviewing how pilots are trained on the system, the agency stopped short of agreeing to review its design.
“We’re pleasantly surprised that NTSB recognized that Boeing is actually the first and last line of defense in these types of situations,” said Ilyas Akbari, associate attorney at Baum, Hedlund, Aristei & Goldman in Los Angeles, which represents 16 passengers on the flight. “We really hope that Boeing really takes these recommendations to task.”
The NTSB called for establishing a review committee like the one established last year after a fire broke out on a 787 lithium-ion battery. The review should look at ways to improve existing and future auto-flight systems, the NTSB said.
Boeing has maintained that crew actions caused the accident. Various 777 models have been flown for 200 million hours and made more than 55 million safe landings, the company said in its statement.
The investigation showed that “all of the airplane’s systems performed as designed,” it said.
The 777, the largest twin-engine jetliner, began commercial service in 1995 and has one of the industry’s best safety records, according to Boeing’s annual aircraft accident summary.
Incidents with an almost identical auto-throttle issue arose in certification of the Boeing 787, NTSB documents show.
The FAA required Boeing to add a note to the then-new 787’s documentation warning pilots they could lose speed protection under the same circumstances, according to the documents. An FAA test pilot flying the 787 in 2010 said he was surprised to learn that the plane’s speed protection could be lost in some cases. The changes weren’t required for the 777.