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An Asiana Airlines Inc. pilot nervous about making a manual landing in San Francisco inadvertently disabled a speed-control system before the plane crashed on July 6, newly released documents show.
Captain Lee Kang Kuk, a veteran pilot with Seoul-based Asiana who was being trained on the Boeing Co. 777-200ER wide- body, had momentarily adjusted the power without realizing the plane’s computers then assumed he wanted the engines to remain at idle, according to information released today by the U.S. National Transportation Safety Board.
The documents released at the start of a hearing into the first U.S. fatal airline crash since 2009 raise new questions about how the auto-throttles on Boeing planes are designed and whether pilots are trained enough on how to use them. The safety board hasn’t concluded what caused the accident.
Lee told investigators the approach “was very stressful, very difficult.” He wasn’t accustomed to landing without an instrument-landing system guiding him to the runway, as pilots had to do in San Francisco that day because of airport construction, according to an NTSB summary of his statement.
In most modes of operation, the speed-protection system on the 777 and several other Boeing aircraft won’t allow planes to slow too much, protecting against accidents such as the Asiana crash. The plane, on the verge of losing lift because it was almost 40 miles (64 kilometers) an hour slower than its target speed, slammed into a seawall short of the runway and broke apart. Three teenage girls died.
In some combinations of auto-throttle and autopilot settings, such as during Asiana Flight 214’s approach to San Francisco, the system becomes dormant, according to NTSB documents.
A pilot for the U.S. Federal Aviation Administration told investigators he was surprised in 2010 when a 787 Dreamliner slowed that way during a test flight. The issue raised safety concerns from the FAA and the European Aviation Safety Agency, according to NTSB documents.
An FAA study released last month found that pilots’ growing reliance on automation in the cockpit has led to occasional confusion and new safety risks.
Autopilots, automatic throttles and computerized navigation systems have helped improve safety in recent decades, the FAA study concluded. The price for that is occasional confusion because the systems, which sometimes interact with each other, may be improperly set or act in ways that crews don’t anticipate, it said.
Pilots accustomed to having automation handle mundane flying tasks may also lose basic manual flying skills, the report said.
Lee, asked whether he was concerned about his ability to perform the visual approach, told investigators he was “very concerned, yea,” according to the NTSB.
He didn’t think he could turn down the air-traffic controller’s clearance to land because other pilots were accepting approaches using visual guidance instead of instruments, he said in an interview.
Two former Asiana pilots said in interviews that most of the carriers’s crews were uncomfortable with manual flight maneuvers, according to NTSB documents. The pilots gave a similar account in interviews with Bloomberg News in July.
As Flight 214 from Seoul neared San Francisco, it was being flown by Lee, 45. Because he was so new to the 777, Lee Jung Min, 49, an instructor pilot, was monitoring him from what would normally be the co-pilot’s seat. Another pilot, Bong Dong Won, 40, one of two crew members on board to give the pilots a rest break, was seated behind the other two in the cockpit.
While descending near the runway, the training pilot entered a series of parameters into the flight-management and auto-throttle systems that made the plane think he wanted to accelerate and climb.
To counter the plane’s increase in thrust, he pulled the power back so he could resume his descent, according to the documents.
Because of the way the auto-throttle had been set, combined with the fact that he had shut off the autopilot, the throttles stayed in the lowest setting, according to the NTSB. Neither pilot noticed the plane slowing until adding power and attempting to climb seconds before the impact.
The collision with the seawall and the runway sheared off the tail section and one of the engines, according to the NTSB. Besides the three passengers who died, an estimated 182 people were taken to hospitals. The plane held 291 passengers, 12 flight attendants and four pilots.
The airline since the accident has increased the hours of flight-simulation training its pilots receive and taken other steps to make a “fundamental improvement” in safety, Akiyoshi Yamamura, senior executive vice president of safety and security management, said Dec. 3.
A Boeing spokesman, Marc Birtel, said in an e-mail prior to the hearing that the company declined to comment.
The interaction between pilots and cockpit automation has come up in several previous accident investigations involving planes made by different manufacturers.
A Boeing 737 also lost lift and almost crashed while on approach to Hampshire, England, on Sept. 23, 2007, after its auto-throttle disconnected for undetermined reasons, the U.K.’s Air Accidents Investigation Branch concluded. The pilots recovered and none of the 137 people aboard was hurt.
Investigators weren’t able to determine what caused the auto-throttle to switch off, according to the report.
Such failures were “not an unusual event,” the investigation concluded. The AAIB found another case on a 737-300 in June 2007 in which the auto-throttle shut off while the plane was approaching Belfast, Northern Ireland. The pilots lost 300 feet of altitude before recovering, it said.
In a survey of data from more than 2,300 flights, the AAIB found that in 2.5 percent of them pilots had gotten an auto- throttle warning for more than 9 seconds, an indication that pilots hadn’t noticed it.
After the AAIB recommended further study, the FAA issued a mandatory directive to improve the 737’s warning system when the auto-throttle disconnects, according to AAIB’s 2013 annual report.
Automation-related accidents have also occurred in Airbus SAS planes, according to crash reports. On Feb. 14, 1990, an A320 operated by Indian Airlines crashed short of the runway in Bangalore, India, killing 92 of the 146 aboard, according to AviationSafetyNetwork, an accident-information website.
The plane descended too rapidly because it was in an automation mode that kept the throttles at idle, the investigation concluded, according to AviationSafetyNetwork. Investigators couldn’t determine why the pilots selected that mode, it said.
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