WASHINGTON -- The trainee pilot flying Asiana Airlines flight 214, which crashed in San Francisco in July, told investigators he was stressed about the approach to the unfamiliar airport and thought the autothrottle was working before the plane came in too low and too slow, federal crash investigators revealed Wednesday.
Investigators found that theautothrottle on the Boeing 777-200ER changed from "thrust" to "hold" at 1,600 feet in the air, when the pilot called out "manual flight," according to a 45-page report from the National Transportation Safety Board's investigator in charge of the case.
The plane was targeted to go 137 knots, but fell to only 103 knots just before striking the seawall at the airport, spinning around, breaking into parts and catching fire. Three passengers died in the crash, but the other 288 passengers and 16 crew members were able to evacuate. More than 200 were sent to hospitals.
Two other Asiana pilots told investigators that the trainee pilot had been in class with them in April and they warned him that if the autothrottle goes to "hold," it won't automatically re-engage in a descent.
"The ground school instructor stated that he provided this training because he had personally experienced, in flight, an unexpected activation of HOLD mode and thus the failure of the autothrottle to re-engage," the report said.
The autopilot governs the path and altitude of the plane, while the separate autothrottle deals with just the plane's speed. In a summary of interviews between investigators and pilots, the flying pilot described how he thought the autothrottle was on.
"He said the autothrottle always maintains speed, so he did not think about that, but in case of manual throttle condition, he should maintain it," the summary report said.
The flying pilot, Lee Gang Guk, was landing for the first time at San Francisco and had spent just 33 hours flying the 777, although he had clocked nearly 10,000 hours on a variety of other jets. Another pilot serving as an instructor on the flight, Lee Jeong Min, had spent 3,220 hours flying 777s.
The flying pilot Lee told investigators after the crash that he found the approach "very stressful" and "difficult to perform" with such a large plane and the absence of an electronic system that tracks a plane's glide path, which was down for maintenance, according to the report.
"The trainee captain was asked how confident he felt about his knowledge of the B777 autoflight system just prior to the accident," the report said. "He stated he was not so confident because he felt he should study more."
The hearing didn't find assign blame for the crash or make recommendations, but explored through expert testimony how and why it happened.
The NTSB didn't set a deadline to complete its investigation, but will ultimately issue a report that determines probable causes of the crash and make recommendations about how to avoid another one.
Deborah Hersman, NTSB chairman, said experts from the Federal Aviation Administration and academia described pilots occasionally becoming confused with complex cockpit equipment, which she said safety experts must scrutinize.
"We can always do better," Hersman said.
Testimony focused on the training pilot who flew the plane rather than the more-experienced instructor pilot who was monitoring his performance. But Hersman said there were three experienced pilots in the cockpit -- the pilot in training, the instructor pilot and a relief pilot in the jump seat -- who should have monitored the equipment and could have made suggestions about the flight.
"We want to understand the roles of each of those pilots, the communication that took place in the cockpit and what can be learned from this event so that we can prevent future accidents," Hersman said.
The July 6 crash marked the first passenger-airline fatalities in the USA in 4½ years. The crash killed three passengers, including one who was thrown from the plane and run over by a fire truck.
Several factors emerged in the initial investigation, including the plane flying lower and slower than expected and the inexperience of the flying pilot.
But questions were also raised about whether the autothrottle was operating properly, how closely pilots monitor their cockpit equipment and why pilots don't abort more difficult landings.
Boeing designed the 777 with low-speed warnings that escalate from a yellow light, a yellow light with chimes, and then a red light with a continuous noise warning that says "airspeed low." The instructor pilot flying on the Asiana flight said he heard a low-speed warning, but the flying pilot said he didn't.
"Asked whether he heard an aural low-speed warning, he said no, he heard no sounds," the summary of the pilot interviews said.
Another pilot on the flight, first officer Bong Dongwon, called out "sink rate" repeatedly about one minute before the crash to warn the flying and instructor pilots that the plane was descending at the wrong rate.
"Regarding their alertness, he noticed 'a little late response' to his sink rate callout, but they did respond," according to the interview summary with Bong.
Capt. John Cashman, the former 777 chief pilot, said the cockpit equipment was designed to offer pilots choices so that they could fly the plane, with warnings when conditions warrant.
"Pilot automation is to aid the pilot and not replace the pilot," Cashman said.
Pilots are supposed to monitor cockpit equipment throughout a flight, even when not personally handling the controls.
"In the case of a final approach, we assume that is an area where the crew is actively monitoring the critical flight parameters," said Bob Myers, Boeing's chief engineer of flight-deck engineer. "There is no more critical parameters than glide path and air speed."
At 1.5 seconds before impact, a crew member was heard on the cockpit voice recorder suggesting they abort the landing, but at that point it was too late. Research has found an aversion among pilots to performing a go-around, although the reasons are still being studied.
Policies vary by airline, but pilots typically are supposed to veer off and make another attempt if a plane is making an "unstable" approach that isn't lined up correctly with a runway, or is at the wrong height or speed, when it reaches 500 feet above the ground on a clear day.
The Flight Safety Foundation surveyed 2,500 pilots worldwide and discovered planes approached in unstable ways in 3.5% to 4% of all approaches. But pilots performed go-arounds in only 3% of the unstable approaches, according to a February report.
The flying pilot, Lee, told investigators that Korean culture makes it difficult for a lower-level pilot such as him to order a go-around, while the instructor pilot held that power.
Capt. Sung-kil Lee, chief 777 pilot for Asiana, insisted that the airline's pilots receive enough simulator training to remain familiar with how to land planes. For the 777, captains have five years of experience and first officers have three years, he said.
"Capt. Lee is a very experienced pilot," Sung-kil Lee said. "He has enough experience... He was a very experienced pilot for visual approach."
Asked about the role culture plays in the investigation, Hersman said all countries and airlines deal with cultural differences.
"Our job is to be very fair," Hersman said.
In terms of emergency response, the most glaring problem was that one casualty, Ye Meng Yuan, 16, was lying on the tarmac when she became covered in firefighting foam and was then run over when a fire truck was moved.
Another problem involved the emergency slides used to evacuate the plane. One slide deployed incorrectly, temporarily pinning a flight attendant, and other slides didn't work at all.