WASHINGTON --

The pilot-in-training who crashed an Asiana Airlines jet at San Francisco International Airport in July was anxious because he had to land the plane manually, and he did not respond to repeated warnings from another crew member that his descent was too steep, according to federal documents released Wednesday.

Lee Kang Kuk, who had flown jetliners for Asiana for eight years but was a novice with the Boeing 777 he was landing at San Francisco, told investigators three days after the July 6 crash that he found making a visual approach "very stressful," according to reports released by the National Transportation Safety Board on the day the agency held a hearing in Washington, D.C., into the crash.

Testimony during the hearing also revealed that Lee and two other pilots in the cockpit were apparently confused over the operation of the jet's automated controls, which led to the craft's speed dipping to a dangerously low level and contributed to the crash.

System was down

Lee, 46, told investigators he was comfortable landing with automation - with the help of a piece of airport equipment known as a glide slope indicator, which guides airplanes on a 3-degree descent path to the runway, according to the safety board documents. But that system was down in San Francisco last summer because of a runway expansion project.

The pilot "stated it was very difficult to perform a visual approach with a heavy airplane," according to a safety board summary of an interview with Lee, who did not testify Wednesday. "Asked whether he was concerned about his ability to perform the visual approach, he said, 'Very concerned, yea.' "

Three passengers, all Chinese teenagers, were killed and 181 people were injured when Asiana Flight 214 slammed into a seawall short of the runway, broke apart and caught fire. One of the three who died was killed when she was run over by a San Francisco Fire Department rig battling the blaze, according to the San Mateo County coroner.

'Very well experienced'

Lee was "very well experienced" and should have been able to make the landing with no stress, Kwang Hee Lee, Asiana's air operations safety division director, told the safety board Wednesday. He said he "cannot tell how much stress Capt. Lee received because he was such an experienced pilot."

Lee had no record of accidents or discipline. But he was new to the Boeing 777, having begun to fly the aircraft with an instructor just three weeks earlier, according to the safety board reports.

Before the crash, Lee - referred to as a trainee captain - had flown just four round-trip flights on the 777. All originated in South Korea, where Asiana is based.

His instructor on a flight to Narita, Japan, two days before the crash told the safety board that he was "not sure if the trainee captain was making normal progress because the trainee captain did not perform well during the trip," investigators wrote. "He said that the trainee captain was not well-organized or prepared, that he conducted inadequate briefings, and that he deviated from multiple standard operating procedures."

In addition, the instructor said, Lee allowed his descent to go too low.

Flying too slowly

"He stated the trainee captain was not carefully monitoring, examining or focusing on the operations and he accepted the (instructor's) advice 'very lightly' and was not seriously focused on operating the right way," the safety board said.

During Wednesday's hearing, investigators said the Asiana plane approaching SFO had been flying at 118 mph when it hit the seawall, well below the desired speed of 157 mph. The problem was apparently due to the crew's inadequate use of the automated flight controls, witnesses said.

Investigators said the crew hadn't effectively monitored the intricate interplay between the airplane's automated throttle and manual controls as the plane made its final approach after an 11-hour flight from Seoul.

About 3 1/2 miles south of the airport, the jet's autopilot began to take the craft higher, so Lee disconnected it to take better control. But as the plane got closer to the runway, the crew apparently didn't properly toggle between manual and automated controls, so by the time the plane was about 1 mile away from landing - and 24 seconds from impact - it was going too slowly.

Warnings ignored?

In the last minute of the flight, Lee and his captain instructor, Lee Jung Min, did not react to several warnings from a third member of the crew, First Officer Bong Dong Won, that the descent was too steep, the safety board said.

The first officer, sitting in a jump seat in the cockpit, told investigators that he noticed the steep descent as the plane dropped below 1,000 feet. Investigators said he "prepared in his mind to recommend something, to advise them, but he did not."

About 40 seconds before impact, he repeatedly called out, "sink rate," according to a transcript of the cockpit conversations. There was no apparent response.

In interviews with safety board investigators, Lee Jung Min "stated he heard this callout," but said the plane was still high in the air and appeared to be descending properly.

He said that after the plane had descended to 200 feet, he realized the speed had dropped to 138 mph. He had thought the plane's auto-throttles would keep it from dropping below the desired speed of 157 mph.

"He thought at the time maybe the auto-throttle was not operating," the investigators wrote. "He pushed the thrust levers up; the airplane was sinking."

At 11 seconds from impact, a low-speed caution bell was sounded in the cabin.

'Go around'

The captain recalled telling his crewmates, "I have the controls, go around," and pushing the thrust levers forward. But it was too late.

At a news conference Wednesday, safety board Chairwoman Deborah Hersman said, "We want to understand the roles of those pilots, the communication that took place in the cockpit and what can be learned from this event so we can prevent future accidents."

The board's final report on the crash causes is not expected to be issued for several months.