Pilots delayed evacuation to talk to tower, official says

By Matthew L. Wald, New York Times News Service

Thursday, July 11, 2013 | 12:45 a.m.

SAN FRANCISCO — When the battered Asiana Boeing 777 skidded to a stop after its crash-landing here on Saturday, two flight attendants went to the cockpit to ask the three pilots inside what to do, and the pilots told them to delay evacuating the airplane while they communicated with the tower, the chairwoman of the National Transportation Safety Board said Wednesday.

The evacuation did not begin until another flight attendant seated just forward of the wing sent a message to the front that he saw a fire outside, said the chairwoman, Deborah A.P. Hersman. The safety board is using the crash of the plane, in which two passengers died, to learn all it can about what it calls “survival factors.”

Hersman also said that two of the exit-door emergency slides, one at the front right door (normally used for catering at the gate) and one at the right-side door just in front of the wing, had deployed inside the plane, each trapping a flight attendant, a worrisome turn of events with fire approaching the fuselage from the burning right engine. Both flight attendants were freed but were injured by the slides, she said.

And, in something of a mystery, the pilot who was actually flying the plane, a veteran captain who was transitioning to the 777 and making his first landing here in that model, reportedly told Korean investigators that he had been blinded by a flash of light at an altitude of about 500 feet.

“We really don’t know what it could have been,” Hersman said at a news conference.

The evacuation started about one and a half minutes after the plane came to rest, according to video evidence, she said. The cockpit crew’s decision is certain to be the subject of second-guessing, but she said that the men in the cockpit were not able to see behind them, where the tail and engines had been torn away.

Hersman remained vague about what had happened to the auto-throttles, devices that can be set to maintain a minimum safe speed, which the crew believed were working but were not. In the last minutes of the flight, the autopilot, which interacts with the auto-throttles, had been set in several different “modes,” she said, and it may have been programmed by the crew to execute several commands given by air traffic control to turn and descend. Experts on the 777 said that the auto-throttles will work in some modes but not others.

Asked why the supervising pilot, who was assigned to oversee the flying pilot’s first trip to San Francisco in a 777, did not intervene, Hersman said the investigators were “certainly interested to see if there are any issues where there are challenges to crew communication, if there is an authority gradient where people won’t challenge one another.”

The board has investigated a previous accident, in 1997, in which a junior officer in a Korean crew repeatedly tried to tell the captain that he was making a serious error, but the captain continued on course until the crash.

Among other factors investigators are considering is a dangerous practice called unstabilized approach, as well as circumstances that led to two previous crashes during approach and landing after uneventful flights.

An unstabilized approach is one in which the cockpit crew is adjusting the plane’s position — left and right, up and down — or adjusting flaps, the throttle or other controls while close to the ground. Airlines now routinely capture reams of data from the digital flight data recorders of advanced aircraft to record such setting changes in the last minutes of flight, as a tool to identify approaches with hidden difficulties that could contribute to a crash.

Boeing, for example, lists unstabilized approaches as a leading cause of tail strikes, in which a plane lands with its nose too high, so that the tail hits the runway. The crash on Saturday was an extreme example of this, with the landing gear, tail and rear part of the fuselage torn off by the impact with the sea wall beyond the end of the runway.

The precise definition of unstabilized approach, prescribing the altitude at which everything must be set up for landing, differs by airline. One question for the investigators is whether Asiana’s procedures are too lax in allowing such approaches, or whether the procedures were followed.

Investigators were extensively documenting the conditions inside the 300-seat cabin. They would like to know if the passengers were wearing seat belts, and what they took with them when they evacuated the plane.

Though the Asiana crash is likely to produce changes in years to come, the Federal Aviation Administration issued an important new rule on Wednesday growing out of the last domestic crash, of a twin-engine turboprop on approach to Buffalo in February 2009. That accident resulted from an error by the captain that was not corrected by a very junior first officer.

The new rule, mandated by a law passed by Congress in 2010, will require that the first officers on commuter carriers — the second-in-command in a two-person cockpit — have 1,500 hours of flight experience. The current requirement is 250 hours. The rule sets various other requirements, including that first officers be qualified on the type of airplane they are flying.