The safety board chairwoman, Deborah Hersman, said Sunday at a briefing that a crew member called for an increase in speed seven seconds before the plane clipped an embankment at the edge of the runway. She said the plane was traveling well below the speed needed to maintain a stable angle of approach. The jetliner’s cockpit recorder included the sounds of an automatic shaking of the control yoke just before the crash, an indication that the plane was about to stall.
The device also recorded a pilot’s voice calling for a go-round 1.5 seconds before the crash. While the engines responded normally, the move came too late to prevent the crash, Ms. Hersman said. The plane’s tail section then snapped off, and the plane skidded across the runway and caught fire.
Ms. Hersman’s description of how the plane slowed generally tracks other data showing the jetliner began to descend too fast because it did not have enough airspeed. Data collected by an aviation firm suggested the plane was descending more than four times faster than normal shortly before it crashed.
At 800 feet over San Francisco Bay, the plane was descending at 4,000 feet a minute on Saturday, according to data gathered from FlightAware, a company that listens to navigation broadcasts and sells the data to airlines and others. The normal approach profile is 600 to 800 feet a minute.
At the briefing, Ms. Hersman focused mainly on whether the pilots erred while making a series of calculations needed to land.
While the pilot should have recognized the abnormally strong descent, the safety board also said Sunday that it was investigating whether construction at the airport — which had temporarily shut down an electronic system that helps guide pilots to the proper landing slope — might have played a role in the crash.
“The glide slope had been out since June,” Ms. Hersman said on CBS’s “Face the Nation.”
“We’re going to take a look into this to understand it,” she said. “But what’s important to note is there are a lot of tools that are available to pilots.”
The FlightAware data indicated that at 100 feet above the water, the plane was descending at more than 270 feet a minute when it should have been slowing to a rate of a few feet per second. FlightAware’s data is not as precise as the information available to investigators from the plane’s flight data recorder, which the safety board began examining on Sunday. But it provides an indication that in the last moments of the flight, unless there was some as-yet undisclosed mechanical problem, crew members, from their own instrumentation, should have been aware that the plane was descending too fast.
Aviation experts said that the pilots, who were both veterans, could have also relied on red and white signal lights on the runway to visually guide the plane to touch down or, if they chose, on the plane’s onboard computers to generate the angle of approach.
Witnesses and passengers have described the jetliner as coming in too low and clipping a rocky embankment at the edge of the water just before the runway. The plane’s tail section then snapped off, and the plane skidded across the runway and caught fire.
Two passengers were killed, and at least 180 people were injured. The dead passengers were identified on Sunday as two 16-year-old Chinese students on their way to a summer camp. The students, both women, were believed to have been seated toward the back of the passenger jet, the president of Asiana Airlines, Yoon Young-doo, said. Their bodies were found on the runway.
Mr. Yoon said Asiana Airlines did not believe there was anything wrong with the Boeing 777, which had been bought in 2006. At least 180 people were injured in the crash.
Norimitsu Onishi reported from San Francisco, and Ravi Somaiya from New York. Reporting was contributed by Vindu Goel, John Markoff and Somini Sengupta from San Francisco; Christopher Drew, Jad Mouawad, Marc Santora and Michael Schwirtz from New York; Matthew L. Wald from Washington; and Choe Sang-hun from Seoul, South Korea. Susan Beachy, Shi Da and Stephanie Yang contributed research.
Article source: http://www.nytimes.com/2013/07/08/us/san-francisco-plane-crash.html?partner=rss&emc=rss
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