Tuesday, 03.04.08

Textbook

Photo by flickr user caribb under a Creative Commons license

Amateur video captured a Lufthansa Airbus 320's near-crash in Hamburg, Germany.

These 66 seconds of YouTube footage are as close as we'll come to seeing an airplane crash without having to feel bad or ghoulish for the victims. It is as close as those hundred-plus people aboard will come to dying before they actually do.

The episode was "textbook" in some ways, illustrating procedures pilots drill again and again. One is the challenge of the crosswind landing. Some news accounts said that the plane seemed to be approach at an odd angle. That angle, visible especially starting about 28 seconds into the clip, is known as a "crab." It's the main way an airplane can get down when the wind is blowing across the runway rather than straight down it. As it prepares to land, the airplane's path across the ground must be lined up with the runway -- which means, because of the wind, that its nose must be pointed sharply into the wind, so that the plane appears to be trying to land side-first.

The pilot's handling of the crab was by the book. So was what he tried to do 38-40 seconds into the clip: "kick in the rudder," which means quickly swinging the plane's nose around so that, at the instant it touches the ground, it is pointing straight ahead along the runway's axis. Kick out of the crab too early, and the plane will drift sideways off the runway before it touches down, risking a crash on the tarmac. Kick out of the crab too late, and the wheels will still be pointed sideways when they strike the runway, also likely causing a crash.

The pilot crabs the airplane's gear down toward the runway, and kicks the rudder in just barely in time. When everything goes wrong, he does one last thing exactly right: engines are immediately and instinctively thrown in full power to get the airplane as far as possible away from where the danger is: close to the ground. He "goes around" and brings the airplane back for a safe landing -- on a different runway, better aligned with the wind.

Every pilot practices these procedures -- in training, it's routine to have an instructor yell, two seconds before touch down, "Go around! Go around!" to see how quickly you can switch from preparing to land the plane to preparing to ascend. This pilot is alive, and so are his passengers, because he reacted well under pressure.

But why was he under pressure? The airport weather forecast for that time called for crosswind gusts of 55 knots -- about 63 miles an hour. Every airplane has a "crosswind component limit," a degree of crosswind it cannot overcome. Not enough is clear yet to know how those winds related to the airplane's limits and who made the judgment that it was worth trying to land. But the video itself brings up one other item from the basic pilot's textbook. This is the homily learned on the first day and repeated constantly after: A superior pilot uses his superior judgment to avoid situations which require the use of his superior skill. — James Fallows

Filed Under: aviation, Germany, Lufthansa

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