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Icing and Crashes

Q: One sometimes hears of “icing” after a crash. How can ice or snow cause a plane to crash?

During flight ice can accumulate in different areas — on leading edges of the wings, engine inlets, etc. (It will stick to the thinner, lower profile areas, but usually not the larger expanses or fuselage — a function of aerodynamics; let’s not go there.) This occurs during visible precipitation, or when suspended moisture sublimates directly to the surface. The monster here isn’t the weight of the frozen material, but the way it changes the contouring of the wings. Even a half-inch ridge of ice can wreak havoc with an airfoil. This is especially important during takeoff and landing, when speed is slowest and the margin of lift is most critical.

Sitting at the terminal, a plane will collect precipitation the same way your car does — via snowfall, sleet, freezing rain or frost. Thanks to supercooled fuel in the wings, frost can form insidiously even during temperatures above freezing. But not to worry (you were waiting for that), as all of this is scouted out before flight. An airline’s preflight de-icing checklist can take up several pages of a pilot’s manual.

Whether aloft or gateside, rules and equipment are on hand for the occasion.

This article is part of a collection that originally appeared on Patrick Smith, 38, is an erstwhile airline pilot, retired punk rocker and air travel columnist. His book, Ask the Pilot (Riverhead) was voted “Best Travel Book of 2004” by Patrick has traveled to more than 55 countries and always asks for a window seat. He lives near Boston.