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View Diary: How Airliners Work - Wings and Stuff (67 comments)

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  •  Supercritical wings and shocks (12+ / 0-)

    When an airliner is going 80-84% of the speed of sound, because it's accelerating the air over the top of the wing, that portion of the air actually gets to higher than 100% of the speed of sound. As that air gets toward the back of the wing and slows down again to the same speed as the surrounding air, it tends to form a shock surface.

    Shocks are wasteful, i.e. draggy. A supercritical wing has a flatter upper surface that delays the formation of the shock to further back on the wing, where it's weaker.

    Fun airliner trick: if you're sitting over the wing on the sunny side during cruise, and if the wingtip happens to be lined up with the sun, sometimes that means the sun's light is traveling exactly parallel to the shock surface. When that happens, the violent air density disruption in the shock actually bends the light like a lens, and you'll see a wiggly line of light down the wing, 1/2 to 2/3 of the way back from the leading edge.


    by Simplify on Wed Apr 03, 2013 at 11:41:30 AM PDT

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