XKCD: Airfoil

Are you able to answer this students question? Why *can* airplanes fly upside down if this is how an airfoil works.

Or better yet: Why does the air above the airfoil have to meet up with the air below the airfoil?

4 Responses

  1. Ramiel says:

    I know this is half jokingly so here’s the serious answer: I think they use symmetrical airfoils.
    and the air above has to meet the air below because its just a law of conservation of mass…mass flow rate in = mass flow rate out 😛
    now that better answer: they can fly upside down because their wing is installed upside down. and it has to meet because they like each other..i dont know..that wasn’t very creative

  2. Blake says:

    Ramiel,
    You have the right spirit though 😛

  3. Zhatt says:

    Hum.
    Well, a plane can fly upside-down because of angle of attack. If the oncoming air hits the wing at a sharp enough angle it will create lift inspite of the airfoil.

    The air moves faster and has a lower pressure over the top of an airfoil because of Bernoulli’s principle (not that I know how that works).

    The “conservation of mass” if an oversimplified model and the air doesn’t need to meet up at the tailing edge. In fact, I think the air moving over the top moves much faster than the air below which creates the downwash.