How Planes Fly: What You Learned Was Wrong

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1. In all fairness, the bottom of the wing is used. It also deflects air downward, but by much simpler means. Air smacking into the angle-of-attack rebounds off the bottom of the wing and provides a lot of lift.

   How do you think kites stay up? Or the little rubber band powered balsa toy planes? Neither of those have any chamber to their airfoils, nor use the Coanda effect.

   Comment by kk — 10/19/2007 @ 10:41 am

2. the coanda-effect is only working with a small stream flowing along a surface. it requires that the air/medium outside the stream is in rest, i.e. it dowsn’t move. only then the coanda-effect is possible. in normal streamings the bernoulli-effect is working not the coanda-effect. however, the latter is indeed used in aircraft design, but only in combination with other effects. the mathematics required is fairly complex but it suffice to say that the coanda-effect is not the reason why planes fly.

   if you don’t believe it, try the above water-stream experiment not with a very thin but a strong, fastly flowing, broad stream, which resembles the air around a wing much more correctly. you’ll see no coanda-effect this time.

   Comment by as — 10/19/2007 @ 10:54 am

3. An interesting concept. If this is the case, though, why does a circular wing work? The forces ought to cancel each other, but they obviously don’t. This is evidenced by taking a piece of paper, folding it into a rough airfoil, joining the ends in a circle, and throwing it like you would a football.

   Further, isn’t the the main force of the attraction of the water to the glass because of intermolecular electromagnetic forces, not because of fluid dynamics?

   Also, you have a few things wrong:

   “This results in the air being forced toward the ground as it leaves the wing, which — according to Newton’s 2nd law — results in an equal and opposite force upwards, i.e. lift.” That’s Newton’s Third Law. The Second Law is “F=ma”.

   “It was created by a physicist at Fermi Labs and explains everything in detail.” It’s “Fermilab”. Or Fermi National Accelerator Laboratory, if you want to get technical. “Fermi Labs” makes it sound corporate, like “Bell Labs”.

   Comment by Cyrus — 10/19/2007 @ 11:07 am

4. [...] planes take off and fly.  Turns out, I’m wrong — though the Bernoulli effect collaborates, it’s the Coanda effect that actually makes most of the work. Text continues [...]

   Pingback by Why planes fly — no, really! — 10/19/2007 @ 12:08 pm

5. How do planes fly upside down?

   Comment by Rob — 10/19/2007 @ 1:04 pm

6. hey rob,

   i was not supporting the equal transit time theory. the blogger is correct in saying that the bernoulli theory does not explain the lift correctly since it does not explain why aircrafts can fly upside down. i’m sure you know why they do. the angle of attack is important for generating the lift. it doesn’t matter which side is up or down.

   besides, it’s a common misconception that airfoils cannot be symmetrical because they wouldn’t produce any lift. but modern airfoils are very often symmetrical. this misconception seems to have started in the early times of aircrafts when the foils were not symmetrical. however, the design of those wings caused a strong lift, but it was the turning the wings caused in the air stream. the coanda effect, i think, is still not responsible for it.

   regards as

   Comment by as — 10/19/2007 @ 2:44 pm

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