How airplanes fly

With sufficient thrust, pigs fly just fine.

18 11 18 - 19:24 Used tags: , ,

By now I'm sure you've all seen that elementary school show: airfoil, airstream, Bernouli, pressure difference, lift. Boom, magic gone. However, there's much more to it than that.

Airfoil in airstream picture is a sideview of an airplane's wing. Have you ever asked yourself how does that lift look if you look at an airplane from the front or the rear? How is the lift distributed over the wing spanwise? How it should be distributed?

One very smart german engineer figured it all out back about 100 years ago. His name was Ludwig Prandtl and his work forms the basis of every aeronautical engineer's knowledge today. Prandtl's result was that elliptical lift distribution is the best for a given wing span and this was taken as a fact.

Until now.

During my childhood years flying my first model airplanes I was explained all about elliptic lift distribution, even before I fully understood what an ellipse is. Even then I remember being uneasy about it, but mostly due to "these people are way smarter than me, they know what they're doing". And I tried to live with that attitude.

Then some things happened that bought all those toughts and doubts back:

This is my model at a competition back in 2016 in Hungary, after a successful 10min flight. It got hit by another airplane about 3 minutes into the flight at about 250m in a crowded thermal. Another plane hit it on the aft fuselage, which pushed it into a flat spin at such a force that one of the wing tips simply flew out. (It was later recovered without damage.) Model recovered after four or five spins and after initial shock I discovered it is suprisingly controllable and flies more or less as before. It turned out that fuselage was badly cracked and whole tail was flapping around about 20 degrees in all directions and it was that that gave me most of the control issues. Roll control was fine.

It was one of those things that you would never try on purpose ... flying without a third of your wing. Just by looking at it, it can't fly like this, right? It shoul spin out of control, having much more lift on one side than on the other ... obvious, right?

Well, my successfull flight says otherwise. 

And then the image of elliptic lift distribuion comes back again ... and one starts to wonder whether it is really there ... and if is that a good thing or not.

More in part 2 :)

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