# Aeroplane flying upside down

## Main Question or Discussion Point

When a aeroplane is flying due to its shape of aerofoil it gets lift. But it is common to see (as in stunt shows) that they can fly upside down too. When they do so they must experience a "downward" lift and start falling down. but they maintain a constant altitude.
How can they do it?

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I would guess the tail's elevators tilt the plane at an angle so that it doesn't fall as fast.

rcgldr
Homework Helper
All that is needed to generate lift is some amount of forward speed and an angle of attack. Most stunt planes use symmetrical airfoils that have the same shape above and below. For normal (not upside down) flight, a cambered airfoil will produce the same amount of lift but with less drag than a similar symmetrical airfoil. A longer wingspan will also increase the ratio of lift to drag, but there are limitations to making long wings strong enough and the pratical aspect of trying to taxi (drive on the ground) or store an aircraft with a long wing span.

Here's a link to one of many web sites with information about wings:

http://www.avweb.com/news/airman/183261-1.html

This wik article has a reasonable animation of the air flow being diverted downwards by a wing:

http://en.wikipedia.org/wiki/Lift_(force)

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Also note that the cross section of aerobatic airplane wings are quite symmetrical.

DaveC426913
Gold Member
Also note that the cross section of aerobatic airplane wings are quite symmetrical.
post #3:
Most stunt planes use symmetrical airfoils that have the same shape above and below.

A.T.
Here is a nice java applet from NASA, where you can try different profiles at different angles of attack. Just play around with the "Angle" silder, and you will see that you can produce lift in both directions (positive and negative):

http://www.grc.nasa.gov/WWW/k-12/airplane/foil3.html

AlephZero