flying upside down

[ivanovitch57]

i understand the aerodynamic theory of how the shape of an aeroplane wing provides lift, so how does a plane fly upside down?

[Panic Button]

I think they fly nose up / tail lower, so that an element of the engine's thrust is upwards - providing sufficient lift.

Also by tilting the wing at a greater angle of attack, the air flow over the 'top' has further to go. This recreates the aerodynamic lift effect even though the wing is upside down.

[Clanad]

Panic isn't far off. Airplanes that are designed for aerobatics use a laminar flow wing cross section that is a symmetrical airfoil section (cambered nearly equally on both sides)... Now, explain how an aircraft can fly straight up!

[748rhydhir]

when flying straight up no lift is required only thrust.i think

[beso]

A wing can provide lift when upside down provided it is at the right angle.

Indeed even a flat board can provide lift. The special shape of an airfoil provides lift with minimum drag but given enough thrust, a half reasonable aspect ratio and the right angle of attack, just about anything will provide lift.

Incidentally, the familiar classic description of the operation of an airfoil as "faster moving air has a lower pressure" is a myth. That neat diagram with arrows above and below the wing is rubbish.

Although the lift is indeed generated by a low pressure region above the wing this is ultimately produced by a downthrust of air created by the wing.

[Teddio]

Beso's correct. The rate of change of momentum of the downward-deflected air (the lift force) must be equal in magnitude to the weight of the aeroplane (for horizontal flight)

[ivanovitch57]

thanks everybody...you have answered a conundrum that's been bugging me on and off for years!

[fo3nix]

The way I understand it, the usual understanding that beso is talking about isn't a myth or rubbish, just a very small effect (much smaller than people think), so almost worthless, compared to other far more dominating effects.