Flying upside down
 

I know the basics of flight..thrust, drag, lift ect, and the basic aerofoil shape that produces lift, and the reverse as on F1 cars that pin them to the floor.
So call me stupid but why can aircraft fly upside down?

PA38, I'm not even an uni student yet, but I can answer that Q for you! :D

Consider, oh i dunno, any small plane, let's say a Yak-52, flying along straight and level. Wings are doing their job etc etc etc. Then the pilot just happens to see a crowd that had come for an airshow. As he passes them, he brings the stick to the right until the ground, to him, is where the sky was (180 deg roll). all the time, he's kept his nose at level.

One, the plane's nose will start to drop groundward, he sees the green half of the outside world coming down the windscreen and he will have to push the stick down (away from him) to counteract this.

two, he will start to drop. He sees this on the altimeter and pushes the stick even further to counteract this.

So he ends up upside down, but with the nose pointed at about 20-30 degrees or more from horizontal.

Fact is, the loss of aerofoil lift is compensated by both the downforce of the twisted aerilons and the engine prop, which is now providing a bit of upward thrust.

Keep in mind also that when the wings are inverted, while they're not providing the same amount of lift as they would right way up, they still are contributing to the net (total) forces upward.

There. that's it explained. Can I get a sponsorship for AeroEng in Cranfeild now?:D :D :D

PA38, no one should call you stupid. There are no stupid questions asked in good faith.

You have mostly answered your own question by mentioning those 'basics of flight' ... thrust, drag, lift ... and the last is gravity.

Any airframe, even one shaped like a brick, will fly if thrust is equal to or greater than drag and lift is equal to or greater than gravity.

Now an aircraft has no idea whether it is inverted or not. It has no idea if it is up-side-down or right-side-up. It cares little if a wing is pointed to the earth or the heavens. But the aircraft will and must respond to those forces of flight above (thrust, drag, lift and gravity).

You also answer your own question by mentioning the 'aerofoil shape'. The shape is only significant in terms of lift when we consider airflow about it.

Think of a box kite, for a moment. See it up there in the sky, steady in the breeze at the end of your string. Now pull it in, retrieve it, and restring it so that the kite is rotated 180 degrees: up-side-down. Send it aloft and lo...it flies!

The point is that the angle of airflow over the kite provides lift whether the kite is inverted or not. Similarly, skillful pilots in some aircraft can arrange the airflow about their aircraft to provide lift by deft adjustment of the attitude of their inverted aircraft in the face of the airflow.

Now, I'm not a skillful pilot. In fact I'm not an engineer or a pilot at all and I'm hoping that some here more qualified than me can assist you better.

Nonetheless, I hope this is a start for you.

There is no major aerodynamic problem with flying upside down (systems might be a consideration .. eg batteries, oil, fuel and so on).

If the wing section has a conventional camber, inverted flight will not be terribly effective or efficient .. which is why many aerobatic aircraft have wing sections which tend more towards a symmetrical profile.