How do military jets and stunt planes fly upside down?
I have only rudimentary understanding of the physics of how airplanes fly. From what I understand planes couldn’t possibly fly upside down. Empirical evidence would suggest otherwise however, so my understanding must be flawed or lacking (or both).
Wings produce lift, right? In right-side-up flight the lift is being produced in the opposite direction than gravity. Lift > gravity = ascent, lift = gravity = level flight, lift < gravity = descent. Right?
But upside-down, those same wings are still producing lift, right? However, the lift is now being produced in the **same ** direction as gravity. So…. What’s keeping the plane up?
I also understand that thrust plays a role in ascent and descent thusly: point the nose of the plane up and the combination of lift (from the wings) and being “pushed” up will make the plane climb faster than with just “wing-lift” along. Likewise point the nose down and you overcome some (all?) of the “wing-lift” because the entire plane is being “pushed” down. The extreme example of this is rockets like those used to launch satellites – they ascend completely from “push” (thrust) but no “wing-lift”.
So I can see that a plane could fly upside down if the “push” from the engines completely overcomes both gravity and the “wing-lift”, both of which are now pointed in the same direction (the ground). However, this makes me think that the nose of the plane would have to be pointed away from gravity/“wing-lift”/the ground at a very severe angle.
But I’ve seen film, pictures, etc. of military jets and stunt planes flying upside down with their wings apparently parallel to the ground. How??? What am I missing here?