I understand that the wing of the plane creates downforce, lifting the plane into the air, so how do planes fly upside-down? Wouldn’t the wings start pushing the plane down into the ground once flipped?
In: 373
This one is gonna be fun since… WE DONT KNOW.
We can fly. But science cannot put forth a complete and accurate model of WHY flight works. Not yet, at least.
Commercial airplanes are built to fly efficiently and rely heavily on the shape of their wings. They generally cannot fly upside-down despite what various movies might claim. Acrobatic planes are made with more symmetrical wings so that it is easier to fly upside-down.
And… Someone correct me if I’m wrong, but it isn’t the wing of the plane creating downforce. The increased speed of the air going *over* the wing creates a low pressure area, lifting the wing.
Well, yes, but also no.
You care correct that if you took a plane that was flying perfectly straight and level, and inverted it, the lift (from the wings) would now push the plane towards the ground.
BUT, a plane can still pitch down, pushing opposite the wings’ lift, and go down. While inverted, that can help keep the plane from falling.
Another factor is the fact that any plane that can fly for extended periods of time (typically fighter jets) rely more on the direction of their thrust (by angling up while flying) than the shape of their wings to stay airborne.
Thus, while flying upside down, they just need to keep their thrust “pointed somewhat towards the ground”, which will push them back up.
First we have to fix the question:
>understand that the wing of the plane creates downforce
It does not. Downforce is what sports cars have. Effectively, they’re upside-down airplane wings. They push the car into the ground, rather than make it fly. What planes do, is simple “up-force”. Now for the answer:
A plane can, in effect, transform its wings during flight. It used to be that they twisted the entire wing, but now they do it with ailerons instead (Thanks Tom Scott). For instance, when pitching down, what you are effectively doing is making the wings create downforce instead of upforce. So it goes to reason that if you turn the plane up-side down, and pitched “down”, what would otherwise be downforce is now creating upforce again, making it able to fly like normal
Riddle me this, Batman . . . How does the fuel flow properly when inverted?
Forget the wing shape for a moment and imagine a plane with a sheet of plywood for each wing…
Add a engine to pull the plane forward through the air…
Nose the plane up slightly so the wings are on a slight upward angle… the front of the plywood wing hits the air and the plywood tries to deflect the air downwards. The air doesn’t really want to compress/move that much so the plywood wing (and thus the entire plane) is forced up a little. This is the primary way planes produce lift – plane is moving forward (engine) and the wings are angled slightly up (air deflected downwards).
Next you have the engine exhaust. If the engine is pointing slightly up then the air blast out the back of the engine is pushing the plane up slightly like how a fighter jet can go almost straight up. The effect isn’t nearly as much as the wing angle on a normal plane but it adds to the lift.
Finally you add the familiar wing shape and you optimize it really well you can add maybe 3-5% more lift.
Flying upside down…
If the wing shape was adding 3% lift and you fly upside down up you have lost your 3% benefit and it is now a 3% loss.
But that doesn’t matter… the lift is coming from the wings being on a slight angle deflecting the air downwards. As long as you the engine can pull you forward with the wings at the angle needed to maintain or climb you are good. Remember you control the wing angle by nosing up or nosing down.
Talking about mysteries…
If a plane has a take-off speed of 100mph, and you put it on a treadmill running backwards at 100mph, will it still take-off?
(the classics are the best)
I got into this discussion in a similar thread, and one topic was Bernoulli’s principle (air moving faster over a larger surface area) versus Newtonian principle (angle of the wing).
Really, it comes down to the design of the plane…the wings, the flaps, the angles. Most planes aren’t designed to fly upsidown. Certainly not commercial passenger planes.
They are flying within the air, not on top of it. So being upside down in a plane in air is like a person being upside down in water. That’s how I think about it.
Ignore air liners for now because they can’t really fly upside down anyways. The wings on fighter jets mostly don’t generate lift because of their shape, but because of the angle of attack. Angle of attack (AoA) is the angle between the oncoming air and the plane of the wings. What it means is that when a fighter aircraft is flying straight, its nose is actually pointing up slightly. [This is an example.](https://theaviationist-com.cdn.ampproject.org/i/s/theaviationist.com/wp-content/uploads/2019/04/ItAF-Typhoon-Seahawak.jpg) Because the fighters have to go so slow to keep up with the helicopter, and lift decreases the slower you are going, they have to increase their AoA (point nose up) to generate enough lift to stay in the air.
So when you want to fly upside down in a fighter aircraft, you just have to keep your nose pointed up into the oncoming air, [like this.](https://qph.cf2.quoracdn.net/main-qimg-d3352e0adf3a1307de80c724b48bc40c)
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