Whenever I see an explanation about how airplanes can fly, I see that the shape of the wing is different on the top side to create a dragging force that pushes the airplane up. The top is curved and the bottom is flat. If a airplane turn upside down, should it fall faster because it’s dragging down ? I saw airplanes doing acrobatics on air , and some of them looks impossible because of this.
In: Engineering
> I see that the shape of the wing is different on the top side to create a dragging force that pushes the airplane up. The top is curved and the bottom is flat. If a airplane turn upside down, should it fall faster because it’s dragging down
You probably heard some variation of the [equal transit time](https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html) fallacy, which is bullshit. Wings do not have to be curved on the top and flat on the bottom – in fact, aerobatic airplanes often have a symmetrical airfoil, which works just as well when flying inverted as it does upright.
The direction of the lift on an airfoil depends on the *angle of attack*, which is the angle the wing makes with the oncoming airstream. The pilot can control the angle of attack with the elevator. If the plane rolls inverted while maintaining a constant angle of attack then the lift would indeed point towards the ground; if the pilot intends to maintain level inverted flight then he must push forward on the stick until the lift balances the weight again.
Also note that an aircraft can be upside down while still maintaining positive G loading. [Here’s a nice demonstration of that fact](https://www.youtube.com/watch?v=DjHD1U-QWv4). In this case, the lift on the wings never changes direction and does point towards the ground at the apex of the maneuver.
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