Only the asymmetric airfoil has higher efficiency and higher lift-drag ratio. When flying backwards, as long as the angle of attack is larger, the engine thrust is enough and the wing can generate enough lift.

There is a famous saying in aviation that as long as the thrust is large enough, bricks can fly. This is no joke.

By the way, it seems that you haven't studied aerodynamics seriously. Many terms are obviously unknown, and inference depends entirely on speculation.

Let me give you a summary, so I won't talk about the process. If you have a chance, find an aerodynamic book and study it well.

1, in the formula for calculating lift, the lift coefficient and angle of attack of airfoil are the same level coefficient, and they are multiplied. There is no question about who contributes more to the airfoil and the angle of attack, and the lift they produce is inseparable.

The kite is flat, why can it fly? Because of its light weight, large area and high angle of attack.

2. What is the function of the angle of attack? The greater the angle of attack, the greater the resistance and the greater the power required. Therefore, aircraft need an airfoil with as large a lift coefficient as possible. For a general subsonic aircraft, the lift generated by an asymmetric airfoil is more than five times that of a flat plate under the same thrust and speed.

3. At a certain angle of attack, the airfoil can produce a positive lift coefficient even if it is inverted. If it is a common biconvex airfoil, its lift coefficient may even be greater than that when the flat plate is inverted. When flying backwards, because the lift coefficient of the airfoil becomes very small, it needs a large angle of attack and a large engine thrust.

Finally, you know nothing about the basic concepts of airfoil, camber and flap.

Again, find a book and study hard.