Why is the wing of a passenger plane tilted?

It's called a slightly smaller wing to save fuel. Boeing 737 is a typical example, but it was added later. And many Airbus planes. However, the winglets of some Airbus models are not bent upward, but bent up and down, just like a small arrow, such as the Airbus A320 A380. A slightly smaller wing is not available in every plane, such as Boeing 777, and it is impossible to install winglets.

The winglet's function is to readjust the tip vortex, so that it is far away from the outside of the wing and moves upward to laminar flow. Due to the pressure difference on the tip surface, air tends to flow outward around the tip along the lower surface, while on the inner wing, air flows along the upper surface. After the winglet is installed, the vortex of the winglet rearranged by it produces a transverse airflow around the winglet, which is usually perpendicular to the airflow flowing over the wing surface. The lateral force generated by the lateral airflow contains a forward component, thus generating resistance. At the same time, the winglet at the tip of the blade generates corresponding thrust. In principle, it is similar to a sailboat. When sailing against the wind, the sails will encounter strong headwinds. At this time, the underwater keel presses the sailboat forward. It should also be noted that winglets have the aerodynamic effect of increasing the aspect ratio (thus reducing the induced drag), but in fact they do not significantly increase the wingspan. In addition, the increase of wingspan is minimized, so the increase of wing bending distance and structural weight is also minimized. There are many schemes for the structure and layout of winglets, some of which have been patented. /question/ 18699 1 17 . html