As you know, an aeroplane has fixed (immovable) wings that create lift as the aeroplane moves forward. A helicopter, on the other hand, has rotary wings which whirl in the air, and generate lift.

The special shape of the rotary wings helps them create lift. A wing’s upper surface is curved, while its lower surface is less curved or flat.

As a wing whirls through the air, air flows over and under the wing. In the same amount of time, the air flowing over the curved upper surface travels farther than the air flowing under the wing. The air thus flows faster over the wing than under it. This difference in air speed creates a difference in air pressure above and below the wing.

There is less pressure on the upper surface than on the lower surface. Because air pushes more strongly against the bottom of the wing than against the top, lift is created.

Helicopter pilots can control the amount of lift by changing the angle that wings make with the airflow.

NOTE : The first drawings of helicopters are nearly 500 years old and were made by the painter and inventor, Leonardo da Vinci.