The helicopter is a device capable of taking flight vertically because it has a propeller at the top, which works as a propeller.
When the engine starts, the main propeller rotates, pushing the air downward. By the principle of action and reaction, the air applies an upward reaction force to the propeller; the pressure difference generated by it due to the passage of air faster over it than below it generates a pressure difference and the union of these two effects is what makes the helicopter rise.
Any variation in the angular velocity of the helix produces a variation in its angular momentum, which is the physical quantity that relates the mass of a body around an axis of rotation with its velocity angular.
The rotation of the main propeller tends to rotate the entire body of the helicopter due to the torque of the propulsion forces. To solve this problem, helicopters are equipped with a side propeller, located in the tail of the aircraft. This, when rotating, pushes the air and, by the principle of action and reaction, the air pushes the propeller in the opposite direction. This “push” cancels the rotation of the helicopter's body, stabilizing the movement of the device.
There are helicopters equipped with two main propellers, not having a lateral propeller. In this case, the stability of the equipment happens because the two propellers rotate in opposite directions to each other, preventing the rotation of the device body.
Helicopter equipped with two main propellers
By Kléber Cavalcante
Graduated in Physics
Brazil School Team
mechanics - Physics - Brazil School
Source: Brazil School - https://brasilescola.uol.com.br/fisica/como-helicoptero-pode-voar.htm
