How Does the Rotor System of a Rotary-Wing Aircraft Generate Lift?

Posted on April 3, 2023 Jacob Luiz

Helicopters are a marvel of modern engineering, and their ability to take off vertically and hover in the air is an impressive feat. But how do they do it? The answer lies in the way that helicopters create lift. To better understand this phenomenon, we will explore the science behind how these rotary-wing aircraft produce the necessary lift to achieve flight.

To understand how helicopters create lift, we need to first understand the basics of lift. Lift is the force that opposes the weight of an object and keeps it in the air. Generally, it is created by the movement of air over a surface, such as the wings of an airplane or the rotor blades of a helicopter. In the following sections, we will provide an in-depth understanding of the two main factors that influence a helicopter’s ability to generate lift.

  1. Pressure Difference

The rotor blades of a helicopter are essentially rotating wings that create lift. Similar to an airplane, they use specially shaped airfoils which affect the surrounding airflow; in the case of a helicopter, the airfoils create a lower pressure above each blade, enabling them to rise as it rotates. Within this rotor system, the rotor engine valve is a critical component that controls the flow of fuel and air into the engine, which drives the rotation of the rotor blades and allows the rotorcraft to generate lift and maneuver in the air. More specifically, the helicopter’s main rotor system can have between 2 and 8 main rotor blades that work as a whole when being rotated by the engine. The engine of the helicopter drives a main transmission that rotates each blade around a central mast, whereas an airplane has to push its wing through the air in a linear path to achieve such ends.

  1. Air Deflection

Another major way that a rotorcraft creates lift is through air deflection. On a helicopter, each main rotor blade changes its pitch angle in relation to its connection to the main rotor hub, and as the blade increases its pitch, it begins to deflect air downwards. The more its pitch angle increases, the more air molecules it deflects downwards – until its pitch angle increases too far that it stalls. By changing the pitch angle of the rotor blades, the pilot can control the direction and speed of the helicopter.


In conclusion, the combination of the pressure differences between the rotors and air deflection allows a helicopter to generate lift and stay in the air. It is also important to keep in mind that the rotor blades of a helicopter are like rotating wings that create lift, and by changing the pitch angle of each rotor blade, the pilot can deflect air downwards and control the helicopter's movement.

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