During the development of helicopters, various configurations have emerged, which can be classified in the following three different ways: 1.
According to the different ways of balancing rotor counter-torque, it can be divided into single rotor type, double rotor type (including vertical column type, horizontal column type, coaxial type, cross-type double rotor), multi-rotor type and so on.
2. According to the different ways of driving the rotor, it can be divided into mechanical drive type, jet drive type, etc.
3. According to the different ways of providing lift and propulsion force, it can be divided into normal type, winged type, tilt-rotor type, compound type and other new types under study.
Some of the above types have not been developed due to technical problems (such as the multi-rotor type), while others are still in the process of development.
Let’s take a look at the main ways in which the technology has matured into practical use.
A single rotor is installed on the helicopter, and the lift and propulsion forces are generated by it. The tail rotor installed at the tail of the fuselage provides the countertorque of the rotor.
It is the most technologically mature and numerous helicopter type available today.
Now there are also single-rotor helicopters that use other ways to balance countertorque, such as tailless single-rotor helicopters.
The vertical twin-rotor helicopter is referred to as the “vertical helicopter”.
The two rotors are arranged forward and backward along the longitudinal axis of the body, and the reverse steering makes the countertorque balance each other.
The horizontal twin-rotor helicopter is referred to as the “horizontal helicopter”.
The two rotors are aligned to the right and left laterally along the body, and their steering is opposite.
The common – axis Sunda helicopter is referred to as the “common – axis helicopter”.
The two rotors are mounted in common shaft and turn opposite to each other, and countertorque is balanced.
The cross-rotor helicopter is simply called “cross-rotor helicopter”.
The two rotors are aligned to the right and left laterally along the body, but their axes cross in a “V” shape and rotate in a coordinated reverse direction.
Tiltrotor aircraft is essentially a combination of helicopter and fixed wing aircraft.
For vertical takeoff and landing, flight and hovering, the rotors provide lift, which is tilted into propulsive propellers during forward flight, and the lift is provided by the fixed engine.
The compound helicopter is equipped with wings and propulsion devices. The propulsion force is mainly provided by the propulsion device in forward flight, and the lift force is produced by the wings and rotors together.
Vertical flight, hover and vertical takeoff and landing are mainly lifted by rotors.
A jet engine is installed at the tip of the rotor blade, or compressed air supplied from the rotor is ejected through the tip nozzle to drive the rotor rotation.
This rotor does not produce reverse torque to the body, so there is no need for balancing measures.
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