What is the helicopter main rotor system?

Although the typical helicopter is considered an aircraft by definition, it would be more accurate to refer to it more specifically as a rotorcraft. Rotorcraft, or rotary-wing aircraft, are defined as aircraft that generate lift with the use of rotary wings or blades that spin around a mast. In the case of a helicopter, the blades spin around with the use of a main rotor, providing for flight and full axis directional control. While a commercial jet may use the combustion of fuel to produce exhaust that propels the aircraft forward, the helicopter rotor produces flight in a much different way. In this blog, we will discuss the helicopter rotor system and how the various parts work together to achieve heavier-than-air flight.

There are three main different types of rotor systems to be familiar with, including the fully articulated, semirigid, and rigid rotor. Each describes a different rotor configuration, including the semirigid rotor that describes rotorcraft with two helicopter blades and the rigid rotor having blades that do not have the ability of flapping or lead-lag. Fully articulated rotors feature blades that are capable of pitching axis and adjust independently to create more control over movement. There are many different helicopters that utilize each of these configurations. As different benefits can be found from each type, manufacturers ultimitely choose based on the intended application of the rotorcraft.

Fully articulated rotor helicopters and similar rotorcraft are able to achieve much of their movement abilities due to the aircraft bearings and hinges within the rotor system. With the use of aircraft bearings, the helicopter blades are able to change their pitch with motion across the pitch axis. Between the swash plates that function to translate pilot control into movement, ball bearings are installed to allow the upper plate to rotate on top of the lower plate. Aircraft hinges play an important role as well, as they allow the blades to move up, down, fore, and aft utilizing flap and lag hinges.

Within semirigid and rigid rotor systems, the parts and movement capabilities of the helicopter blades may differ somewhat from those with fully articulated rotors. With semirigid systems, the blades are fixed to the hub, creating a rigid installation but still allowing flap movement to change the pitch of the blades independently from one another. Rigid systems, on the other hand, are not capable of flap or lag movement, but their blades have high strength and flexibility that allow them bend as needed without the use of hinges.

While the main helicopter rotor is sufficient enough to achieve flight, the torque that the blades produce would spin the body of the helicopter in circles by itself. To avoid this, a second rotor is placed on the helicopter to counteract this torque, and these are the tail rotors and blades that keep the helicopter straight. Tail rotors rotate vertically and can be controlled by the pilot in terms of thrust. By varying the thrust of the tail rotor, the pilot can change the direction that the helicopter nose is facing, adding to the benefits that they bring. Helicopters may also feature dual counter-rotating rotors instead of a tail rotor which counteract the torque effect. This configuration is also beneficial for helicopters that may need or warrant extra lift capabilities on top of maintaining nose direction. Configurations of these types of dual rotors include those such as having two rotors placed on top of each other or on different sides of the helicopter.

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1. elvis clinton
2. Posted on February 25, 2020
aviation

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