Types of Aircraft Rotorcraft Controls

Similar to fixed-wing aircraft, rotorcraft, or rotary-wing aircraft, have numerous flight controls that allow them to work optimally. With so many controls, it can be difficult to distinguish what each control does. To better understand the importance of rotorcraft controls, where they are located, and how they work, this blog will outline the most basic controls below.

Swash Plate Assembly

The swash plate transmits control inputs from the collective and cyclic controls to the main rotor blades. This assembly consists of two main parts, those of which are the stationary swash plate and the rotating swash plate. The stationary swash plate is attached around the main rotor mast and is linked to the cyclic and collective controls through several pushrods. It is kept in place by an antidrive link, but has the ability to tilt in all directions and move vertically. The rotating swash plate, on the other hand, is mounted to the stationary swash plate with the help of a uniball sleeve. It is affixed to the mast by drive links and can rotate with the main rotor mast. Furthermore, the rotating swash plate is connected to the pitch horns by the pitch links. Keep in mind that both swash plates tilt and slide up and down as one unit.

Collective Pitch Control

The collective pitch control is situated to the left of the pilot’s seat and is operated with the left hand. The collective is utilized to make changes to the pitch angle of all the main rotor blades. This is achieved via a series of mechanical linkages, and the amount of movement in the collective lever determines the amount of blade pitch change. Meanwhile, an adjustable friction control prevents inadvertent collective pitch movement.

Throttle Control

The throttle is used to regulate engine rpm. In the event that the correlator or governor system do not maintain the desired rpm when the collective is raised or lowered, or if those systems are not installed, one must move the throttle manually with the twist grip to maintain rpm.

Governor/Correlator

A governor is a type of sensing device that senses rotor and engine rpm, and it makes the necessary adjustments to keep a constant rotor rpm. Once the rotor rpm is set in normal operations, the governor maintains a constant rpm, meaning that throttle adjustments are not required. Furthermore, they find use in all turbine helicopters and are used on some piston-powered helicopters. By contrast, a correlator is a mechanical connection between the collective lever and the engine throttle. When the collective lever is raised, power is automatically increased, and when it is lowered, power is decreased. For fine tuning, the throttle must be adjusted.

Some rotary-wing aircraft are not equipped with correlators or governors and necessitate the coordination of all collective and throttle movements. Lastly, one must be careful to ensure that large adjustments are not made.

Cyclic Pitch Control

The cyclic pitch control is vertically mounted from the cockpit floor, between the pilot seats or between the pilot’s legs, depending on the model. This control enables pilots to fly rotary-wing aircraft forward, backward, and sideways. The main purpose of the cyclic pitch control is to tilt the tip-path plane in the desired horizontal direction. Furthermore, the cyclic pitch controller changes the direction of this force as well as controls the attitude and airspeed of the helicopter.

The rotor disk tilts in the same direction that the cyclic pitch control is moved. Since the rotor disk acts like a gyro, the mechanical linkages for the cyclic control rods are positioned in a way that they decrease the rotor blade’s pitch angle by 90 degrees before the rotor disk reaches the direction of cyclic displacement. Once it passes the direction of displacement, the pitch angle must be increased by 90 degrees. Keep in mind that an increase in pitch angle increases the angle of attack, and a decrease in pitch angle decreases the angle of attack. 

Antitorque Pedals

The antitorque pedals are positioned on the cabin floor at the pilot’s feet. They are responsible for controlling the pitch and thrust of the tail rotor blades, and they allow the pilot to control the pitch angle of the tail rotor blades. They are generally connected to the pitch change mechanism on the tail rotor gearbox and enable the pitch angle on the tail rotor blades to be increased or decreased. Rotary-wing aircraft that lack antitorque rotors are usually those that are designed with tandem type rotors. Instead, they are designed with both rotor systems rotating in opposite directions to counteract the torque, rather than using a tail rotor.

Conclusion

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