A helicopter has four flight control inputs: cyclic, collective, antitorque pedals, and throttle. The cyclic control is usually located between the pilot’s legs and is commonly called the “cyclic stick” or simply “cyclic.” On most helicopters, the cyclic is similar to a joystick. Although, the Robinson R-22 and R-44 have a unique teetering bar cyclic control system and a few helicopters have a cyclic control that descends into the cockpit from overhead. The control is called the cyclic because it can vary the pitch of the rotor blades throughout each revolution of the main rotor system (i.e., through each cycle of rotation) to develop unequal lift (thrust). The result is to tilt the rotor disk in a particular direction, resulting in the helicopter moving in that direction. If the pilot pushes the cyclic forward, the rotor disk tilts forward, and the rotor produces a thrust in the forward direction. If the pilot pushes the cyclic to the side, the rotor disk tilts to that side and produces thrust in that direction, causing the helicopter to hover sideways. [Figure 1]
|Figure 1. Cyclic controls changing the pitch of the rotor blades|
The collective pitch control, or collective, is located on the left side of the pilot’s seat with a pilot selected variable friction control to prevent inadvertent movement. The collective changes the pitch angle of all the main rotor blades collectively (i.e., all at the same time) and independently of their position. Therefore, if a collective input is made, all the blades change equally, increasing or decreasing total lift or thrust, with the result of the helicopter increasing or decreasing in altitude or airspeed.
The antitorque pedals are located in the same position as the rudder pedals in a fixed-wing aircraft, and serve a similar purpose, namely to control the direction in which the nose of the aircraft is pointed. Application of the pedal in a given direction changes the pitch of the tail rotor blades, increasing or reducing the thrust produced by the tail rotor and causing the nose to yaw in the direction of the applied pedal. The pedals mechanically change the pitch of the tail rotor, altering the amount of thrust produced.
Helicopter rotors are designed to operate at a specific rpm. The throttle controls the power produced by the engine, which is connected to the rotor by a transmission. The purpose of the throttle is to maintain enough engine power to keep the rotor rpm within allowable limits in order to keep the rotor producing enough lift for flight. In single-engine helicopters, the throttle control is a motorcycle-style twist grip mounted on the collective control while dual-engine helicopters have a power lever for each engine. [Figure 2] Helicopter flight controls are discussed in greater detail throughout Helicopter Flight Controls.
|Figure 2. The throttle control mounted at the end of the collective control|