Hover (helicopter)

A helicopter pilot manipulates the helicopter flight controls to achieve and maintain controlled aerodynamic flight. Changes to the aircraft flight control system transmit mechanically to the rotor, producing aerodynamic effects on the rotor blades that make the helicopter move in a deliberate way. To tilt forward and back (pitch) or sideways (roll), requires that the controls alter the angle of attack of the main rotor blades cyclically during rotation, creating differing amounts of lift (force) at different points in the cycle. To increase or decrease overall lift requires that the controls alter the angle of attack for all blades collectively by equal amounts at the same time, resulting in ascent, descent, acceleration and deceleration.

A typical helicopter has three flight control inputs—the cyclic stick, the collective lever, and the anti-torque pedals. Depending on the complexity of the helicopter, the cyclic and collective may be linked together by a mixing unit, a mechanical or hydraulic device that combines the inputs from both and then sends along the "mixed" input to the control surfaces to achieve the desired result. The manual throttle may also be considered a flight control because it is needed to maintain rotor speed on smaller helicopters without governors. The governors also help the pilot control the collective pitch on the helicopters main rotors, to keep a stable, more accurate flight.

The cyclic control is usually located between the pilot's legs and is commonly called the cyclic stick or just cyclic. On most helicopters, the cyclic is similar in appearance to a joystick in a conventional aircraft. But on the Robinson R22, the cyclic is a central pillar that either pilot can manipulate.

The control is called the cyclic because it changes the pitch angle of the rotor blades cyclically. That is, the pitch, or feathering angle, of the rotor blades changes depending upon their position as they rotate around the hub, so that all blades have the same incidence at the same point in the cycle. The change in cyclic pitch has the effect of changing the angle of attack, and thus the lift generated by a single blade as it moves around the rotor disk. This in turn causes the blades to fly up or down in sequence, depending on the changes in lift affecting each individual blade.

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Wikipedia