Helicopter flight controls

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.

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 helicopter's main rotors, to keep a stable, more accurate flight.

Helicopters with fly-by-wire systems allow a cyclic-style controller to be mounted to the side of the pilot seat.

Therefore, if a collective input is made, all the blades change equally, and as a result, the helicopter increases or decreases its total lift derived from the rotor.

In level flight this would cause a climb or descent, while with the helicopter pitched forward an increase in total lift would produce an acceleration together with a given amount of ascent.

If a helicopter suffers a power failure a pilot can adjust the collective pitch to keep the rotor spinning, generating enough lift to touch down and skid in a relatively soft landing.

This air stream is generated in the fuselage by a small fan or turbine, and directed out of the rear of the tail-boom through vent holes.

Thus, frequent control inputs and corrections must be made by the pilot to keep the helicopter at a desired location and altitude.

The pilot's use of control inputs in a hover is as follows: the cyclic is used to eliminate drift in the horizontal plane (e.g., forward, aft, and side to side motion); the collective is used to maintain desired altitude; and the tail rotor (or anti-torque system) pedals are used to control nose direction or heading.

Moving the cyclic forward makes the nose pitch down, thus losing altitude and increasing airspeed.

At certain airspeeds, this can create a dangerous condition in which the receding rotor blade stalls, causing unstable flight.