Enstrom F28A Cyclic control Blue button: Trim/center cyclic Red button: 1st click intercom, 2nd radio Green button: Cargo release/No Function

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 looks to a joystick in a conventional aircraft. By contrast, the Robinson R22 and Robinson R44 have a unique teetering bar cyclic control system and a few early helicopters have had a cyclic control that descended into the cockpit from overhead.

The control is called the cyclic because it changes the pitch 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 will change their angle the same amount 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.

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 vector in the forward direction. If the pilot pushes the cyclic to the right, the rotor disk tilts to the right and produces thrust in that direction, causing the helicopter to move sideways in a hover or to roll into a right turn during forward flight, much as in a conventional aircraft.

On any rotor system there is a delay between the point in rotation where a change in pitch is introduced by the flight controls and the point where the desired change is manifest in the rotor blade's flight. This phenomenon has been confused with gyroscopic precession for ease of teaching in some organizations but is more appropriately referred to as phase lag. The lag varies with the geometry of the rotor system but is never more than ninety degrees. The lag is the time it takes for the blade to change its flapped position after the change in lift and is an example of a dynamic system in resonance.

Source: Helicopter flight controls - Wikipedia, the free encyclopedia