by Richard Sheffield
Control in Forward Flight
An aircraft that can only move up and down is not much use to anyone. To perform useful tasks, the helicopter must be able to move from point A to point B in a controlled manner. How the helicopter accomplishes this is one of the subtle operations I mentioned earlier.
A helicopter will fly in the direction that the rotor disc tilts. If the disc tilts forward the aircraft will fly forward, and so forth. The problem is that the gyroscopic force generated by the spinning blades tries to keep the blades spinning in the same dimensional plane. The disc does not want to tilt.
The solution is to make the disc tilt itself. This is accomplished using the cyclic control stick, so called because it changes the rotor blade's pitch for just one portion of its cycle. Pushing forward on the cyclic stick increases the pitch on the rotors during the back half of the cycle. This increases the lift for this portion of the disc. At the same time it decreases the pitch during the front portion of the cycle and causes a decrease in the lift for that part of the disc. This imbalance in lift causes the rotor disc to tilt forward—making the aircraft move in the forward direction. Moving the cyclic stick to the right, left, or back causes a similar tilt of the rotor disc and aircraft movement in that direction.