4A. EFFECT OF CONTROLS IN FORWARD FLIGHT

Cyclic:

The cyclic pitch control tilts the main rotor disc by changing the pitch angle of the rotor blades individually throughout their CYCLE of one full rotation. When the main rotor disc is tilted, the horizontal component of lift moves the helicopter in the direction of tilt.

The rotor disc tilts in the direction that pressure is applied to the cyclic pitch control.

If the cyclic is moved forward, the rotor disc tilts forward; if the cyclic is moved aft, the disc tilts aft, and so on. The aft movement of the cyclic is called a flare.

Because the rotor disc acts like a gyro, the mechanical linkages for the cyclic control rods are rigged in such a way that they decrease the pitch angle of the rotor blade approximately 90° before it reaches the direction of cyclic displacement and, increase the pitch angle of the rotor blade approximately 90° after it passes the direction of displacement. An increase in pitch angle increases angle of attack; a decrease in pitch angle decreases angle of attack.

For example: if the cyclic is moved forward, the angle of attack decreases as the rotor blade passes the right side of the helicopter and increases on the left side. This results in maximum downward deflection of the rotor blade in front of the helicopter and maximum upward deflection behind it, causing the rotor disc to tilt forward.

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