Tuesday, July 26, 2011

Cyclic Pitch Control Stick

The cyclic pitch stick is positioned centrally in front of the pilot & co-pilots seats, and is used to tilt the disc, causing the helicopter to move horizontally in any direction. Like all other flight controls it operation is purely instinctive, moving the cyclic pitch stick forwards will tilt the disc forwards, and the helicopter will move forwards, moving the cyclic stick rearwards has the opposite effect. Movement of the cyclic stick to left or right, will cause the helicopter to move in that direction. 



The cyclic pitch stick is pivoted at its lower end and is connected to 2 push/pull tubes, one transmitting left/right (roll) movements and the other fore and aft (pitch) movements. A yoke assembly allows these movements to be made independently so that only roll or pitch inputs may be made without causing movement of the other, however, simultaneous roll and pitch movements can be made if required.

In fore and aft movement, one push/pull tube transmits movements to the control mixing unit, Side to side movements operate 2 push/pull rods which operate in opposite directions, when the cyclic stick is moved to the left one rod will move forwards and the other rearwards, when the stick is moved to the right the opposite will occur. This is required because there are 2 lateral (roll) main rotor actuators which must operate in opposition to achieve lateral control, whereas, fore and aft pitch movements are achieved by only one main rotor actuator, that uses the fixed or non-rotating scissors as a datum point about which movements are made.

Like the collective pitch lever, the cyclic stick grip will incorporate switches for operation of important systems, these are normally associated with control trimming, autoflight or autostabilisation, cargo release and communication systems.


Follow Aviamech Blog