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How are linear control inputs transformed into rotary control output in a helicopter system?
  • A
    Through pitch change horns.
  • B
    Using pitch control arms.
  • C
    Via the swash plate assembly.
  • D
    Utilizing a fixed scissor link.

Refer to figures.
Swashplate assembly:

The purpose of the swash plate is to convert stationary, linear control inputs from the pilot into rotating inputs which can be connected to the rotor blades or control surfaces. It consists of two main parts:

  • stationary swash plate and
  • rotating swash plate.

The stationary swash plate is mounted around the main rotor mast and connected to the cyclic and collective controls by a series of pushrods. It is restrained from rotating by an anti-drive link but can tilt in all directions and move vertically.

The rotating swash plate is mounted to the stationary swash plate by means of a uni-ball sleeve. It is connected to the mast by drive links and must rotate in constant relationship with the main rotor mast. Both swash plates tilt and slide up and down as one unit. The rotating swash plate is connected to the pitch horns by the pitch links.


The scissors are responsible for ensuring the rotating swash plate is driven by the rotor mast relieving the stresses on the pitch change rods (arms).

Pitch change arms:

The pitch control rods (arms) allow the rotating swash plate to change the pitch of the rotor blades.
Therefore, the correct answer is "Via the swash plate assembly".

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