Swash Plate Assembly

A Major part of a helicopter flight control system is the mechanism used to transfer control inputs from the non-rotating parts of the system, to those that are rotating. There are 2 commonly used methods used to achieve this:

• Swash Plate
• Spider Control

Of these, the swash plate is perhaps the most common device used for main rotors, and the spider for tail rotors, although a there are some helicopters that use spider control for main rotors too.

The swash plate assembly consists of a rotating and non-rotating plate, normally referred to as ‘stars’  because of their shape, they may be made from steel, titanium or light alloy, with the choice of material being dependent upon the in-service loads that the swash plate will have to withstand.

The non-rotating star is mounted onto the main rotor gearbox shaft by a large spherical ball, housed in its centre, sometimes referred to as a ‘Uniball’. This ball is free to run up and down a slider sleeve, fitted around the shaft. The rotating star is fitted to the non‑rotating star on a bearing, and so can freely rotate about it. The rotating and non‑rotating swash plates move as a single entity in the horizontal plane, and any change in the horizontal angle of the non-rotating swash plate, will be transferred to the rotating swash plate, which will move to the same angle.