CABLE TENSION REGULATORS
Cable tensioners are fitted to aircraft with the purpose of maintaining constant cable tension regardless of temperature changes due to altitude and varying climates and flexing of the airframe. The flexing of the airframe could be down to structural loading i.e. take-off and landing or varying rates of expansion of the airframe components due to different materials being used within the structure.
If these cable tension regulators do not function correctly or were not fitted then the cables would be pulled or relaxed moving the controlled unit which could be disastrous and would most certainly impair flight safety if not cause an accident regardless of whether it was a flying control surface or fuel control unit on the engine.
How Does The Cable Tension Regulator Work?
The cable tension regulator is a unit located on the cable run which consists of two quadrants, pivoted on their centres and sprung loaded to open out when the cable slackens. These springs are calibrated so always use the springs recommended in the Illustrated Parts Catalogue (IPC). When the cable is required to operate the quadrants are locked together using some sort of brake device which normally consists of a Rotating assembly of Left and Right hand threaded fork ends, Brake disc in the centre and friction discs or washers which grip on the brake disc. When There is equal movement of the fork ends i.e. due to thermal expansion then the brake remains off but when there is a control input the fork ends move varying amounts and cause one of the friction discs to grip the brake disc thus applying the brake to the quadrants.
Note: This is a based upon a typical purely mechanical Cable tension regulator so it is imperative that you always work from the maintenance manual.