Control Cable Tension - Flight Controls IV

This one is perhaps one of those items a maintenance person must pay particular attention to. Incorrect cable tension can quite easily go unnoticed. The results of this can lead to failures such as cable slippage which may result in cable runs or twisting which could further lead to the cable jamming and subsequently lead to system component failures such as pulley system wear, or internal cable wear, broken wires etc.

Cable tension varies with temperature, and to understand the principle behind that you will need to read up on Thermal Conductivity and Coefficient of Thermal Expansion.
The way I understand this is by the analogy of electricity/telephone lines between poles. Why do these cables always give the impression that they are ‘hanging’ or rather slack between poles. The reason for providing that slack is to give allowance for expansion and contraction of the cables with changes in outside air (ambient) temperature.

Just like that, control cables in aircrafts must be set with the correct tension based on the ambient temperature. In aircraft design, every component has it’s own coefficient of expansion. Therefore, it becomes all the more important to rig cables for the correct tension even based on the expansion coefficients of components they’re attached between.

As part of the Aircraft rigging procedure cable tension is set with reference to charts that compare rigging loads to be applied the cable for a given ambient air temperature.

As mentioned in the section on cable components, Cable temperature compensators and turnbuckles are used to fine tune the cable tension after the application of rigging loads.