What is the minimum cable size permissible in aircraft primary control systems?

The minimum cable size permissible in aircraft primary control systems is 1/8 inch. This specification is crucial because primary control systems are integral to ensuring aircraft safety and performance. The cable must be strong and robust enough to handle the loads and stresses encountered during operation.

Using a cable size smaller than the specified minimum can lead to issues such as inadequate strength, potential failure under load, or reduced control response, which jeopardizes flight safety. Therefore, the 1/8 inch size is established as a baseline that balances safety, performance, and manageability within the constraints of aircraft design and engineering.

Other options would not meet the necessary standards set by aviation regulatory bodies for such critical applications due to their smaller diameters, which could compromise the integrity of the control system.