Control cables are an important part of most airplanes. They are used to link controls in the cockpit to the airplane’s movable surfaces and landing gear. When a pilot turns the yoke, for instance, a control cable will move the airplane’s ailerons up and down. Control cables, however, are often run in conjunction with fairleads. What are fairleads exactly, and why do airplanes use them?
The Basics of Fairleads
Fairleads are mechanical assemblies that guide cables or wires along a fixed path. They are commonly used in mechanical flight-control systems. Control cables used in these systems are often installed with fairleads to ensure they function as intended.
Why Airplanes Use Fairleads
Airplanes use fairleads to prevent unwanted cable movement. Without some form of guidance, control cables could rub against an adjacent surface. Over time, this friction can cause them to degrade or even snap. Fairleads prevent this from happening by forcing control cables to stay along a fixed path that’s free of objects or surfaces.
In addition to protecting control cables from friction-related damage, fairleads prevent tangling. Control cables often operate with varying levels of tension. If two or more cables are close together, they may wrap together as their tension changes.
Tangled cables, of course, may not function properly. If two cables are wrapped around each other, they won’t be able to engage the flight control surfaces to which they are connected. Fairleads prevent tangling by guiding control cables along a fixed path. Even as their tension changes, the cables won’t be able to wrap around other nearby cables.
How Fairleads Work
While they are all designed to guide cables, there are different types of fairleads. Some of them consist of blocks with predrilled holes designed to fit specific cable sizes. The cable runs through the predrilled hole, at which point it won’t be able to rub against adjacent surfaces or wrap around other nearby cables.
There are also two-piece fairleads. They typically consist of two equally sized halves held together by a clip or ring. You can place the two halves around a control cable, after which you can secure it with the appropriate clip or ring.
Regardless of style, many fairleads support mounting. They can be mounted to a secure structure of the aircraft itself using fasteners. Mounting further reinforces and stabilizes the cable so that unwanted movement doesn’t occur.
