One common method of safetying is to secure with safety wire, a highly flexible but strong metal strand. Stainless steel safety wire is commonly used to prevent loosening of cylinder studs, control cable turnbuckles, and engine accessory attaching bolts.
Safety wire is threaded through an anchoring component such as the engine block, a structural member of the airframe, or another bolt head; twisted using a special tool; and then threaded through a small-diameter hole in the head of the screw or bolt. More twists are applied to the pigtail, which is then bent over and inward to keep the sharp ends from rubbing against and damaging nearby wires, hoses, or components - or a mechanic's bare skin.
As simple as safety wire seems, the FAA has a detailed procedure to follow when applying safety wire. For example, a certain type and size of wire must be used depending on what is being safetied, and the wire must have six to eight twists per inch to achieve the necessary strength. (A single, untwisted wire may be used on screws, bolts, and/or nuts that are closely spaced or are in a closed geometrical pattern such as a triangle, square, rectangle, or circle. The single-wire method may also be used on parts in electrical systems and in places that are difficult to reach.)
Most important, the wire must be installed so that it tends to tighten the screw or bolt rather than loosen it. For example, on a conventional right-hand-threaded bolt that tightens clockwise, the safety wire should loop around the head of the bolt to the right, or in a clockwise direction.
During a thorough preflight inspection you should come across various safety-wired components on the airframe and when peering inside the engine cowling. Check to make sure that the wire is not broken. If you find a broken wire, ask a mechanic to take a look before proceeding with the flight. Remember, it's called safety wire.
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