Aircraft experience a lot of stress, facing strain from takeoff to landing and the time in between. Fortunately, there are a number of safety measures set in place to ensure an aircraft is working optimally. One of these safety measures, while small, packs quite the punch. A safety wire, or locking wire, is an integral part of aviation maintenance and performance. Since many are unfamiliar with the importance of such a device, this blog will cover what it is and what it does.
A safety wire, as the name suggests, is just a wire, but there is a bit more to it than that. Without safety wire, fastening components like bolts, nuts, screws, and more cannot be safely secured. When used correctly, the wire prevents these fasteners from moving. More than that, safety wire is a necessary precaution in aircraft areas that experience a lot of vibration that can potentially lead to the loosening of fasteners.
Safety wire is threaded through a hole that has been drilled into the fastener. Then, it is twisted and anchored to another fastener or another surface and twisted again. In fact, these twists in the wire are what make it so secure. To ensure that it has been installed properly, check to see if the twists pass the “righty tighty” test. However, you must be careful not to over-tighten the safety wire as this can make it break when additional stress is added to it. Keep in mind that the safety wire cannot be under-twisted either. A general safety rule is that you want about 6 to 8 twists per inch.
Different Types of Safety Wire
Since there are so many mechanisms for securing different parts and surfaces, there are varying types of safety wire. The most common sizes for safety wire fall between 0.032 and 0.041 inches. Thicker wire, on the other hand, will be needed to hold larger screws in place. Meanwhile, the most popular material for safety wire is stainless steel as it prevents secured parts from moving with ease.
In some cases, however, you may want safety wire to be able to shear or break. For instance, copper or brass wire is utilized when securing emergency equipment such as switch handles, emergency exits, and fire extinguishers. The successful operation of this emergency equipment depends on the safety wire being able to break. More malleable than stainless steel, copper and brass safety wire is usually available in 0.015 to 0.020 inch options for diameter. While it may be obvious, safety wire should always be new upon each application since it is single use and disposable. If, upon inspection, the safety wire is loose or missing, it must be replaced promptly.
Rules for Installation and Use
Before installation, ensure that whatever you are securing has been correctly assembled first. Safety wire serves as a failsafe against the vibration and loosening of fasteners, not as a replacement for tightening those fasteners. Furthermore, one must always utilize twisting pliers to grip the two loose ends of a piece of safety wire and twist it properly. Additionally, safety wire should not be chafing or rubbing against any other parts, causing them to weaken or break. The length of wire between two aviation fasteners should also be as short as possible.
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