Common Washers Used in the Aviation Industry

Washers are a common, yet overlooked, fastener that finds use in a wide variety of applications, being especially important in the aviation industry. While coming in a number of forms, washers are generally notable for their flat, circular design where a hole is provided for the insertion of a bolt or similar threaded fastener. Depending on the application, type of washer, and other such factors, washers may perform roles ranging from acting as a spacer to preventing the loosening of bolts. In this blog, we will provide a brief overview of the most common types of washers used on aircraft, allowing you to have a better understanding of their potential uses and benefits for such applications. 

Plain Washer

The plain washer is considered to be the most basic and popular form of washer, often coming in AN960 and AN970 variations. Plain washers are very commonly used alongside hex nuts, offering a smooth bearing surface. As plain washers may also act a shim, they can allow one to establish an optimal grip length between a bolt and nut. For their last common use, many aviation applications use plain washers to adjust the position of castellated nuts so that they are accurately set in relation to drilled cotter pin holes. To avoid issues like corrosion, it is important that dissimilar metals are avoided.

Lock Washers

Lock washers are a more specialized form, capable of preventing attached components and fasteners from coming loose. Lock washers may vary in how they prevent the loosening of assembly elements, some using spring action to increase friction and others relying on teeth that bite into the surface of fastener heads. Within the aviation industry, the most common forms of lock washers are the AN935 and AN936 variations, both of which are often used with screws or bolts. In many instances, lock washers are an optimal solution in the case that a self-locking or castellated nut is not optimal for securing an assembly.

Shakeproof Lock Washers

Shakeproof lock washers are a more specialized form of lock washer, consisting of a rounded hardware element that has tabs or lips that are bent up. When a shakeproof lock washer is paired with a suitable hex nut or fastener, the tabs can be bent downward to secure everything in place. Unlike other common types of aircraft washers, those like the shakeproof lock washer are known for their ample resistance to heat and vibration. As these washers require the bending of tabs to secure an assembly, they should never be used more than once as the structural integrity of tabs will be jeopardized with further manipulation. 

Specialized Washers

Aside from the more common types found in aviation applications, there are also a number of other specialized washers that find use in aircraft construction. For example, ball socket and sear washers are often used in instances where a bolt is installed at an angle and needs perfect alignment. These washers are generally used in unison, and they come in the form of AC950 and AC955 types. Aside from these examples, there are many other specialized washers that one may take advantage of to conduct their operations. 


Whether you need to protect the surface of an aircraft from bolt damage or need to secure components that may come loose during operations, washers are a perfect solution. Here on NSN Purchasing, we can help you secure competitive pricing and rapid lead times on everything you need. Take the time to explore our database as you see fit, and make sure to take advantage of our online RFQ services to request quotes for your comparisons. If you have any particular questions or concerns, be sure to give us a call or email at your earliest convenience, and we would be more than happy to discuss your needs and how we may meet them. 

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