In the aviation realm, aircraft engineers benefit immensely from the use of fasteners. In fact, aircraft construction and repair depends on the employment of fasteners to assemble detailed parts and complete aircraft installations. Fasteners are utilized to connect different components within primary structural areas, secondary structures, and pressurized and unpressurized applications. To put it into perspective, aircraft fasteners make up around 3 million of the parts used to construct a Boeing 747-800 aircraft. With this in mind, this blog will cover the importance of fasteners, their design specifications, and installation requirements.
When engineers choose fasteners for their operations, there are a few factors to consider. First, one must think about the joint the fasteners will be exposed to. Next, one must determine the type of loads that will be transferred through the joint. Keep in mind that loads vary, some of which include loads experienced during towing, normal flight operations, wind-gusts, pressurization, engine-out operations, landing, and more. These factors are all determinate of how thick or thin the structure needs to be, the material used for the original structure, and the appropriate fasteners.
Ability to Support Various Loads
One of their most important qualities is their ability to transfer load from one part to another. As such, fastener numbers and diameters are calculated precisely to ensure they can transfer certain loads. Other criteria include weight, inspection ability, tooling requirements, aerodynamic smoothness, access, corrosion resistance, and most importantly, low price points.
Similar to other aircraft parts and components, fasteners can be grouped as either structural fasteners that take aircraft loads or nonstructural fasteners that connect non-load bearing parts. For areas that require both support and connecting characteristics, standard rivets, structural bolts, and Hi-Lok fastening system fasteners can be used. Such fasteners benefit from aluminum, steel, and titanium as their materials of choice with the added protection of a corrosion resistant coating.
While fasteners typically have straightforward designs, you must keep in mind that styles of fasteners vary based on their heads. For example, it is standard for fasteners to be installed head-up, or head-forward. One must pay attention to manufacturer instructions for installation, ensuring you are properly fitting your fasteners. In some cases, aircraft doubler applications require that thin titanium doublers be installed on the inner layer of aircraft skin. This particular application necessitates that the fastener take on a certain angle to guarantee the optimal functionality of the assembly.
It is especially important to ensure that the fastener joint design and fasteners fit properly. If the fastener fails due to not being able to support a specific load, the joint will simply come apart, resulting in the ultimate failure of the entire assembly. Improper joint design can be sourced from material tension failure, material shear-out failure, or fastener shear failure. The latter can be the result of an insufficient edge-margin. Edge-margins are defined as the distance from the center of the fastener to the edge of the part, and the distance from the center of a fastener to the center of the next fastener. Both of these parameters must be observed closely as aircraft fatigue testing has shown that equally spaced fasteners can outperform a staggered fastener joint design. Nonetheless, these design specifications vary according to the application at hand.
Beyond fastener design, proper fastener installation is critical, making sure that fastener-hole sizes correspond with the fastener and the assembly. Additionally, you must verify that the fastener material will not be obstructed by the hole. In some cases, a protective coating can be used to prevent wear on the fastener during installation. With all this said, one of the best ways one can guarantee their fasteners offer extended service lives and perform optimally is to carry out routine maintenance checks of both internal and external structures.
If you find yourself in need of aircraft fasteners, aircraft bolts, or other related fastening components, rely on Paragon Purchasing Services. Paragon Purchasing Services is a premier supplier of aviation, NSN, and electronic parts, all of which have been sourced from reputable manufacturers across the globe. Peruse our ever-expanding listings and fill out an RFQ form when you find an item that sparks your interest. Within 15 minutes of submitting a form, a dedicated representative will reach out with a customized solution fit for your needs.
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