A bearing is a common machine element found in countless assemblies, often serving to mitigate the friction generated between moving parts while also constraining motion as needed. Within the realm of aviation, bearings are commonly used due to their durable and lightweight properties, and they are present in a number of assemblies ranging from the engines of an aircraft to its wings. While coming in the form of a small component, the properties and functionalities of bearings make them an indispensable part of any aircraft. In this blog, we will discuss aircraft bearings and the various types that are commonly used for assemblies, allowing you to better understand the roles that they play for flight operations.
There are many bearings that may be used for a particular aircraft assembly or device, all of which may be categorized into a few classifications that operate on different principles. Plain bearings are those that consist of a rotating shaft within a hole, acting as the most simplistic type that can assist in bearing high loads and providing linear motion. Rolling element bearings, such as the ball and roller bearing, are those that utilize rolling elements which are placed within races to deter friction. Generally, such bearings are capable of taking on radial and axial loads, often being capable of handling one more than the other depending on their type. While the plain and rolling element bearing types are the most commonly used variations, there are also jewel bearings, fluid bearings, magnetic bearings, and flexure bearings that all feature different operational characteristics and capabilities.
When implemented within various aircraft assemblies such as the engine and landing gear, bearings ensure that all critical components are capable of moving. Bearings also allow for two mated surfaces to adjust in a linked fashion or independently from one another. As aircraft systems and devices are often subject to heavy forces and stresses, it is crucial that the bearings present are also well capable of handling such conditions. When placed within the turbofan of an aircraft, for instance, the bearings will have to take on both axial and centrifugal loads at the same time during operation, and they must be able to efficiently rotate without exhibiting high amounts of friction. If a particular bearing is unable to meet these needs, it can quickly break down and fail and present a risk to other surrounding components and devices.
Unlike standard bearings that may be found in simplistic applications and settings, the bearings implemented on aircraft are built to achieve longer service lives, operate efficiently under extreme temperatures, resist corrosion, and more. With the addition of low weight construction, these various characteristics benefit aircraft in the form of reduced maintenance and the conservation of fuel. As such, having robust bearings can be very useful for cost reductions and efficiency.
The temperature range of aircraft bearings is especially important in areas where high amounts of heat is generated, such as within the engine, landing gear assembly, and rotors. For the landing gear, bearings are often present within brakes, tires, wheels, and other various assemblies. While high in the atmosphere, these bearings must withstand freezing temperatures without facing damage, often being subject to temperatures as low as 40 degrees below zero. Upon landing, however, temperatures will intensely rise as extreme amounts of friction occur from braking. During these conditions, temperatures can reach as high as 900 degrees Fahrenheit, and the bearings must be well capable of withstanding such heat without breaking down. Additionally, such bearings will face these temperatures over and over again across flight operations, and they must be able to maintain the same amount of efficiency through continuous temperature fluctuations.
In order to meet the various standards and requirements of aviation operations, there are a number of materials that are used to construct such bearings. Typically, materials are carefully controlled to determine the physical characteristics and properties of the final component. Additionally, each material may be chosen based on the environment that it will be used in, as one material may benefit landing gear operations while another can be best for engine operations. In general, there are six common materials that are used for manufacturing aerospace bearings, each of which provides different characteristics.
Alloy 52100 steel is one of the most widely used materials in the bearing industry, exhibiting a hardness that remains equal from the core to the surface of the component. Typically hardened to a 58-60 or 62 Rockwell C level, such components are very strong. Despite this, their hardness makes them less ductile, and thus they are unable to flex as well as other materials.
M50 tool steel is a variant of Alloy 52100 steel, featuring slightly less hardness throughout the component. Despite this, they are able to handle higher temperature ranges which may benefit certain assemblies. M50 NiL is a nickel-low carbon variant of M50, modified with nitrogen to achieve a soft core and hardened outside. As such, the inner core can remain flexible for expansion without cracking, all while the outer surface prevents wear.
For a more corrosion resistant bearing, one may take advantage of 440C stainless steel. Such bearings are well suited for exposed applications, ensuring the component can withstand contact with saltwater, oxygen, and hot and cold thermal cycling. SiN ceramic materials, meanwhile, are highly wear resistant and can exhibit longer service lives as compared to heat-treated steel. As such, SiN bearings often come in the form of high-speed ball bearings. The final common aerospace bearing materials are HRSAs, or heat-resistant superalloys. These bearings are also capable of resisting corrosion like 440C bearings, all while being able to withstand high temperatures with their strength and hardness.
Whether taking advantage of an actuator bearing, adapter bearing parts, or other various bearing types, all should be installed with specialized tools to ensure proper installation. If bearings are not seated correctly or are damaged during installation, they can exhibit reduced performance and may eventually fail. If you find yourself in need of bearings, tools, and other various aircraft parts, look no further than Just NSN Parts. Just NSN Parts is a premier supplier of aviation, NSN, and electronic parts, and we are your sourcing solution for top quality bearing components such as Adapter Assembly Bearing, 7Bearing Roller, 7Bearing Ball, and 3 Section Solid Bearing parts. If you find particular items from our inventory that you are interested in, fill out and submit an RFQ form as provided on our website and a dedicated account manager will reach out to you in just 15 minutes or less, 24/7x365.
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