How Are Commercial Aviation Lubricants Designed and Approved?

A lubricant is a substance used to minimize friction and heat between moving surfaces, and they may be used in a variety of applications ranging from vehicles to industrial machinery. While the lubrication used for aviation applications provides for the reduction of friction just like many other types, aircraft lubrication in particular must meet higher performance requirements in order to be approved for use in commercial models. This is due to the extreme conditions that many aviation parts operate under as well as the immensely regulated industry that demands the highest degree of scrutiny for safety and efficiency.

One of the most important sections of the aircraft where lubricants are used is within the engine. This is because bearing lubrication can be used to absorb heat and pass it onto fuel, ensuring that heat is taken from the system and transferred to fuel for more optimal combustion. Additionally, jet engine lubricants assist in the protection of moving parts so that minimal wear and tear results from friction. Lastly, aircraft lubricants will also remove particles and debris from components with the help of filters to mitigate the formation of deposits.

Regarding modern jet engine lubricants, most utilize esters which are synthetic fluids derived from reacting fatty acids and alcohols. Two esters serve as the most basic types used for aircraft, and they are diesters and polyesters. Diesters are fairly simple molecules with a viscosity that is below polyesters. Nevertheless, both diesters and polyesters exhibit optimal fluidity in colder environments, that of which makes them very useful for aircraft applications where temperatures can be as low as -50 degrees Celsius.

The specifications and requirements that lubricants must meet for approval often change over the years, regularly demanding increased performance characteristics or qualities to accommodate newer engines and technologies. Type I lubricants were first developed in the 1950s, and they still serve the auxiliary power units of many commercial airliners due to their low-temperature viscosities. In the 1960s, Type II synthetic lubricants were created to meet rising requirements, and the lubricant featured higher thermal stability due to its polyester makeup. As the decades continued, new specifications for lubricants such as MIL-PRF-23699 HTS and AS5780 were released to meet changing engine requirements with higher performance capabilities.

As the aviation industry is highly regulated, the process for which aviation lubricants are approved is much more rigorous as compared to other industries. As an example of some of the requirements, lubricants are tested for their thermal stability, tribological and deposition properties, whether they have additives that are ashless, and much more. Additionally, specifications will often provide alternate materials for substitution, aiding in instances where a supplier goes out of business and cannot supply a material any longer. With the approval process encompassing numerous steps ranging from product development to lengthy testing before FAA consideration, the entire process can often take up to a decade from start to finish.

While the approval process for aviation lubrication is strenuous, it ensures higher performance and safety for engine parts and systems. As lubricants are specifically designed for backwards compatibility, airliners can often rely on a single lubricant type for managing all their hardware and more. At Just NSN Parts, we are your sourcing solution for jet engine lubricants, bearing lubrication, and other types of aircraft lubrication that you need. Just NSN Parts is a premier supplier of aviation, NSN, and electronic parts, and we provide competitive pricing and rapid lead-times on all we carry for the benefit of our customers. Get started today and see how we can fulfill your operational needs with ease.


December 20, 2022
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