The Common Types of Aircraft Hydraulic Fluid

Hydraulic systems are highly beneficial for aircraft, allowing for enough force to be created to reliably operate and adjust various assemblies, systems, and surfaces. The hydraulic fluids that are used in the aviation industry are known for being thinner than industrial fluids, and they are also partly chosen by their fire resistance due to the extreme hazards that flames can present to aircraft while they are high up in the atmosphere. To keep hydraulic fluid safe, it needs to remain in a temperature range of -65 degrees to 275 degrees Fahrenheit so that it will not freeze or boil. As there are different types of hydraulic fluid available for aircraft based on the application and environment, it can be useful to have a basic understanding of the most popular options.

Mil-H-5606 Fuel: With the “Mil” prefix, this type of hydraulic fluid meets military specifications for performance. While Mil-H-5606 fuel has long been in use for over fifty years now, it currently sees the most use by various U.S. Air Force aircraft and business jets. The reasoning for its fall from popularity is due to the slight flammability that it presents, that of which potentially can be traced back to the loss of military aircraft in the past. With other options now superseding Mil-H-5606 fuel, its use is rendered obsolete.

Mil-H-83282: Mil-H-83282 fuel is another hydraulic fuel type that meets military specifications, and it has been relied on by the Air Force since 1982, as well as has served as the Navy’s primary type of hydraulic fuel for aircraft since the later 1990s. The higher flame resistance of Mil-H-83282 caused it to quickly replace Mil-H-5606 fuel, though its lower limit of -40 degrees Fahrenheit made it more viscous at lower temperatures as well, making its popularity finite.

Mil-H-87257: As the final popular form of mil-spec hydraulic fuel, Mil-H-87257 fuel is considered a new formation that is now used in C135, U2, and E3 aircraft alike. The popularity of this option comes as a result of its ability to present flame resistance that surpasses Mil-H-5606 fuel while also having a lower limit of -65 degrees to surpass the capability of Mil-H-83282 fuel as well.

Skydrol: Skydrol is a trademarked fuel that was developed by Eastman Aviation Solutions, and it is a type of phosphate ester technology. The popularity of Skydrol comes as a result of being the first fire-resistant hydraulic fluid in the industry with a flash point of 350 degrees Fahrenheit.

Hyjet: Hyjet is the final popular form of aircraft hydraulic fluid that we will discuss today, and it is a trademarked fuel made by ExxonMobil. Hyjet is useful as it holds compatibility with all Type IV and V hydraulic fluids, elastomers, and other hydraulic system materials. Additionally, Hyjet is known for its fire-resistance that benefits the service lives of various hydraulic systems, and it is approved for all 5,000 PSI commercial hydraulic pressure systems.

If you own or operate an aircraft and are in the market for hydraulic fluids, hydraulic system parts, or other various aviation products, we have you covered here on Buy NSN with our unrivaled inventory of items. As of the present, we provide customers access to over 2 billion new, used, hard-to-find, and obsolete items that trace back to thousands of manufacturers we trust, and all are readily available for purchase today with highly competitive pricing and rapid lead times. Explore our massive inventory as you see fit, and our team is always ready to support your needs through the purchasing process with customized quotes for your comparisons.

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