Posted on June 30, 2025 Jacob Luiz
Hydraulic systems power landing gear deployment, flight control surfaces, braking systems, and so many other vital functions on an aircraft. While hydraulic fluid is mainly essential for transmitting force within these systems, the right fluid formulation must also reduce friction, prevent corrosion, and maintain overall cleanliness in order to uphold performance long-term. To help you identify the best option for different system demands, this blog will discuss the composition, advantages, and limitations of three main types of lubricating hydraulic fluids used in aviation.
Before discussing specific hydraulic fluids, it is important to understand the baseline standards they need to meet for aviation use. Because these fluids circulate throughout hydraulic systems under high pressure, directly lubricate moving internal surfaces, they must have:
Derived from refined petroleum, mineral-based fluids are suitable for low-load applications with minimal failure risk, including ground support equipment (GSE), jacks, cargo lifts, and some apron-level hydraulic subsystems. This is largely because these fluids do not meet the fire-resistance or thermal durability standards required of primary flight systems.
Phosphate ester fluids like Skydrol® are formulated for primary flight controls, landing gear, and braking systems. Their chemistry prioritizes thermal stability and fire resistance, which is why they are considered the standard for many civil aviation platforms.
Synthetic hydrocarbon fluids, such as MIL-PRF-5606 and MIL-PRF-83282, serve as the main working fluid in military aircraft, business jets, and some rotary-wing platforms. Offering a performance middle ground, these fluids have better fire resistance than mineral oils, with less toxicity and handling risk than phosphate esters.
First and foremost, be sure all hoses, gaskets, and sealants are rated for use with the specific lubricant that is to be used in a system to avoid swelling, cracking, or leakage.
Install high-efficiency filters and consider using portable filtration carts for fluid transfer or decontamination. This is because maintaining low particle counts and moisture levels directly correlates to longer component service life and reduced downtime.
Always adhere to the fluid change intervals recommended by the equipment manufacturer and applicable military specifications, as overextended use can degrade fluid performance. Additionally, regular fluid sampling should be implemented to check for contamination from air, moisture, particulates, or chemical breakdown. Catching early signs of oxidation, acid formation, or foreign matter can help prevent expensive system failures.
Store hydraulic fluids in clean, sealed containers away from direct sunlight and moisture, and use color-coded labeling and dedicated equipment to prevent cross-contamination between fluid types. As previously mentioned with phosphate ester fluids, be extremely careful to handle and dispose of them properly to avoid personal safety or environmental concerns.
Quality hydraulic lubricants are essential for the wellbeing of aircraft hydraulic systems, meaning that it is vital to source them from dependable suppliers to validate their safety and reliability. ASAP Semiconductor, via its ASAP Aerospace platform, is a dependable provider of top-quality hydraulic fluids, seals, and many other related components. Prioritizing industry compliance and full traceability so you can shop with confidence, everything you can expect to come across on this website is strictly sourced from reputable manufacturers and suppliers.
In addition to our extensive, curated inventory, we consistently deliver advantageous and competitive procurement solutions. You can trust in us to present fair-market pricing and on-time delivery options for each order, without requiring you to sacrifice on your unique fulfillment needs. Taking this into account, get in touch with a team member today to see how we can serve you.
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