Choosing the Right Hydraulic Fluid for Aircraft Systems

Hydraulic systems are one of the most powerful systems on the entire aircraft, second only to engines themselves. The standard hydraulic system is pressurized to 3,000 PSI of hydraulic fluid and is used to power the largest systems on the aircraft: flaps and slats, leading edge flaps, landing gears, brakes, and more. 

Royco 756 is a popular hydraulic fluid used on many different aircraft, both commercial and military. It is a mineral oil-based hydraulic fluid that gives solid all-weather performance. Greenwood Aerospace is a trusted provider of Royco 756 red dyed mineral oil hydraulic fluid and other fluids that meet MIL PRF 5606H requirements. Let’s take a look at Royco 756 and use it for your fleet. 

Aircraft Systems

Aircraft systems require a reliable, robust, and dependable hydraulic fluid that can withstand pressurized systems operating at high pressures (the standard is 3,000 psi, but aircraft often operate at higher pressures). A mineral oil-based hydraulic fluid is commonly used in older, legacy aircraft that were designed before synthetic fluids became a standard fluid. 

Red dyed mineral oil fluids are also commonly used in general-purpose hydraulic applications outside of aviation and aerospace. Of course, aerospace and industrial service is the primary purpose with severe duty demands, and Royco 756 hydraulic fluid is a great choice for this. Hydraulic fluids were designed for use in aircraft and then adopted for industrial service because if they work in airplanes that operate in some of the harshest conditions on the planet, they will work just about anywhere else. 

Key Features and Specs

Here are the key specifications of all MIL PRF 5606H high viscosity index fluid:

Base Type: Mineral oil-based fluid

Temperature Range: Operates from -54°C to +135°C (-65°F to +275°F)

Color: Dyed red for easy identification

Viscosity: Maintains stable flow properties across wide temperature extremes

Anti-Wear Protection: Formulated with additives to reduce wear on system components

Corrosion Resistance: Inhibits rust and corrosion in hydraulic systems

Foam Inhibition: Includes anti-foam agents for stable system performance

Metal Deactivators: Prevent degradation from metal ions in the system

Legacy jet aircraft rely on Ryco 756 when severe duty demands hydraulic fluid to enhance performance, offer shear stability, and be equipped with foam inhibitors. Jets also need outstanding low-temperature fluidity. 

Benefits and Applications 

From shock absorbers to boom trucks, landing gears and brakes to rudders and stabilizers, hydraulic power it all. Jets fly at high altitudes routinely, so excellent low-temperature fluidity is an absolute necessity. MIL PRF 5606H fluids are formulated to operate in both the lowest cold and highest heat. 

Additionally, the internal workings of the hydraulic systems are sensitive to the demanding duties of aerospace and require meticulous cleanliness. Corrosion inhibition is truly key to longevity, as witnessed by the KC-135R and B-52H, both of which are pushing seven decades of service with many more on the horizon, and both of which were built using dyed mineral oil-based hydraulic fluid. 

Always consult the tech data for your airframe and see what MIL PRF is approved for your systems. If you are looking for MIL PRF 5606H, you are in the right place, as we source Royco 756 in a variety of sizes and quantities to fit your mission profile. 

Selecting and Buying the Right Product

When your mission MDS calls for MIL-PRF-5606H hydraulic fluid, Royco 756 is the obvious choice. With exceptional anti-wear properties (again, see KC-135R and B-52H), mineral oil-based hydraulic fluids may be for legacy aircraft systems, but that does not mean they are inadequate. Royco 756 will support both pressurized and unpressurized systems for the duty demands of aerospace applications (including aircraft and missile systems), with a shelf life of four years. 

Greenwood Aerospace will source this and notify you of the in-stock status for each quantity and volume. Please let us know if you require bulk purchasing, and we will work with you to secure the best possible price. Call us at (580) 762-2580, or email our team at contact@governmentprocurement.com!