Hydraulic Fluids



Hydraulic Oil - The Need Of Every Airplane Hydraulic System

Virtually every aircraft makes use of some hydraulically powered components which need hydraulic oil to operate. In a simple or general aviation system, hydraulic oil is used in providing pressure to activate the wheel brakes. But in larger and more complex airplanes, the use of hydraulic oil is more common in all hydraulically powered components. They might include:

  • wheel brakes
  • landing gear retraction/extension
  • nose wheel steering
  • thrust reversers
  • flaps and slats
  • flight control surfaces
  • spoilers/speed brakes
  • windshield wipers
  • cargo doors/loading ramps
  • propeller pitch control


Buying hydraulic fluid in bulk becomes necessary if you belong to the aviation industry. This is where ACI Lubes Co comes in; we have a huge variety of different hydraulic fluids for you to choose from.

Importance Of Hydraulic Oil

A hydraulic system consists of the hydraulic fluid plus three major mechanical components. Those components are the "pressure generator" or hydraulic pump, the hydraulically powered "motor" which powers the component concerned, and the system "plumbing" which contains and channels the fluid throughout the aircraft as required. With mobile hydraulic fluids, there are two main considerations - the hydraulic oil type and the viscosity grade. These specifications are usually determined by the kind of hydraulic pump involved in the system, the operating system's pressure and its temperature. Not every hydraulic fluid is the same; some are specially made for the aviation industry and must have the following properties.

High Flash Point

Under normal operating temperatures, an aviation fluid is designed not to ignite in the event of a hydraulic leak. These fluids are phosphate esters, and, unlike petroleum-based hydraulic fluids, they are very difficult to catch fire at room temperature. Although, if the fluid is heated to temperatures that exceed 180 degrees, it will most likely sustain combustion. The auto-ignition temperature of many aviation hydraulic fluids is in the range of 475 degrees.

Adequate Viscosity

An aircraft hydraulic system must operate efficiently over a wide temperature spectrum. The hydraulic fluid used must flow smoothly at very low temperatures while maintaining adequate viscosity at high temperatures. The ideal hydraulic fluid must have a very high boiling point and a low freezing point.

Thermal Capacity/Conductivity.

In aviation systems, the hydraulic fluid acts as a system coolant. The fluid should be able to readily release and absorb heat. ACI Lubes Co has plenty of Hydraulic Fluids for sale for you to choose from.

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