The aircraft hydraulic system is an extremely important element of numerous aircraft, allowing for high amounts of energy to be transferred for the actuation of systems and flight surfaces. As a system that relies upon contained liquids under pressure, hydraulics may be used for opening cargo doors, deploying landing gear, actuating aircraft rudders and spoilers, operating windshield wipers, and much more. As hydraulic systems help both small and large tasks be carried out, their proper functionality is paramount. While a number of factors can affect the functionality of hydraulic systems, the most important are temperature and pressure.
A hydraulic fluid is a liquid that serves as the medium for energy transfer, and almost any liquid may serve well due to their extremely low compressibility. Despite this, the operating pressure that is exhibited across most aircraft hydraulic systems will range between 3000 and 5000 psi. Furthermore, hydraulic fluids may be exposed to a variety of environmental conditions and safety standards which narrows down the liquids that may serve well for aircraft applications.
When deciding upon a liquid for a hydraulic system, there are a few properties that it should have. As leaks are always a possibility with a hydraulic system, it is important that the liquids contained within do not easily combust. Generally, hydraulic fluids are those with auto-ignition temperatures reaching upwards of 475 degrees Celsius, ensuring that they are safe as standard operating temperatures can reach upwards of 180 degrees Celsius. Viscosity is also important as it dictates how liquids will flow and act, and hydraulic fluids should be able to flow optimally whether temperatures are cool or hot. The lubrication properties of fluids is also a concern as the fluids should be able to lubricate the hydraulic motor components, pumps, and actuators they pass through. Lastly, the fluids should be able to act as a coolant through the absorption of heat.
With the various requirements for hydraulic fluids, one can see why temperatures are a concern for the performance of hydraulic systems. One of the most significant threats to a hydraulic system is overheating, and this occurs when the system exceeds the maximum operating temperature. When overheating occurs, the hydraulic system can lose functionality and thus the operability of all components that the system powers will be lost as well. When overheating occurs, the system must be de-energized for its protection.
The pressure of hydraulic fluids is also paramount, as it is what ensures that energy can be sufficiently transferred throughout the system. Pressure is created through a variety of components, namely pumps and valves. With the use of gear pumps, fixed displacement piston pumps, variable displacement piston pumps, and other such types, fluids can be pressurized and forced throughout the system to ensure proper force for procedures to be carried out. A loss of fluid pressure is often due to the failure of a hydraulic pump, though it may also result from the direct loss of fluids such as in the case of leaking. In either circumstance, the loss of fluid pressure will cause the hydraulic system to lose functionality and thus be unable to extend or retract landing gear, actuate primary flight controls, assist in nose wheel steering, and much more.
With the proper maintenance and servicing of aircraft hydraulics and their related parts, the operability of numerous aircraft systems and components can be preserved. Purchasing Management 360 is a premier online distributor of aviation components, computer hardware, electronic parts, networking devices, and much more. We invite you to explore our expansive part and manufacturer catalogs at your leisure, and our team of industry experts are readily available 24/7x365 to assist you through the purchasing process as required. If you would like a competitive quote on the item list that you seek to fulfill, send us a completed RFQ form and a dedicated account manager will reach out to you within 15 minutes of reviewing your request.
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