How Aviation Hydraulics Work

Modern aircraft are much more complex and robust than their early predecessors, regularly featuring modern landing systems, flight control surfaces, brakes, and other such assemblies that require large amounts of force to be actuated and adjusted. While mechanical linkages were quite popular for a time, many have since been superseded with powerful hydraulic assemblies that rely on an incompressible fluid medium to apply, multiply, and transmit force between spaces. As hydraulics have now become a staple of most light and large aircraft alike, it can be very beneficial to have a basic understanding of their design and functionality.

Whether an aircraft hydraulic system is used to actuate the brakes of an aircraft or to deploy winglets, all work on the principle of Pascal’s Law and the conservation of energy. In Pascal’s Law, it is stated that any change in pressure at any point within contained, incompressible fluid will result in an equal change of pressure everywhere else during transmission. As such, any change of pressure within an aircraft hydraulic system will be equally transmitted throughout the network, an example being the force of a depressed cockpit brake pedal being transmitted to the brake system itself for actuation.

When discussing the principle of the conservation of energy, one should understand that a hydraulic system cannot do any more work than is done on it. What this means is that the output work or pressure will be equivalent to the pressure change that was carried out as the input. That being said, input and output areas can affect the ratio of displacement. As an example, if the output cylinder of a hydraulic system features an area that is greater than the input cylinder, the output displacement will be smaller when considering the ratio.

Unlike air, fluids are nearly incompressible, though not all fluids can be used for a hydraulic system. Generally, fluids will have to have the proper viscosity, stability, and vaporization resistance to effectively transmit and multiply forces for a system. Viscosity is a fluid’s internal resistance to flow, and this property often varies with temperature. For a particular fluid to be most suitable for a hydraulic system, viscosity has to be high enough for lubrication and protection while maintaining flow.

As hydraulic system components and aircraft assemblies regularly face high amounts of heat, hydraulic fluids must also have a proper flashpoint and fire point to prevent hazardous situations that may threaten safety and operations. Lastly, chemical stability will determine how well a fluid will resist oxidation and deterioration, higher resistances being best for long-term operations. Once you have narrowed down your particular needs, you can take advantage of mineral based fluids, polyalphaolefins, phosphate esters, and more.

Just like any other aircraft system, reservoirs, filters, pumps, valves, accumulators, and other hydraulic system components will face wear and tear over time, making it essential that you conduct inspections on a regular basis. During these checks, if any parts are past their service life, broken, or otherwise dysfunctional, you should make a replacement as soon as possible to ensure that you are flying safely and in accordance with any regulations. Luckily for you, ASAP Purchasing can help you rapidly source any items you require while guaranteeing highly competitive pricing and rapid lead times for your benefit.

On our database, we list over 2 billion items that cater to a diverse set of applications and industries, and we encourage you to explore our offerings as you see fit to find items of interest. With our online RFQ service, you can always request quotes on items of interest at any time, and we guarantee customized responses from our team members within 15 minutes or less. If you have any further questions or concerns regarding our offerings or services, be sure to give us a call or email at your earliest convenience!

December 7, 2022

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