Hydraulic systems are common on many commercial aircraft, allowing for the pilot to easily adjust and actuate systems such as the landing gear, brakes, and flaps. Hydraulic systems are highly beneficial as their fluids are effectively incompressible, and they are able to transmit high pressures with ease. Despite their great benefits to aircraft, hydraulics are prone to failure just like all other systems. When hydraulic systems fail, it is important to quickly identify and address the problem, ensuring that your aircraft can return to operation as soon as possible. In this blog, we will discuss some of the common causes of hydraulic system failure, allowing you to monitor and prevent issues before they occur.
Across all failures that occur in hydraulic systems, a majority of them are caused by contamination in the hydraulic fluid. Contamination can come from various factors, those including temperature problems, a worn hydraulic pump, or even a breach in the system. Air may also cause contamination in the system, leading to issues such as overheating and wearing of surrounding components. To prevent the contamination of hydraulic fluid for aircraft, one should always ensure that fluids and components are inspected and well cleaned before use. In general, the telltale sign that the hydraulic fluid has become contaminated is if the water has a milky appearance.
Temperature of fluids and components within the hydraulic system is also a possible issue that can affect integrity, and a hydraulic system that operates too hot or too cold can run into fluid thinning, fluid oxidation, or fluid thickening. Fluid thinning is often caused by a hydraulic system that is too hot, causing a lack in lubrication and possible leaks of fluids. Oxidation of fluids may also be caused by excess heat, and this can result in buildups within the system that may impede the flow of fluids. Furthermore, buildups may lead to more excess heat that cannot escape the system, thus becoming more of a pressing issue. Lastly, fluid thickening may be caused when temperatures of the system are too low and the viscosity of the liquid increases. Because of this, oil has a harder time reaching the hydraulic pump and may lead to cavitation of system parts.
Another cause of hydraulic system failure that is preventable through regular inspection and maintenance is the levels and quality of hydraulic fluids as those can highly affect the performance of the system as a whole. Low levels of fluids may lead to problems such as air contamination and temperature issues and thus may also cause leaking. When obtaining hydraulic fluids, ensuring that the correct type of fluids is paramount, as various oils are beneficial to certain applications. Additionally, there are also special hydraulic oil types that can be implemented with the system that provide anti-wear and anti-foam additives to protect components.
Lastly, the other major cause of hydraulic unit failure is due to human error, whether through faulty installation or a lack of maintenance. When installing parts such as the hydraulic pump, hose assemblies, or pump shaft, one should always ensure that each component is oriented in the correct direction, as well as is fitted correctly to avoid leaks, contamination, or other issues. Incompatible parts are also a pressing matter, as a wrong hydraulic pump may utilize an nonoptimal motor speed which may cause issues. In general, ensuring that all parts, fluids, and oils of the hydraulic system are consistently inspected can help you catch problems early, allowing you to fix or replace components quickly as needed before they lead to a failure.
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