Which fluid is typically used in aircraft hydraulic systems?

In aircraft hydraulic systems, Skydrol is the fluid of choice due to its unique properties that make it suitable for the demanding conditions found in aviation. Skydrol is a phosphate ester-based hydraulic fluid, specifically designed to withstand high temperatures, resist fire, and provide excellent lubrication. Its composition also prevents corrosion and degradation, providing reliable performance over a wide range of operational conditions.

A significant advantage of Skydrol is its compatibility with various materials used in aircraft construction, reducing the risk of adverse reactions that could lead to system failure. This fluid is not only non-flammable; it also offers a high degree of thermal stability, which is crucial in the fluctuating temperature environments that aircraft encounter during flight.

Other fluids mentioned, like water, mineral oil, and brake fluid, do not possess the necessary properties for aviation hydraulic systems. Water can freeze and is not an effective hydraulic medium, while mineral oil, commonly used in other industrial applications, does not provide the fire resistance and chemical stability required in aviation. Brake fluid, although useful in automotive applications, is also unsuitable due to its lower boiling point and potential for vapor lock under extreme conditions encountered in flight.