Hydraulic pumps create the fluid flow that pressurizes the system’s fluid. This pressurized fluid is then routed to motors and actuators that go on to operate a variety of mechanical parts. Because the fluid is nearly incompressible, hydraulic systems are incredibly reliable which means increased safety. They are sturdier and capable of transmitting higher pressures than pneumatic counterparts.
For in-flight systems, hydraulics are typically run by engine-driven pumps, operated by the jet engine’s rotation. On the other hand, in emergency situations, pilots rely on hand-operated hydraulic systems. For example, these hand-operated electric powered hydraulic pump can be used to extend the landing gear in the instance the plane loses its normal hydraulic pressure.
In an aircraft, the hydraulic fluid is pushed through the system, to an actuator or servo cylinder. A piston located inside the cylinder transforms the fluid power into the force that is needed to move the aircraft system controls. There are two types of cylinders, single-acting and double-acting. Pressure can be applied to one or both sides of the cylinder depending on the type.
A typical aircraft hydraulic system consists of many components all with individual job sets. Such parts include a reservoir to hold the hydraulic fluid, pto driven hydraulic pump to pressurize the system, an actuator to control amount the force. Other auxiliary parts to keep the system running properly include a filter to keep the fluid clean, selector valves to control the direction of flow, and relief valve to relieve excess pressure. A common modern jet’s hydraulic system is pressurized at an unbelievable force, ranging from 3,000 pounds per square inch and upwards.