15/09/2026
What Is an Aircraft Hydraulic System?
An aircraft hydraulic system is a system that uses pressurized hydraulic fluid to transmit power and operate aircraft components.
In simple terms: the hydraulic system uses fluid pressure to create mechanical movement.
How does the Hydraulic System in Aircraft Work?
The working principle of the hydraulic system in aircraft is based on Pascal’s law.
The engine drives the hydraulic pump to suck hydraulic oil from the reservoir and pressurize it, converting mechanical energy into hydraulic energy. The working pressure of modern aircraft hydraulic systems usually ranges from 3000 psi to 5000 psi. These high-pressure fluids are regulated by the control valve and then delivered to the designated actuators.
The hydraulic cylinder drives the retraction and extension of the landing gear, as well as the adjustment of the flaps, through the linear movement of the piston. The hydraulic motor achieves operations such as front wheel steering and engine reverse thrust through the rotational motion of the rotor.
After the actuator completes its operation, the hydraulic oil will return to the reservoir through the return channel and enter the next cycle.
Main Flight Control System
In large aircraft, hydraulic systems are widely used to drive the main flight control surfaces. The main flight control surfaces include the ailerons, elevators and rudder, which control the rolling, pitching and yawing movements of the aircraft.
During the flight, the system will receive control instructions from the pilot. The system will accurately regulate the pressure and flow rate of the hydraulic oil, driving the actuator to start working. The actuator then drives each control surface to make corresponding actions.Main Flight Control SystemQuick Inquiry Now
Landing Gear System
The retraction and extension of the aircraft landing gear and the turning action of the front wheels are all driven by the hydraulic system.
After takeoff, the hydraulic system drives the hydraulic cylinders to extend and retract, retracting the landing gear back into the fuselage. Before landing, the landing gear will be smoothly lowered and locked by the hydraulic power.
When taxiing on the ground, the hydraulic system drives the front wheel steering actuators to make the aircraft turn and make U-turns.
Meanwhile, the hydraulic system, in conjunction with the shock absorbers of the landing gear, can absorb the impact force during landing, reduce the vibration of the fuselage, and protect the fuselage structure and onboard equipment.
Wheel Braking System
The braking power of the aircraft wheel braking system is provided by the hydraulic system. When the plane landed, the pilot issued the braking command. The hydraulic system immediately responded and rapidly supplied high-pressure hydraulic oil to the wheel braking components.
Under the pressure of the oil, the brake disc and the brake pad were closely attached, generating braking force through friction. This process makes the plane decelerate smoothly and shortens the landing taxiing distance.
The hydraulic system can accurately adjust the brake pressure according to landing speed, load and other working conditions, avoiding tire blowouts or body skidding caused by excessive braking.
Engine Thrust Reverser Device
During the deceleration process after the aircraft lands, the hydraulic system will drive the deflector doors or cascade vanes in the engine compartment. The reverse thrust device changes the direction of the engine exhaust to generate reverse thrust, helping the aircraft decelerate rapidly and shortening the taxiing distance.Engine Thrust Reverser DeviceQuick Inquiry Now
Flap and Spoiler Control
The flaps and spoilers on the wings are also driven by hydraulic systems. The flaps increase lift during takeoff and landing by changing the shape of the wings. The spoiler increases drag or reduces lift by disrupting airflow.
Other Components
The cargo doors or loading ramps of large transport aircraft and passenger planes are usually driven by hydraulic pressure.
In some aircraft, the hydraulic system is also used to drive the windshield wipers, components of the air management system, and the deicing system of the leading edge flaps.
