Most airplanes don’t use all-mechanical flight controls. Instead, they rely heavily on hydraulics. Hydraulic systems give pilots the force needed to move otherwise large and heavy control surfaces, such as flaps. To learn more about hydraulic systems and how they power flight controls, keep reading.
The Basics of Hydraulic Systems
Hydraulic systems are characterized by the use of pressurized fluid to convert or transmit power. They typically contain oil in a sealed space, such as a cylinder. In addition to cooling and lubricating this sealed space, oil facilitates the transmission of power. When oil is pumped into the sealed space, it creates pressure that moves a piston. There are many different types of hydraulic systems, but most work in this way.
Hydraulic Systems and Flight Controls
How do hydraulic systems power flight controls exactly? Airplanes feature a wide range of flight controls, some of the most common being yokes, sidesticks and pedals. Pilots move and interact with these flight controls to engage the airplane’s control surfaces.
Some airplanes, particularly older and smaller airplanes, use hydro-mechanical linkages, whereas others use fly-by-wire. Both types rely heavily on hydraulic systems, but they work in different ways.
With hydro-mechanical linkages, manual input travels mechanically to a hydraulic valve. The valve will then open, allowing pressurized oil to enter an actuator. With fly-by-wire linkages, computers automatically convert manual input into electronic signals. The computer sends these signals to the appropriate valves to guide the pressurized oil.
Why Airplanes Use Hydraulic Systems
Moving a control surface can be challenging. When flying at speeds of 500 to 600 mph, airplanes encounter heavy forces. Air flows rapidly over the wings and tail, applying significant pressure to the airplane’s control surfaces. Hydraulic systems solve this challenge. They send pressurized oil through lines to actuators, which then convert the pilot’s input into actual movement.
Multiple Hydraulic Systems
Most commercial airplanes have multiple hydraulic systems. Each of these systems is capable of powering the airplane’s flight controls. With multiple hydraulic systems, pilots can continue to control the airplane even if one fails.
Hydraulic systems feature lines through which pressurized oil flows. Over time, these lines can become compromised. If a line ruptures, it will allow oil to leak out of the hydraulic system. Fortunately, there are multiple hydraulic systems to ensure the safe and effective transmission of power during flight.
