Which system is responsible for extending and retracting the landing gear?

The hydraulic system is the primary mechanism responsible for extending and retracting the landing gear in many aircraft. This is due to the ability of hydraulic systems to generate a significant force using relatively small components and fluids. When the landing gear is to be deployed or retracted, hydraulic fluid is directed into the appropriate actuators that move the landing gear to its desired position. This efficient transfer of force allows for quick and reliable operation, essential during critical phases of flight such as landing and takeoff.

While pneumatic and mechanical systems can also be employed in landing gear systems, they are not as common in modern aircraft compared to hydraulic systems. Pneumatic systems use compressed air to move components, and while they can provide similar functions, they lack the power density and reliability of hydraulics in this context. Mechanical systems might include manual or cable-operated systems, which can be more complex and less reliable than hydraulic actuation. Therefore, the hydraulic system's effectiveness and efficiency make it the primary choice in aircraft design for landing gear operation.