What is the function of a relief valve in a hydraulic gear circuit?

• A. To seal the hydraulic circuit and prevent leaks.
• B. To limit system pressure and protect components from overpressure.
• C. To cool the hydraulic fluid.
• D. To feed hydraulic fluid to the actuators.

Answer: (B)

The relief valve in a hydraulic gear circuit acts as a safety device that keeps pressure from getting too high. It stays closed during normal operation so the system can develop the required force, but when pressure reaches its preset limit, it opens and allows hydraulic fluid to flow back to the reservoir or to the pump inlet. This shunts excess pressure away, preventing damage to components such as pumps, seals, hoses, and actuators.

In a landing gear system, this is crucial because actuators can experience high pressure if a load spike or binding occurs. By limiting the maximum pressure, the relief valve protects the hardware from overpressure while the system continues to operate within safe limits. It does not seal the circuit, cool the fluid, or feed fluid to the actuators—those functions are handled by other components in the system.