The purpose of a restrictor valve in the hydraulic line downline of a landing gear is to prevent what condition?

• A. Cavitation
• B. Overpressure
• C. Leakage
• D. Contamination

Answer: (A)

The main idea here is preventing cavitation in the hydraulic system. A restrictor valve throttles the flow downline to the landing gear, which reduces the velocity and slows the pressure changes as fluid moves through the line. By creating a controlled pressure drop, it helps keep the downstream pressure from falling below the fluid’s vapor pressure. If the pressure gets too low, vapor bubbles form in the fluid; when they collapse, they can cause pitting, noise, and damage to pumps and valves. So the restrictor helps maintain enough pressure to keep the fluid in a single, liquid state as it reaches the gear actuators, enabling smooth, reliable operation.

Other issues like overpressure, leakage, or contamination aren’t the primary reason for this valve. Relief or pressure-control devices handle overpressure, while seals and filtration address leakage and contamination.