Definition
A hydraulic system component that controls the output of a constant-delivery pump by unloading the pump (routing its output back to the reservoir at low pressure) when system pressure reaches a preset upper limit, and re-loading the pump when pressure drops to a preset lower limit. This keeps system pressure within a working range without overworking the pump or wasting power.
Plain English
A device that keeps the hydraulic system pressure between a high and low limit. When pressure gets high enough, it tells the pump to stop pushing fluid into the system. When pressure drops, it puts the pump back to work.
Context Anchor
Seen in aircraft hydraulic system diagrams, maintenance descriptions, and troubleshooting for systems that move items such as landing gear, flaps, or brakes.
Derivation
"Regulator" comes from the Latin regula, meaning "rule" or "straight stick used as a measure." A regulator keeps something within set limits — here, hydraulic pressure within a defined working range.
Why Pilots Care
Ensures reliable pressure for flight controls, brakes, and landing gear while preventing damage from overpressure.
Analogy
Think of a thermostat for a heater. When the room gets warm enough, the thermostat shuts the heater off. When it cools down, the heater kicks back on. The system-pressure regulator does the same job, but for hydraulic pressure instead of temperature.
Intuition Check
Do not think of a system-pressure regulator as just a pressure gauge. A gauge shows pressure; a regulator actively controls pressure.
Example Sentence 1
When the landing gear finished retracting and the lines were full, the system-pressure regulator unloaded the pump and the gauge held steady near the upper limit.
Example Sentence 2
During system checkout the regulator kept pressure within limits even when multiple actuators were operated at once.