Definition
A hydraulic or pneumatic valve that allows full, unrestricted fluid flow in one direction and a reduced, metered flow in the opposite direction through a small orifice. It combines the one-way action of a check valve with the flow-limiting action of a fixed orifice.
Plain English
A valve that lets fluid flow freely one way and only a trickle the other way. The trickle is controlled by a small hole built into the valve.
Context Anchor
Seen in aircraft hydraulic and pneumatic system diagrams and maintenance procedures, especially where the movement speed of a part such as landing gear, a flap, or a door must be controlled.
Derivation
Orifice comes from the Latin orificium, meaning 'an opening' or 'mouth.' Here it refers to the small calibrated hole that restricts return flow. Check in valve terminology means 'to stop or restrain' — a check valve checks (blocks) flow in one direction.
Why Pilots Care
These valves are what stop something like landing gear from slamming down or retracting too fast. If the orifice clogs or the valve fails, components can move at the wrong speed, causing damage or unsafe operation.
Intuition Check
“Check” does not mean “inspect” here. It means the valve controls flow direction; the orifice controls how fast the flow can pass in the restricted direction.
Example Sentence 1
The orifice check valve in the landing gear circuit allows fast retraction but meters the extension flow to prevent a hard, jolting drop.
Example Sentence 2
Technicians replaced the orifice check valve after noticing the actuator extended too rapidly during ground testing.