Plain English Meaning
A hydraulic device that pushes one way under pressure and is brought back the other way by something else, like a spring.
Full Definition
A hydraulic actuator that uses fluid pressure to move its piston in one direction only, relying on a spring, gravity, or some other external force to return the piston to its starting position.
Context Anchor
Seen in hydraulic system descriptions, especially where pressure is used to move a part but the return movement comes from a spring, weight, or outside force.
Derivation
Single-acting means the fluid acts on the piston from one side only. A servo, from the Latin servus meaning servant, is a device that does work on command. Together: a servant that is pushed by fluid in only one direction.
Why Pilots Care
Knowing how single-acting work helps pilots understand and diagnose issues during or in- hydraulic .