Definition
In aircraft hydraulic and pneumatic systems, the maximum distance a piston, ram, or actuator can travel from its fully retracted to its fully extended position. Reach defines the working range of an actuating component and determines how far it can move the device it operates, such as a landing gear strut, flap, or control surface.
Plain English
How far a moving part can extend out before it hits the end of its travel. It's the full length of motion available from one end of its stroke to the other.
Context Anchor
Seen when selecting, inspecting, or installing spark plugs on an aircraft engine.
Derivation
From Old English ræcan, meaning 'to extend' or 'to stretch out.' In mechanical use, reach kept the same plain idea: how far something can stretch or extend before it stops.
Why Pilots Care
A spark plug with the wrong reach can fit incorrectly, run too hot, collect deposits, or damage engine parts, so mechanics must install the correct plug for that engine.
Intuition Check
Reach does not mean how far the spark travels or how easy the plug is to access. Here it means the installed length of the spark plug's threaded end.
Example Sentence 1
The technician confirmed the actuator's reach matched the manufacturer's specification before installing it on the landing gear assembly.
Example Sentence 2
An incorrect reach can allow the plug to contact the piston or leave the electrode too far from the mixture.