Definition
A switch designed to operate, or change state, at a precise and repeatable point in the travel of its actuator. Small movements of the actuator produce a clean, consistent make-or-break of the electrical contacts, with little variation between operations.
Plain English
A switch that turns on or off at an exact, repeatable point when something pushes against it. Each time the actuator reaches that point, the switch acts the same way.
Context Anchor
Seen in aircraft electrical systems, especially where the airplane must sense a specific position, such as a door, landing gear, flap, or control reaching its proper place.
Derivation
‘Precision’ comes from the Latin praecisio, meaning ‘a cutting off’ — a sharp, exact point. The name reflects the switch’s clean, exact trip point rather than a vague or gradual one.
Why Pilots Care
Many warning and indication systems depend on precision switches reporting the exact moment a component reaches its commanded position. A worn or misadjusted precision switch can cause false warnings or hide a real problem, such as a gear that is not fully down and locked.
Intuition Check
Precision does not mean the switch makes the whole system more accurate. Here it means the switch itself operates at a closely controlled point.
Example Sentence 1
A precision switch on the landing gear confirms when the gear is fully down and locked.
Example Sentence 2
During preflight the mechanic verified that the precision switch triggered the warning light at the correct hydraulic pressure.