Definition
A temperature-sensitive control device that automatically opens or closes a valve, switch, or other actuator to maintain a system within a desired temperature range. In aircraft systems, thermostats are used to regulate engine oil temperature, cabin heat, carburetor air temperature, and similar heat-controlled circuits.
Plain English
A device that senses temperature and turns something on or off, or opens or closes, to keep that temperature where it should be.
Context Anchor
Pilots may encounter thermostats in engine temperature control, oil or coolant systems, cabin heat systems, and other aircraft equipment that must stay within a safe temperature range.
Derivation
From Greek 'thermo' (heat) and 'statos' (standing or stationary). The original idea was a device that keeps heat 'standing still' — holding it steady at a chosen level.
Why Pilots Care
Maintains the engine within its safe operating temperature range, preventing overheating damage and supporting efficient performance.
Intuition Check
A thermostat is not the heater or cooler itself. It is the control that senses temperature and tells a valve or switch when to act.
Example Sentence 1
The oil cooler thermostat opens once the oil reaches operating temperature, allowing oil to flow through the cooler.
Example Sentence 2
Once the cylinder head temperature rose, the thermostat opened and allowed coolant to circulate through the radiator.