Definition
A unit of temperature measurement on the Celsius scale, in which water freezes at 0 degrees and boils at 100 degrees at standard sea-level pressure. Written as °C. Used throughout aviation for outside air temperature, engine temperatures, and weather reporting.
Plain English
A way of measuring how hot or cold something is, where freezing water is 0 and boiling water is 100. Pilots use this scale for almost all temperature readings in flying.
Context Anchor
Seen on temperature gauges, engine limitation charts, weather information, and performance charts, including turboprop engine discussions.
Derivation
Named after Anders Celsius, an 18th-century Swedish astronomer who proposed a 100-point temperature scale based on the freezing and boiling points of water. The word 'degree' comes from Latin 'gradus,' meaning a step — each degree is one step on the scale.
Why Pilots Care
Accurate Celsius readings are required for engine temperature limits, takeoff performance calculations, and icing risk assessment.
Intuition Check
Do not read degrees Celsius as an angle or heading. Here, degrees means temperature steps on the Celsius scale.
Example Sentence 1
The outside air temperature gauge read 5 degrees Celsius, so the pilot stayed alert for possible icing in visible moisture.
Example Sentence 2
During the takeoff roll the ITT climbed steadily toward six hundred degrees Celsius.