Definition
A unit of temperature measurement on the Celsius scale, in which 0 °C is defined as the freezing point of water and 100 °C as the boiling point of water at standard sea-level atmospheric pressure. It is the standard temperature unit used in aviation for outside air temperature, engine temperatures, and weather reporting worldwide.
Plain English
A way of measuring how hot or cold something is. Water freezes at 0 and boils at 100 on this scale.
Context Anchor
Seen in turboprop engine discussions, cockpit temperature readings, weather information, and aircraft operating limits.
Derivation
Named after Anders Celsius, the 18th-century Swedish astronomer who proposed the 100-point scale between water's freezing and boiling points. The degree symbol (°) and the letter C identify the scale.
Why Pilots Care
Aircraft performance tables for takeoff, climb, and engine operation are based on Celsius readings because air density and engine output change directly with temperature.
Grounding Statement
If an engine temperature limit is given in °C, the cockpit indication must be read against that Celsius limit, not a Fahrenheit one.
Intuition Check
Degrees does not mean an angle here. In this term, degrees means temperature units on the Celsius scale.
Example Sentence 1
The METAR reported an outside air temperature of 24 °C, which the pilot used when calculating takeoff performance.
Example Sentence 2
Turbine inlet temperature remained within limits at 850 degrees Celsius throughout the climb.