Definition
A unit of temperature measurement on the Fahrenheit scale, in which water freezes at 32°F and boils at 212°F at standard sea-level pressure. In aviation, °F is one of two scales (alongside °C) commonly displayed on outside air temperature gauges and used in performance and weather information.
Plain English
A way of measuring how hot or cold something is, using the Fahrenheit scale. On this scale, water freezes at 32 and boils at 212.
Context Anchor
Seen on an outside air temperature gauge and in some aircraft performance information.
Derivation
Named after Daniel Gabriel Fahrenheit, an 18th-century physicist who developed the scale. The degree symbol (°) marks the unit as a temperature reading rather than a plain number.
Why Pilots Care
Temperature readings in °F are used to calculate density altitude, determine icing risk, and assess engine and aircraft performance limits.
Intuition Check
°F is not the temperature itself; it is the unit used to report the temperature. The same air temperature will have a different number if shown in °F instead of °C.
Example Sentence 1
The OAT gauge showed 45°F at cruise altitude, well above the freezing level.
Example Sentence 2
When the temperature drops below 32 °F, the pilot checks for possible frost or icing on the wings.