Definition
The process of warming an aircraft engine and its oil before starting in cold weather, typically by directing heated air into the engine compartment or by using electric heating elements attached to the cylinders, oil sump, or crankcase. Preheating raises engine and oil temperatures enough to allow proper oil flow, normal lubrication, and safe starting without damaging internal components.
Plain English
Warming up a cold engine before you try to start it, so the oil can flow and the engine isn't damaged by being started while frozen.
Context Anchor
Seen in cold-weather engine starting procedures and in aircraft maintenance work such as welding or repair of metal parts.
Derivation
From 'pre-' (before) and 'heating' (applying warmth). The word literally means 'heating beforehand' — warming the engine before the act of starting it, rather than relying on the start itself to bring it up to temperature.
Why Pilots Care
Cold oil is thick and does not circulate immediately, so preheating prevents metal-to-metal contact and possible engine damage on startup.
Analogy
It is like letting a cold car engine warm up before asking it to work hard, instead of starting it cold and immediately putting it under load.
Grounding Statement
Preheating reduces the shock of going from very cold to working temperature too quickly.
Intuition Check
Preheating does not mean simply making something comfortable or warm to the touch. In aviation, it means warming an engine, part, or material enough to make the next operation safer and less damaging.
Example Sentence 1
On a January morning at minus ten degrees Celsius, the pilot plugged in the engine heater two hours before the flight to ensure proper preheating.
Example Sentence 2
After preheating, oil pressure rose normally within seconds of engine start.