Definition
An electrically driven fan in a combustion heater system that moves cabin air across the heater's heat exchanger to circulate warm air into the cabin, and that also provides airflow for ground operation of the heater when ram air is not available.
Plain English
A fan that pushes cabin air past the heater so warm air flows into the cabin. It is especially needed on the ground, where the airplane is not moving fast enough to push air through the heater on its own.
Context Anchor
Seen in combustion-heater descriptions, heater checks, and cabin heat troubleshooting.
Derivation
From Latin ventilare, meaning to fan or to expose to air. A ventilation fan is simply a fan that moves air through a space. In the heater context, it specifies that the fan's job is moving cabin air, not combustion air.
Why Pilots Care
It delivers heated air to the cabin while maintaining separation from exhaust, preventing both cold cabins and carbon monoxide hazards.
Intuition Check
Do not assume the ventilation fan is the part that burns fuel. In this context, it moves cabin air; the burning happens in a separate part of the heater.
Example Sentence 1
Before turning on the combustion heater during preflight, the pilot switched on the ventilation fan to ensure airflow across the heat exchanger.
Example Sentence 2
During the preflight, the instructor confirmed the ventilation fan was working so the heater could provide usable warm air.