Plain English Meaning

A small heater that burns aviation fuel to warm air, then blows that warm air into the cabin. The exhaust from the burning fuel is sent outside the aircraft so it never reaches the people inside.

Full Definition

A cabin heating system that warms the cockpit and cabin by burning a small amount of the aircraft's own fuel in a sealed combustion chamber. Outside air is passed around (not through) the chamber, picks up heat from its hot walls, and is then ducted into the cabin. Combustion gases are vented overboard separately so they do not mix with the cabin air.

Context Anchor

Seen in aircraft heating system descriptions, preflight checks, and operating , especially in aircraft that do not use engine exhaust heat for cabin warming.