Definition
A cabin heating system that produces heat by burning a small amount of the airplane's fuel inside a sealed combustion chamber. Outside air is drawn across the outside of this chamber, warmed by contact with its hot surface, and then ducted into the cabin. The exhaust gases from the burning fuel are vented overboard and never mix with the cabin air.
Plain English
A small fuel-burning furnace built into the airplane that heats cabin air by passing it over a hot metal chamber. The flame and its fumes stay sealed inside; only clean, warmed air reaches the cabin.
Context Anchor
Seen in cabin heat system discussions, especially on airplanes that use a separate heater instead of taking cabin heat from the engine area.
Derivation
Combustion comes from the Latin comburere, meaning 'to burn up.' The name simply tells you how the heater makes its heat: by burning fuel, rather than by borrowing heat from the engine like a typical small airplane heater does.
Why Pilots Care
It supplies independent cabin heat when the engine is not producing enough warmth, but must be operated and maintained correctly to avoid carbon monoxide leaks into the cabin.
Analogy
It is similar to a home furnace: the fire stays in one protected part of the unit, while clean air is warmed and sent into the living space.
Intuition Check
Do not assume a combustion heater sends burned air into the cabin. The burning happens in a sealed part of the heater; only warmed clean air should enter the cabin.
Example Sentence 1
Before the first cold-weather flight, the pilot had the combustion heater inspected for cracks and leaks during the annual.
Example Sentence 2
During the preflight inspection the pilot checked the combustion heater exhaust for soot that could indicate incomplete burning.