Plain English Meaning

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.

Full 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.

Context Anchor

Seen in cabin heat system discussions, especially on airplanes that use a separate instead of taking cabin heat from the engine .