Definition
A cabin heating system on light aircraft that warms outside air by routing it through a shroud or jacket surrounding the engine's hot exhaust pipe (muffler). The heated air is then ducted into the cabin and to the windshield defroster. Because the heating air passes near hot exhaust gases, any crack or leak in the exhaust system can allow carbon monoxide to enter the cabin.
Plain English
Cabin heat in most small piston aircraft is made by passing fresh outside air around the hot exhaust pipe and then sending that warmed air into the cockpit. It is simple and effective, but a leak in the exhaust pipe can let poisonous fumes into the cabin along with the heat.
Context Anchor
Seen in aircraft systems discussions, preflight inspection, cabin heat use, defrost use, and carbon monoxide safety.
Derivation
“Exhaust” comes from a word meaning “to draw out” or “empty out.” In aviation, it refers to the hot gases leaving the engine after combustion. That helps the term make sense: this system uses heat from the gases leaving the engine, not the gases themselves.
Why Pilots Care
Proper use prevents carburetor icing that can cause sudden engine power loss; improper use or failure can lead to engine stoppage in flight.
Intuition Check
Do not read “exhaust heating system” as a system that sends exhaust into the cabin. It sends warmed fresh air into the cabin; the exhaust should remain separate.
Example Sentence 1
After noticing a faint smell during cruise, the pilot shut off the cabin heat, opened the fresh air vents, and landed to have the exhaust heating system inspected for cracks.
Example Sentence 2
Cabin temperature rose quickly once the exhaust heating system began routing warm air from around the muffler.