Definition
The gases and particles released from an aircraft engine's exhaust system as a byproduct of combustion. In a piston engine the principal emissions are carbon monoxide, unburned hydrocarbons, oxides of nitrogen, and small amounts of lead compounds from leaded avgas. In a turbine engine the principal emissions are carbon dioxide, water vapor, oxides of nitrogen, carbon monoxide, unburned hydrocarbons, and smoke (fine carbon particles).
Plain English
The mix of gases and tiny particles that come out of an aircraft engine's exhaust pipe after the fuel burns.
Context Anchor
Seen in engine operation, aircraft environmental discussions, maintenance troubleshooting, and carbon monoxide safety discussions.
Derivation
From Latin 'exhaurire,' meaning to draw out or empty, and 'emittere,' meaning to send out. Together the phrase simply describes what is sent out of the engine after combustion is complete.
Why Pilots Care
Pilots monitor exhaust emissions to assess engine combustion efficiency and meet environmental regulations.
Grounding Statement
When the engine burns fuel, the used gases leave through the exhaust system and enter the outside air.
Intuition Check
Exhaust emissions do not mean only visible smoke. Many exhaust emissions are invisible, and some can still be harmful or indicate a problem.
Example Sentence 1
The mechanic checked the muffler and exhaust stacks for cracks because a leak in that area can let exhaust emissions enter the cabin through the heater.
Example Sentence 2
Maintenance records track exhaust emissions to confirm the engine meets certification standards.