Definition
A solid residue of carbon and partially burned fuel that builds up on internal engine surfaces, particularly on spark plug electrodes, piston crowns, valve faces, and combustion chamber walls, as a by-product of incomplete combustion in a reciprocating aircraft engine.
Plain English
A black, sooty crust that slowly forms inside an engine when the fuel does not burn completely. Over time it coats parts of the cylinder and spark plugs, and it can interfere with how the engine runs.
Context Anchor
Seen in engine operation, combustion, spark plug inspection, and discussions of rough running or abnormal engine heat.
Derivation
From Latin carbo, meaning charcoal or burnt material. Whenever fuel does not burn cleanly, some of the carbon in it is left behind as solid residue rather than leaving as exhaust gas.
Why Pilots Care
Excessive carbon deposits can foul spark plugs, reduce engine efficiency, and lead to pre-ignition or detonation.
Grounding Statement
Picture a thin, hard layer of black residue baked onto a hot engine part after many heating and cooling cycles.
Intuition Check
A carbon deposit is not ordinary dirt sitting in the engine. It is baked-on residue from burning fuel or oil, and it can affect how the engine runs.
Example Sentence 1
Running the engine too rich for long periods can lead to carbon deposits on the spark plugs.
Example Sentence 2
Heavy carbon deposits in the combustion chamber can cause the engine to run roughly and require cleaning.