Definition
Ice formation in the air intake system of a piston aircraft engine, which restricts the flow of air to the cylinders and reduces engine power. It can occur in the carburetor, the air intake duct, or on the air filter, and is caused either by the cooling effect of fuel vaporization and pressure drop through the carburetor venturi, or by visible moisture (rain, wet snow, clouds) freezing on intake surfaces at near-freezing temperatures.
Plain English
Ice forming where air enters a piston engine, choking off its air supply and causing the engine to lose power.
Context Anchor
Seen in instrument flying, engine operation, and weather discussions when a pilot is watching for power loss in cold or moist conditions.
Derivation
Reciprocating refers to the back-and-forth motion of pistons inside the engine. Induction comes from the Latin inducere, meaning 'to lead in' — here it refers to the process of leading air into the engine. So 'induction icing' is ice forming on the path that leads air into the engine.
Why Pilots Care
It reduces or stops engine power output and must be cleared promptly with carburetor heat or alternate air to avoid loss of control or forced landing.
Grounding Statement
Moist air can cool as it moves through the intake, and if it cools enough, water can freeze onto engine intake parts and choke off the airflow.
Intuition Check
Do not read “induction” as an electrical process here; it means the engine’s air-intake system. Also, induction icing can occur even when the outside air is above freezing because the air can cool inside the intake.
Example Sentence 1
When the engine began running rough during a humid descent, the pilot suspected reciprocating engine induction icing and applied full carburetor heat.
Example Sentence 2
High humidity and temperatures just above freezing created a high risk of reciprocating engine induction icing during the instrument approach.