Definition
The accumulation of ice on the blades and hub of an aircraft propeller when flown through visible moisture at temperatures at or below freezing. Ice forms first and most heavily near the propeller spinner, where blade speed is lowest, and reduces propeller efficiency by disrupting the airflow over the blades, decreasing thrust, and creating imbalance and vibration as ice sheds unevenly.
Plain English
Ice building up on the spinning propeller. It changes the shape of the blades, so they push less air, the engine has to work harder, and the uneven ice can make the propeller shake.
Context Anchor
Seen in instrument flying, winter weather, and any discussion of aircraft icing while flying in clouds, precipitation, or freezing moisture.
Derivation
Propeller comes from Latin words meaning “to drive forward.” Icing means becoming covered with ice. Together, the term points to the part that drives the airplane forward becoming coated with ice, which directly weakens its ability to do that job.
Why Pilots Care
Ice changes blade shape and weight, reducing thrust, creating imbalance and vibration, and risking engine damage or loss of control.
Analogy
It is like trying to use a fan with rough, uneven ice stuck to the blades. The motor may still spin, but the blades no longer move air smoothly or evenly.
Grounding Statement
Picture the propeller spinning through freezing cloud droplets, with ice collecting unevenly on the blade edges as the airplane flies.
Intuition Check
Do not assume icing only matters on the wings. Ice on the propeller can reduce pull and cause vibration before the pilot sees much ice elsewhere.
Example Sentence 1
After climbing through a layer of freezing drizzle, the pilot felt a low-frequency vibration and suspected propeller icing.
Example Sentence 2
Propeller icing caused noticeable vibration that stopped once the aircraft descended below the icing layer.