Plain English Meaning

A switch in the cockpit that turns on a small heater inside the pitot tube so it does not freeze over and stop the airspeed indicator from working.

Full Definition

A cockpit switch that turns on an electrical heating element inside the pitot tube to prevent or remove ice blockage of the ram-air inlet, ensuring the airspeed indicator continues to receive accurate impact pressure in visible moisture or freezing conditions.

Context Anchor

Seen on cockpit switch panels and in pitot-static system diagrams, especially when discussing airspeed indications and icing conditions.