Definition
A combined pitot-static probe fitted with an internal electrical heating element that prevents ice from blocking the ram-air inlet and static ports during flight in visible moisture or cold conditions. It senses both impact (ram) air pressure for airspeed indication and static (ambient) air pressure for the altimeter, vertical speed indicator, and airspeed indicator, while the heater keeps the sensing openings clear of ice.
Plain English
A small probe sticking out of the aircraft that measures the air rushing at it and the still air around it, with a built-in heater so ice cannot plug it up.
Context Anchor
Seen on the aircraft exterior and in pitot-static system diagrams, especially when discussing airspeed, altitude, vertical speed, and pitot heat.
Derivation
Pitot is named after Henri Pitot, the 18th-century French engineer who invented the tube that measures moving fluid pressure. Static comes from the Latin staticus, meaning 'at rest' -- the still air pressure around the aircraft, as opposed to the moving air hitting the probe.
Why Pilots Care
Ice on an unheated pitot-static head blocks the ports and produces dangerous errors in airspeed, altitude, and vertical speed indications during instrument flight.
Intuition Check
Do not read static as inactive or unimportant; in this term, static means outside air pressure. Electrically heated does not mean the probe is for warming the airplane; it means the probe warms itself to reduce ice blockage.
Example Sentence 1
Before entering the clouds, she switched on the pitot heat to keep the electrically heated pitot-static head clear of ice.
Example Sentence 2
During the preflight inspection the pilot confirmed that current was flowing to the electrically heated pitot-static head by checking the ammeter.