Pitot heat is an anti-icing device: a small but vital component of aviation safety. Built into the pitot tube-the slender probe mounted on the aircraft's exterior that measures total, or dynamic, pressure-an electrical heating element warms the tube whenever the Pitot Heat Switch is selected.
Activated in flight when icing may occur, the system prevents blockage by ice and ensures the pitot-static system remains free of ice, allowing the airspeed indicator to deliver accurate, reliable data in cold or moist conditions.
Although it is not a de-icing device for the airframe, pitot heat can cause overheating if left on without airflow. Conversely, it must be turned on during ground operations with engines running.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is the definition of pitot heat on an aircraft?
Pitot heat is a critical system in aviation designed to prevent ice from forming in the pitot tube, which measures airspeed by using the dynamic pressure of the air. The pitot tube is located on the aircraft's exterior and is exposed directly to the oncoming airflow.
Pitot heat is the built-in electrical heating of the pitot tube, the small, forward-facing tube protruding from the wing or nose that collects the pressure created by the aircraft's forward motion. Because the pitot tube measures pitot pressure-total pressure made up of static pressure plus the extra pressure due to forward speed,its narrow opening must stay unobstructed. At altitude and in visible moisture, ice blocks the tube, so current is fed to an internal element, raising the metal to several hundred degrees. The airflow passing over the tube in flight then keeps the element from overheating. The hot tube will burn you or melt its cover when securing the aircraft. It is normally covered only when the aircraft is parked, a step included in preflight checks to keep dirt, insects, or ice from entering.
What does pitot heat do?
By keeping the pitot tube clear of ice, pitot heat ensures the airspeed indicator provides reliable data. Two heaters warm the entire tube, stopping ice from forming. Because the system works as anti-ice rather than de-ice, it must be switched on before entering potential icing conditions.
The pitot tube measures dynamic pressure of the airflow and connects only to the airspeed indicator. Accurate airspeed readings maintain safe flight. Without them, the pilot's ability to maintain safe and efficient flight is compromised.
During preflight, removing covers helps prevent blockages caused by dirt, insects, or ice. The tube can reach several hundred degrees and can burn you or melt the cover when securing the aircraft.
How does the pitot heat work?
Inside every pitot tube is an electrical heating element built in during manufacture. The heating element raises the metal temperature high enough to stop ice from forming on or in the small front opening or the delicate internal pressure chamber. By keeping both the front hole and the hidden passages warm, the element maintains a clear path for total pressure all the time, even when freezing conditions surround the aircraft.
Pilots operate the heat switch from the cockpit so power flows to the element throughout the flight. Although designers run the device continuously, they limit the duty cycle to avoid premature failure and excessive current draw. During preflight inspection the pilot checks both the tube and its drainage hole for damage or blockage, but once energized the heat becomes a silent guard that prevents ice from ever forming inside. The pitot-static system is unchanged for decades because it works well when warm air, free from contamination, reaches the airspeed indicator unimpeded.
Should pitot heat be turned off?
Pitot heat must be turned off after landing.
The after-landing checklist instructs the pilot to select pitot heat OFF once the aircraft is stationary and airflow is insufficient. This action prevents the heater from overheating and failing while on the ground. Instructors caution that prolonged operation on the ramp weakens the element, so the switch is normally kept OFF until just before take-off.
Where does pitot heat come from?
Pitot heat comes from an electrical heating element fitted inside the metal pitot tube. A cockpit switch sends electrical current to this element, and the current warms the tube so that it stays clear of ice, bugs, or dirt. Because the surrounding air cools the pitot tube in flight, the electric heat must stay on whenever ice is possible, without it, the pitot tube will become blocked and the pressure chamber will no longer deliver reliable total pressure to the airspeed indicator.
What does the pitot heat warning indicate?
A pitot heat warning is provided to alert the flight crew whenever any pitot tube heating element is inoperative while the system is switched on. The indication must incorporate an amber light positioned in clear view of a flight crewmember, and it must appear whenever the pitot heating system is not operating. When the system is selected off, a PITOT HEAT OFF message appears on the Crew Alerting System. When an element fails, a PITOT HEAT FAIL message appears on the same display. These messages ensure the crew knows that ice forms inside the pitot tube, blocking the entry and trapping erroneous pressure in the line, which in turn causes the airspeed indicator to read falsely high during climbs and falsely low during descents.
