The general rule is to activate pitot heat whenever icing conditions are present or likely. Because the activation is predicated on the occurrence of possible icing conditions, pilots of light aircraft operating at low altitudes (<10,000 ft) turn the heat on whenever the flight path may enter visible moisture at temperatures near or below freezing. If the weather report shows freezing temperatures, rain, snow, or fog, engaging the system before take-off is considered good practice.
If used, the pitot heat is normally switched on just before take-off and switched off just after landing, thus preventing ground personnel from being burned by the hot probes; this timing also gives a convenient opportunity to perform any required leak checks or non-RVSM accuracy checks on the Pitot-Static systems.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is the purpose of the pitot heat switch?
The pitot heat switch operates the electric heating element that warms the pitot tube. When turned on, this switch ensures that the pitot system remains free of ice by stopping ice from forming within the tube. By preventing blockage of the pitot tube by ice, the switch supports reliable airspeed data that the pitot-static system uses to determine airspeed, Mach number, altitude, and altitude trend. Accurate readings of dynamic pressure captured by the pitot tube are critical during all phases of flight, especially in IFR conditions where a failed airspeed indicator leads to serious issues. Additionally, if the system is left off, an indication system must alert the flight crew to protect against the potential for icing at altitudes where the temperature below freezing and visible moisture indicate such risk.
Should pitot heat always be on?
It depends on phase and conditions. Pitot heat is generally on during most flight phases. In many GA aircraft, it is not run continuously. Instead, it is switched off while on the ground because prolonged ground operation wastes power and risks element overheating.Whenever the aircraft is stationary, manufacturers and aviation authorities strongly recommend use of pitot covers, removing the need for pitot heat. Once airborne, the principle is similar to engine anti-ice: we only turn pitot heat on as required when we're entering potential icing conditions, activating it whenever conditions warranting use include anticipated icing, some aircraft have a manual override switch to satisfy that requirement.
I operate under a simple principle: the danger of neglecting to twist it on during a sudden run into in sight moisture long exceeds any small advantage. Impacts of an iced over measuring instrument pipe are serious, so giving the measuring system temperature operational gives an unbroken blanket of security. Electrical requirement is a derived portion of the aircraft's system, yet I handle it with the identical significance as place wings and the equivalent significance as checking flying commands. My individual credo is set in repetition and danger reduction; this exercise does away with any possibility for individual fault.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
When do you need to use pitot heat?
Activate pitot heat before takeoff and keep it on whenever visible moisture exists at temperatures near or below freezing. Engage the heating element when you anticipate entering clouds or other areas where icing conditions are present or likely. The system must remain on in flight while the airplane is in visible moisture, because the warm tube stops ice from forming and preserves accurate airspeed indication. Leave pitot heat off only when the sky is clear, temperatures are well above freezing, and no clouds or precipitation are expected.
What temperature to use pitot heat?
Turn pitot heat on any time conditions include cold temperatures with visible moisture or when icing is anticipated. Evaporative cooling can drive a 26.7-degree-Celsius (80-degree-Fahrenheit) airstream below freezing in roughly half a minute, so waiting for the thermometer to read 0 C (32 F) is too late. Power the element before you enter the layer and leave it on until the air is demonstrably dry and above 0 C (32 F).
My judgment is not founded on a solitary heat threshold, it is founded on the mixture of heat and the possibility for moisture. I handle pitot heat as a vital portion of setting up the cockpit for secure flying, and I flip it on during pre-flight inspections whenever outdoor air is near or below freezing. I operate the switch before engine start if any suspicion of moisture exists, because danger of a plugged measuring device pipe guiding incorrect airspeed readings is good. A precipitation shower can induce the measuring instrument pipe to change owing to evaporative chilling, and measuring device pipe chilling possibly comes to freeze shape. I do not act only when I glimpse frost come up, I guess apparent wetness could halt on the probes, so I find out that particular temperature is crucial, yet the existence of seeable moisture matters more.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
Should pitot heat be used in rain?
Yes. Rain interferes with the pitot tube by allowing water droplets to accumulate, and heavy rain contaminates both pitot and static systems. Moderate to heavy rain leads to failures of the pitot-static system, while high humidity allows water droplets to accumulate inside the tube. Once the tube or port is water-contaminated, pitot tube icing follows even when the outside air temperature is above 0 C (32 F), rain becomes supercooled as freezing rain and ice forms rapidly under these conditions. The resulting blockage distorts airspeed indication and causes failure of the entire pitot-static system. Because visible moisture such as rain is present, pitot heat must be selected before entering the condition so that water will not freeze and adhere.
Pilots sometimes misunderstand what icing conditions are: temperature +35.6 to -4 F and visible moisture present is the cue, and rain satisfies the moisture requirement even when no clouds are visible. Static ports are vulnerable to the same contamination, and the farther you fly from the blockage altitude, the greater the ASI error becomes.The approved procedure is therefore simple: whenever heavy rain or high humidity interferes with the pitot tube, turn pitot heat on, continue to monitor for airspeed anomalies, and be ready to fly pitch and power instead of airspeed if errors appear.
From my view the judgment to initiate pitot heat in precipitation is a basic security routine. Moisture can preclude the tiny opening of the pitot pipe, and a little quantity can lead to incorrect or icy measurements. A plugged pitot hose can give an erratic velocity hint during way or touchdown, so the outcomes are serious. My custom is to activate the measuring device heat system whenever I am piloting in rainfall, I act the change before locomotive opening whenever there is any chance of seeable moisture. I leave the system on until I am confident I am in a clean dried atmosphere, because I work under the rule that it is best to use measuring device heat unnecessarily rather than to chance a malfunction.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
How to turn on pitot heat?
To turn on pitot heat, follow the instructions given below.
- Shift+H turn on Pitot heat
- Pitot heat turns on after engine starts
Where is the pitot heat button located?
A pitot tube is a small probe located on the aircraft's exterior, usually mounted ahead of the cockpit on the nose or underside of the wing. In Cessna Skyhawks, pitot tubes are located under the wing. The heaters are controlled by one switch on the Ice Protection System control panel, marked PITOT STALL WARN HEAT. An indication system must incorporate an amber light in clear view of the flight crewmember to confirm activation.
How to check pitot heat?
To check pitot heat follow the steps listed below.
- Check pitot heat during A' Check
- Check pitot heat again during After Start checks
- Select PITOT STALL WARN HEAT to OFF during After Start checks
- Check for PITOT HEAT FAIL message on CAS
- Connect pitot-static tester to pitot tubes through aircraft adapters
- Perform pitot leak check at 200 knots
- Test pitot-static systems in accordance with CFR 25.1325
- Check pitot and static port openings
- Check pitot tube for blockage
- Ensure PITOT HEAT OFF message on CAS extinguishes
- Remove pitot tube cover preflight
- Inspect static port for blockage or damage
- Simulate various altitudes to test system accuracy
The same indicators are checked again during the A' Check, always mindful that the heaters reach skin-burn temperatures within seconds and must not be left on longer than the 3-minute limitation. Battery condition is assessed first, because good battery condition means zero risk of leaving pitot heat on to check that it gets hot. Preflight, both openings in the pitot tube must be inspected visually and by touch to ensure that neither is blocked by ice, insects, or dirt and that the pitot tube cover has been removed. The static port is given the same inspection for blockage or damage.
Functional testing of the heating circuits is limited to the cockpit indications and the single switch on the Ice Protection System control panel that controls both heaters. Leak checks of the pitot/static systems are performed by an airframe certified technician or repair station in accordance with CFR 25.1325 and the airframe manufacturer's instructions. Static system integrity is verified by blocking the static ports and applying suction until the altimeter reads about 2 000 ft (609.6 m) above field elevation, then watching for an altitude drop of no more than 100 ft (30.48 m) per minute after the VVI goes to zero. The system's accuracy is tested by simulating various altitudes to confirm that no pumps are required in flight to maintain airspeed indication.
How hot does pitot heat get?
Heater temperatures of 200 C (392 F) are reported. On the ground a couple of hundred degrees develop inside the short exposed metal. Laboratory records show the internal temperature of the pitottube was around 270 degrees Celsius while the unit was placed in submerged water. The tube's surface temperature rose to 70 C (158 F) when current increased to 3.3 A, then stabilized at 105 C (221 F) with 4.29 A.
An industrial pitot device is rated up to 200 C (392 F). A 120-watt heater heats the body of the probe. Applying 100 mA of constant current to the tube's heater resulted in a total thermal resistance of about 10 degrees C per watt. An electrically heated pitot tube gets warm very quickly, yet overheating the pitot tube damages it.
