Total air temperature (TAT) sensors are heated probes mounted the aircraft’s surface. Readings from TAT sensors are utilized in essential functions, including air data computer calculations and pilot decisions. Their core function is reading the temperature of air outside the aircraft. When the aircraft is on the ground, TAT sensor covers protect these instruments, ensuring that pilots are accurately informed of environmental conditions while flying.

Understanding Total Air Temperature

Two different temperature readings are important to pilots. One is static air temperature (SAT), which is the temperature of undisturbed air around the aircraft. This is also known as outside air temperature (OAT). The other is total air temperature (TAT), which is the temperature of the air hitting the aircraft. When flying at high speed, TAT rises significantly because of compression. This temperature increase is called ram rise. The TAT sensor measures the total air temperature, which the aircraft’s air data computer uses to derive the SAT.

Applications of Total Air Temperature

These readings are not just used for understanding the temperature of the air surrounding the aircraft but also help monitor fuel temperature, determine necessity of anti-ice measures, and make other calculations.

In extremely cold conditions, fuel freezing becomes a concern. Pilots may increase speed or lower their altitude to raise total air temperature and thus prevent the fuel from freezing. Jet fuel has a very low freezing point, so this is not a major concern unless operating in extremely harsh weather conditions. International pilots should be mindful of different fuel types encountered globally, as they may differ in freezing point. For the average pilot, structural icing is the main concern in cold weather.

Pilots use both total air temperature and static air temperature to help them determine whether they need to use anti-ice measures. Recommendations for what actions they should take and at what temperature are dependent on the aircraft they are flying.

In aircraft equipped with an air data computer, TAT probes are also used to calculate true airspeed and Mach number. In simpler aircraft without the capacity to calculate airspeed, pilots may use a handheld E6B flight computer to make such calculations.  True airspeed represents the actual speed of the aircraft, adjusted for variations in air density based on changes in altitude and temperature. Indicated airspeed is the unadjusted reading based on the pitot-static system. At altitudes close to sea level, average temperatures, and slow speeds, your indicated airspeed and true airspeed are very close, but they begin to diverge as temperature, altitude, and speed change during flight. Once true airspeed is calculated, Mach number can be as well. It is the ratio of the aircraft’s true airspeed and the local speed of sound.

Protecting Your TAT Probes with Sesame Technologies, Inc.

TAT probes are susceptible to many of the same issues as other openings on the surface of aircraft such as damage and blockages caused by insects, debris, and ice. A damaged or blocked TAT probe can lead to incorrect airspeed calculations and potential safety risks. Without accurate TAT data, pilots’ abilities to make decisions about anti-ice measures will be hampered and they may not understand the environmental conditions they are flying in.

Because ice is a common cause of TAT probe blockages, many probes are equipped with a heating element to combat the buildup of ice and snow. That’s why Sesame Technologies, Inc. TAT probe covers are built to withstand heat. If the heating element is accidentally triggered, Sesame’s TAT probe covers will not melt but withstand the heat up to 800°F.

Many TAT sensors, including those made by Collins Aerospace, operate in a range well below this threshold, typically from -94°F to 662°F. Covers made from materials that are not heat resistant may melt, blocking TAT sensors, impairing the pilot’s knowledge of speed and environmental conditions, and compromising safety.

By investing in covers made from heat resistant materials such as DuPont™ Nomex®, aircraft owners can prioritize the safety of their flights, protecting pilots and passengers. Durable covers such as the FTC-102, -102A, and -102EP provide peace of mind by ensuring that your aircraft’s temperature readings remain accurate and reliable, no matter what conditions you’re facing.

By protecting critical flight systems, Sesame Technologies, Inc. enables pilots to make decisions in the air with confidence. Let us be your partner in-flight safety. Reach out today to learn more about our TAT sensor covers and how we can best benefit your operation.

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