What is OAT in Aviation? (Outside Air Temperature)

Outside Air Temperature (OAT) in aviation refers to the temperature of the air surrounding an aircraft during its flight. It is a crucial parameter that affects various aspects of aviation, including aircraft performance, engine efficiency, and aircraft systems. OAT is measured in degrees Celsius (°C) or Fahrenheit (°F) and is influenced by various factors such as altitude, humidity, and weather conditions. Understanding and accurately monitoring OAT is essential for pilots and aviation professionals to ensure safe and efficient flight operations.

How is outside air temperature measured?

In aviation, there are several methods to measure outside air temperature. The most commonly used method is through the use of a temperature probe or sensor. These sensors are typically located on the exterior of the aircraft, exposed to the airflow. They detect the temperature of the ambient air by using temperature-sensitive elements such as thermocouples or resistance temperature detectors (RTDs).

The sensor converts the temperature into an electrical signal, which is then transmitted to the cockpit instruments for display and analysis. Pilots can monitor the OAT using dedicated instruments such as the Outside Air Temperature Indicator (OATI) or through a multifunction display (MFD) integrated into the aircraft’s avionics system.

It’s worth mentioning that the measurement of OAT is affected by factors such as aircraft speed and positioning. As the aircraft moves through the air, it may experience a rise in temperature due to compressibility effects. To account for this, accurate measurements are typically obtained when the aircraft is in unaccelerated flight, referred to as true airspeed (TAS) or calibrated airspeed (CAS).

Why is outside air temperature important in aviation?

The outside air temperature plays a critical role in aviation, influencing various aspects of flight operations. Let’s take a closer look at why it is important:

1. Aircraft Performance

OAT significantly affects aircraft performance. As the temperature increases, the air density decreases, resulting in reduced engine performance and aerodynamic efficiency. This translates into longer takeoff distances, reduced climb rates, and decreased aircraft maneuverability. Pilots must account for these effects when planning their flight, especially in extreme temperature conditions.

For instance, at high temperatures, the engines may produce less thrust, affecting an aircraft’s ability to achieve the desired climb rate or maintain a specific airspeed. In these situations, pilots may need to adjust their flight profiles, including reducing the aircraft’s weight or altering the route to mitigate performance limitations.

On the other hand, in cold temperatures, the air density increases, providing better engine and aerodynamic performance. This can result in shorter takeoff distances and more efficient climbs. However, pilots must also be aware of the potential hazards associated with icing conditions during cold weather flights.

2. Flight planning and fuel calculations

OAT is a crucial factor in flight planning and fuel calculations. It directly affects the aircraft’s fuel consumption, as colder temperatures increase the density of the fuel, resulting in higher fuel burn rates. Understanding the OAT enables pilots and dispatchers to accurately estimate the required amount of fuel for a particular flight.

Additionally, OAT is considered when determining the aircraft’s maximum takeoff weight and landing performance. Warmer temperature conditions may limit the maximum weight at which an aircraft can safely take off or land due to reduced engine performance and the need for longer runway distances.

Moreover, the OAT also affects the aircraft’s range and endurance. As the air density decreases with higher temperatures, the aircraft may experience reduced range due to increased fuel consumption. Pilots need to consider these factors during flight planning to ensure they have sufficient fuel reserves for the entire journey, accounting for temperature variations at different altitudes.

3. Engine Monitoring and Systems

OAT is crucial for monitoring engine performance and ensuring the health of the aircraft’s systems. High or low OAT readings can indicate potential engine malfunctions or irregularities. For example, abnormally high OAT readings could point to engine overheating or inadequate cooling, requiring pilots to take immediate action and possibly divert the aircraft to a nearby airport for inspection and maintenance.

Furthermore, OAT is essential for the correct functioning of anti-icing and de-icing systems. These systems are designed to prevent ice accumulation on critical surfaces, such as wings, tail, and engine components, which can disrupt airflow and reduce the aircraft’s performance. Pilots rely on accurate OAT measurements to determine whether these systems should be activated or deactivated during flight.

The OAT also affects cabin temperature control in passenger aircraft. The air conditioning and heating systems on board adjust the temperature based on the OAT readings to maintain a comfortable environment for passengers and crew.


Outside Air Temperature (OAT) is a critical parameter in aviation that impacts various aspects of flight operations, including aircraft performance, fuel calculations, and engine monitoring. Accurate measurement and understanding of OAT are essential for pilots to plan and execute safe and efficient flights. By considering the effects of OAT, pilots can optimize their flight profiles, ensure fuel efficiency, and effectively manage their aircraft systems.

Next time you hop on a plane and look out into the sky, remember that the outside air temperature is not just a number, but an essential factor that contributes to the safe and successful journey to your destination.

For More: What is A/T in Aviation? (Autothrottle)