This glossary is written for virtual airline and flight simulation use within Virtual Air Canada Airline. It is not intended as a real-world aviation reference.
OAT
Outside Air Temperature
Outside Air Temperature is the ambient temperature of the air surrounding the aircraft, measured by sensors mounted on the fuselage away from heat sources. On transport-category aircraft, OAT is displayed on the flight deck as part of the air data system and is referenced during performance calculations at every phase of flight. In standard atmosphere, OAT decreases at approximately 2°C per 1,000 ft of altitude up to the tropopause, above which it remains roughly constant.
OAT directly influences engine thrust, fuel burn, aircraft performance, and the risk of icing. A high OAT on departure reduces air density, which lowers available engine thrust and increases take-off distances - requiring performance corrections to V-speeds and thrust settings. Conversely, cold temperatures improve density altitude and engine performance but introduce risks of ice accretion on airfoils and engine inlets. Crews use OAT in conjunction with ISA deviation (the difference between actual OAT and standard atmosphere temperature) to assess climb performance, cruise Mach limits, and fuel planning.