aviation Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' includes airplane, fixed-wing and helicopter, rotary-wing types, morphable wings, wing-less lifting bodies, as well as aerostat, lighter- ...

terminology, the outside air temperature (OAT) or static air temperature (SAT) refers to the temperature of the air around an

aircraft An aircraft is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or by using the Lift (force), dynamic lift of an airfoil, or in ...

, but unaffected by the passage of the aircraft through it.http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/897d269dbf5d731b8625766400563924/$FILE/AC%20251419-2.pdf

Aviation usage

The outside air temperature is used in many calculations pertaining to flight planning, some of them being

takeoff Takeoff is the phase of flight in which an aerospace vehicle leaves the ground and becomes airborne. For aircraft traveling vertically, this is known as liftoff. For aircraft that take off horizontally, this usually involves starting with a ...

performance,

density altitude The density altitude is the altitude relative to standard atmospheric conditions at which the air density would be equal to the indicated air density at the place of observation. In other words, the density altitude is the air density given as a ...

cruise A cruise is any travel on a cruise ship. Cruise or Cruises may also refer to: Tourism * Booze cruise * Music cruise * River cruise Aeronautics and aircraft * Cruise (aeronautics), a distinct stage of an aircraft's flight * Aviasouz Cruise, a R ...

performance and

go-around In aviation, a go-around is an aborted landing of an aircraft that is on final approach or has already touched down. A go-around can either be initiated by the pilot flying or requested by air traffic control for various reasons, such as an unsta ...

performance. In most texts, the abbreviation, "OAT" is used.

Units

Most performance and flight planning graphs and tables use either degrees

Celsius The degree Celsius is the unit of temperature on the Celsius scale (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the Kelvin scale. The d ...

Fahrenheit The Fahrenheit scale () is a temperature scale based on one proposed in 1724 by the physicist Daniel Gabriel Fahrenheit (1686–1736). It uses the degree Fahrenheit (symbol: °F) as the unit. Several accounts of how he originally defined hi ...

or both. The

Kelvin The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and ...

scale, however, is used for

Mach number Mach number (M or Ma) (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound. It is named after the Moravian physicist and philosopher Ernst Mach. : \mathrm = \f ...

calculations. For example, the

speed of sound The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. At , the speed of sound in air is about , or one kilometre in or one mile in . It depends strongly on temperature as we ...

in dry air is :

= 38.945 \sqrt,

where: :

c

is the speed of sound in

knots A knot is a fastening in rope or interwoven lines. Knot may also refer to: Places * Knot, Nancowry, a village in India Archaeology * Knot of Isis (tyet), symbol of welfare/life. * Minoan snake goddess figurines#Sacral knot Arts, entertainme ...

, :

K

is the outside air temperature in

kelvin The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and ...

Sources

Outside air temperature can be obtained from the aviation

meteorological Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not ...

services, on the ATIS or measured by a probe on the aircraft. When measured by the airplane's probe in flight, it may have to be corrected for adiabatic (ram effect) rise and

friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of ...

,{{cite web, url=https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/, title=Pilot's Handbook of Aeronautical Knowledge, work=Federal Aviation Administration, date=2016-08-24 particularly in high performance aircraft. Therefore, the outside air temperature is usually calculated from the total air temperature.

References

Aviation meteorology Atmospheric temperature

Aviation usage

Units

Sources

See also

References