In
aviation
Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' includes fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air craft such as hot air ...
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 fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...
, 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
Flight planning is the process of producing a flight plan to describe a proposed aircraft flight. It involves two safety-critical aspects: fuel calculation, to ensure that the aircraft can safely reach the destination, and compliance with air t ...
, 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 t ...
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 ...
,
cruise 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 unstab ...
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 ...
or
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 his ...
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 phys ...
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 = \frac ...
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 w ...
in dry air is
:
where:
:
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 ...
,
:
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 phys ...
s.
Sources
Outside air temperature can be obtained from the aviation
meteorological 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 t ...
,
[{{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
In aviation, stagnation temperature is known as total air temperature and is measured by a temperature probe mounted on the surface of the aircraft. The probe is designed to bring the air to rest relative to the aircraft. As the air is brought to ...
.
See also
*
Acronyms and abbreviations in avionics
Below are abbreviations used in aviation, avionics, aerospace and aeronautics.
A
B
C
D
E
F
G
H
I
J
K
L
M
N
N numbers (turbines)
O
P
Q
R
S
T
U
V
V speeds
W
X
Y
Z
See also
* List of avia ...
*
Hot and high
In aviation, hot and high is a condition of low air density due to high ambient temperature and high airport elevation. Air density decreases with increasing temperature and altitude. The lower air density reduces the power output from the airc ...
References
Aviation meteorology
Atmospheric temperature