Speed of an aircraft relative to the air mass through which it is flying
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An analog true airspeed indicator for an airplane. The pilot sets the pressure altitude and air temperature in the top window using the knob; the needle indicates true airspeed in the lower left window. Here the speed is displayed both in knots (kn) and miles per hour (mph).
The true airspeed (TAS; also KTAS, for knots true airspeed) of an aircraft is the speed of the aircraft relative to the air mass through which it is flying. The true airspeed is important information for accurate navigation of an aircraft. Traditionally it is measured using an analogue TAS indicator, but as the Global Positioning System has become available for civilian use, the importance of such air-measuring instruments has decreased. Since indicated, as opposed to true, airspeed is a better indicator of margin above the stall, true airspeed is not used for controlling the aircraft; for these purposes the indicated airspeed – IAS or KIAS (knots indicated airspeed) – is used. However, since indicated airspeed only shows true speed through the air at standard sea level pressure and temperature, a TAS meter is necessary for navigation purposes at cruising altitude in less dense air. The IAS meter reads very nearly the TAS at lower altitude and at lower speed. On jet airliners the TAS meter is usually hidden at speeds below 200 knots (370 km/h). Neither provides for accurate speed over the ground, since surface winds or winds aloft are not taken into account.
The trueairspeed (TAS; also KTAS, for knots trueairspeed) of an aircraft is the speed of the aircraft relative to the air mass through which it is flying...
difficult to measure the exact airspeed of the aircraft (trueairspeed), but other measures of airspeed, such as indicated airspeed and Mach number give useful...
The airspeed indicator (ASI) or airspeed gauge is a flight instrument indicating the airspeed of an aircraft in kilometres per hour (km/h), knots (kn...
indicated airspeed in knots is typically abbreviated KIAS for "Knots-Indicated Air Speed" (vs. KCAS for calibrated airspeed and KTAS for trueairspeed). The...
(15 °C, 1013 hPa, 0% humidity) calibrated airspeed is the same as equivalent airspeed (EAS) and trueairspeed (TAS). If there is no wind it is also the...
at the trueairspeed (TAS) and altitude at which the aircraft is flying. In low-speed flight, it is the speed which would be shown by an airspeed indicator...
high-altitude aerospace vehicles use flight Mach number to express a vehicle's trueairspeed, but the flow field around a vehicle varies in three dimensions, with...
aligned with the air temperature and the pressure altitude, allowing the trueairspeed (TAS) to be read at the needle. In addition, computer programs emulating...
aircraft pitot-static system flight instrument that shows the ratio of the trueairspeed to the speed of sound, a dimensionless quantity called Mach number....
aircraft ground speed rather than airspeed. Ground speed can be determined by the vector sum of the aircraft's trueairspeed and the current wind speed and...
referencing one's indicated airspeed fed by the pressure from a pitot tube. This measurement is converted to an equivalent airspeed based upon known atmospheric...
order to enable the computation of static air temperature and hence trueairspeed. The relationship between static and total air temperatures is given...
aircraft's airfoils, and the relation between its indicated airspeed (IAS) and its trueairspeed (TAS), are also subject to air-density changes. Furthermore...
motion of the aircraft through the airmass. It is described by trueairspeed and true heading. The wind vector represents the motion of the airmass over...
{m}}_{air}(V_{j}-V)} The speed of the jet V j {\displaystyle V_{j}\;} must exceed the trueairspeed of the aircraft V {\displaystyle V\;} if there is to be a net forward...
indicators. The formula for calculating the angle of bank for a specific trueairspeed (TAS) in SI units (or other coherent system) is: ϕ = arctan v t 2...
Va is the freestream fluid velocity in m/s, typically the trueairspeed of the aircraft or the water speed of the vessel n is the rotational speed of...
pressure. The indicated airspeed (IAS) must be corrected for nonstandard pressure and temperature in order to obtain the trueairspeed (TAS). The instrument...
able to provide a Mach number and, if static temperature is known, trueairspeed.[citation needed] Some authors in the field of compressible flows use...
known as total air temperature, to help calculate the aircraft's trueairspeed. Trueairspeed is needed for high altitude navigation, but is not so important...
temperature. This enables computation of static air temperature and trueairspeed. In Airbus aircraft the air data computer is combined with attitude...
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