airspeed indicator

Aeron.
a flight instrument showing the airspeed of an aircraft. Abbr.: ASI

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      instrument that measures the speed of an aircraft relative to the surrounding air, using the differential between the pressure of still air (static pressure) and that of moving air compressed by the craft's forward motion (ram pressure); as speed increases, the difference between these pressures increases as well.

      Pressures are measured by a Pitot tube, a U-shaped apparatus with two openings, one perpendicular to the flow of air past the aircraft and one facing directly into the flow. Mercury or a similar liquid fills the bend in the tube, forming parallel columns balanced by the air pressure on each side. When static and ram pressure are equal, the columns have the same height. As the ram pressure increases, mercury on that side of the tube is pushed back and the columns become imbalanced. The difference between the two columns can be calibrated to indicate the speed; this value, called the indicated airspeed, may be given in knots, miles per hour, or other units.

      Since the airspeed indicator is calibrated at standard temperature and pressure, its readings are inaccurate at different temperatures and altitudes. An (uncorrected) indicated airspeed is still used to estimate an aircraft's tendency to stall. Instruments that electronically correct for altitudinal differences and temperature give the true airspeed, which is used to calculate the aircraft's position. In faster aircraft, indicators that measure airspeed relative to the speed of sound, called Machmeters, are used.

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Universalium. 2010.

Look at other dictionaries:

  • Airspeed indicator — The airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the craft s airspeed, typically in knots, to the pilot. Markings Light aircraft Airspeed indicator markings use a set of standardized colored bands and lines …   Wikipedia

  • airspeed indicator — greičio rodytuvas statusas T sritis Gynyba apibrėžtis Prietaisas, kuris rodo orlaivio greitį ore, nustatytą pagal Pito vamzdelių ir statinio slėgio duomenis. atitikmenys: angl. airspeed indicator pranc. badin; indicateur de vitesse air …   NATO terminų aiškinamasis žodynas

  • airspeed indicator — noun or airspeed meter : a dial gauge showing the airspeed of an aircraft * * * Aeron. a flight instrument showing the airspeed of an aircraft. Abbr.: ASI …   Useful english dictionary

  • airspeed indicator — An instrument which displays the indicated airspeed of the aircraft derived from inputs of pitot and static pressures …   Military dictionary

  • airspeed indicator — noun An instrument that displays an aircrafts current airspeed …   Wiktionary

  • airspeed indicator — /ˈɛəspid ɪndəkeɪtə/ (say airspeed induhkaytuh) noun a device in an aeroplane to measure its speed relative to the air …   Australian English dictionary

  • combined airspeed indicator — sudėtinis oro greičio rodytuvas statusas T sritis Gynyba apibrėžtis Prietaisas, kuris kartu rodo orlaivio greitį ir Macho skaičių. atitikmenys: angl. combined airspeed indicator pranc. badin combiné; indicateur combiné de vitesse air …   NATO terminų aiškinamasis žodynas

  • true airspeed indicator — tikrojo skrydžio greičio rodytuvas statusas T sritis Gynyba apibrėžtis Prietaisas, kuris rodo orlaivio greitį ore. atitikmenys: angl. true airspeed indicator pranc. indicateur de vitesse propre …   NATO terminų aiškinamasis žodynas

  • combined airspeed indicator — An instrument which displays both indicated airspeed and mach number …   Military dictionary

  • true airspeed indicator — An instrument which displays the speed of the aircraft relative to the ambient air …   Military dictionary

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