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Calibrated airspeed (CAS) is the speed shown by a conventional airspeed indicator after correction for instrument error and position error. Most civilian EFIS displays also show CAS. When flying at sea level under International Standard Atmosphere conditions (15 °C, 1013 hPa, 0% humidity) calibrated airspeed is the same as equivalent airspeed (EAS) and true airspeed (TAS). If there is no wind it is also the same as ground speed (GS). Under any other conditions, CAS may differ from the aircraft's TAS and GS. Calibrated airspeed in knots is usually abbreviated as ''KCAS'', while indicated airspeed is abbreviated as ''KIAS''. In some applications, notably British usage, the expression ''rectified airspeed'' is used instead of calibrated airspeed.〔Clancy, L. J. (1975) ''Aerodynamics'', pp 31, 32. Pitman Publishing Limited, London. ISBN 0 273 01120 0〕 ==Practical applications of CAS== CAS has two primary applications in aviation: * for navigation, CAS is traditionally calculated as one of the steps between indicated airspeed and true airspeed; * for aircraft control, CAS (and EAS) are the primary reference points, since they describe the dynamic pressure acting on aircraft surfaces regardless of density, altitude, wind, and other conditions. EAS is used as a reference by aircraft designers, but EAS cannot be displayed correctly at varying altitudes by a simple (single capsule) airspeed indicator. CAS is therefore a standard for calibrating the airspeed indicator such that CAS equals EAS at sea level pressure and approximates EAS at higher altitudes. With the widespread use of GPS and other advanced navigation systems in cockpits, the first application is rapidly decreasing in importance – pilots are able to read groundspeed (and often true airspeed) directly, without calculating calibrated airspeed as an intermediate step. The second application remains critical, however – for example, at the same weight, an aircraft will rotate and climb at approximately the same calibrated airspeed at any elevation, even though the true airspeed and groundspeed may differ significantly. These V speeds are usually given as IAS rather than CAS, so that a pilot can read them directly from the airspeed indicator. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Calibrated airspeed」の詳細全文を読む スポンサード リンク
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