![]() Therefore, for a given CAS, TAS increases as altitude increases or for a given TAS, CAS decreases as altitude increases.Ī pilot can find TAS by two methods. True Airspeed is Calibrated Airspeed (CAS) corrected for altitude and nonstandard temperature.īecause air density decreases with an increase in altitude, an aircraft has to be flown faster at higher altitudes to cause the same pressure difference between pitot impact pressure and static pressure. You can find the calibrated airspeed for your airplane in the calibration chart of the aircraft manual.Ĭalibrated airspeed is the same as true airspeed when you are flying at sea level under International Standard Atmosphere (ISA) conditions. In the cruising and higher airspeed ranges, IAS and CAS are approximately the same. This error is generally greatest at low airspeeds. ![]() Calibrated Airspeed (CAS)Ĭalibrated Airspeed is Indicated Airspeed (IAS) corrected for installation error and instrument error.Īlthough manufacturers attempt to keep airspeed errors to a minimum, it is not possible to eliminate all errors throughout the airspeed operating range.Īt certain airspeeds and with certain flap settings, the installation and instrument errors may total several knots. Takeoff, landing, and stall speeds listed in the Aircraft Flight Manual (AFM) / Pilot’s Operating Handbook (POH) are IAS and do not normally vary with altitude or temperature. ![]() Manufacturers use this airspeed as the basis for determining aircraft performance. This difference is the dynamic pressure, which translates into a reading. The Airspeed Indicator (ASI) measures the difference between the static pressure from the aircraft’s static ports, and the ram pressure (dynamic + static) from the pitot tube. The direct instrument reading obtained from the Airspeed Indicator (ASI), uncorrected for variations in atmospheric density, installation error, or instrument error.
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