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True airspeed (TAS) is the actual speed the airplane is moving through the air. When combined with aircraft direction, wind speed and direction, it can be used to calculate ground speed and direction. Equivalent airspeed (EAS) is true airspeed times root density ratio. It is a useful way of calculating aerodynamic loads and airplane performance ...
An airspeed indicator indicates the aircraft's speed relative to the air mass it is flying through. The air mass may be moving over the ground due to wind, and therefore some additional means to provide position over the ground is required to determine ground speed. This might be through navigation using landmarks, radio aided position location ...
The IAS is not the actual speed through the air even when the aircraft is at sea level under International Standard Atmosphere conditions (15 °C, 1013 hPa, 0% humidity). The IAS needs to be corrected for known instrument and position errors to show true airspeed under those specific atmospheric conditions, and this is the CAS (Calibrated ...
TAS can be calculated as a function of Mach number and static air temperature: =, where is the speed of sound at standard sea level (661.47 knots (1,225.04 km/h; 340.29 m/s)),
where a 0 is 1,225 km/h (661.45 kn) (the standard speed of sound at 15 °C), M is the Mach number, P is static pressure, and P 0 is standard sea level pressure (1013.25 hPa). Combining the above with the expression for Mach number gives EAS as a function of impact pressure and static pressure (valid for subsonic flow):
Approximation of the speed of sound in dry air based on the heat capacity ratio (in green) against the truncated Taylor expansion (in red) In addition, we switch to the Celsius temperature θ = T − 273.15 K, which is useful to calculate air speed in the region near 0 °C (273 K).
Unpowered aircraft range depends on factors such as cross-country speed and environmental conditions. The range can be seen as the cross-country ground speed multiplied by the maximum time in the air. The fuel time limit for powered aircraft is fixed by the available fuel (considering reserve fuel requirements) and rate of consumption.
The true ground speed is determined by matching the center hole to the speed portion of the grid. The mathematical formulas that equate to the results of the flight computer wind calculator are as follows: (desired course is d, ground speed is V g, heading is a, true airspeed is V a, wind direction is w, wind speed is V w. d, a and w are angles.