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The Mach number is named after the physicist and philosopher Ernst Mach [3] according to a proposal by the aeronautical engineer Jakob Ackeret in 1929. [4] The word Mach is always capitalized since it derives from a proper name, and since the Mach number is a dimensionless quantity rather than a unit of measure, the number comes after the word Mach; the second Mach number is Mach 2 instead of ...
True airspeed. 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 is commonly given in knots (kn). Since 2010, the International Civil Aviation Organization (ICAO) recommends using kilometers per hour (km/h) for airspeed (and meters per second for wind speed on runways), but allows using the de facto standard of knots, and has no set date on when to stop.
Indicated airspeed (IAS) is the airspeed of an aircraft as measured by its pitot-static system [1] and displayed by the airspeed indicator (ASI). [2] This is the pilots' primary airspeed reference. This value is not corrected for installation error, instrument error, or the actual encountered air density, [2] being instead calibrated to always ...
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):
Machmeter. A Machmeter is an aircraft pitot-static system flight instrument that shows the ratio of the true airspeed to the speed of sound, a dimensionless quantity called Mach number. This is shown on a Machmeter as a decimal fraction. An aircraft flying at the speed of sound is flying at a Mach number of one, expressed as Mach 1.
Simulation of hypersonic speed (Mach 5) While the definition of hypersonic flow can be quite vague and is generally debatable (especially due to the absence of discontinuity between supersonic and hypersonic flows), a hypersonic flow may be characterized by certain physical phenomena that can no longer be analytically discounted as in supersonic flow.
Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately 343.2 m/s (1,126 ft/s; 768 mph; 667.1 kn; 1,236 km/h). Speeds greater than five times the speed of sound (Mach 5) are often referred to as hypersonic.