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T 25 is 298.15 K (= 25 °C = 77 °F), giving a value of 346.1 m/s (= 1 135.6 ft/s = 1246 km/h = 774.3 mph = 672.8 kn). In fact, assuming an ideal gas , the speed of sound c depends on temperature and composition only, not on the pressure or density (since these change in lockstep for a given temperature and cancel out).
Speed limit sign in the Republic of Ireland, using "km/h.". The SI representations, classified as symbols, are "km/h", "km h −1" and "km·h −1".Several other abbreviations of "kilometres per hour" have been used since the term was introduced and many are still in use today; for example, dictionaries list "kph", [3] [4] [5] "kmph" and "km/hr" [6] as English abbreviations.
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):
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.
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)),
The Mach number (M or Ma), often only Mach, (/ m ɑː k /; German:) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound.
The fastest wind speed not related to tornadoes ever recorded was during the passage of Tropical Cyclone Olivia on 10 April 1996: an automatic weather station on Barrow Island, Australia, registered a maximum wind gust of 113.3 m/s (408 km/h; 253 mph; 220.2 kn; 372 ft/s) [6] [7] The wind gust was evaluated by the WMO Evaluation Panel, who found ...
Some airspeed indicators in aircraft prior to the mid-1970s indicate in miles per hour plus knots (1 knot = 1.15 mph) or kilometers per hour (1 knot = 1.85 km/h). A primary flight display with the indicated airspeed (IAS) displayed in the form of a vertical "tape" on the left.