international standard atmosphere


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international standard atmosphere (ISA)

international standard atmosphere (ISA)click for a larger image
Atmosphere in which the sea level pressure is 1013.25 hectopascals, temperature is 15°C, air density is 0.002378 slugs/ft3 or 1.225 kg/m3, acceleration due to gravity is 32.174 ft/s2 (9.809 m/s2), and the speed of sound is 761 mph, or 1116.4 ft/s (1225.35 km/h). It has a uniform lapse rate until the temperature drops to −56.5°C, at 36,090 ft (11 km), after which the temperature is constant until tropopause. All aerodynamic calculations are based on the ISA. See also ICAN atmosphere.
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