For calculations in the troposphere and stratosphere.
In the International Standard Atmosphere (ISA), sea-level pressure, sea-level temperature and temperature variation with altitude are specified. The pressure, density, and other properties within the Earth's atmosphere, appropriate to these conditions, can then be calculated. Aircraft performance is specified under ISA conditions and can be corrected for deviations from ISA occurring in the actual atmosphere in which an aircraft operates.
See ESDU 73017 and ESDU 77021 in the ESDU Aerodynamics Series.
Constants used in calculation
Atmospheric Data
Velocity Data
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