https:\/\/skybrary.aero\/articles\/international-standard-atmosphere-isa<\/a><\/p>\r\n\r\n\r\n\r\n <\/p>\r\n\r\n\r\n\r\n
ISA is known as the ICAO Standard Atmosphere, ISA is a standard against which to compare the actual atmosphere at any point and time.<\/p>\r\n\r\n\r\n\r\n
ISA condition, at mean sea level:<\/p>\r\n\r\n\r\n\r\n
\r\n- Pressure of 1013.2 millibar<\/li>\r\n\r\n\r\n\r\n
- Pressure fall at about 1 millibar per 30 feet (up to about 5,000 feet)<\/li>\r\n\r\n\r\n\r\n
- Temperature of +15 \u00b0C\u00a0<\/li>\r\n\r\n\r\n\r\n
- Temperature falls at a rate of\u00a02 \u00b0C\u00a0per\u00a01,000 feet\u00a0(more precisely 1.98C) until the tropopause is reached at\u00a036,000 feet\u00a0<\/li>\r\n\r\n\r\n\r\n
- above tropopause the temperature is assumed to be constant at -56.5 \u00b0C\u00a0<\/li>\r\n\r\n\r\n\r\n
- Density of 1,225 kg\/m3<\/li>\r\n<\/ul>\r\n
<\/p>\r\n