ISA Conditions MET

The International Standard Atmosphere (ISAISA —International Standard Atmosphere) provides a reference that aircraft engineers can use to calibrate aircraft performance. If the difference from ISAISA —International Standard Atmosphere is known, pilots can then use that information to calculate the performance of the aircraft on that particular day. Knowing ISAISA —International Standard Atmosphere conditions will be required for many of the ATPLATPL —Airline Transport Pilot Licence subjects, and the required numbers are +15°C, 1013.25hPa, 1.225kg/m3 (all at mean sea level) and a roughly 2°C/1000' temperature lapse rate. Watch out for the examiner switching the numbers around and throwing in spurious units - metres instead of feet, fahrenheit instead of celsius, Pa instead of hPahPa —Hectopascal - to give wrong answers.