I believe one atmosphere is still 100 kPa, the 1013,25 comes from the International Standard Atmosphere.
Commonly referred to as the ISA it's what manufacturers use to calibrate instruments and what aircraft makers use to calibrate the performance of aircraft. In the aviation world we constantly refer to the temperature being below or above ISA, the lapse rate is fixed under ISA as 1.98 C up to 36090 (11000 m) where it's supposed to be constant. Obviously in the real world it changes which has an affect on performance. Mike Payne On 03/09/2011, at 13:57 , G. Stanley Doore wrote: > The 1013.25 mbar (101.325 kPa) pressure for altimeter settings is NOT > "arbitrary" as Kilopascal & Wiki write. The standard altimeter setting for > worldwide altimeter settings was determined from the mean surface pressure > level. > Stan Doore > > On Sep 3, 2011 11:36 AM, "Michael Payne" <[email protected]> wrote:
