|Quoting c5load (Thread starter):|
My question is why?
|Quoting Northwest727 (Reply 4):|
Imagine how many times a pilot would theoretically have to reset his/her altimeter on a coast-coast flight, especially crossing multiple pressure systems (mid latitude cyclones).
|Quoting ShyFlyer (Reply 6):|
To further expand, 29.92 is used as it is the pressure used in the International Standard Atmosphere model.
|Quoting moose135 (Reply 2):|
What pressure reading would you use? The one from the airport you took off from? How about the guy coming the other way, with a different pressure reading from the airport 1,500 miles away which departed from? To provide positive altitude control, everyone uses the same setting, so you don't have aircraft that should be at different altitudes running into one another.
|Quoting zeke (Reply 10):|
No it is not, it is 1013.25 HPa.
The most commonly used atmosphere model is the International Civil Aviation Organization (ICAO) Standard Atmosphere, of which the main part is the International Standard Atmosphere (ISA). At all altitudes of interest to an aircraft performance engineer, the ISA model is the same as that of the 1976 U.S. Standard Atmosphere, and the MIL-STD Standard Atmosphere.