What is Air Pressure?
Pressure is basically the air that we feel around if we go out.
In aviation, to express ‘pressure’, the term HPA (hecto pascal) in Europe or I.n. of mercury in the U.S
is being used.
Pressure is the result of our weather systems and varies everywhere. It usually decreases with an increase in altitude. What does that mean? The pressure on the ground is always higher compared to the
pressure at a given distance above ground level (for example – 300 ft). And vice versa of course.
What is the standard decrease of pressure?
pressure at MSL = 30.06 I.n. → pressure at 500ft AGL = 30.04 I.n.
1013.0 hPa → pressure at 500 AGL = 1011.0 hPa