uwochris
Flightinfo's sexiest user
- Joined
- Dec 21, 2001
- Posts
- 381
CEO,
I had the exact same problems as you are having now... I would highly recommend you take a meteorology course at university (as I got to do) or read up on met in other books, especially those non-aviation related as they tend to get into more detail.
First off, colder air does not necessarily imply higher pressure than warmer air. It is possible to have an altimeter setting of 29.63 on a cold day, and the same setting on a warm day as well. Also, you can have a setting of 30.02 on a cold day, and on a hot day as well. Temperature is only one of variables to consider, there are others.
Second of all, the reason why your altimeter underreads in cold air has to do with the workings of the altimeter. You see, the altimeter is nothing more than an aneroid barometer that registers changes in height as the surrounding pressure changes. Now, since cold air tends to be more dense than warm air, the rate of pressure decrease with height is greater in cold air than it is in warm air, and so the constant pressure level at which you fly at (recall- since the altimeter is a barometer, pilots do not fly at constant altitudes, but at constant pressure levels) in colder air will be lower than it is in warmer air. It all has to do with the rate of pressure change with altitude, which in turn is affected by air densities, which in turn is affected by temperature (and other factors, such as moisture content).
I hope this helps a bit.
I had the exact same problems as you are having now... I would highly recommend you take a meteorology course at university (as I got to do) or read up on met in other books, especially those non-aviation related as they tend to get into more detail.
First off, colder air does not necessarily imply higher pressure than warmer air. It is possible to have an altimeter setting of 29.63 on a cold day, and the same setting on a warm day as well. Also, you can have a setting of 30.02 on a cold day, and on a hot day as well. Temperature is only one of variables to consider, there are others.
Second of all, the reason why your altimeter underreads in cold air has to do with the workings of the altimeter. You see, the altimeter is nothing more than an aneroid barometer that registers changes in height as the surrounding pressure changes. Now, since cold air tends to be more dense than warm air, the rate of pressure decrease with height is greater in cold air than it is in warm air, and so the constant pressure level at which you fly at (recall- since the altimeter is a barometer, pilots do not fly at constant altitudes, but at constant pressure levels) in colder air will be lower than it is in warmer air. It all has to do with the rate of pressure change with altitude, which in turn is affected by air densities, which in turn is affected by temperature (and other factors, such as moisture content).
I hope this helps a bit.
