FFF,. .. .you say you are not an airline pilot, i sure hope that when you fly those pipers of yours, you don't go anywhere cold. Your story about true altitude is incorrect, the opposite is true. . .When the temperature drops, the density increases. This means that when you fly at 1000' from a warm area into a cold area the volume of air below you will shrink. In order to maintain that 1000' on your altimeter you will have to descend. Therefore your true altitude will decrease and you will have to correct for it if your flying in very cold weather. From -15C to -30C increase your MOCA/MORA by 10%. Ever heard of:"From high to low, look out below"? This is about density, and of you know density is temperature and pressure related.. .Happy landings. <img border="0" title="" alt="[Smile]" src="smile.gif" />. . . . <small>[ 26 March 2002, 10:00: Message edited by: N4641P ]</small>