How do I calculate pressure altitude at cruise altitude?
Further to what one answerer had mathematically stated: calculation of Pressure Altitude is done by calc. the difference bet. the current altimeter setting and the standard altimeter setting. The difference is then converted into feet based on the given 1″ Hg = 1000′ (which is refered to as the Standard Pressure Lapse Rate.). Accordingly, if the current altimeter setting is 30.12″ Hg, we would then calc. as follows: 30.12 minus 29.92 = .2 Using the Standard Lapse Rate, .2 is converted to 200 feet. So then if we want to determine the pressure alt. for an airfield we must add or subtract the 200 relative to the airport’s elevation. If we want to calc.the pressure altitude of an intended altitude that we want to cruise at, we must add or subtract the 200′ relative to the planned cruising altitude. The question of adding or subtracting the CORRECTION VALUE is determined by whetehr the current air pressure is higher or lower than standard. Since pressure decreases with altitude —and the c
