Altimeter-and-VSI (1).pdf

The standard temperature pressure setting is 29.92 ‘’Hg This is the vertical distance above the theoretical plane where atmospheric pessure is equal to 29.92 in. Hg. The theoretical pressure line is referred to as the standard datum plane. Pressure altitude is the height above the standard datu...

The standard temperature pressure setting is 29.92 ‘’Hg This is the vertical distance above the theoretical plane where atmospheric pessure is equal to 29.92 in. Hg. The theoretical pressure line is referred to as the standard datum plane. Pressure altitude is the height above the standard datum plane when 29.92 is set in the altimeter scale Is indicated altitude corrected to compensate for instrument error Absolute altitude is the height, or vertical distance, above the surface. The actual height of the airplane above the earth' s surface. It is commonly referred to as height above ground level (AGL). A blockage of the static system also affect the altimeter and VSI. Trapped static air pressure causes the altimeter to freeze at the altitude which the blockage occurred and VSI will have a zero indication. A blocked static system affects all pitot static instruments in some way In some airplanes there is an alternate static source it is vented inside the cockpit whre ambient air pressure is lower than static pressure. As a result minor pitot-static can occur.