Pressure is measured in pounds per square inch (PSI). If the pressure on one surface of the object becomes less than the pressure exerted on the other surfaces, the object will move in the direction of the lower pressure.
There are multiple kinds of pressure. As pilots the main pressure we need to be a where of is atmospheric pressure. This pressure is everywhere and is one of the factors in weather changes, helps in lift of the aircraft, and actuates some of the important flight instruments.
Altimeter
Airspeed Indicator
Vertical Speed Indicator (VSI)
Manifold pressure gauge
Atmospheric pressure
Atmospheric pressure affects weather changes, allows aircraft to lift and gives information to important flight instruments. As mentioned earlier, air has weight. At sea level under standard conditions the atmosphere weighs approximately 14.7 pounds per square inch (psi). As you go higher in altitude the atmospheres weight at 18,000 feet is one-half than sea level.
The atmospheric pressure varies with location. The reference for the standard atmospheric temperature at sea level is 15 degrees Celsius and the standard pressure at sea level is 29.92 inches of mercury.
Pressure altitude
Pressure altitude is the height above a standard datum plane (SDP), which is a theoretical level where the weight of the atmosphere is 29.92 "Hg (1,013.2 mb) as measured by a barometer.
An aircrafts altimeter is a basically a sensitive barometer.
Is the altitude shown on the altimeter when the pressure is set to 29.92” This can be done at airports that do not have an ATIS or any other weather observation.
Simple set the pressure to 29.92" and ready the altitude.
Remember:
Standard atmospheric temperature at sea level is 15 degrees Celsius.
Standard pressure at sea level is 29.92 inches of mercury.
References:
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