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In aviation, pressure altitude is the height above a standard datum plane (SDP), which is a theoretical level where the weight of the atmosphere is 29.921 inches of mercury (1,013.2 mbar; 14.696 psi) as measured by a barometer. [2]
In aviation, a flight level (FL) is an aircraft's altitude as determined by a pressure altimeter using the International Standard Atmosphere. It is expressed in hundreds of feet or metres. The altimeter setting used is the ISA sea level pressure of 1013 hPa or 29.92 inHg. The actual surface pressure will vary from this at different locations ...
SPS/STD - 'Standard Pressure Setting' or just 'Standard' refers to the altimeter being set to the standard pressure of 1013.25 hPa. It is the setting that causes an altimeter to read the aircraft's flight level (FL). Flight levels are given in hundreds of feet (for example: FL100 = 10 000 ft). Atmospheric pressure changes over time and position.
at each geopotential altitude, where g is the standard acceleration of gravity, and R specific is the specific gas constant for dry air (287.0528J⋅kg −1 ⋅K −1). The solution is given by the barometric formula. Air density must be calculated in order to solve for the pressure, and is used in calculating dynamic pressure for moving vehicles.
Air pressure decreases with an increase of altitude—approximately 100 hectopascals per 800 meters or one inch of mercury per 1000 feet or 1 hectopascals per 30 feet near sea level. The aneroid altimeter is calibrated to show the pressure directly as an altitude above mean sea level , in accordance with a mathematical model atmosphere defined ...
Pressurization becomes increasingly necessary at altitudes above 10,000 ft (3,048 m) above sea level to protect crew and passengers from the risk of a number of physiological problems caused by the low outside air pressure above that altitude. For private aircraft operating in the US, crew members are required to use oxygen masks if the cabin ...
A pitot–static system is a system of pressure-sensitive instruments that is most often used in aviation to determine an aircraft's airspeed, Mach number, altitude, and altitude trend. A pitot–static system generally consists of a pitot tube , a static port, and the pitot–static instruments. [ 1 ]
Typical usages are as a basis for pressure altimeter calibrations, aircraft performance calculations, aircraft and rocket design, ballistic tables, and meteorological diagrams." [1] For example, the U.S. Standard Atmosphere derives the values for air temperature, pressure, and mass density, as a function of altitude above sea level.