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Atmosphere
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
A pressure altimeter measures the pressure of air at the level an aircraft (Figure 1.10) is flying and converts the pressure measurement to an indication of height above sea level according to a standard pressure–altitude relationship. In essence, a pressure altimeter is a highly refined aneroid barometer since it utilizes an evacuated capsule whose movement or force is directly related to the pressure on the outside of the capsule. Various methods are used to sense the capsule function and cause a display to respond such that the pilot sees the altitude level much as one looks at a watch.
A proposed new model for the prediction of latitude-dependent atmospheric pressures at altitude
Published in Science and Technology for the Built Environment, 2021
The most recent definition of the standard atmosphere is the U.S. Standard Atmosphere (1976) developed jointly by the National Oceanic and Atmospheric Administration (NOAA), National Aeronautics and Space Administration (NASA), and the United States Air Force (USAF). The definition of a standard atmosphere stated there is as follows: “A hypothetical vertical distribution of atmospheric temperature, pressure and density which, by international agreement, is roughly representative of year-round, midlatitude conditions. Typical usages are as a basis for pressure altimeter calibrations, aircraft performance calculations, aircraft and rocket design, ballistic tables, and meteorological diagrams. The air is assumed to obey the perfect gas law and hydrostatic equation which, taken together, relate temperature, pressure and density with geopotential. Only one standard atmosphere should be specified at a particular time and this standard atmosphere must not be subjected to amendment except at intervals of many years.” The International Organization for Standardization (ISO) publishes the standard atmosphere as International Standard, ISO 2533:1975 (International Organization for Standardization 1975). The U.S. Standard Atmosphere is the same as the ISO International Standard Atmosphere for altitudes up to 32,000 m. The International Civil Aviation Organization (ICAO 1993) publishes the same atmospheric model under its own standards-making authority.