Sea-Level Standard Atmosphere (SLSA)
Overview[edit | edit source]
The Sea-Level Standard Atmosphere (SLSA) is a hypothetical model representing the Earth's atmosphere at sea level, defining standard values for pressure, temperature, and density. It is not a real-time depiction but a reference used for calculations and comparisons in aviation and engineering.
Standard Values[edit | edit source]
- Temperature: 15°C (59°F) or 288.15 K
- Pressure: 101,325 Pascals (1013.25 millibars or 760 mmHg)
- Density: 1.225 kg/m³
Purpose[edit | edit source]
SLSA is used for a variety of applications:
- Pressure altimeter calibrations
- Aircraft performance calculations
- Aircraft and missile design
- Ballistic tables
- Aviation standards and flying rules
Historical Context[edit | edit source]
Early Development (1920s)[edit | edit source]
The concept emerged from international agreements made in the 1920s.
U.S. Standard Atmosphere (1958)[edit | edit source]
First published by the U.S. Committee on Extension to the Standard Atmosphere. It has been updated in 1962, 1966, and 1976.
International Standard Atmosphere (ISA)[edit | edit source]
Developed by the International Civil Aviation Organization (ICAO), the ISA defines atmospheric properties with altitude at mid-latitudes.
ICAO Standard Atmosphere (1993)[edit | edit source]
Extended the altitude coverage to 80 kilometers and formalized in ICAO Doc 7488-CD.
Current Use[edit | edit source]
The 1976 U.S. Standard Atmosphere and the ISA are the primary standards in aviation today.