Adacalc is an accurate aeronautical calculator including the following modules:
Downloads
Adacalc v6.10
Adacalc v5.20 (latest v5 version)
Revision history

Adacalc DLL v3.21
[An aeronautical mathematical library including exported functions to include in C++, C#, VB or .NET programs]
Adacalc DLL documentation

Database editor v6.23
[Allow edition of Adacalc v5.xx and V6.xx databases]
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ICAO standard and non-standard atmosphere: high precision calculation of all atmosphere parameters up to a geopotential altitude of 80 km
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Speed calculations: calculation of any speed (CAS, TAS, EAS, Mach) at a given altitude and temperature, based on exact equations (compressibility equations)
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Changeover level for any IAS-mach pair of values
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Descent calculator based on a 2/3-step precise numerical integration of constant Mach then constant IAS descent segments
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Density and true altitude calculations (with humidity correction)
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Wind calculations
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IFR turn parameters:  bank, rate of turn and radius at constant or limited bank and calculation of turn anticipation angles
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Tracks and distances between 2 points from different earth models (spherical, ellipsoid, loxodromic (spherical and ellipsoid), equirectangular
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Latitude and longitude calculations from track and distance or radials intersection using different earth models
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Magnetic variation (from 2015 to 2025) at any world place calculated from IGRF-12/13 and WMM2015/2020 magnetic models (exact equations)  
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Sunrise, sunset and twilight time values (UTC or local time) calculated from accurate NOAA algorithms
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Unit conversions, stall speed calculation
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Holding pattern data (with wind corrections) and holding entry calculator
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Tiny mathematical calculator
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Aviation weather data (from NOAA) and customizable aviation data links (with provided default set)

An updatable worlwide database is included for modules requiring latitude and longitude entries.
Aero calculator (Adacalc)