Atmosphere

International Standard Atmospheric (ISA) model

Only metric units are used.

Functions

• T Atmospheric temperature [K]

• p Air pressure [Pa]

• ρ Air density [kg/m³]

• a Speed of sound [m/s]

• Vcas2Vtas True airspeed Vtas [m/s] as a function of the calibrated airspeed Vcas [m/s]

• Vtas2Vcas Calibrated airspeed Vcas [m/s] as a function of the True airspeed Vtas [m/s]

• M2Vtas True airspeed Vtas [m/s] as a function of the Mach number

• Vtas2M Mach as a function of the True airspeed Vtas [m/s]

• M2Vcas Calibrated airspeed Vcas [m/s] as a function of the Mach number

• Vtas2M Mach as a function of the True airspeed Vtas [m/s]

• Hp_trans Transition altitude [m]

• θ temperature ratio

• δ pressure ratio

• σ density ratio

Constants

• T₀ Standard atmospheric temperature [K] at Mean Sea Level (MSL)
• p₀ Standard atmospheric pressure [Pa] at Mean Sea Level (MSL)
• ρ₀ Standard atmospheric density [kg/m³] at Mean Sea Level (MSL)
• a₀ Speed of sound [m/s] at Mean Sea Level (MSL)
• κ Adiabatic index of air []
• μ constant used for Vtas<->Vcas conversion
• R Real gas constant for air [M²/(Ks²)]
• g₀ Graviation acceleration [m/s²]
• βT∇ ISA temperature gradient [K/m] with altitude below the tropopause
• Hp_trop Geopotential pressure altitude [m] of Tropopause

Source: EUROCONTROL BADA 4 User Manual Chapter 2.2 Atmosphere Model