ATMOS

Standard atmosphere lookups, airspeed conversions and speed-altitude charts — run it in the browser

ATMOS is a small standard-atmosphere and air-data tool. It interpolates a tabulated atmospheric model, converts between Mach and true, calibrated and equivalent airspeed (subsonic and supersonic, using the Rayleigh pitot formula above Mach 1), and draws speed-altitude charts with optional V_MO/M_MO-style envelope boundaries. The desktop version is a terminal program; this page runs the same engine (source). Nothing you enter is stored.

Atmospheric properties

Atmospheric model Nelson, Flight Stability and Automatic ControlUS Standard Atmosphere 1976

Given Pressure altitudeStatic pressure

Value

Units ftm psfpsiPaatmbar

compute

Speed conversion

Atmospheric model Nelson, Flight Stability and Automatic ControlUS Standard Atmosphere 1976

Pressure altitude

Altitude units ftm

Given MachKTASKCASKEAS

Speed

Speed units (not used for Mach) ktsm/s

convert

Speed-altitude chart

Atmospheric model Nelson, Flight Stability and Automatic ControlUS Standard Atmosphere 1976

Horizontal axis KCASKEASKTAS

Speed envelope None — grid onlyExample 777 Speed Envelope

draw

Pressure altitude vs KCAS — Example 777 Speed Envelope

Constant KCAS (blue, solid), KEAS (green, dashed), KTAS (coral, dotted) and Mach (grey) lines.