Airspeed Calculator

Convert indicated airspeed to true airspeed using pressure altitude and temperature for low-speed (incompressible) flight.

knots
ft
°C

True Airspeed (TAS)

280.6 knots

True Airspeed144.4 m/s
Density Ratio (sigma)0.7936

True Airspeed (TAS) vs Indicated Airspeed (IAS)

Vedi formula →

Formula

## Indicated vs True Airspeed Indicated airspeed (IAS) is what the pitot-static system reads, calibrated for sea-level standard density. As altitude increases and air density decreases, the true airspeed (TAS) becomes higher than the indicated reading. ### Simplified Relationship **TAS = IAS / sqrt(sigma)** where sigma is the density ratio (local density divided by sea-level standard density). This approximation is valid for low subsonic speeds where compressibility effects are negligible.

Esempio Risolto

An aircraft reads 250 KIAS at 10,000 ft pressure altitude with OAT of -5°C.

  1. 01ISA temperature at 10,000 ft = 15 - 1.981 × 10 = -4.81°C
  2. 02Temperature ratio component = 288.15 / 268.15 = 1.0746
  3. 03Pressure ratio component = (1 - 0.000006875 × 10000)^4.2561 = 0.6877
  4. 04Density ratio sigma = 1.0746 × 0.6877 = 0.7392
  5. 05TAS = 250 / sqrt(0.7392) = 250 / 0.8598 = 290.8 knots