IAS and Navigation
For navigation, it is necessary to convert IAS to TAS and/or ground speed (GS) using the following method:
- correct IAS to calibrated airspeed (CAS) using an aircraft-specific correction table;
- correct CAS to true airspeed (TAS) by using Outside Air Temperature (OAT), Pressure-altitude and CAS on an E6B flight computer or equivalent functionality on most GPSs;
- convert TAS to ground speed (GS) by allowing for the effect of wind.
With the advent of Doppler radar navigation and, more recently, GPS receivers, with other advanced navigation equipment that allows pilots to read ground speed directly, the TAS calculation in-flight is becoming unnecessary for the purposes of navigation estimations.
TAS is the primary method to determine aircraft's cruise performance in manufacturer's specs, speed comparisons and pilot reports.
Read more about this topic: Indicated Airspeed