Influence of Airspeed Measurement Error – Implications for Dead Reckoning Navigation

Errors in navigational instruments can significantly affect flight safety. Airspeed is a key piece of navigational data that depends on accurately measured air pressure, which in turn depends on accurately measured air temperature. Instead of measuring the outside air temperature in real time, cockpit instruments are preprogramed with standard air temperature values for different flight altitudes, but atmospheric conditions can cause the actual temperature to deviate substantially from these standard values. In the present study, test flights were conducted under various atmospheric conditions to examine how the actual temperature affects the deviation of the actual airspeed from the measured airspeed. Results indicate that the differences between the actual and the standard temperature, and not those between the actual and the standard pressure, are the primary cause of deviations of the measured from the actual airspeed. The results of this study may help establish aircraft flight models based on more accurate estimates of navigational parameters.