TABLE OF CONTENTS An understanding of airspeed is critical to interpreting and discussing aircraft performance. To this point, we have only dealt with true airspeed. This section addresses indicated, calibrated, equivalent, and ground speed.
A pilot needs a direct indication related to the performance of the aircraft. This is done by measuring, and displaying, airspeed on an airspeed indicator. However, we'll see that the airspeed the pilot reads can be quite different than the true velocity ( V ?) of the aircraft.
First, we will introduce some terminology:
Static pressure ( p) is the pressure because of random molecular motion and is devoid of any contribution from the flow velocity.
Total pressure ( p o) is the pressure that exists at a stagnation point, or would exist at any point in the flow, if it were isentropically slowed to zero velocity.
Indicated airspeed ( V i) is the airspeed displayed in the cockpit and is obtained from pitot-static instrumentation and "fed" into the airspeed indicator.
Calibrated airspeed ( V c) is the indicated airspeed corrected for position error.
Equivalent airspeed ( V e) is the calibrated airspeed corrected for nonstandard sea-level pressure.
True airspeed ( V) is airspeed relative to the air mass. It is equivalent airspeed corrected for non-standard, sea-level density.
Ground speed ( V g) is speed relative to the ground. It is true airspeed corrected for wind.
Position error ( ? V p) is obtained from flight test and...
