Groundspeed

Groundspeed is the actual speed of an aircraft over the ground — the combination of true airspeed (TAS) and the wind component along the flight path. Groundspeed is what determines arrival time and fuel consumption on a specific route.

Groundspeed vs. Airspeed

Airspeed is the speed through the air mass. Groundspeed is the speed over the ground. In a headwind, groundspeed = TAS − headwind component. In a tailwind, groundspeed = TAS + tailwind component. An aircraft with a TAS of 120 knots flying into a 30-knot headwind has a groundspeed of only 90 knots.

GPS Groundspeed

Modern GPS receivers provide a direct readout of groundspeed from the rate of position change. This replaces the need for the traditional wind triangle calculation for in-flight groundspeed determination. However, pilots should still understand the wind triangle to cross-check and for situations where GPS is unavailable.

On the TC Written Exam

Groundspeed calculations using the flight computer (E6-B) are a core navigation exam topic. Know how to solve the wind triangle: given TAS, true course, and wind, find groundspeed and true heading.

Related Terms

See also: True Airspeed, Dead Reckoning, Heading.