What Does Ground Speed And AirSpeed Mean? What is the Difference Between Them?

02/04/2022 M.Durgut 2514 Views Air Speed, Ground speed

Maybe you paid attention during your flight. The speed value in flight information monitor can sometimes reach very high values indicated on the screen, this is quite surprising for those who do not know the details behind.

Sometimes the ground speed of the aircraft seen on the information screen of the aircraft can increase up to 1,200 km. This is quite an exciting speed for those who know that the speed of sound is 1,225 km per hour. But for those familiar with the concepts of Ground speed and Airspeed, it’s pretty commonplace.

Let’s explain AirSpeed – Ground Speed briefly.

The term airspeed refers to the speed of the aircraft relative to the air. The term ground speed refers to the speed of the aircraft relative to the ground. That is, if we consider the concept of ground speed in the simplest form in formula, We can write it as [speed of the plane + speed of the air]. But the addition here is vector addition. That is, we take the component of the wind force that is parallel to the direction of the aircraft and add it with the speed of the aircraft.

Ground Speed Basic Calculation Principle — Ground Speed – Relation Between TAS and Wind

Therefore, when the air flow direction is the same as the airplane, the wind contributes positively, while the opposite is true when the air flow direction and the plane’s direction are opposite each other. Therefore, for example, when the aircraft is cruising at a speed of 950 km, when it enters an air stream with a speed of 200 km and blowing directly from the tail, it is normal to display a figure such as 1,150 km/h in front of the ground speed phrase on the cabin information screens. In the opposite case, a ground speed of 950 – 200 = 750 km can be calculated.

As a result of the Earth’s rotation around its axis, air currents generally move from west to east. As a result, a plane going from Istanbul to Bangkok covers this distance in 8.5 hours, while on the way back, the same distance can only be covered in 10-odd hours. It is possible to encounter these high-speed air currents, especially in the region between Iran and India.

You can also check out a video clip below that explains how high-speed air currents called Jet Streams are formed.

For more detailed article about Ground Speed – True AirSpeed – Indicated AirSpeed and Calculated AirSpeed click.