The Earth
The Solar System & Time
Charts
Using Aeronautical Charts
Basics of Navigation
Distance, Speed & Time
Vertical Navigation
Fuel Planning
Practical Navigation Techniques
Radio Navigation
Practice Exam

Airspeed & Groundspeed

The wind also affects the speed of the aircraft, which leads to the two speeds we use in aviation:

Airspeed – the speed of the aircraft through the air
Groundspeed – the speed of the aircraft over the ground

Picture a hot air balloon in the sky – by using a flame, the pilot can control its climb or descent but it can only move forwards when blown by the wind.

So in conditions of nil wind, the balloon will not move forwards.

When the wind starts to blow, the balloon will move forwards with the wind. So the balloon’s groundspeed (speed over the ground) will increase but since the balloon is not moving relative to the wind, its airspeed (speed through the air) will still be 0.

The whole parcel of air moves forwards with the wind, taking the balloon with it. The balloon is still not moving relative to the parcel of air it is in, so the airspeed is zero.

However if you imagine an aircraft in nil wind conditions, it will still be moving forwards since it has power from the engine. With no wind, the aircraft will have the same forward speed through the air as over the ground (airspeed = groundspeed).

If the same wind that pushed the balloon forwards started blowing, the aircraft would get blown forwards with the air. The aircraft’s speed through the air would be the same (airspeed doesn’t change) but because it has the help of the wind pushing it forwards, its groundspeed would be faster than its airspeed (groundspeed changes).

Flying into the wind the aircraft is said to have a headwind (groundspeed slower than airspeed)

Flying away from the wind the aircraft is said to have a tailwind (groundspeed faster than airspeed)