Why do planes take off and land into the wind?

There's a question that many participants in Fear of Flying courses ask themselves: what impact does the wind have on take-off? To understand its contribution, you need to understand the difference between ground speed and air speed.

The difference between ground speed and air speed

In aeronautics, we take into account two "speed" parameters: a ground speed and an air speed. The ground speed is identical to that of your car; it is the speed of displacement in relation to the ground, which, by its very nature, is fixed. AIR speed is the speed at which the aircraft moves through the air mass, which is rarely static (i.e. totally windless). This speed is measured using "Pitot" tubes. These are steel tubes placed at the front of the aircraft. In simple terms, they measure the impact of the air inside the tube. To get a better idea, imagine sticking your hand out of the window when you're driving, and the air pressure acting on your hand gives you the speed of your car. Well, the Pitot tube works on the same principle!

Why planes take off into the wind

Let's return to our aircraft. It takes off at AIR speed (it enters an air mass), not SOL speed. Let's imagine our plane on the runway, ready to take off, but stationary, with a 50 km/h headwind. We could say that its SOL speed is zero, since it's not moving! On the other hand, it already has an AIR speed of 50 km/h!!!! If our plane takes off at 250 Km/h AIR, it will only have to reach a speed of 200 Km/h SOL, since it already has 50 Km/h AIR. Conversely, if it were to take off with a 50 Km/h tailwind, it would have to reach 300 Km/h SOL to be able to take off. So our planes always take off and land (for the same reasons) with the wind against them! This makes for "shorter" and "safer" take-offs, and saves fuel.

Why planes land into the wind

It's for the same reason that airplanes land into the wind. A headwind on landing enables them to maintain a high airspeed, while reducing their ground speed. So, once in contact with the ground, they need less distance to brake and come to a stop. For these reasons, runways are generally oriented towards the prevailing wind. At Marseille-Provence airport, for example, the runways face north, into the Mistral. If there is no prevailing wind, the runways are laid out crosswise (as at John F. Kennedy airport in New York) so that, whatever the wind, you can always take off (or land) "most opposite" to the prevailing wind. So don't be afraid of the wind - it's your best ally!