What would you like to know?
Print

Into the wind!

Aircraft take of and land into the wind. They do not as one “aviation journalist” explained on the radio take off in one direction and land in the other. At DUB the prevailing wind is from the west or southwest so as DAA explains about 70% of operations are on 28R and 28L.

Why?

The single most important measurement for an airplane is airspeed. This measures the speed of the air over the wings which is what keeps it in the sky. When landing or taking off the aircraft is flown at a particular design speed for that phase of flight. For example a Boeing 737 or similar will land around 130kts. Everything aviation is in knots because they’re just sailing ships in the sky. A knot is 1.852km/h.

Aerospaceweb explains it on their site, but here’s a summary:

Aircraft fly through a body of air, obviously, but remember that body of air often moves over the surface of the earth. We call this phenomenon by its technical name “wind”! If the body of air is traveling in the same direction as the aircraft it’s a tailwind and the other way it’s a headwind. This is really only a safety thing when landing or taking off, assuming you have enough fuel to get where you’re going. The reason it affects safety is that landing with a tailwind means the speed of the airplane and the body of air are added together to get the airplane’s speed over the ground. When you touch down with a 20kt tailwind you’re doing 130+20=150kts along the runway; that’s 278km/h. However, land on the same runway in the other direction so it’s a headwind and your ground speed it 130-20=110kts which is 204km/h.

Airspeed vs Groundspeeed

204 km/h is not slow, but it sure beats 278 when you’re trying to stop. Taking off it’s the same thing. I’d rather reach my 130kt takeoff airspeed at 110kts over the ground instead of 150kts as the ditch at the end of the runway starts to fill the windscreen!

Table of Contents