Why can headwind assist planes when taking off and landing? Why does tailwind not help with takeoff?
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The plane’s flight characteristics are affected by its air speed, that is how fast it’s moving through the air, or how fast the air is moving over the plane. The faster the air is moving over the aircraft the more lift the wings generate and the more authority the control surfaces have, which work by deflecting air to change the airplane’s attitude. Since the air is not stationary but it moves independently from the ground due to wind what matters most for an aircraft in flight and not groundspeed, that is how fast it’s moving relative to the ground. Sure you can tell how fast it’s travelling but it’s important to know the airspeed because that determines the flight characteristics of the airplane. It’s important to know since the stall speed, the maximum speed for having the landing gear or flaps extended, the maximum aircraft speed, take off and landing speed and the maneuvering speed, are all dependent on the airspeed and not the ground speed.
So with a headwind, that is the wind blowing from the front of the aircraft, this effectively increases the airspeed, so it’s faster than the groundspeed. This means that with a headwind the airplane needs less distance for its take off run, since the speed of the headwind is effectively added to its air speed. The take off is the most dangerous part of the flight, since the plane is picking up speed on the ground and is at its heaviest so any help it can get to get airborne is very crucial. When landing a headwind is helpful because it does two things, 1) it helps the airplane slow down and 2) it helps it make the approach at a higher air speed, so it’s more stable, but a lower groundspeed, so the touch down happens at a lower than usual speed which makes it smoother and less of a strain on the aircraft’s landing gear. When approaching to land the aircraft has to slow down but it mustn’t stall, a stall is when the air is not going over the plane fast enough to keep it flying stable and it falls down with no control.
[This video](https://www.youtube.com/shorts/7vP13XPMNfc) is a great example of how a strong headwind can help with landing. This is a very lightweight plane so the effect is very exaggerated compared to passenger planes but the principles are the same. Even though the plane is basically stationary relative to the ground, which would normally be well below the stall speed, its air speed is high enough that it can maintain control and safely touch down. There’s videos of similar planes taking off nearly stationary in similar conditions.
Tail winds, that is wind blowing from the rear of the aircraft, have the exact opposite effect, of essentially detracting from the aircraft’s airspeed. So take off runs need to be longer and landings need to be faster. Of course aircraft can still fly with a tailwind because they’re moving forward through the air much faster than any wind can blow from the rear but the tailwind is still there and since aircraft are not designed to be as aerodynamic from the rear, it makes the airflow over the aircraft more turbulent which in turn makes controlling the aircraft harder and the flight less smooth. In most cases however planes don’t take off or land with tail winds because most airports are made, if possible, with the most common weather of the area in mind and offer multiple runways so that even if one runway has a tailwind, another might not. Even if they have to planes can and do take off and land with a tail wind, there’s obviously defined acceptable parameters for each aircraft.
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