Question

Why do airplanes normally take off into the wind?

Short answer

Airplanes normally take off into the wind to reduce the required ground speed.

Step-by-step solution

Understanding the concept of Bernoulli’s equation

Bernoulli’s equation states that when the pressure is low in an area, the flow of fluid or wind is larger. Therefore, greater speed will result in lesser pressure.

Determine the reason behind the airplanes taking off into the wind.

As you know, the airfoils of an airplane move faster than the relative air. Therefore, it can deflect the air, but the streamline flow is always maintained because the streamlines are crowded together on the above side of the wing.

The streamlines on the above side of the wing indicate that the airspeed is larger than below the wing. Therefore, there is the presence of upward force known as dynamic lift, which can help the airplane rise.

Also, the wings of the airplane are tilted in an upward direction. The air striking on the bottom surface will be reflected in the downward direction, and the change in moment of air particles will result in the additional upward forces acting on the wings.

When the plane moves with the wind, the wind acts in the opposite direction, which acts as a drag force to stop the plane's motion. Therefore, less speed is required to lift the plane when it moves in the off direction of the wind.