It's a may day suitable for traveling, whenever you travel for a long trip, everyone usually sends such blessings: "I wish you a smooth journey", then, maybe someone will tell you that to send off at the airport, you can't say "all the way to the wind" Oh, why is this?
The principle of aircraft take-off
First of all, we need to understand that most aircraft are composed of 5 parts: wing, fuselage, tail, landing device and power unit. The fundamental principle of aircraft flight is that the pressure difference between the air flowing through the air flow produces lift.
When the aircraft takes off, the aircraft can only leave the ground if the lift generated by the wings is greater than the weight of the aircraft. The size of the lift has a lot to do with the air velocity flowing through the surface of the aircraft wing: the greater the air velocity, the greater the pressure difference between the upper and lower surfaces of the wing, so the greater the lift.
If taken off against a wind, the velocity of the airflow flowing through the surface of the wing is equal to the speed at which the aircraft is sliding plus the wind speed. Therefore, when taking off against the wind, the lift generated by the aircraft is relatively large, and the sliding distance is correspondingly shortened.
If you often take a civil airliner, you may find that the take-off direction of the aircraft will change, and the direction of each take-off will be adjusted according to the direction of the wind. According to the concept of relative velocity in physics, when taking off against a wind, the surface velocity of the wing = the speed of the aircraft itself ± wind speed.
For a simple example: the aircraft takes off against the wind on the runway, in a certain state, the speed of the aircraft is 180KM/H, the wind speed at this time is 28.8KM/H (8M/S), then the speed acting on the surface of the aircraft wing at this time is: the speed of the aircraft + wind speed = 208.8KM/H. In the same state, if the aircraft takes off with the wind, the speed acting on the surface of the aircraft wings at this time is: the speed of the aircraft - wind speed = 151.2KM / H.
Wind
Aircraft speed
wind velocity
Relative speed of the wings
Headwinds
180 kph
28.8 kph
208.8 kph
downwind
151.2 kph
Aircraft wing surface speed
This is similar to the principle of flying a kite, we have to drag the kite against the wind for a distance, increase the speed of the kite relative to the air, so that it gets a greater lift, so as to rise faster.
How much does the wind affect flights?
In total, there are 5 types of winds that affect flights:
Headwind: The wind that blows head-on towards the aircraft. Since headwinds increase lift, aircraft mostly take off or land in headwinds.
Downwind: Wind blowing from the back of the plane. Downwinds reduce lift, and aircraft typically avoid taking off or landing in downwind conditions.
Crosswind: Wind blowing from the side. If the aircraft encounters a crosswind upheaval when landing, it may deviate from the runway midline.
Wind shear: Refers to a change in buoyancy caused by a change in the headwind or downwind that lasts more than a few seconds. Reduced buoyancy can cause the aircraft to deviate downwards and below the intended flight path.
Turbulence: Caused by the rapid and irregular flow of the atmosphere. It causes the plane to jolt, and in severe cases the plane can briefly lose control.
What winds are airplanes most afraid of?
The wind that the plane is most afraid of when it takes off is the crosswind.
Landing under strong crosswinds is one of the most complex and dangerous maneuvers for civil aviation aircraft, as crosswinds can blow the aircraft off the midline of the runway.
When encountering a large crosswind, the aircraft in the take-off or landing process, the air flow rate of the two wings of the aircraft is different, resulting in different lifts on both sides of the wing, so that an inclination torque is generated; in addition, because the crosswind pressure center does not coincide with the aircraft center of gravity, it will also produce a turning torque that rotates the aircraft in the direction of the headwind; when the crosswind is very large, the runway opposite to the turning torque is facing the reaction force of the wheel, which is not enough to make the aircraft maintain balance, the nose deflects in the direction of the crosswind. Therefore, the aircraft should make timely and correct corrections in the large crosswind.
Credit: Civil Aviation Resource Network
Can a windy plane still take off?
When the wind reaches a certain intensity, the plane cannot take off.
In daily life, if the wind speed is 0 to 8, it is possible to take an airplane. When encountering a strong storm of level 9 or above, it is not suitable for travel by plane. Among them, the wind speed below level 5 has no impact on the aircraft, and the wind of level 6 to 8 (level 8 wind can blow branches, and it is difficult for pedestrians to walk head-on) is rare, at this time, the aircraft takes off, it is necessary to see the direction of the wind.
According to GB/T 28591-2012 "Wind Level", the intensity of the wind is commonly used in meteorology. Wind power levels are divided into 18 levels in turn. If the wind reaches a level of 9, the wind speed is between 20.8 and 24.4 meters per second, which can already affect the navigation of the steamboat, and even the building will have small damage.
GB/T 28591-2012 "Wind Level" Wind Level Classification Table
Finally, when the plane lands, should it be a tailwind or a headwind?