   # Lifting capacity of the aircraft

lifting capacity  - one of the components of the total aerodynamic force, perpendicular to the velocity vector of the body in a stream of liquid or gas, resulting from the asymmetry of the flow around the body. Empirically, Bernoulli found that the static pressure in a liquid or gas flow is inversely proportional to the flow rate at a given point, which means that at those points where the flow rate is higher the pressure is lower. In practice, it is easier to understand this expression using an example: when a large crowd of people forms at the entrance to the escalator at a metro station, there is a crush (in front of the escalator), and when you enter the escalator and start to climb, then there are a maximum of 2 people on the steps and the speed of your movement higher, and so-called. "Pandemonium" (pressure) is lower.

So “acts” and the fluid in the tube of variable cross section. And now, mentally you can imagine that this pipe was “unrolled” and laid out on the 2 surface, like an airplane wing. One of them (upper) has a greater curvature (convexity), and the lower one has a smaller convexity (almost even). Thus, according to the equation of the continuity of a stream of a liquid (or gas) stream, an already understandable physical phenomenon is the pressure difference on the upper and lower parts of the wing. We get that on the lower surface the flow rate is lower and the static pressure is higher, and on the upper part the static pressure is lower (because the flow rate is higher, due to the geometric difference of lengths). This is a simple explanation for the wing of a classic profile and an infinite span.

### Calculation of the lifting force of the wing. Zhukovsky theorem on lift force.

In life, this wing is impossible to do. Therefore, we apply mathematical properties to the solution of this problem: a finite span, a normal vector to a profile, a profile boundary, a pressure value, then we get the following expression:  ## Lifting capacity of the aircraft wing

People who start their acquaintance with aviation or it may continue to have mature question, again all all knew, were outstanding and the opening of minds, but the plane was able to fly only 1903 year, what's the deal? And here's the thing: it could make its maiden flight before, but for a long time, scientists were confused how to calculate the lift and what should be the wing of the aircraft, its length? According to classical physics of Newton and in accordance with the laws of the lift it is proportional to the angle of attack in the second degree, which led to the conclusion that it is impossible to make a small wing span with good load-bearing characteristics. We can imagine the usual parabola, y = x2  and we find that, for example, for a lift force equal to 2, you need to reach the angle of attack in 4, and for good flight you need a lift force in 4, 5, 6 ... sometimes it will be difficult to even calculate attack angle, and if he is also in the critical zone ...

This confusion lasted until the end of the 19 century, and it was only after many experiments by Bernoulli and many other scientists that this relationship was straightforward (!), And already based on such conclusions it was possible to build a small-scale wing with a satisfactory lift. The first was done by the Wright brothers. Avia.problems

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