Why do airplanes fly?

The millet questionón, ¿becauseé airplanes fly? A question fácil, But with an answer MáIt's complex and interesting than you imagine.

post writer by: Juan Matheus

the aviationón commercial has been present in the life of human beings for something moreás of a century. For this reasonón many people todayíThey see it as something normal and there is no longer the capacity for astonishment of cóhow we manage to conquer the heavens. This is why it is worth starting a series of posts that help #AvGeeks and people in general, to understand cómo is that an avión today in día manages to get us from A to B in such a short time and everything that this entails.

This new series of deliveries that aim to inform, educate and teachñar about aspects técynics to people who have no trainingón tétechnique, but yesí the desire to learn and his passionón for aviationóWe will discuss interesting topics thanks to Juan, new blog contributor.

¿Becauseé airplanes fly?

Sin más preáBlot, The first thing we must resolve is the principles físicos báphysics that govern the flight of an aircraft. The first thing we must recognize is the presence of certain forces fíphysics that affect an object, in this case an avión in flight. We must recognize in an avión 4 forces fívery important things and that isán related to each otherí by Newton's laws that everyone will haveánoído ever. Two of them are exerted vertically (Axis y) and two of them horizontally (eje X). This is maybeá one simplify usón (we live in a 3d world) However, it is enough for our purpose.ósite.

So that an aviócan't fly, must be able to overcome two key forces: Aerodynamic resistanceámica which is a force that actsúto horizontally (let's think about “drag”) and the gravity thatógically attracts an object to the ground, i.e. actúa vertically (we'll see whyé The weight of an aircraft is a key and limiting factor in aviation.ón). Each of them, has its counterpart: Thrust and liftón. When the thrust and liftón are greater than the weight of the aircraft and the drag effect (What can friction be?ón of the track with the wheels on the ground or air resistance) we can have an avión that flies. MáLater we will see other components of the designñor modern aircraft that help overcome these forces.

When an avión isá flying at cruising speed and at a fixed altitude, Thrust and drag are of equal magnitude and different direction and the same thing happens with weight and lift.ón. Any imbalance in any of these forces results in an acceleration.óI didn't slow downón (horizontal o vertical). This is just a proof of Newton's laws of motion in action.ón.

Once más, simplifying things, we can see that the supportón of a grandfatherón (the force that pushes the aircraft up) it is due to the wings (and in particular its shape) and the thrust is given by the motors. This may seem likeá obvious but it wasn't fáeasy to understand aerodynamicsámica, a branch of the fíYes, until recently it seemedía “black magic” well the mathádetrás of it is very complex and to the díTo date we have not been able to find the solutionón to many equations that govern it and we have only been able to simulate its effects throughés of a computer. Without understanding aerodynamic forcesámicas will not be ableíwe love to have developed aviationón modern and we owe it in part to the scientistíI'm Swiss Daniel Bernoulli. In other words, not every object that has enough thrust (two jet turbines for example) couldá volar.

El Airfoil

Previously we talked about aerodynamic forcesámicas and how they contribute to an aircraftócan't fly.

Now let's focus on cóhow sustain is generatedón, what is aerodynamic forceámica responsible for an aircraft being able to rise, and máIt's important, stay in the air.

air is a fluid. Not only theíQuidos are. In the case of air, there are different pressures in our atmosphere.ósphere and exert a force on it (máLater we will see other atmospheric factorsérich as the temperature and that alsoén play an important role). And if we talk about movement, We can't help but think of speed as a way of knowing how fastáI ask you to move somethingún object.

Now that we knowáThese are some of the factors that influence the movement of a fluid, we can conclude that the pressureón and air speed are the variables I wantedéwe were to control so that an avión can cross the skies without setbacks. Bernoulli's principle precisely describes what the relationship is.ón between those two variables. In a nutshell, Bernoulli's principle says that velocity and pressureón of a fluid are inversely proportional. Namely, If the velocity of a fluid increases, I took itón decreases and vice versa. If you are interested, you can search for videos about experiments in a Venturi tube so that you can observe it better.

But, ¿thaté Does all this have to do with an avión? Well, all. Above we mentioned that the shape of an airplane's wingón is what generates sustenanceón so that it stays in the air. Well, it's exactly that way., known as airfoil or aerodin profileámonkey, which makes us control Bernoulli's principle in our favor. So that an aviódon't move, we must move the air around it. And we already know that a fluid moves if there is a pressure differentialón. The purpose of an aircraft wing is, then,  generate a pressure differentialón so that air can flow.

If we look at the image of the airfoil we can, by simple inspectionón visual see that the “route” of one partíair bubble on the upper edge will beá different from the route if it is done under the wing. away from the wing, I took itón of air is atmosphereérica. As the air gets closer, what we call relative wind Let's see that a distribution is createdón in pressure gradientón around the airfoil.

There are many theoriesías and ways to explain cóSo at the top of the wing we have high speed and low pressure.ón and the opposite on its lower side however it is too complex to develop hereí.

In conclusionón, the wing profile gives us the pressure differentialóWhat am I looking for?áwe were going and what generates the sustenanceón. Becauseé The result is a force that goes upwards and not backwards.és? The pressure differentialón is greater at the bottom than at the top. increased speed, Menor Presión. Literally, the bottom “press” the air up.

This topic is quite complex and requires reading and rereading it to better understand the lógica detrás from física.