Undoubtedly, understanding why airplanes fly will allow us to fly more quietly. Hence the importance of taking the time to understand how it is that planes stay in the air.
How do airplanes fly?
The simplest answer would be that airplanes fly because they are designed to fly.
In the same way, that a transatlantic ship over 100,000 tons has a particular shape and interior design that allows it to stay afloat, a plane has a shape that allows it to stay in the air.
There is something magical…
The strange and magical that planes would not fly could considering the way they are. The key to its form is in the wings and the design that they have.
A somewhat more elaborate answer would be an aircraft flies through the air flow passing through the wings. So now we can deduce that, for a plane to fly, an air flow is needed, or what is the same, a speed relative to the air. When air flows through the wings upward force is generated, called lift, which sufficient compensates the weight of the aircraft.
So how much capacity has the air moving?
Somehow we tend to underestimate the capacity of the air. It is true that if you throw a stone into the soil seems as if there were a void, nothing restrains the stone. The same happens if we raise our hands reaching out and let fall. It seems that the air is not the work to prevent objects from falling to the ground. But we have all seen how difficult it is to walk when it’s quite windy, we have seen pictures of the devastating effects of tornadoes being able to lift cars, trucks or houses and, sometimes, we have our hand out the car window to ” play “to keep in the air thanks to the vehicle speed.
How wings generate lift?
Continuing with the example above, one can see how it is easier to keep our hand suspended in the air the greater the speed of the vehicle. With wings of an airplane same thing happens: the higher the speed of the aircraft relative to the air, the greater is the lift. For this reason, to take off, planes need a clue where to accelerate to a certain speed.
We can also see how varying the inclination of our hand we can act on the force that rises. The same applies to the wings of the aircraft, and that inclination is known as the angle of attack. To vary the angle of attack is rotated around the plane’s nose up or down, thanks to control surfaces located in the tail: it is what is done to reach takeoff speed of “rotation”.
Getting support is not complicated. The tricky part is getting it efficiently, that will raise heavy weights without generating much resistance to halt us. Our hands are not the ideal way. However, the wings of the aircraft have a very careful design to achieve high efficiency. A very important design feature is the wings called airfoil shape, consisting of a wing cross section viewed from the side. The airfoil is not fixed, it depends on the characteristics of the aircraft and by the use to which it will give (acrobatics, passenger transport, combat, recreation, etc.), but there is usually a common feature: the front (edge attack) and rounded opposite side (trailing edge) sharper.
To better understand what happens in the wing of a plane, the best we can do is change our frame of reference and imagine a fixed wing profile and a stream of air moving from left to right focusing on it (all the same After all, what matters is the relative wind). This is what is done in wind tunnels and adding some smoke at different points, we see the following:
The air flow is divided by taking two roads, one passes over the airfoil and one below. The shape and angle of the airfoil relative to the airstream (angle of attack) make the two paths are not symmetricalthat the air particles take curved paths, varying speed and pressure distribution appears peculiar. Specifically, below the airfoil pressure increases and the air particles are held back, over the profile and the pressure decreases and the particles accelerated. This pressure differential between the two sides, more pressure below and above lower pressure, creates an imbalance that results in an upward force to lift call.
Uhm, and is there an even easier way to understand why airplanes fly?
When the plane flies, the wings push air down around them. If the wings push air downward (action), according to Newton’s third law (With every action an equal and opposite occurs), the air, in turn, should push up the wings (reaction). And how you manage to push the wings up? Then we should return to the above-mentioned explanation by the pressure difference between the two sides of the airfoil. Everything is linked together and one thing would not be possible without the other.
Therefore, a simple and intuitive way to understand the lift would imagine that the wings are “spoilers” of air, keeping the plane up pushing air down. The higher the speed, the air particles are pushed down per unit time, thus increasing the lift. We can also appreciate the importance of the angle of attack: increase the angle of attack is nothing but push the air “further down”, therefore, the reaction is generated “more up”.
The trick lies in the wings to be very efficient pushing air towards the same side, which does not happen with other objects . It should be noted that both palms down air particles that pass under the profile, such as passing overhead. Moreover, not only those that are immediately near the wings, which are also slightly more distant. The wings are very efficient pushing air down.
Both explanations are not intended to be complete explanations. To do so would have to spend far more than a few paragraphs, and not come to mind. Most remarkable of all, and what a person be, it is that the lift is generated by pressing a button to launch some kind of magical mechanism: The lift occurs naturally as the air flow through the wings.
To what extent are important engines?
To generate enough lift preventing the plane from falling like a stone, what is needed is an air flow passing through the wings, that is, having airspeed. A wing given quite like how the speed is achieved compared air. One way to achieve this is pushing the plane forward through the engines, the same way we feel air pedaling a bicycle. But it is not the only way to get it.
Another way to achieve the air flow is exchanging altitude rate ; in the same manner as in our earlier bicycle we can feel, without pedaling, the same air before if we move downhill. This allows the aircraft, the weight it has, to plan. It is true that by maintaining a “cost” down, sacrificing speed altitude at some point reach the ground. But the plane does not fall like a stone, but descends gradually, and the horizontal distance that can be traveled planning from the cruising altitude exceeds 150 kilometers. The descents are made on commercial flights, in fact, are extremely like the glides; because when wanting to go down, it is usually done with engines at idle (on but the minimum).
It should take his mind the idea that tends to be thinking it’s very easy for a plane falling like a stone, because it is not so or so extremely unlikely to be without any engine running cases. Under the plane is filled with air, and it is the air, along with speed, preventing the plane from falling like a stone, and to achieve this speed, just slightly lower the nose of the plane (as in a fall).
As is done in wind tunnels an aircraft parked on the ground could eventually rise if the headwind is high enough. In fact, on windy days, you have to tie down small planes to prevent rise, as these need a lower airspeed to fly.
Funny video of a Boeing 747 parked at a “scrapping aircraft” a windy day. No pilots, no instrumentation and has no engine, but the aircraft continues to maintain the shape and the wings (“an aircraft flies because it is shaped flying”), and therefore, still wants rise if there is a flow of air passing through its wings.