The basic thing is to overcome two forces that stick the “bichão” to the earth. The first is air resistance against the plane or any moving object. To overcome it, planes use propellers, turbines or rockets to achieve thrust greater than resistance. The second is the aircraft’s own weight. In this case, it is necessary to create a force more powerful than the weight to push the plane upwards – the thrust. Easy? Not so much, if we remember a principle of physics translated by the Englishman Isaac Newton: every action generates a reaction of the same intensity, but in the opposite direction. That is, whenever the early inventors forced the plane upwards (thrust), the response was an equal force downwards (weight). And the plane did not fly. The solution appeared in another principle of physics, enunciated by the Swiss Daniel Bernoulli: when the speed of air passing over a surface increases, the pressure decreases. Then the engineers designed wings so that air passed faster at the top and slower at the bottom. With that, the pressure on the top of the wing gets smaller, and on the bottom it gets bigger, right? This pressure difference “sucks” the wing upward, generating enough thrust to make the plane lift. In the air, movable paddles help control lateral and up and down movements, as you see below.
Pressure difference pushes the aircraft upwards and makes it take off
1. To get an airplane off the ground, the first thing to do is overcome air resistance to moving objects. For this, the aircraft needs to be propelled by propellers, rockets or turbines. The latter perform two actions: first, they suck air in with a large propeller, like a giant exhaust fan.
2. After sucking in air, the turbines expel this air from the other side, compressed and accelerated by several smaller propellers. The super-compressed and accelerated air coming out of the turbine generates a force in the opposite direction, which “pushes” the plane forward, making it overcome air resistance.
3. Once air resistance has been overcome, it’s time to overcome the weight of hundreds of tons that holds the plane to the ground. Who will do this are the wings, specially designed to create a powerful thrust (force that pushes the plane upwards)
4. The most used wing on commercial planes has a curved top and a straight bottom. This type of construction induces a difference in speed in the passage of air: the air from above passes faster, as it travels a longer path in the same time as the air from below, which passes more slowly.
5. The difference in velocity in the air passage causes the pressure on top of the wing to be less than that on the bottom. As a result, the weight force (acting toward the ground) becomes less than the buoyant force (acting upward). And the plane starts to fly!
6. So that the pilot can control the angle of ascent or descent and make adjustments to the plane’s speed, the wings have movable blades called flaps. They change the direction of air passage, changing the pressure difference on the wing and, consequently, the thrust of the plane.
7. Finally, the plane does not lose direction thanks to the wing that is standing on the back, the vertical stabilizer. It keeps the aircraft in a straight line. The stabilizer also has a flap, called the rudder, which is moved whenever the pilot wants to turn the aircraft left or right.