Los aviones vuelan gracias a una combinación de principios físicos que actúan sobre ellos, los cuales permiten generar la fuerza necesaria para mantenerse en el aire y desplazarse.
Los más importantes son la aerodinámica, la fuerza de sustentación, la propulsión y el control de vuelo. A continuación, se explicarán estos conceptos en detalle, así como la historia y evolución del vuelo, hasta llegar a los aviones modernos.
Physical principles of flight
1. Support
Lift is the key to aircraft flight and is generated primarily by the wings.
To understand how it occurs, it is necessary to understand some basic principles of aerodynamics, such as Bernoulli's principle and Newton's third law.
Bernoulli's principle
This principle states that the higher the speed of a fluid, the lower its pressure.
In the case of an airplane, the "fluid" is air. An airplane's wings have a particular shape, called an airfoil, which is curved at the top and flatter at the bottom. As the airplane moves forward, air flows over and under the wings. Because of the shape of the airfoil, the air passing over the top of the wing has to travel a greater distance in the same amount of time than the air passing over the bottom, causing the air over the top to move faster.
According to Bernoulli's principle, when moving faster, the pressure on the top of the wing is less than on the bottom. This pressure difference generates an upward force, known as lift, which lifts the aircraft.
Ley de Newton
In addition to Bernoulli's principle, Newton's third law, which states that "for every action there is an equal and opposite reaction," also plays an important role in generating lift.
El flujo de aire que se desvía hacia abajo al pasar por el ala genera una fuerza de reacción hacia arriba, que también contribuye a la sustentación del avión.
2. Propulsion
The next key component in aircraft flight is propulsion, which is the force that propels the aircraft forward. This force is produced by the aircraft's engines, which can be jet engines (on most commercial aircraft) or propellers (on smaller or older aircraft).
Propulsion is what allows the aircraft to maintain sufficient speed for the wings to generate lift.
En el caso de los motores a reacción, funcionan expulsando gases a alta velocidad hacia atrás.
According to Newton's third law, the reaction to this ejection is a force that pushes the plane forward. In the case of propellers, they spin rapidly and push air backward, creating a forward force that moves the plane forward.
3. Resistance and weight
There are two additional forces that must be counteracted for an airplane to fly: drag and weight.
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Drag: This is the force that opposes the movement of the aircraft through the air. It is produced due to the friction of the aircraft with the air molecules, which generates a friction that tends to slow down the aircraft. Aircraft designers work to reduce aerodynamic drag by giving them smooth and optimized shapes.
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Weight: The weight of the plane, which is the downward force due to gravity, must be counterbalanced by the lift force in order for the plane to not fall. The lift must be greater than the weight in order for the plane to rise, and it must equal the weight in order for it to maintain stable flight.
4. Flight control
Para controlar la dirección y estabilidad del avión en el aire, se utilizan diferentes superficies de control ubicadas principalmente en las alas y la cola del avión. Estas superficies son:
- Ailerons: Located on the wings, they allow the aircraft to turn on its longitudinal axis, leaning to one side or the other (this is known as "roll").
- Timón de dirección: Situado en la parte vertical de la cola, permite controlar el giro del avión sobre su eje vertical (movimiento conocido como "guiñada").
- Elevadores: Ubicados en la parte horizontal de la cola, permiten controlar la inclinación del avión sobre su eje lateral, es decir, hacen que el avión suba o baje (movimiento llamado "cabeceo").
5. Speed and altitude
The speed of the aircraft is crucial for lift to occur. At low speeds, the amount of air passing over the wings is not sufficient to generate the necessary lift, and the aircraft may lose altitude or even enter a stall condition (when the airflow over the wing separates from its surface and the wing stops generating lift).
For this reason, aircraft need to reach a minimum speed to take off and stay in the air. Once in flight, they must maintain an appropriate speed depending on the altitude and flight conditions.
As for altitude, as the aircraft climbs, the density of the air decreases, which can affect both lift and engine efficiency. Airplanes are designed to fly at altitudes where the air is less dense, which reduces aerodynamic drag and allows for more efficient flight. However, pilots must take atmospheric conditions into account and adjust speed and angle of attack (the pitch of the wing relative to the airflow) to maintain stable flight.
Comparison with helicopter flight
Airplanes and helicopters fly using similar aerodynamic principles, but there are key differences in how they generate lift and are controlled in the air.
Generation of support
- Aviones: Generan sustentación a través de sus alas fijas. Para volar, deben moverse hacia adelante, lo que permite que el aire fluya sobre las alas y cree una diferencia de presión que los mantiene en el aire.
- Helicopters : Generate lift by means of their rotors , which act as rotating wings. The helicopter's main rotor spins rapidly and moves air downward, creating an upward reaction force, allowing takeoff and vertical flight without the need for forward motion.
Propulsion
- Aviones: Utilizan motores a reacción o hélices para generar una fuerza de empuje hacia adelante, necesaria para que el aire fluya sobre las alas y se produzca la sustentación.
- Helicopters : They do not need to move forward to fly. The main rotor not only provides lift, but also thrust, allowing the helicopter to move in any direction (forward, backward, and sideways).
Control
- Airplanes : They use ailerons, rudders and elevators to control flight. These allow them to turn and go up or down, but they always need to move forward.
- Helicopters : They control flight by adjusting the angle of the rotors (cyclic and collective) and using the tail rotor to control yaw, allowing them to take off and land vertically, and to hover.
Comparison with the flight of a hot air balloon
El vuelo de un avión y el de un globo aerostático se basan en principios completamente diferentes en cuanto a cómo se genera la sustentación, la propulsión y el control.
Generation of support
- Aviones: Generan sustentación a través de sus alas fijas. Para que el avión vuele, necesita moverse hacia adelante, lo que permite que el aire pase sobre las alas y genere una diferencia de presión que lo mantiene en el aire.
- Hot air balloons : These do not generate lift through motion or wings. Instead, they operate based on the principle of buoyancy or Archimedes' principle , which states that an object submerged in a fluid (in this case, air) experiences an upward force equal to the weight of the fluid displaced. The warm air inside the balloon is less dense than the cold air surrounding it, causing the balloon to float upward.
Propulsion
- Aviones: Utilizan motores (a reacción o hélices) para generar empuje hacia adelante, lo que les permite avanzar y generar la sustentación necesaria para el vuelo.
- Globos aerostáticos: No tienen un sistema de propulsión activa. El globo simplemente flota con las corrientes de aire, siendo incapaz de moverse intencionalmente en una dirección específica. Solo sube o baja al calentar o enfriar el aire en su interior.
Control
- Airplanes : Use control surfaces (ailerons, rudder, elevators) to maneuver in the air. Pilots have control over direction, altitude, and speed.
- Hot air balloons : Control is much more limited. Pilots can control only altitude by adjusting the amount of heat in the balloon, but direction depends on wind currents, as the balloon has no direct control over its horizontal displacement.
Evolución del vuelo humano
The pioneers of flight
The idea of flight has fascinated mankind since ancient times. However, it was not until the late 19th and early 20th centuries that the first controlled and sustained flight was achieved.
The Wright brothers, Orville and Wilbur, achieved this milestone on December 17, 1903, with their airplane Flyer I. This aircraft was equipped with fixed wings and one engine, and its success was the result of years of research in aerodynamics, flight control, and light engines.
Development of commercial aircraft
A medida que la tecnología avanzaba, se diseñaron aviones más grandes y eficientes. Durante la Primera y Segunda Guerra Mundial, la aviación militar impulsó muchos avances en el diseño de aviones, que luego se trasladaron a la aviación comercial.
Airplanes began to be used for the transport of passengers and cargo, and civil aviation grew exponentially during the 20th century.
Uno de los hitos más importantes en la aviación comercial fue el desarrollo del Boeing 707 en la década de 1950, uno de los primeros aviones comerciales a reacción. Este avión revolucionó el transporte aéreo al permitir vuelos más rápidos y a mayores distancias, y marcó el inicio de la era de los aviones a reacción.
Modern Aircraft
Today, airplanes are highly sophisticated machines, with advanced navigation, control and safety systems. Modern commercial aircraft, such as the Boeing 787 Dreamliner or the Airbus A350, are designed to be extremely fuel-efficient and reduce carbon emissions.
In addition, improvements in composite materials and aerodynamics allow aircraft to be lighter, reducing weight and therefore fuel consumption.
The introduction of technologies such as high-efficiency engines and the use of lightweight composite materials has allowed modern aircraft to become quieter and more economical.
Automation has also played a key role in flight control, with autopilot systems allowing aircraft to fly predetermined paths with minimal human intervention.