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# How Do Airplanes Fly? : The Scientific Explanation of Aerodynamics

Jagatheesh is a Mechanical Engineer and interested in writing on science and technology in our life.

Airplanes are an engineering wonder in the modern world. It helps to travel long distances in the least time. Flying in the sky was a dream of humanity for many years. The modern flight began in 1783 through hot air balloons. The first powered plane was devised and tested by the Wright brothers. It involves minute techniques and concepts. Let's know more about the science behind airplanes.

## The Basic Principles of Flight

The concepts involved in the flight of a plane are

1.Airfoil(Aerofoil) Shape:

The airfoil is a specific shape that creates an aerodynamic force when moved through the air. The force created will be perpendicular to the airflow. Airplane wings and propeller blades are the best examples of the airfoil shape. It is the basic science behind the flight.

2.Bernoulli's principle:

The principle states that in a fluid, an increase in velocity will decrease the pressure. The air moving in the upper side of the aircraft wing is faster than the air at the bottom. It creates a pressure difference. The upper surface has low pressure and the lower surface has high pressure. This pressure difference produces lift.

3.Newton's third law of motion:

Newton's third law of motion states that for every action, there is an equal and opposite reaction. When the wings force the air downwards, it creates an opposite force that causes the lift on an airplane.

Many controversies question the application of Bernoulli's theorem in the airplane lift. But it is wise to leave controversies for the science world to explain

## Four Forces on an Airplane

The flying of an airplane involves the four basic forces,

### 1.Thrust:

Thrust is the force that moves the plane in the direction of motion(planes running fast on the runway). Plane engines are the major source to generate the thrust. The magnitude of the thrust depends on the type of the engine.

### 2.Drag:

It is a force that acts against the thrust and is caused by air resistance to the motion. It acts in the opposite direction to the motion of an airplane.

### 3.Lift:

The force that lifts the airplane upwards is called a lift. It is produced by the motion of an airplane in the air. The airfoil shape of the wing creates a pressure difference that causes the lift of an airplane. It is opposite to the weight(gravity) of an airplane.

### 4.Weight(Gravity):

It is the weight of the airplane, and it is the force that pulls the flight downwards. The magnitude of this force depends on the weight of the airplane, and the goods carried by plane.
Thrust is opposite to drag, and the lift is opposite to the weight. During takeoff, the lift must be higher than the weight, and the thrust must be higher than the drag. Once the airplane reaches the required altitude, the four forces will be balanced. The plane continues to fly at a constant speed.

## The 3 Axes of Rotation of an Airplane:

• Pitch- Moves the nose of the aircraft up and down(Transverse axis).
• Roll- Move the aircraft wings up and down(Longitudinal axis).
• Yaw- Moves the aircraft sideways(Vertical axis).

## Major Components of an Airplane for Flying

The structure of the wing and the tail plays a major role in the flight of an airplane. Various components are attached to the wings and tail. It determines the flight of an airplane. They are

### 1.Flaps:

Flaps are the high lifting devices on the trailing edge of the wing. Flaps increase the wing area. When the wing is extended, it increases the camber and the surface area of the wing. It will improve takeoff at lower speeds as well as landing performance.

Note: Camber is the convexity of the curve of an airfoil from the leading edge to the trailing edge.

### 2.Slats:

These are the extendable high lifting devices on the leading edge of the wings. They increase the lift during takeoff, initial climb. It is also used to increase drag during landing.

### 3.Aileron:

These are the movable part on the trailing side of the airplane wings. The pilot controls the aileron. It permits him to roll the airplane around its longitudinal axis.

### 4.Spoiler:

These are the panels mounted on the upper surface of the wing. Used to increase the drag and decrease the lift by disrupting the airflow over the wing. The function of the spoiler is to slow the airplane and to make it descend. It can also generate a rolling motion of the airplane.

### 5.Elevator:

Elevators are the Panels in the tail of the airplane. It controls the movements of an airplane on the lateral axis, which is called pitch. Elevators control the position of the nose of the airplane and the angle of attack of the wing.

### 7.Rudder:

The rudder is the movable component fixed on the trailing edge of the vertical stabilizer or the fin. It controls the plane on its vertical axis. It plays a major role in controlling the airplane when one engine fails. The rudder can also control the position of the nose of the airplane.

## The Science of Flight

The plane moves at high speed on the runway, which increases the lift of the airplane. During the running, the wing which is in the shape of an airfoil produces a downwash. It creates a pressure difference between the top and bottom of the wing. This pressure difference will produce the lift. The higher the angle of attack, the greater will be the lift force. An increase in airspeed increases lift. Flaps and slats alter the airfoil shape, it further increases the downwash and the lift.

Ailerons moved up and down to increase or decrease the lift force. The elevator in the tail can be adjusted, which will alter the vertical force in the tail. The rudder will control the horizontal force.

During the takeoff, the elevator is moved upwards. It will increase the tail force and makes the tail tilt. It will further increase the lift. The angle of attack of 15 degrees is maintained to increase the lift force. Thrust must be higher than the drag to increase the lift force.

Once the plane reaches the level of flight the thrust force and drag, as well as lift and weight, will be balanced. If lift and thrust are more than drag and gravity, the plane goes up. When the drag and gravity are more, the planes go down.

In 2019 more than 4.5 billion people traveled all over the world through airlines

## How Does the Airplane Change its Direction.

To change the direction of an airplane, the Pilot uses both Aileron and Rudder. A centrifugal force is needed to turn the flight. One aileron will be raised, which produces more lift, and the other will go down, produce less lift. It will create a difference in lift force between the two wings that make the airplane to roll.

Now the lift is not vertical. The horizontal position of the lift provides the necessary centrifugal force. In this position, the drag force on the wings will not be equal, which creates yaw known as adverse yaw. Rudders, along with the aileron, can control the adverse yaw.

During the descend, the drag is increased by reducing the thrust from the engine. Slats and flats are also used to decrease the thrust and increase the drag. Spoilers are also used to increase the drag. An operation called reverse thrust can reduce the running distance in the runway.

## Airplanes changed the face of Travelling

The modern world is more connected with innovative methods of communication and transportation. Airplanes are now essential means of transport that revolutionized traveling. The invention of flight is an important milestone in the history of humans. With the advent of airplanes, no distance is longer. Let's travel more and explore the diversity of the world.

## Reference

1.A textbook of Fluid Mechanics by R.K.Bansal.

2. "Dynamics of Flight" on NASA's Website.

3."Forces on an Airplane" on NASA's Website.

4.Aerodynamics related articles in Wikipedia.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.