# How do planes fly?

Louise Smyth

Over 5,000 aircraft are in flight throughout peak operational times per day. Hearing a plane fly overhead is such a common occurrence it is easy to forget how complicated it can be to make a plane airborne.

With the assistance of automated systems, flying planes is much easier than years gone by. However, it is physics that really makes the magic happen.

## How planes fly

Through the use of various attachments, pilots can manipulate gravity and wind currents to achieve flight. There are four main types of attachments required for success:

• Flaps and slats: These are located on the wing of a plane and work together during take-off

• Aileron: These are also located on the wing, moving up and down to alter the lift force.

• Elevators: These are located at the tail of the plane and control the vertical force.

These attachments can be manipulated to form an airfoil shape which provides a lift force. This simple action is what allows planes to fly.

### How airfoils make planes fly

When moved relative to the air, the bottom of the airfoil creates a downwash, creating a pressure difference between the top and bottom of the airfoil. This results in lift force, also referred to as simply ‘lift’.

It is through increasing the lift force that a pilot can make an object as large and heavy as a plane fly. There are different actions pilots implement that increases the lift force to get a plane off the ground:

• Raising the angle of attack

• Increasing the airspeed

• Extending the flaps and slats

### How this translates to flight

It is essential that the lift created is greater than the weight of gravity to achieve flight. This is done by the following.

1. The pilot moves the plane, achieving an increased airspeed.

2. The slats and flaps are then extended to create a downwash and lift.

3. When the pilot is ready for take-off, they will move the elevators upwards which tilts the plane; further increasing the angle of attack (usually around 15 degrees).

4.The aircraft takes flight.

The plane will continue to climb so long as the thrust is greater than the drag. To level off, the drag must be equal to the thrust and the lift equal to the weight of the aircraft.

## How does a plane change direction?

There is an additional attachment on the tail of a plane that assists in changing direction by controlling the horizontal force. The rudder will move to one side to make the plane change direction. For this to be a comfortable process, pilots make use of centrifugal force.

This is achieved by moving one aileron upward on one side of the plane and the other on the opposite side downward, which will cause the plane to roll. This also results in the lift force being horizontal rather than vertical, allowing the plane to change direction at any angle without causing discomfort to passengers.

The rudder is essential in this process as, without it, adverse yaw would occur due to the levels of drag being different from one wing of the plane to the other. The rudder can manipulate the horizontal force to prevent yawing.

Through the use of five simple attachments, we can travel anywhere in the world.