# The physics behind why we can fly

Aryan – Year 11 Student (now in Year 12)

Aircraft have been an important invention for mankind. They have provided transport for further global research, they have provided joy for humans and more importantly they have also allowed us to gain greater insight into aerospace and aeronautical engineering with the sophisticated science and engineering that these planes operate on.

In December 1903, when Wilbur and Oliver Wright launched the first plane that was heavier than air in Kitty Hawk, they implemented the axis designs in Figure 1. They realised that their plane had to have this in order to compensate for the forces acting on the plane when it is in the air. The understanding of yaw, pitch and roll the Wright Brothers to further progress and develop their planes with ideas such as gyroscope procession, angular roping and wind warping. This is why humans are able to fly like birds to this day.

## Yaw

As you can see in Figure 1, the yaw is the movement of the nose perpendicular to the wings. However, on its own it can cause the direction and lift of the wings to be asymmetrical and as a result cause one wing to rise and the other to lower (although this can be useful for turning the plane).

The yaw rotation is important for the plane’s rotation because it causes a change in side force which generates a torque about the centre of gravity of the plane. A torque, otherwise known as a moment, can be calculated by multiplying the force and the perpendicular to the force. Therefore, the higher the torque, the higher the rotational speed of the plane’s propeller resulting in more thrust. To put things into perspective, the Wright Brothers’ plane had a propeller rotational speed of 245rpm with a required 90 pounds thrust in order to travel at only 24mph. This shows how much the yaw rotation and the torque matters.

## Pitch

Pitch refers to the rotation of the aircraft around a side-to-side axis. It can be thought of as the “up and down” or “nodding” motion of the airplane. It is important for the plane during take-off especially because it has a positive ‘pitching’ motion which raises the nose of the aircraft and lowers the tail allowing for ascending motion.

## Roll

The third axis is very important too as it allows the plane to steer right or left, hence controlling its horizontal axis. So without it, your plane journey would be one straight line. It allows the plane to do this because it decreases the lift on one wing and increases the lift on the other causing the plane to tilt. This type of motion is facilitated by the ailerons and flaps that open/close and change shape in order to allow for a change in rolling movement of the plane. The ailerons work oppositely to each other: when one moves up the other moves down. For example, if the left aileron moves down and the right one moves up then the pane will move in the anticlockwise direction.

## References

https://www.experimentalaircraft.info/articles/aircraft-engine-performance-1.php

https://www.grc.nasa.gov/www/k-12/airplane/torque.html

https://eu.usatoday.com/story/travel/columnist/cox/2017/02/12/what-is-yaw/97741320/