The Science of Flight

The Four Forces

In flight there are four forces at play: thrust, lift, air resistance or drag, and gravity. In a way, gravity and drag are obstacles we need to overcome, and thrust and lift help us achieve just that.

Air resistance is the opposing force that acts on an object as it moves through the air. The particles of the air hit an object as it moves forward and push it backwards, trying to prevent the object from moving forward. There are multiple ways in which you can try and overcome the effects of air resistance. The main way you can achieve this in aviation is by focusing on the aircraft’s designs, functionality and material.

Objects that can cut through air resistance easily like this can be described as aerodynamic. The nose cone of an aircraft is very important as it is the first to get ‘hit’ by the air as the plane moves forward. The streamline and pointed shape of the nose cone and fuselage allows the aircraft to easily glide through the air, this creates minimum drag.

Main structural elements of an aircraft

The main parts of an aircraft include the nose cone, the fuselage, the wings, the engines and the tale. We are now going to focus on the wings and later on the engines as these affect the lift and thrust we need to create flight.

Lift

Lift is produced by the wings, due to their very special shape; aerofoil. The aerofoil shape is a shape that is curved at the top, a flat at the bottom and is stretched out at one end.

Lift was discovered by 17th century scientist Daniel Bernoulli, who said that ‘The faster air travels, the lower its pressure (or its energy) becomes’. For example, if you were to walk across a room, you would not use as much energy as if you tried to ran across it as fast as you could. You would be far more tired, because you would have used up far more energy running than walking.

Bernoulli’s Principle

The faster the speed of the air, the lower its pressure

If we relate energy to pressure, same thing happens with air.

  1. As the plane moves forward, the air travelling towards the wing is splits into two, some of it travels over the wing and some of it travels under the wings.
  2. The curve at the top of the wing forces the air travelling over the wing to increase its speed, move faster so it can get over the curved top.
  3. As it travels faster it loses energy, creating a low pressure area above the wing.
  4. The universe doesn’t like unbalanced pressure, so the air from below is attracted to the low pressure area above the wing so it can equalise it out.
  5. As the air travel upwards, it hits the wing and pushes it upwards forcing the wing and the plane into the air.