# Principles of Flight

Since the early ages of human history, people have wanted to fly. Our fairy tales are full of humans and animals that can fly supernaturally. So what are Principles of Flight ?

In real life withoud any assistance we don’t have the ability to fly because we don’t have wings and we cannot generate the essential forces like lift and thrust.

Let’s step in to the forces that enables flying. Since Isaac Newton we know the main force of our World the gravity. Gravity pulls down everything towards the Earth’s surface. In this subject we call gravity as weight.

Flying action needs an opposite force against weight. And to fly (Lets look to the picture again) this force must be greater than weight. Its name is Lift. If lift is greater than weight the first condition of flying is checked.

## Opposite forces

Let’s continue with the other opposite forces. Think that you hold an open umbrella in a windy street and you hold your umbrella against the wind. You feel the sense of the force Drag because basically wind hits directly through the umbrellas surface. Let’s think a plane weather has a jet engine or propeller engine. These engine system is mainly deployed because to generate the thrust force. Thrust force is the opposite force of Drag and when thrust is bigger than drag the plane moves forward.

Now we know all the forces of flight. Let’s continue with the relation between these forces. When engine turns on and generates thrust the airflow creates different pressures between upside of the wing and downside of the wing. This pressure difference is due to the physical structure of the wings. And again because of the shape of the wings with the help of the thrust the lift force becomes greater than the weight force and the flying action starts.

Finally lets summarise. Think about a plane on the runway and started to run for departure. With the help of the engines thrust force increases and beats the drag force and simultaneously due to the structure of the wings and because of the preassure diffecence lift force starts to beat the weight (gravity) force and the plane starts to fly.

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