What are the mechanics of flying?

Answer 1

The mechanics of flightI assume by 'flying' the question means powered flight by a heavier than air craft (such as an everyday jet plane). Other types of flight include lighter-than-air (such as a hot air balloon, or helium airship) or hang gliding which generally can't be sustained.

The key to the way an airplane works is the shape of its wing. if you were to slice an airplane wing off halfway and look at its cross-section the shape would be rounded on the top and relatively flat on the bottom, fat and rounded at one side (in the direction the plane moves) and thin and tapered on the opposite side. Think of a water drop falling. It's rounded at the bottom and thin and pointed at the top. Cut the rain drop in half along it's length and you have the basic shape of an airplane wing. This shape is specifically called an airfoil (or aerofoil depending on what part of the world you are from)

The way an airfoil produces lift is by producing relatively high air pressure on the bottom of the wing and low air pressure on the top, making the wing push up on the plane. To do this, the plane uses engines to move forward very fast and makes air flow over the wing. Since the air is being 'split' as it goes over and under the wing, it must rejoin at the back of the wing (otherwise you'd have a vacuum - no air!!) However, the top of the wing is rounded more than the bottom - the air has to go further over the top than it does under the bottom! If the air is going to 'match up' at the back, the top air must move faster than the bottom air

This creates low pressure on the top of the wing, compared to the higher pressure on the bottom with the slower moving air, pushing the wing up and so the plane lifts into the air.

you can think of it like this: everywhere in the earth's atmosphere there is air pressure pushing on us. your hand has air pushing equally on every single part, just like diving deep to the bottom of the swimming pool, where you feel the pressure of the water, it's happening to us everyday, but we're used to it so we don't notice it. this pressure is also pushing on the wing surface. if the top air is moving faster than the bottom, the pressure which is normally on the top is sort of 'blown away' more than the pressure on the bottom. so really, the plane is being sucked up!

Try it yourself. Get a piece of A4 paper (lighter is better), hold it with two hands at the top two corners, so the the part between your fingers is level, but the rest of the sheet drapes down. Blow down across the top of the paper, making sure no wind gets under the sheet. The bottom of the paper will rise up slightly, - but you're blowing across the paper! not up from below! This is the bernoulli principle in action.

The same principle works in helicopter blades which rotate to get air moving over the "wing", and on the hydrofoil boats which rise the hull out of the water at speed.