One widely known Greek myth is that of Daedalus and Icarus, the first men that ever defied gravity and flew like a bird to get away from the king of Crete. Sadly, this venture cost Icarus his life but ever since those times humans have managed to build and develop planes to travel all around the world. Wanna know how they did it?
(Image source: pexels.com)
I suppose they built a powerful engine
Almost right, but it’s not just a powerful engine. The beauty lies in two very basic concepts. Follow me…
To understand the basics of flight we need to look into Newton’s laws of motion and Bernulli’s principle (do you remember it from the last troll-physics post?).
What did these guys say?
Let’s begin with sir Newton and his three laws of movement:
- As long as there is a balance in the forces applied on an object, it will remain motionless or keep moving maintaining a steady velocity (if it was moving in the first place).
- Greater force equals greater acceleration, therefore higher speed and longer distances.
- For every force applied in one direction there is always another force pushing in the opposite direction.
Let’s have a look on the forces applied on an airplane in order to understand better what will push it forward and what upwards.
(Image source: commons.wikimedia.org)
Thrust is the force that pushes forward and drag is the opposite force pushing backwards. In order to get the plane moving thrust must be greater than drag. If you want to stop it or slow it down, then drag must be greater than thrust.
Weight is the force that pushes the plane towards the earth (downwards) and its opposite is lift, the force that works undermining gravity and pushes the plane upwards.
And that other guy, Bernulli?
He said that within a flow of a moving gas or liquid the pressure is lower than the surrounding. As velocity increases the pressure decreases and the other way round.
Ok, in plane terms, please (pun intended)
The key lies in the wings! The shape of a plane’s wings is such that creates a pressure differential. When an air current meets the wing, it gets split in half and deflected. Because of the curvature on the upper surface of the wing, the air molecules don't follow a straight course, but are led slightly upwards and then back downwards, parallel to the wing. As the air meets this curvature it expands gaining more volume, therefore less density and eventually lower pressure than the air on the down part of the wing; so the upper air flow will be accelerated more than the one at the bottom. Now, the air currents will finally meet the tip of the wing (which is slightly bent downwards) having been accelerated downwards and will push the plane upwards (remember the action-reaction rule) generating more lift.
As you can see in the image below, there is an "angle of attack" determining the angle at which the air will meet the wing. There is a certain point up to which this angle works to increase the force of lift (about 15°), after that, the greater the angle, the less the lift.
(Image source: commons.wikimedia.org)
The wings of the planes are designed in this particular way in order to maximize lift. But given their enormous size and heavy loads, planes have also extra wings and components that allow them to take off, land, swerve, rotate and so on.
Is that all?
No, in order to lift the plane in the air you need pretty powerful air currents.
And how am I going to get them?
That’s where the engines step in. We need something to increase thrust if we want our plane to move and engines make use of τhe air by accelerating it as it passes through them. Three are the basic models of engines:
- Propeller engines: that create thrust by spinning a propeller (a set of smaller wings that rotate to create an air current generating thrust)
- Rocket engines: what spacecrafts use (thrust is created by the combustion of the fuel gas)
- Gas turbine engines or jet engines: that combine the mechanism of rocket engines but create thrust using the surrounding air
Let’s put the pieces of the puzzle together now:
To get a plane fly you need to create an imbalance in the forces applied to it. You need lift greater than weight, that's where wings do the most work, it's their shape and size that are responsible for that. And in order to have thrust greater than drag, you need the engines to "push" the plane up in the sky.
Mechanics of flight are a lot more complicated. You can surely find plenty of online information on the topic, some of it is already clearly presented in the references below. I hope I got all the basics covered up well and you're getting to the end of this post with a much better understanding of the forces that work to get you to your destination the next time you're getting on a plane ;)
(Image source: pexels.com)
Those videos explain the whole thing pretty well if you are more of an audiovisual learning type. Enjoy!
References
grc.nasa.gov
livescience.com
explainthatstuff.com
howstuffworks.com
Thank you for stopping by and giving this post a read. I hope you enjoyed it! If you please, feel free to pay a visit to my blog and check out my short stories along with plenty of educational posts and of course my bizarre natural phenomena series.
Until my next post,
Steem on and keep smiling, people!
