The Magic of Flight: Learning Lift

Santa in the flight deck
Posted by JoshWhit

I seriously love the holiday season. It doesn’t matter which holiday because they’re all so magical!

I know that sounds super lame and kind of childish. But just like there’s no better way to describe Disney World than magical, there’s no better way to describe the holiday season than magical. 

Maybe stressful too, but that can be mitigated by everyone chilling out and realizing presents aren’t the point. 

Nothing is more iconic during the holiday season than Santa Claus. 

Everyone knows that he watches kids all year to decide if they are being good or naughty, then he uses that knowledge to build and deliver presents all over the world in a single night. 

Of course, he is powered by milk, cookies, and magic, but flight isn’t straight magic. It’s also attainable by us normal, non-magical people. We use a different kind of magic. One called science.

Science of Flight

Now - more than ever - we should... | Shotton Hall Research School

I don’t want to get too technical and start throwing around all these theories and formulas because, quite frankly, I don’t know the science well enough (yet!) to give you correct information that in depth. 

How an airplane flies is one of those things that I have always wondered since I was little. I understood that the wings made it get in the air, but that was the extent of my knowledge. The sad part was, instead of searching out the answer, I decided to just accept that it was the way it was and didn’t search out the answer. But once I decided I wanted to be a pilot, I figured it was important information to understand at least a basic conceptual understanding of what got an airplane in the sky. 

This is when I was introduced to aerodynamics.

To make aerodynamics the most basic I possibly can, it is summed up as how an object moves through the air. It applies to cars, boats, trains, and aircraft of all kinds. The more aerodynamic an object is, the easier it is to move through the air.

Now in terms of airplanes, there are 4 major forces that are working on it at any given time: Lift, weight, thrust, and drag.

Forces Acting on an Airplane
Image via The Aviation History Online Museum

The only thing I’m going to focus on here is lift. But to understand lift, you need at least a very basic understanding of what the other forces are. 

Lift: the force acting against weight that causes an airplane to go upward.

Weight: the force of gravity acting on an object. It works inversely with lift to pull the airplane down.

Thrust: the force that pushes an airplane forward. It’s the inverse to drag.

Drag: the force that pushes against an airplane to keep it stationary. It works inversely with thrust to hold an airplane in place.

What Causes Lift?

Santa Claus uses magic to give him lift, and reindeer to give him thrust. For an airplane, the entire airplane creates lift, and the engines, whether a propeller or turbofan, gives the airplane thrust.

For an airplane, the wing is designed with a flat bottom and a curved top that tapers toward to tail end of the wing. This design is what promotes lift. 

Wing Shape Optimization - optimization

That coupled with the thrust from the engines to push the airplane forward.

The true reason for what gives an airplane lift is unknown, but there are 2 major theories you’ll see online. They both utilize the same principle, but one explains it incorrectly. That is Bernoulli’s law. 

Bernoulli’s law is that fast-moving air has a lower pressure than slow-moving air. The faster the air moves, the lower the pressure. Which makes the inverse true too.

Aerodynamics: The Theory of Lift - Owlcation - Education

The wrong theory is called “equal transit theory.” 

Essentially it says that the air molecules split upon impact with the leading edge of the wing and they meet again at the trailing edge of the wing. Since there is a curved profile to the wing, the molecule on top has to move further to meet the molecule on the bottom of the wing. This means the molecule on top of the wing has to move faster, which lowers the pressure of the air above the wing. Because the pressure is lower, it pulls the wing upward.

Now, remember this is the wrong theory. The biggest fallacy with this theory is that there is no reason for the air molecules to want to reconnect at the end of the wing. 

It’s also easily disproved by looking at the flat profile of the wing of a paper airplane, a balsa wood airplane, or even the Wright Brothers first flight airplane, The Wright Flyer. All of these have a rectangular profile instead of the curved one of a modern wing.

Instead, the correct theory uses Bernoulli’s law still, but it says that the air hits the leading edge of the wing and splits. The air on the top of the wing has further to go, so it has to fill a larger space than the air on the bottom of the wing, which moves straight across the flat bottom surface. 

Aerodynamics: The Theory of Lift - Owlcation - Education

This air splitting has 2 effects: The air on the top of the wing is moving further, so it’s spread out and causes a lower pressure. At the same time, the air under the wing is compressed into a smaller area and increases the pressure. These two factors create lift and push the wing upward. The wing is attached to the fuselage, or body, of the aircraft making the whole thing go upward. 

The lift created by the wings overcomes the weight and makes the airplane fly.

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