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Planes have gone from a crazy idea, to flying across the world in under 125 years. They’re amazing machines, but how do they really fly?
Planes are able to fly because of the delicate balancing of forces acting on them. The four main things that must work in conjunction with one another for a successful flight are lift, thrust (power), weight, and drag. If these forces are not balanced correctly, the plane can’t safely fly.
Figuring out how to get planes to fly is undoubtedly one of the most intriguing technological advancements in human history. While we can’t get into the intricacies and the math of how it all works, in this article you’ll learn about the four main aspects of flight that need to be accounted for if a plane is ever going to be able to fly successfully.
We know that the science behind how planes fly is far more advanced than the overview that we present here. But to make sure that we’ve explained everything correctly and have given you the most accurate information possible, everything below has been vetted by experts in aviation as well as engineers to make sure what you’re ready is as accurate as it can possibly be.
How Do Planes Fly?
Even after well over 100 years since the Wright brothers changed the world with their first flight, the actual act of flying a plane still seems like a mystery to many. After all, we’ve all been in airports and seen planes, right? Let’s be honest, they’re huge. And also, planes can’t exactly fly like birds or anything like that, you wouldn’t ever see a plane start flapping its wings to generate lift and take off.
So it stands to reason, how exactly does something that big and heavy fly?
The answer comes down to a balancing of forces that are able to not only put a plane in the air to begin with, but to keep it there, flying thousands of feet overhead for extended periods of time. Through the use of a few different forces and differences in pressure around specific areas of the plane, it’s able to keep itself in the air and travel at incredible speeds without just plummeting towards the ground.
Although there are of course differences in the ways that different planes fly — a military jet doesn’t operate exactly the same as a small single-engine aircraft, for example — the general concept is all the same. There are four major components of flight that need to be taken into account and balanced with one another before any plane will be able to make a successful flight.
What Are The Major Components of Flight?
As mentioned a couple of times now, there needs to be a balancing of four major forces on an aircraft for it to be able to fly successfully. These four major components of flight are lift, thrust, weight (gravity), and drag. We’ll get more into the nuances of each shortly, but basically, lift and thrust are generated by the plane to counteract the negative forces of weight and drag.
So let’s dive in a little deeper and take a look at what each of the four major components of flight is and how they interact with one another (as well as the plane itself) to enable the aircraft to fly.
Just based on the name of the term itself, you can probably get a decent idea of what lift is and what it does. It’s the force that keeps a plane flying and prevents it from just staying on the ground or plummeting from the skies under sustained flight. But how does lift work?
Lift is generated by the plane’s wings. The wings of a plane are designed in a unique shape called an airfoil. An airfoil is designed to force air to move across it at different speeds due to the top being curved and the bottom being flatter. With the wing of an aircraft, the air moves faster over the top curved surface than it does along the bottom.
As the air is moving over the wings at different speeds different pressures are also experienced on the top and bottom of the wing. The faster airflow over the top of the wing creates an area of lower pressure, and the slower air under the wing creates an area of higher pressure. This difference in pressure is what generates lift and allows the plane to stay in the air. It’s a simple process, but an ingenious one when it was first discovered!
For most aircraft, when we are talking about power we are talking about thrust. Thrust is the force that pushes the plane forward through the air and is produced by jet engines. Jet engines take in air, spin it at high speeds, compress it, add in jet fuel, and ignite the mixture to produce massive amounts of thrust. These large amounts of thrust and power force the plane forward and help it achieve high speeds of 500+ miles per hour or more.
For smaller aircraft, a piston engine or propeller engine might be used in place of the jet engine on military aircraft and commercial airliners. For these aircraft, the engines are still producing the power needed to force the plane forward, whether that’s through the propeller or piston engine.
So whether you’re talking about thrust or power in general, just know that it’s the forward-pressing force that enables a plane to overcome air resistance and maintain enough speed to stay in the air.
Weight (and Gravity)
We all know what weight is, right? Simply how heavy the plane is. This is one of the most impressive aspects of flight, the fact that a plane that weighs hundreds of thousands of pounds (Boeing 777 has a maximum takeoff weight of 545,000 pounds) can fly through the air. Well thanks to what you just read about lift and thrust, you have an idea of how that can even happen in the first place.
More so than the weight itself, the force that we’re interested in here is gravity. The more an object weighs, the larger the downward force of gravity on that object is, since weight and gravity are one and the same. So as planes get bigger and heavier, more lift needs to be generated to overcome the gravitational pull and allow the plane to fly.
The easiest way to think about it is that lift and gravity need to be correctly balanced to enable the plane to fly and adjust altitude as necessary during flight.
Just like how weight and gravity above counteract lift, drag is the force that mostly counteracts thrust (or power). Drag is largely the same as the air resistance that an object experiences as it flows through the air. Imagine putting your hand out the window of your car on the highway. That force that you feel pushing back on your hand is drag as your hand cuts through the wind.
So when it comes to an airplane, drag is the backward-pulling force that it experiences as it flies through the sky. And since you learned above that thrust and power are the forward-pressing forces that enable a plane to fly, it stands to reason that drag and thrust need to be balanced in order to sustain a controlled flight.