Look up at the sky anywhere in the world, at any time during the day, and you'll likely spot at least one aeroplane.
These massive marvels of engineering travel from one end of the planet to the other, conveying millions of people around the globe every single day. The FAA handles more than 44,000 flights daily — and the average 747 weighs more than 735,000 pounds.
How do pilots get these massive crafts off the ground? Let's take a closer look at the science of flight so we can understand aircraft basics.
While we might not recognize it as the concept of flight that we know today, we've been playing with aerodynamics for centuries. Kites started appearing in China sometime around 1,000 B.C. Today they are considered toys, but they're actually the oldest known flying machine. Kites are the first device that used the principles of flight that we'll discuss in a moment.
Even Leonardo da Vinci explored the possibility of flight, though the famed Italian painter and inventor never actually got off the ground. His drawings included more than 500 sketches of ideas for flying machines, many based on the behaviours he observed when watching birds in flight. While some of his designs might resemble modern aircraft, we didn't see the first plane as we know them today until 1903.
In 1903, in Kitty Hawk, North Carolina, the Wright Brothers — Wilbur and Orville — made history by launching the first heavier-than-air flying machine off the side of a hill. They only got off the ground for 12 seconds during that first iconic flight, but it didn't take long for them to refine their design. By 1909, they were able to fly across the English Channel.
Today, aeroplanes come in all shapes and sizes, from the small single-seaters powered by propellers to the massive passenger liners that fly above 30,000 feet to the super-fast jet fighters that can break the speed of sound. Whether you're looking at the original Wright Brothers plane or a high-tech stealth fighter, they all have one thing in common: They all rely on the four aspects of flight.
Four things make up the science of flight. When they work together, you can get anything from a paper aeroplane to a massive passenger liner off the ground. If one of these four aspects is out of balance, everything comes crashing down. These four aspects are:
These four things work together to help aeroplanes fly.
Finally, we come to the crux of the matter. How do aeroplanes fly? For the sake of argument, we're going to look at a passenger aircraft like the one you might ride in while you visit your grandparents for the holidays. These massive planes weigh hundreds of thousands of pounds and look like they'll never get off the ground, but they do, thousands of times a day.
It's all about balance. In this case, you have to be able to balance the things pushing the plane up and forward with the things that are dragging it down and backwards. On the ground, the first two things you contend with are drag and thrust. The aeroplane has to accelerate hard enough to be able to overcome the drag that wants to keep it still. As it speeds up, the shape of its wings manipulates the air currents around them to start to generate lift.
You get flight when the thrust and lift are enough to overcome the weight of the craft and the drag trying to slow it down. It's that simple, and that complex.
The formula for flight looks something like this: Lift equals the coefficient times the density and velocity squared times the area of the wings times two. What makes it that much more complex is that the coefficient can be pretty much anything. It's a series of dependencies that pilots and engineers often discover experimentally.
In theory, as long as your thrust and lift are enough to overcome the drag and weight of your aircraft, you will get off the ground. We recommend leaving the flying — and especially the landing — to a trained pilot, though.
Flight might look a lot different in the future than it does today. Aerospace engineers are already dreaming of low-orbit craft that can circle the globe in a fraction of the time it would take a 747 to travel the same distance. No matter how high you're flying, the basic science of flight will always be the same. You need to overcome drag and weight with thrust and lift if you hope to touch the sky.
Megan Ray Nichols is a science writer by day & an amateur astronomer by night (at least when the weather cooperates). Megan is the editor of Schooled By Science, a blog dedicated to making science understandable to those without a science degree. She also regularly contributes to Smart Data Collective, Real Clear Science, and Industry Today. Subscribe to Schooled By Science for the latest news.