Aerodynamics is the concept of how something moves through the air. How aerodynamic an object is depends on its shape and the four forces of flight. Whether you’re flying a kite or a jet plane, all the forces must work together to sustain flight.

Did you know that air has weight? That’s why some craft are called “lighter-than-air;” balloons, for example, weigh less than the air around them because they’re filled with hot air, which is lighter than cold air. However, it wasn’t until the 1600s that Evangelista Torricelli actually discovered air has weight. With that concept in mind, humankind could start to develop flying machines that would manipulate air and create lift.

Developing the Physics of Flying

The 1600s proved to be a beneficial time for strengthening our understanding of flight. Sir Isaac Newton proposed his laws of motion in 1665, stating that objects need a force to act upon them to create motion or stop it. Additionally, objects will move farther and faster if they have greater forces applied to them. Building upon Torricelli’s and Newton’s research, ambitious inventors would attempt to take to the skies for years to come.

Principles of Flight

Many of us know famous figures such as Leonardo DaVinci, Jean-Francois Pilatre de Rozier, Francois Laurent, Alexander Fyodorovich Mazhayskiy, and the Wright brothers spent years trying to fly. But how is flight successfully accomplished? Let’s dive into the principles of flight, and how they allow objects that, today, weigh tens of thousands of pounds to glide overhead.

Lift 

The opposite of weight, lift is the force that moves objects up. Lift can be manipulated with the use of hot air (which rises above cold air), or the shape of an object.

Thrust 

This is the force that propels objects forward. If thrust is stronger than drag, an object can move. In airplanes, it can be created with propellers or jet engines.

Drag

This principle of flight is the amount of resistance experienced by an object. Drag is a force that slows something down. It can be affected by factors such as an object’s shape or texture.

Weight

Gravity is the weight that keeps everything grounded on the Earth. Weight is how much mass an object has. 

A little more on these principles, and more, below.

Lift

The wings of an airplane are what keep it in flight. Due to their teardrop shape, airplane wings create lift and can move a plane higher or lower. Their shape and moving panels called ailerons can also reduce or increase drag to change the plane’s speed and direction of travel.

Since airplane wings are thicker at the front than they are at the back, this creates a curve to the top of the wing, while the underside is flatter. As a result, air travels over the top of the wing faster than it travels under the wing. This creates an airfoil, which amplifies lift since the air pressure on top of the wing is less than the air pressure underneath. Similarly, helicopter blades are also curved to assist with creating lift.

Downwash

Let’s take a look at lift created by helicopters, as it varies from how it’s created by airplanes. The rotors on the top of a helicopter spin in a circle and create a downwash. This is a rush of air moving down toward the ground, just like the rush of air created by stationary airplane wings. The difference is that the downwash created by a helicopter is a bit more pronounced than the downwash created by an airplane. 

Thrust

Aircraft engines generate thrust, as do propellers. They create the forward motion that helps overcome the weight and drag of the aircraft. Working with the principle of lift, thrust helps a plane take flight and gain altitude. 

Yaw

A rudder (or multiple rudders) on the tail of the aircraft assists with turns, or yawing the aircraft. The rudder is one or more vertical panels on the tail, and moving it side-to-side (like opening or closing a door) in conjunction with the ailerons helps direct the nose of the plane in the desired direction.

Roll

If a pilot wants to execute a maneuver such as a roll, or a bank into a turn, the ailerons on one wing are raised, while the ailerons on the other are lowered. In order to turn the plane with a roll, one wing needs to be higher than the other. When the ailerons are lowered, they create more lift and raise that particular wing. When they’re raised it reduces lift by increasing drag, which can lower the wing.

Pitch

Pitch refers to the direction in which the nose of an aircraft is pointing. In addition to a rudder, there are also elevators on the tail of an airplane. They are situated horizontally on either side of the rudder, and when their position is altered, can lift or lower the nose of the aircraft. Raising the elevators will help aircraft gain elevation.

From the first flights of human-manned kits to jets that can break the sound barrier, our understanding of aerodynamics and the mechanics of flight has come a long way.