Everything You Need To Know About How Airplanes Actually Fly

The four forces that act upon a plane: lift, weight (or gravity), drag, and thrust.

Every day, approximately ten to twelve million people fly on airplanes to quickly reach their destinations. But, there has been a long-run question about airplanes: how do these massive machines stay in the air? That’s simple. Airplanes stay afloat through a combination of physics, aerodynamics, and mechanical engineering. 

The Four Primary Forces of Flight

First, in order for an airplane to fly, it must balance four primary physics forces: lift, weight (also known as gravity), thrust, and drag. Lift is an upward force that counteracts the plane’s weight and allows it to stay afloat in the air. This force is primarily generated by the wings as air flows over and under them. Second, weight is the downward force created by the plane’s mass as it’s being weighed down by gravity. Lift and weight need to counteract each other perfectly, as the plane has to generate enough lift to overcome its weight and fly. 

A plane not only needs to float in the air but also propel itself forward and backward. This is where the physics principles of thrust and drag come into play. Thrust is defined as the forward force produced by the airplane’s engines, which propels the plane forward through the air. Drag is defined as the resistance created when air pushes against the plane as it moves. In order for a plane to fly properly and travel effectively, thrust must overcome drag. 

How Wings Generate Lift

The wings of an airplane are the most important parts of an airplane for generating lift and allowing it to stay afloat in the air. There are two main scientific principles to explain how lift works: Bernoulli’s Principle and Newton’s Third Law of Motion.

First, Bernoulli’s Principle states that as the speed of a fluid, which is air in this case, increases, its pressure decreases. Airplane wings are designed with a curved upper surface, which causes air to move faster over the top than underneath. This creates a pressure difference, where there is a region of low pressure above the wing and a region of high pressure below, which ultimately results in an upward lift force. 

Second, Newton’s Third Law of Motion—for every action, there is an equal and opposite reaction—is also important for airplanes to fly. As the airplane’s wings move through the air, they push air downward. When applying Newton’s Third Law of Motion, this means that each downward push of air results in an equal and opposite upward force, producing lift. Newton’s Third Law of Motion complements Bernoulli’s Principle, since they both play a key role in how upward and downward forces are manipulated. 

The Key Parts of an Airplane

The different parts of an airplane labeled (via Glenn Research Center).

An airplane consists of several major components, with each being crucial for enabling airplanes to fly and push forward. First, as mentioned before, the wings of an airplane are one of the most important components that allow airplanes to fly. They not only generate lift but they also hold fuel tanks. Additionally, the wings feature important control surfaces that help balance and keep the airplane stable and controllable, including ailerons, which are hinged surfaces located on the wings’ trailing edges that help the plane bank left or right; flaps, which are small extendable “strips” located along the bottom edge of the airplane that increase lift at lower speeds; and slats, which are adjustable panels on the wing’s leading edge that also improve lift at slow speeds. Every aspect of the wings of an airplane contributes to generating lift and keeping the airplane afloat. 

Second, the airplane’s engines help provide thrust to propel the plane forward. Commercial airplanes that people typically ride on usually either have jet engines that use compressed air and fuel combustion to produce high thrust or propeller engines, which use rotating blades to push air backwards in order to produce forward thrust. 

Third, the tail, or empennage, of an airplane helps with maintaining stability and control as an airplane climbs, descends, and maintains altitude. The vertical stabilizer, which is the front part of the fin of an airplane, prevents unwanted side-to-side movements, and it does not move. The rudder, which is the back part of the fin, does move and allows the pilots to move the airplane side-to-side. Finally, the horizontal stabilizers, which are fixed, prevent unwanted up-and-down movements, while the elevators, which are controlled by the pilots, allow for the plane to climb and descend.

How an Airplane Takes Off, Flies, and Lands

First, for an airplane to take off, the pilot has to increase engine thrust to accelerate the plane down the runway. Then, as the speed increases, there is more air flow over the wings, creating a higher pressure difference and generating lift. Then, once lift exceeds weight, the plane ascends in the air while the wings and tail of the plane work hard to stabilize and balance the plane. 

Then, while the plane is cruising in the air, the pilot adjusts thrust to maintain speed and prevent the weight of the airplane from overcoming lift. If the weight overcomes lift, it leads to a stall, and the airplane can no longer maintain flight. However, stalls are rare, and the pilots work together with multiple control surfaces, as well as navigation systems and autopilot, to help maintain the airplane’s course, altitude, and stability. This means that passengers don’t have to worry about the plane’s stability and control while the pilot goes to take a break. 

When the airplane is near its destination, the pilot gradually reduces thrust and extends the airplane’s flaps to increase lift at lower speeds. As the pilot does this, the plane descends gradually, and the plane is aligned with the runway. If everything is successful, the wheels of the airplane touch down on the runway, and the brakes slow down the plane to an eventual stop. 

Conclusion

To wrap up, airplanes are the creation of human creativity, research, and intelligence, as they can only operate when a careful balance of physics and engineering exists. Lift, weight, thrust, and drag are all carefully manipulated to allow the plane to reach destinations quickly, while advanced aerodynamics and control systems ensure stable, effective, and comfortable travel. Every single component of an airplane works to make air travel one of the fastest and most reliable forms of transportation, allowing the world to stay connected.