Understanding How Do Airplanes Fly

A message from a reader recently landed in my inbox, stating, “sir Mond, you’ve been writing a lot of technical stuff on airplanes but there are still some who do not understand how do airplanes fly. They think its the same as riding a bus, which is not.” This made me realize how crucial it is to circle back to the fundamentals of aviation. So today, we’ll discuss the physics of flight and the forces that influence an aircraft. No matter how deep we delve into the complexities, our understanding of current aviation technologies and intricate details will remain limited if we overlook the core principles of how airplanes fly.

Achieving Perfect Harmony Amidst Forces in the Skies

To understand the science that makes flight possible, one must first grasp the principles of balance in the skies. Flight is a balance of four primary forces: lift, weight (or gravity), thrust, and drag.

The first thing to consider is that airplanes have a certain weight, attributed to their own mass and the cumulative mass of the passengers, cargo, and equipment they carry. This weight generates a force that pulls the airplane downwards – this is simply gravity doing its job. On the flip side of gravity, we have lift, which works in opposition to the weight of the plane. Lift is the force that propels an airplane upwards, generated primarily by the design and movement of the wings.

But gravity and lift are just half of the story. The forward movement of the airplane is powered by another force known as thrust. Thrust pushes the airplane ahead, enabling it to cover distance. Counteracting the forward motion of thrust, we have drag, a force that attempts to hold the airplane back, resisting its forward movement.

Lift

To truly grasp the mechanics of flight, we must look into the dynamics of lift, an indispensable component of the process. An airplane’s wings, or airfoils as they’re scientifically termed, are engineered to create lift. The design is such that the air flowing over the wing’s upper surface moves faster than the air flowing beneath it. This difference in airspeed generates a pressure differential – higher underneath the wing and lower on top. The resulting upward force is what we know as lift.

The wing’s shape, along with its angle of inclination or the “angle of attack,” plays a critical role in this process. The wings of a plane are slightly tilted upward, causing air molecules to strike the bottom of the wing with greater vigor than those gliding over the curved top surface. This slight difference in pressure dynamics leads to lift, the force that keeps the plane aloft.

Aerodynamics

The overall aerodynamic blueprint of an airplane, and particularly its wings, is a fundamental aspect of successful flight. Ever noticed the diagonal slant of airplane wings, as opposed to a simple rectangular design? That’s not an aesthetic choice, but a meticulous design strategy to minimize resistance. Slanted wings enable smoother airflow around the wings and the fuselage, mitigating drag and enhancing the airplane’s speed and efficiency.

Nonetheless, even this aspect has its limits. If the angle of the wings is too steep, the airflow around them becomes turbulent and unpredictable, compromising the airplane’s ability to sustain lift. According to most aviation engineers, a tilt of 15 degrees typically represents the maximum sustainable angle for achieving efficient, stable flight.

Thrust and Drag

So, we’ve gotten our plane into the air, but how does it keep moving forward? This is where thrust, the propelling force, steps into the picture. Thrust propels the airplane forward, allowing it to maintain its momentum. However, for continuous forward motion, the force of thrust needs to overcome the opposing force of drag.

In the nascent stages of flight technology, propellers were the primary tools used to generate thrust. With the advent of jet propulsion technology, however, jet engines have become the mainstay. Regardless of the method, both follow the same fundamental principle, derived from Newton’s Third Law: for every action, there is an equal and opposite reaction. When a jet engine or propeller expels air backwards, the resulting reaction propels the airplane forwards.

From the earliest propeller-driven planes to today’s modern jet aircraft, the goal has always been to efficiently, forcefully, and rapidly push air backwards to generate enough thrust to counteract drag. In doing so, the airplane can overcome gravity, and we witness then witness flight.

Gaining insight into the forces that make airplanes fly can deepen your appreciation for the meticulous design of contemporary aircraft, and how each aspect influences its in-flight performance.