In this blog post, we’ll explore how humanity’s long-held dream of flight became a reality through advances in science and technology, along with the principles behind how airplanes work.
He must have been flying high in a clear, cloudless sky. This is because beeswax only begins to melt when the temperature exceeds 62°C. Long ago, Icarus—who had crafted wings by attaching bird feathers with beeswax and flapped those wings to escape the Labyrinth of Crete—ignored his father’s warning not to fly too high and soared even higher. Unable to withstand the increasingly intense sunlight, the wax melted, causing the feathers to scatter in midair. Having lost his wings, Icarus plummeted and drowned in the Aegean Sea.
Although humanity’s first attempt at flight—spanning some 3 million years of history—ended in failure, Icarus’s death was not in vain. Icarus’s flight was passed down to future generations as part of mythology and inspired many scientists and engineers. Humanity’s long-held dream of flight—which evolved through Leonardo da Vinci’s sketches of flying machines and French author Jules Verne’s science fiction novels—was finally realized by the Wright brothers. Since then, aircraft technology has advanced dramatically, and even today, countless airplanes operate in the skies around the world, transporting people and cargo. How was humanity’s long-held dream finally realized?
The secret of the airplane lies in the structure of its wings. The cross-section of a modern airplane wing is streamlined, with a rounded front and a tapered rear. This shape closely resembles the cross-section of a bird’s wing. When an airplane flies through the air, thrust, drag, gravity, and lift act on the wings. Thrust is the force generated by the airplane’s engines to propel the aircraft forward, while drag is the resistance caused by friction with the air. Gravity is the force that pulls the airplane toward the center of the Earth—that is, toward the ground. Finally, lift is the key force that lifts the aircraft upward, enabling the heavy airframe to fly through the sky.
In mechanical engineering, the cross-section of an airplane wing is called an “airfoil,” and the angle formed by the straight line connecting the leading edge and trailing edge of the airfoil with the direction of the aircraft’s flight is called the angle of attack. Airplanes adjust the shape of the airfoil to change the angle of attack and generate lift appropriate for the situation. Air striking the airplane flows along the wing’s surface and, as it exits the wing, flows downward relative to its initial direction. This means that the speed and direction of the air flowing along the airframe have changed, indicating that the air has received a downward force from the airfoil. At this point, according to Newton’s law of action and reaction, the air also exerts an upward force on the airfoil. This force is the lift that keeps the airplane aloft.
In order for an airplane to maintain a proper altitude, lift must be adjusted according to the situation. The magnitude of lift, Fy, is calculated as Fy = 1/2·ρV²SC. In this equation, S represents the wing area, V represents the airflow velocity, ρ represents the density of air, and C represents the lift coefficient based on the angle of attack. Lift is proportional to the wing area, the square of the airflow velocity, the density of the air, and the lift coefficient. An airplane controls these factors by adjusting engine power and moving the flaps located on the rear of the main wing. Unlike the main wing, which has a fixed shape and angle, the flaps can move up and down, much like a fish’s fin. Lowering the flaps increases the angle of attack of the airfoil, which in turn increases the lift coefficient, resulting in greater lift.
Contrary to the common belief that flaps are lowered during takeoff to increase lift, airplanes take off with the flaps only slightly extended. During takeoff, the aircraft builds up sufficient speed to generate lift and uses that force to take off. This is because lowering the flaps excessively not only creates significant drag, making it difficult to accelerate, but can also place a greater structural load on the aircraft at high speeds. Conversely, during landing, as speed decreases, lift drops sharply, creating a risk of the aircraft colliding with the ground. Therefore, flaps are lowered significantly during landing to compensate for the lack of lift and ensure a safe landing.
Humanity’s dream of soaring through the skies has become a reality thanks to advances in science and technology. It is not just the dream of flight. The desire to travel faster and more conveniently led to the invention of the automobile, and the wish to transport goods more easily led to the creation of the railroad. The dream of turning seawater into drinking water spurred the development of desalination technology.
After Icarus’s death, “Icarus’s wings” became a metaphor for unfulfilled desires. However, mechanical engineers have identified the countless “Wings of Icarus” floating around us, analyzed them closely, and developed technologies that turn human dreams into reality. Even at this very moment, another “Wing of Icarus” is hovering near us, and engineers are studying it. And yet another new dream will become a reality.
