The Essence of Flying

Podstata létání


The Essence of Flying or Why Does an Airplane Fly?

Have you ever observed birds and wondered how simple flying looks? The essence of flying has intrigued people since ancient times. For centuries, humans have dreamed of soaring through the air like birds. Some went even further and unsuccessfully attempted to lift off by flapping wings made of feathers. However, the human body is too heavy for flying, and it lacks the necessary muscles. The pioneers of aviation soon realized that to fly like birds, they must first understand the principles of their flight.

Created for Flight

They discovered that bird wings have a unique shape. When air flows around them, it creates a difference in air pressure above and below them. This generates a force called lift, which is greater than the bird’s weight, allowing objects heavier than air to fly.

Flight in Nature

Birds exhibit remarkable capabilities in flight, surpassing other airborne creatures in terms of height, distance, and speed. Many species display the extraordinary ability to migrate across entire oceans and continents. A distinctive feature of avian flight is the utilization of wind dynamics. The wings of birds are under the control of two pectoral muscles, constituting a significant portion of their total body weight in most cases. These muscles manipulate long, rigid feathers. Feathers at the tips of the wings are called primaries. It’s important to note that the primary feathers contribute to both lift and thrust. During the downstroke of the wingbeat, the primaries open and provide lift, allowing the bird to stay airborne. Simultaneously, the air pressure difference created by the flapping motion contributes to thrust, propelling the bird forward. The interaction between lift and thrust is essential for the bird’s ability to fly efficiently. The specific shape of a bird’s wing is intricately linked to its lifestyle. While long wings are more efficient, they pose a greater challenge for flapping, often seen in birds that soar to great heights. On the other hand, birds with shorter wings sacrifice endurance but can rapidly achieve high speeds.

The Essence of Flying – Aircraft in Flight

And now: how does an airplane fly? There are four forces – weight, lift, thrust, and drag – that act on the airplane during flight. These forces collaborate to craft the invisible magic that propels machines, seemingly too heavy for the air, into the flight. The airplane is lifted due to the difference in air pressure below and above the wing. This force is called lift. Lift overcomes the weight of the aircraft. Thrust, or the forward motion force, comes from the engine and overcomes the drag of the air, which naturally affects the airplane during forward motion. When an airplane flies straight with constant speed and altitude, these four forces are in balance. This means that the lift force is equal in magnitude and opposite in direction to weight, and thrust is equal in magnitude and opposite in direction to drag.

Aircraft Stability and Flight Control

For a smooth and serene flight, an airplane must also possess stability. The tail surfaces and the upward tilt of the wings (known as dihedral) stabilize the airplane. Both the wings and the tail feature movable control surfaces, namely ailerons, elevators, and rudders. These surfaces adjust the airflow around the wings and tail, allowing the pilot to modify the direction and altitude of the flight with precision. Just as a skilled puppeteer manipulates the strings, a pilot utilizes these control surfaces to choreograph the “dance” of the aircraft through the skies.


When the elevators are deflected upward, the nose of the aircraft rises above the horizon, causing the airplane to climb. The rudder and ailerons remain in a neutral position during this maneuver. Conversely, when descending, the elevators are deflected downward. This upward and downward motion of the aircraft’s nose is referred to as “pitch.”

Wing Flaps

Birds spread their feathers and alter the shape of their wings to land slowly. Similarly, an aircraft pilot accomplishes this by deploying flaps and slats on the leading edges of the wings. These devices increase lift, allowing even large jet aircraft to take off and land at lower speeds.

Principles of airflow around wings and the creation of lift under the wings are utilized by airplanes and gliders.

How does a helicopter work?

Helicopters are capable of flying backward, forward, sideways, hovering in the air, and landing on very small surfaces. Compared to conventional airplanes, they have many advantages. The essence of helicopter flight involves a set of rotating blades called a rotor. The rotor provides lift and determines the direction of the aircraft’s movement. The rotor is connected to the collective and cyclic control levers of the rotor blades, which the helicopter pilot uses for control. A small tail rotor keeps the helicopter’s fuselage stable.

  • Ascend – The pilot raises the collective control lever, increasing the angle of the rotor blades until the lift exceeds the weight of the helicopter.
  • Descend – The pilot lowers the collective control lever. The angle of the rotor blades decreases until the lift force is less than the weight of the helicopter.
  • Forward flight – The pilot tilts the cyclic control lever forward. The rotor tilts forward, redistributing lift and providing forward thrust.
  • Sideways flight – The pilot tilts the cyclic control lever sideways. The rotor tilts sideways, once again redistributing lift, creating sideways thrust.

Principle of Flight: Balloons and Airships

Balloons and airships, whether filled with hot air (which, being less dense than the colder surrounding air, naturally ascends) or gases like helium or hydrogen (which are inherently lighter than air), operate on a distinct principle. The core of hot air balloon flight lies in the principle that a lighter gas ascends, and when a sufficient amount of it is present, it surpasses the weight of the balloon, allowing it to rise.