Aircraft

An aircraft is any device used or intended for flight in the air.

To fly, a vehicle must overcome the constant downward pull of gravity. This is achieved by generating lift, which is an upward force. The study of how aircraft are designed and built is called aeronautics. The human activity surrounding these machines is known as aviation. Aircraft can be categorized by how they stay aloft, how they move, or how they are used. Some are flown by a pilot, while others are unmanned aerial vehicles, often called drones. These drones can be controlled by a person from a distance or by onboard computers.

There are two primary ways to achieve flight: through buoyancy or through dynamic lift. Lighter-than-air aircraft, or aerostats, use buoyancy to float. They function much like a ship floating on water. These craft use large cells or canopies filled with gases like helium or hydrogen. They may also use hot air. Because these gases are less dense than the surrounding atmosphere, they create upward pressure.

Small versions, such as sky lanterns, were invented in China before the 3rd century BC. While balloons are general aerostats, the term airship usually refers to large, powered designs.

Heavier-than-air aircraft, known as aerodynes, are denser than the air around them. They must generate enough lift to counteract their own weight. This is often done using an airfoil, which is a specific wing shape.

When air flows across an airfoil, it creates aerodynamic lift. Fixed-wing aircraft, such as airplanes and gliders, move the entire vehicle forward to force air over the wings. Gliders are unique because they do not use an engine to achieve this movement.

Another method is through rotorcraft, which include helicopters and autogyros. These machines use a rotor, which is an assembly of blades spinning around a vertical mast.

This spinning motion creates the necessary lift to stay airborne.

Some specialized designs use different methods to fly. A lifting body generates lift through the shape of its entire fuselage rather than using separate wings. NASA experimented with these designs during the 1960s and 1970s. There are also powered-lift aircraft capable of vertical takeoff and landing (VTOL). This includes jet aircraft like the Harrier or tiltrotors like the Bell Boeing V-22 Osprey. These machines must transition from vertical to lateral movement during flight. An ornithopter is another type that produces lift by flapping wings, similar to a bird.

The history of aviation spans over two thousand years. Early examples include Chinese kites, which used air pressure differences to fly. In the 15th century, Leonardo da Vinci designed flying machines based on aeronautical concepts. However, these remained unworkable due to the technology of that era. In the late 18th century, the Montgolfier brothers invented the hot-air balloon. This era also saw the discovery of hydrogen gas, leading to hydrogen balloons. Sir George Cayley later helped develop modern aerodynamics by studying fluid dynamics and Newton's laws of motion.

Significant progress occurred in the 19th and 20th centuries. Scientists like Otto Lilienthal and Octave Chanute conducted glider experiments to understand wing dynamics. In 1903, the Wright brothers achieved the first controlled, powered, manned flight in an airplane. By 1909, aircraft began to adopt a standard configuration, including a cruciform tail.

Ferdinand von Zeppelin pioneered rigid, steerable airships that dominated long-distance travel until the 1930s. After World War II, the development of jet engines revolutionized both military and civilian aviation. In the latter half of the 20th century, digital electronics introduced "fly-by-wire" systems to improve flight control.

Aircraft vary wildly in size and capability. The Airlander 10 is a massive hybrid blimp that can stay airborne for two weeks. It can carry a payload of up to 5,000 kilograms. On the other hand, the Antonov An-225 Mriya was the largest fixed-wing aircraft ever built.

This Soviet-built transport had a wingspan of 88.4 meters. It held the world record for payload and was the heaviest aircraft ever constructed, with a maximum loaded weight of 640,000 kilograms. While the An-225 was destroyed during the Russo-Ukrainian War, it remains a famous example of heavy-lift engineering.