Flight

The act of passing through the air by the use of wings.

Humans have dreamed about flying for thousands of years. They probably watched birds, insects, bats, or leaves and imagined and wondered what it must be like.

However, it took many years for humans to understand the properties of earth and air necessary for flight and be able to measure them accurately, develop relevant theories, and predict outcomes. Only then could people build the wings and engines needed to fly.

Around 350 BC the Chinese began to make kites from bamboo frames covered in paper and silk. Many of today's kites use a similar design. A kite is a form of a glider, as it does not technically fly, but instead sails on air currents.

In 1492 the Italian scientist, artist, and inventor Leonardo da Vinci observed the flight of birds and analyzed their anatomy. He used those bird observations to create designs for some of the first human flight ideas.  Hundreds of years later, his designs for parachutes, helicopters, and flying machines were used in the early attempts at making flying machines in the 1900's.

In 1670 another Italian scientist, Giovanni Borelli, who studied the mechanics of animal movement, proved that human muscles wouldn't be strong enough to hold the big wings needed to lift a human off the ground.

In June 1783 two French brothers, Joseph and Jacques Montgolfier, who owned a paper mill, noticed that a piece of fabric would float over a fire. They had observed that hot air rises and decided to see if they could create a craft based on this newly discovered science. Their unmanned fabric balloon creation rose into the sky when filled with hot air. This led to additional attempts at flight.

On September 19, 1783, three passengers along with a sheep, a rooster, and a duck were successfully launched into the air in a hot air balloon. The Montgolfier brothers continued to play with balloon flight, and soon others were experimenting with this type of flight.

Many additional attempts in flight were made over the next 120 years — mostly glider crafts. However, it was the brothers Wilbur and Orville Wright who, in 1903, for the first time ". . . in the history of the world . . . [created] a machine carrying a man . . . [which] raised itself by its own power into the air in full flight, . . . sailed forward without reduction of speed and . . . finally landed at a point as high as that from which it started."

You can view sample pages from the Wright Brothers' notebooks at the Franklin Institute's Flight pages. And you can learn more about the Wright Brothers' experiments and view some aeronautical simulations at the Open University's First Flight website..

In the 1920s and 1930s, a craft known as a dirigible became a common mode of transportation for intercontinental travel. A dirigible was a frame covered with fabric and filled with a gas. The craft could be steered, which made it different from a hot air balloon. Learn more about dirigibles at the Centennial of Flight website.

Blimps and zeppelins are kinds of dirigibles. The most famous of these is probably the Hindenburg, which during its landing on May 6, 1937, burst into flames and crashed, killing 35 persons on the airship and one member of the ground crew. Another famous dirigible is the Goodyear Blimp, which can be seen hovering above many sporting events.

Air travel is now very common, with thousands of airplane flights worldwide every day. Commercial planes, private aircraft, and space travel would not be possible without the pioneers of flight.

Gliding flight is accomplished with little or no movement or flapping of wings. Leaves, maple seeds, or dandelion seeds seem to float with the wind like they are flying, but they aren't true flyers but are instead gliding.

Man has built gliders which have no engines but are towed into the air by an airplane. These gliders look a lot like airplanes but depend on air currents to "glide" through the air. It can take hours for a glider to return to Earth. A number of animals use this method of movement but do not actually "fly." Flying squirrels, flying fish, and some snakes have skin that they can stretch out and use to glide through the air.

True Flight is accomplished only by birds, insects, and bats. Wings allow these creatures to push on the air to give them lift, thus allowing them to get airborne. Other bodily structures such as muscles and bones provide additional support for flight.

Some birds, in addition to flying, will actually seek out warm updrafts of air known as thermals which travel up from the ground. The birds will glide on these thermals, sailing around in circles or hovering in place.

There are 4 aerodynamic forces which are present when air is moving past an object. Weight, lift, drag, and thrust must all be understood before anyone can design an aircraft. The study of these forces as they relate to flight is the science of aeronautics.

Weight is caused by the pull of Earth's gravity on our body. A flying object must overcome this force.

Lift is the upward force that works against gravity and weight.

Thrust is the forward push made when an engine turns a propeller. The propeller is shaped to push the air backwards. This results in a reaction force (thrust) on the propeller that moves the aircraft forwards.

Drag, or air resistance slows down the forward movement of an aircraft. It is caused by friction between the moving object and the air around it.

Flight is achieved when the lift and thrust overcome the weight and drag. While in flight, the airplane is supported by lift. Lift is the force acting opposite of gravity and is generated whenever air flows smoothly over a wing. As air flows over and under the wing, an area of low pressure is created above the wing, acting to pull the airplane up. When lift exceeds gravity, the aircraft will leave the ground and climb.

Learn more about these four forces at NASA's Dynamics of Flight website.