HISTORY OF FLIGHT

Myths and Legends of Flight

Greek Legend - PegasusBellerophon the Valiant, son of the King of Corinth, captured Pegasus, a winged horse. Pegasus took him to a battle with the triple headed monster, Chimera.

Icarus and Daedalus - An Ancient Greek LegendDaedalus was an engineer who was imprisoned by King Minos. With his son, Icarus, he made wings of wax and feathers. Daedalus flew successfully from Crete to Naples, but Icarus, tired to fly too high and flew too near to the sun. The wings of wax melted and Icarus fell to his death in the ocean.

Early Efforts of Flight

Around 400 BC – ChinaThe discovery of the kite that could fly in the air by the Chinese started humans thinking about flying and is thought to be the earliest example of man-made flight. Kites were used by the Chinese in religious ceremonies. They built many colorful kites for fun, also. More sophisticated kites were used to test weather conditions. The ancient Chinese also flew small hot-air lanterns and bamboo-copter toys with spinning rotors. Kites have been important to the invention of flight as they were the forerunner to balloons and gliders

Humans try to fly like birds

For many centuries, humans have tried to fly just like the birds. Wings made of feathers or light weight wood have been attached to arms to test their ability to fly. The results were often disastrous as the muscles of the human arms are not like a birds and can not move with the strength of a bird.

Man-carrying kites

Man-carrying kites are believed to have been used extensively in ancient China, for both civil and military purposes and sometimes enforced as a punishment. Stories of man-carrying kites also occur in Japan, following the introduction of the kite from China around the seventh century AD. It is said that at one time there was a Japanese law against man-carrying kites.

Efforts to analyze the atmosphere from the 17th to 19th centuries led to the discovery of gases such as hydrogen, which in turn led to the invention of hydrogen balloons. Various theories in mechanics by physicists during the same period of time, notably fluid dynamics and Newton's laws of motion, led to the foundation of modern aerodynamics. Tethered balloons filled with hot air were used in the first half of the 19th century and saw considerable action in several mid-century wars, most notably the American Civil War, where balloons provided observation during the Battle of Petersburg

Hero and the Aeolipile

Aeolipile

The ancient Greek engineer, Hero of Alexandria, worked with air pressure and steam to create sources of power. One experiment that he developed was the aeolipile which used jets of steam to create rotary motion.

Hero mounted a sphere on top of a water kettle. A fire below the kettle turned the water into steam, and the gas traveled through pipes to the sphere. Two L-shaped tubes on opposite sides of the sphere allowed the gas to escape, which gave a thrust to the sphere that caused it to rotate.

Leonardo da Vinci (1485) - The Ornithopter

Leonardo da Vinci's Ornithopter

Leonardo da Vinci's 15th-century dream of flight found expression in several rational but unscientific designs, though he did not attempt to construct any of them.

He’s made the first real studies of flight in the 1480's. He had over 100 drawings that illustrated his theories on flight.

The Ornithopter flying machine was never actually created. It was a design that Leonardo da Vinci created to show how man could fly. The modern day helicopter is based on this concept.

Joseph and Jacques Montgolfier (1783 ) - The First Hot Air Balloon

One of The Montgolfier's Balloons

The brothers, Joseph Michel and Jacques Etienne Montgolfier, were inventors of the first hot air balloon. They used the smoke from a fire to blow hot air into a silk bag. The silk bag was attached to a basket. The hot air then rose and allowed the balloon to be lighter-than-air.

In 1783, the first passengers in the colorful balloon were a sheep, rooster and duck. It climbed to a height of about 6,000 feet and traveled more than 1 mile.

After this first success, the brothers began to send men up in balloons. The first manned flight was on November 21, 1783, the passengers were Jean-Francois Pilatre de Rozier and Francois Laurent.

George Cayley (1799 - 1850's)

One Version of a Glider

Sir George Cayley and the first modern aircraft

George Cayley worked to discover a way that man could fly. He designed many different versions of gliders that used the movements of the body to control. A young boy, whose name is not known, was the first to fly one of his gliders.

Over 50 years he made improvements to the gliders. He changed the shape of the wings so that the air would flow over the wings correctly. He designed a tail for the gliders to help with the stability. He tried a biplane design to add strength to the glider. He also recognized that there would be a need for power if the flight was to be in the air for a long time.

Sir George Cayley was first called the "father of the aeroplane" in 1846. During the last years of the previous century he had begun the first rigorous study of the physics of flight and would later design the first modern heavier-than-air craft. Among his many achievements, his most important contributions to aeronautics include:

Clarifying our ideas and laying down the principles of heavier-than-air flight. Reaching a scientific understanding of the principles of bird flight.

Conducting scientific aerodynamic experiments demonstrating drag and streamlining, movement of the centre of pressure, and the increase in lift from curving the wing surface. Defining the modern aeroplane configuration comprising a fixed wing, fuselage and tail assembly.

Demonstrations of manned, gliding flight.

Cayley's first innovation was to study the basic science of lift by adopting the whirling arm test rig for use in aircraft research and using simple aerodynamic models on the arm, rather than attempting to fly a model of a complete design.

In 1799 he set down the concept of the modern aeroplane as a fixed-wing flying machine with separate systems for lift, propulsion, and control.

In 1804 Cayley constructed a model glider which was the first modern heavier-than-air flying machine, having the layout of a conventional modern aircraft with an inclined wing towards the front and adjustable tail at the back with both tailplane and fin. A movable weight allowed adjustment of the model's centre of gravity.

One of the many drawings of gliders

Cayley wrote On Ariel Navigation which shows that a fixed-wing aircraft with a power system for propulsion and a tail to assist in the control of the airplane would be the best way to allow man to fly.

19th And 20th Century Efforts

Otto Lilienthal (1891)

One of Lilienthal's Gliders

German engineer, Otto Lilienthal, studied aerodynamics and worked to design a glider that would fly. He was the first person to design a glider that could fly a person and was able to fly long distances.

He was fascinated by the idea of flight. Based on his studies of birds and how they fly, he wrote a book on aerodynamics that was published in 1889 and this text was used by the Wright Brothers as the basis for their designs.

After more than 2500 flights, he was killed when he lost control because of a sudden strong wind and crashed into the ground.

Lilienthal's Glider in Flight

Samuel Pierpont Langley (1891)

Langley's Aerodrome

 Samuel Langley was an astronomer, who realized that power was needed to help man fly. He built a model of a plane, which he called an aerodrome, that included a steam-powered engine. In 1891, his model flew for 3/4s of a mile before running out of fuel.

Langley received a $50,000 grant to build a full sized aerodrome. It was too heavy to fly and it crashed. He was very disappointed. He gave up trying to fly. His major contributions to flight involved attempts at adding a power plant to a glider. He was also well known as the director of the Smithsonian Institute in Washington, DC

First failure of Langley's manned Aerodrome on the Potomac River, October 7, 1903

After a distinguished career in astronomy and shortly before becoming Secretary of the Smithsonian Institution, Samuel Pierpont Langley started a serious investigation into aerodynamics at what is today the University of Pittsburgh. In 1891 he published Experiments in Aerodynamics detailing his research, and then turned to building his designs. He hoped to achieve automatic aerodynamic stability, so he gave little consideration to in-flight control. On May 6, 1896, Langley's Aerodrome No. 5 made the first successful sustained flight of an unpiloted, engine-driven heavier-than-air craft of substantial size. It was launched from a spring-actuated catapult mounted on top of a houseboat on the Potomac River near Quantico, Virginia. Two flights were made that afternoon, one of 1,005 metres (3,297 ft) and a second of 700 metres (2,300 ft), at a speed of approximately 25 miles per hour (40 km/h). On both occasions the Aerodrome No. 5 landed in the water as planned, because in order to save weight, it was not equipped with landing gear. On November 28, 1896, another successful flight was made with the Aerodrome No. 6. This flight, of 1,460 metres (4,790 ft), was witnessed and photographed by Alexander Graham Bell. The Aerodrome No. 6 was actually Aerodrome No. 4 greatly modified. So little remained of the original aircraft that it was given a new designation.

With the successes of the Aerodrome No. 5 and No. 6, Langley started looking for funding to build a full-scale man-carrying version of his designs. Spurred by the Spanish-American War, the U.S. government granted him $50,000 to develop a man-carrying flying machine for aerial reconnaissance. Langley planned on building a scaled-up version known as the Aerodrome A, and started with the smaller Quarter-scale Aerodrome, which flew twice on June 18, 1901, and then again with a newer and more powerful engine in 1903.

With the basic design apparently successfully tested, he then turned to the problem of a suitable engine. He contracted Stephen Balzer to build one, but was disappointed when it delivered only 8

hp (6.0 kW) instead of 12 hp (8.9 kW) he expected. Langley's assistant, Charles M. Manly, then reworked the design into a five-cylinder water-cooled radial that delivered 52 hp (39 kW) at 950 rpm, a feat that took years to duplicate. Now with both power and a design, Langley put the two together with great hopes.

To his dismay, the resulting aircraft proved to be too fragile. Simply scaling up the original small models resulted in a design that was too weak to hold itself together. Two launches in late 1903 both ended with the Aerodrome immediately crashing into the water. The pilot, Manly, was rescued each time. Also, the aircraft's control system was inadequate to allow quick pilot responses, and it had no method of lateral control, and the Aerodrome's aerial stability was marginal.

Langley's attempts to gain further funding failed, and his efforts ended. Nine days after his second abortive launch on December 8, the Wright brothers successfully flew their Flyer. Glenn Curtiss made 93 modifications to the Aerodrome and flew this very different aircraft in 1914. Without acknowledging the modifications, the Smithsonian Institution asserted that Langley's Aerodrome was the first machine "capable of flight".

Model of Langley Aerodrome

Orville and Wilbur Wright and the First AirplaneOrville and Wilbur Wright were very deliberate in their quest for flight. First, they read about all the early developments of flight. They decided to make "a small contribution" to the study of flight control by twisting their wings in flight. Then they began to test their ideas with a kite. They learned about how the wind would help with the flight and how it could affect the surfaces once up in the air.

A Drawing of a Wright Brothers Glider (1900)

The next step was to test the shapes of gliders much like George Cayley did when he was testing the many different shapes that would fly. They spent three years testing and learning about how gliders could be controlled at Kitty Hawk, North Carolina.

Picture of the actual 12 horsepower engine used in flight

They designed and used a wind tunnel to test the shapes of the wings and the tails of the gliders. In 1902, with a perfected glider shape, they turned their attention to how to create a propulsion system that would create the thrust needed to fly.

The early engine that they designed generated almost 12 horsepower. That's the same power as two hand-propelled lawn mower engines!

 

The first heavier-than-air flight traveled one hundred twenty feet in twelve seconds. The two brothers took turns flying that day with the fourth and last flight covering 850 feet in 59 seconds. But the Flyer was unstable and very hard to control.

The brothers returned to Dayton, Ohio, where they worked for two more years perfecting their design. Finally, on October 5, 1905, Wilbur piloted the Flyer III for 39 minutes and about 24 miles of circles around Huffman Prairie. He flew the first practical airplane until it ran out of gas.

 

The "Flyer" lifted from level ground to the north of Big Kill Devil Hill, North Carolina, at 10:35 a.m., on December 17, 1903. Orville piloted the plane which weighed about six hundred pounds.

Using a methodological approach and concentrating on the controllability of the aircraft, the brothers built and tested a series of kite and glider designs from 1900 to 1902 before attempting to build a powered design. The gliders worked, but not as well as the Wrights had expected based on the experiments and writings of their 19th-century predecessors. Their first glider, launched in 1900, had only about half the lift they anticipated. Their second glider, built the following year, performed even more poorly. Rather than giving up, the Wrights constructed their own wind tunnel and created a number of sophisticated devices to measure lift and drag on the 200 wing designs they tested. As a result, the Wrights corrected earlier mistakes in calculations regarding drag and lift. Their testing and calculating produced a third glider with a higher aspect ratio and true three-axis control. They flew it successfully hundreds of times in 1902, and it performed far better than the previous models. By using a rigorous system of experimentation, involving wind-tunnel testing of airfoils and flight testing of full-size prototypes, the Wrights not only built a working aircraft, the Wright Flyer, but also helped advance the science of aeronautical engineering.

The Wrights appear to be the first to make serious studied attempts to simultaneously solve the power and control problems. Both problems proved difficult, but they never lost interest. They solved the control problem by inventing wing warping for roll control, combined with simultaneous yaw control with a steerable rear rudder. Almost as an afterthought, they designed and built a low-powered internal combustion engine. They also designed and carved wooden propellers that were more efficient than any before, enabling them to gain adequate performance from their low engine power. Although wing-warping as a means of lateral control was used only briefly during the early history of aviation, the principle of combining lateral control in combination with a rudder was a key advance in aircraft control. While many aviation pioneers appeared to leave safety largely to chance, the Wrights' design was greatly influenced by the need to teach themselves to fly without unreasonable risk to life and limb, by surviving crashes. This emphasis, as well as low engine power, was the reason for low flying speed and for taking off in a head wind. Performance, rather than safety, was the reason for the rear-heavy design, because the canard could not be highly loaded; anhedral wings were less affected by crosswinds and were consistent with the low yaw stability.

Airship and Zeppelin

Construction of the first Zeppelin airship began in 1899 in a floating assembly hall on Lake Constance in the Bay of Manzell, Friedrichshafen. This was intended to ease the starting procedure, as the hall could easily be aligned with the wind. The prototype airship LZ 1 (LZ for "Luftschiff Zeppelin") had a length of 128 m (420 ft) was driven by two 10.6 kW (14.2 hp) Daimler engines and balanced by moving a weight between its two nacelles.

Its first flight, on July 2, 1900, lasted for only 18 minutes, as LZ 1 was forced to land on the lake after the winding mechanism for the balancing weight had broken. Upon repair, the technology proved its potential in subsequent flights, bettering the 6 m/s speed attained by the French airship La France by 3 m/s, but could not yet convince possible investors. It would be several years before the Count was able to raise enough funds for another try.

Although airships were used in both World War I and II, and continue on a limited basis to this day, their development has been largely overshadowed by heavier-than-air craft.

WORLD WAR

World War I (1914–1918)

Aviation in World War I

It was not long before aircraft were shooting at each other, but the lack of any sort of steady point for the gun was a problem. The French solved this problem when, in late 1914, Roland Garros attached a fixed machine gun to the front of his plane, but while Adolphe Pegoud would become known as the first "ace", getting credit for five victories, before also becoming the first ace to die in action, it was German Luftstreitkräfte Leutnant Kurt Wintgens, who, on July 1, 1915, scored the very first aerial victory by a purpose-built fighter plane, with a synchronized machine gun.

Aviators were styled as modern day knights, doing individual combat with their enemies. Several pilots became famous for their air to air combats, the most well known is Manfred von Richthofen, better known as the Red Baron, who shot down 80 planes in air to air combat with several different planes, the most celebrated of which was the Fokker Dr.I. On the Allied side, René Paul Fonck is credited with the most all-time victories at 75, even when later wars are considered

France, Britain, Germany and Italy were the leading manufacturers of fighter planes that saw action during the war, with German aviation technologist Hugo Junkers showing the way to the future of much of 20th century aviation, through the pioneering of practical all-metal aircraft in late 1915.

Between the World Wars (1918–1939)

Aviation between the World Wars

The years between World War I and World War II saw great advancements in aircraft technology. Airplanes evolved from low-powered biplanes made from wood and fabric to sleek, high-powered monoplanes made of aluminum, based primarily on the founding work of Hugo Junkers during the World War I period and its adoption by American designer William Bushnell Stout and Soviet designer Andrei Tupolev. The age of the great rigid airships came and went. The first successful rotorcraft appeared in the form of the autogyro, invented by Spanish engineer Juan de la Cierva and first flown in 1919. In this design, the rotor is not powered but is spun like a windmill by its passage through the air. A separate powerplant is used to propel the aircraft forwards.

World War II (1939–1945)

Aviation in World War II

World War II saw a great increase in the pace of development and production, not only of aircraft but also the associated flight-based weapon delivery systems. Air combat tactics and doctrines took advantage. Large-scale strategic bombing campaigns were launched, fighter escorts introduced and the more flexible aircraft and weapons allowed precise attacks on small targets with dive bombers, fighter-bombers, and ground-attack aircraft. New technologies like radar also allowed more coordinated and controlled deployment of air defense.

Me 262, world first operational jet fighter

The first jet aircraft to fly was the Heinkel He 178 (Germany), flown by Erich Warsitz in 1939, followed by the world's first operational jet aircraft, the Me 262, in July 1942 and world's first jet-powered bomber, the Arado Ar 234, in June 1943. British developments, like the Gloster Meteor, followed afterwards, but saw only brief use in World War II. The first cruise missile (V-1), the first ballistic missile (V-2), the first (and to date only) operational rocket-powered combat aircraft Me 163 — with attained velocities of up to 1,130 km/h (700 mph) in test flights — and the first vertical take-off manned point-defense interceptor, the Bachem Ba 349 Natter, were also developed by Germany. Not only airplanes, but also helicopters saw rapid development in the Second World War, with the introduction of the Focke Achgelis Fa 223, the Flettner Fl 282 synchropter in 1941 in Germany and the Sikorsky R-4 in 1942 in the USA.

Apollo 11 lifts off on its mission to land a man on the moon

The Harrier Jump Jet, often referred to as just "Harrier" or "the Jump Jet", is a British designed military jet aircraft capable of Vertical/Short Takeoff and Landing (V/STOL) via thrust

vectoring. It first flew in 1969. The same year that Neil Armstrong and Buzz Aldrin set foot on the moon, and Boeing unveiled the Boeing 747 and the Aérospatiale-BAC Concorde supersonic passenger airliner had its maiden flight. The Boeing 747 was the largest commercial passenger aircraft ever to fly, and still carries millions of passengers each year, though it has been superseded by the Airbus A380, which is capable of carrying up to 853 passengers. In 1975 Aeroflot started regular service on the Tu-144—the first supersonic passenger plane. In 1976 British Airways and Air France began supersonic service across the Atlantic, with Concorde. A few years earlier the SR-71 Blackbird had set the record for crossing the Atlantic in under 2 hours, and Concorde followed in its footsteps.

in 1979 the Gossamer Albatross became the first human powered aircraft to cross the English channel. This achievement finally saw the realization of centuries of dreams of human flight.

The digital age (1980–present)

Aviation in the digital age

Concorde, G-BOAB, in storage at London Heathrow Airport following the end of all Concorde flying. This aircraft flew for 22,296 hours between its first flight in 1976 and final flight in 2000.

The last quarter of the 20th century saw a change of emphasis. No longer was revolutionary progress made in flight speeds, distances and materials technology. This part of the century instead saw the spreading of the digital revolution both in flight avionics and in aircraft design and manufacturing techniques.

In 1986 Dick Rutan and Jeana Yeager flew an aircraft, the Rutan Voyager, around the world unrefuelled, and without landing. In 1999 Bertrand Piccard became the first person to circle the earth in a balloon.

Digital fly-by-wire systems allow an aircraft to be designed with relaxed static stability. Initially used to increase the manoeuvrability of military aircraft such as the General Dynamics F-16 Fighting Falcon, this is now being used to reduce drag on commercial airliners.

In the beginning of the 21st century, digital technology allowed subsonic military aviation to begin eliminating the pilot in favor of remotely operated or completely autonomous unmanned aerial vehicles (UAVs). In April 2001 the unmanned aircraft Global Hawk flew from Edwards AFB in the US to Australia non-stop and unrefuelled. This is the longest point-to-point flight ever undertaken by an unmanned aircraft, and took 23 hours and 23 minutes. In October 2003 the first totally autonomous flight across the Atlantic by a computer-controlled model aircraft

occurred. UAVs are now an established feature of modern warfare, carrying out pinpoint attacks under the control of a remote operator.

“Humankind was now able to fly! During the next century, many new airplanes and engines were developed to help transport people, luggage, cargo, military personnel and weapons. The 20th century's advances were all based on this first flights by the American Brothers from Ohio.”

Wing structure

Airplanes have flexible wing surfaces which are stretched across a frame and made rigid by the lift forces exerted by the airflow over them. Larger aircraft have rigid wing surfaces which provide additional strength.

Whether flexible or rigid, most wings have a strong frame to give them their shape and to transfer lift from the wing surface to the rest of the aircraft. The main structural elements are one or more spars running from root to tip, and many ribs running from the leading (front) to the trailing (rear) edge.

Early airplane engines had little power and light weight was very important. Also, early airfoil sections were very thin, and could not have strong frame installed within. So until the 1930s most wings were too light weight to have enough strength and external bracing struts and wires were added. When the available engine power increased during the 1920s and 30s, wings could be made heavy and strong enough that bracing was not needed any more. This type of unbraced wing is called a cantilever wing.

Wing configuration

Captured Morane-Saulnier L wire-braced parasol monoplane

The most important wing characteristics are:

Number of wings – Monoplane, biplane, etc. Wing support – Braced or cantilever, rigid, or flexible.

Wing planform – including aspect ratio, angle of sweep, and any variations along the span (including the important class of delta wings).

Location of the horizontal stabilizer, if any.

Dihedral angle  – positive, zero, or negative (anhedral).

A   monoplane   has a single wing plane, a   biplane   has two stacked one above the other , a tandem wing has two placed one behind the other. When the available engine power increased during the 1920s and 30s and bracing was no longer needed, the unbraced or cantilever monoplane became the most common form of powered type. The four-winged quadruplane and other multiplane designs have had little success.

The wing   planform  is the shape when seen from above. To be aerodynamically efficient, a wing should be straight with a long span from side to side but have a short chord (high aspect ratio). But to be structurally efficient, and hence light weight, a wing must have a short span but still enough area to provide lift (low aspect ratio).

At transonic speeds (near the speed of sound), it helps to sweep the wing backwards or forwards to reduce drag from supersonic shock waves as they begin to form. The swept wing  is just a straight wing swept backwards or forwards.

Two Dassault Mirage G prototypes, one with wings swept

The   delta wing  is a triangle shape which may be used for a number of reasons. As a flexible Rogallo wing it allows a stable shape under aerodynamic forces, and so is often used for ultralight aircraft and even kites. As a supersonic wing it combines high strength with low drag and so is often used for fast jets.

A variable geometry wing can be changed in flight to a different shape. The   variable-sweep wing   transforms between an efficient straight configuration for takeoff and landing, to a low-drag swept configuration for high-speed flight. Other forms of variable planform have been flown, but none have gone beyond the research stage.

Fixed-wing

A Qantas Airbus A380, the world's largest passenger airliner

The forerunner of the fixed-wing aircraft is the kite. Whereas a fixed-wing aircraft relies on its forward speed to create airflow over the wings, a kite is tethered to the ground and relies on

the wind blowing over its wings to provide lift. Kites were the first kind of aircraft to fly, and were invented in China around 500 BC. Much aerodynamic research was done with kites before test aircraft, wind tunnels, and computer modelling programs became available.

The first heavier-than-air craft capable of controlled free-flight were gliders. A glider designed by Cayley carried out the first true manned, controlled flight in 1853.

Wing-in-ground-effect vehicles may be considered as fixed-wing aircraft. They "fly" efficiently close to the surface of the ground or water, like conventional aircraft during takeoff. Man-powered aircraft also rely on ground effect to remain airborne with a minimal pilot power, but this is only because they are so underpowered — in fact, the airframe is capable of flying higher.

Rotorcraft

An Autogyro

Rotorcraft, or rotary-wing aircraft, use a spinning rotor with aerofoil section blades (a rotary wing) to provide lift. Types includehelicopters, autogyros, and various hybrids such as gyrodynes and compound rotorcraft.

Helicopters have a rotor turned by an engine-driven shaft. The rotor pushes air downward to create lift. By tilting the rotor forward, the downward flow is tilted backward, producing thrust for forward flight. Some helicopters have more than one rotor and a few have rotors turned by gas jets at the tips.

Autogyros have unpowered rotors, with a separate power plant to provide thrust. The rotor is tilted backward. As the autogyro moves forward, air blows upward across the rotor, making it spin. This spinning increases the speed of airflow over the rotor, to provide lift.  Cyclogyros rotate their wings about a horizontal axis.

Compound rotorcraft have wings that provide some or all of the lift in forward flight. They are nowadays classified as powered lift types and not as rotorcraft. Tiltrotoraircraft (such as the V-22 Osprey), tiltwing, tailsitter, and coleopter aircraft have their rotors/propellers horizontal for vertical flight and vertical for forward flight.

Propulsion

Unpowered aircraft

Gliders are heavier-than-air aircraft that do not employ propulsion once airborne. Take-off may be by launching forward and downward from a high location, or by pulling into the air on a tow-line, either by a ground-based winch or vehicle, or by a powered "tug" aircraft. Many gliders can

'soar' – gain height from updrafts such as thermal currents. Common examples of gliders are sailplanes, hang gliders and paragliders.

Balloons drift with the wind, though normally the pilot can control the altitude, either by heating the air or by releasing ballast, giving some directional control (since the wind direction changes with altitude).

Kites are aircraft that are tethered to the ground or other object (fixed or mobile) that maintains tension in the tether or kite line; they rely on virtual or real wind blowing over and under them to generate lift and drag.

Powered aircraft

Powered aircraft have one or more onboard sources of mechanical power, typically aircraft engines although rubber and manpower have also been used. Most aircraft engines are either light weight piston engines or gas turbines. Engine fuel is stored in tanks, usually in the wings but larger aircraft also have additional fuel tanks in the fuselage.

Propeller aircraft

A turboprop-engined DeHavilland Twin Otter adapted as a floatplane

Propeller aircraft use one or more propellers (airscrews) to create thrust in a forward direction. The propeller is usually mounted in front of the power source in tractor configuration but can be mounted behind in pusher configuration. Variations of propeller layout include contra-rotating propellers and ducted fans.

Many kinds of power plant have been used to drive propellers. Early airships used man power or steam engines. The more practicalinternal combustion piston engine was used for virtually all fixed-wing aircraft until World War II and is still used in many smaller aircraft. Some types use turbine engines to drive a propeller in the form of a turboprop or propfan. Human-powered flight has been achieved, but has not become a practical means of transport. Unmanned aircraft and models have also used power sources such as electric motors and rubber bands.

Jet aircraft

Lockheed Martin F-22A Raptor

Jet aircraft use airbreathing jet engines, which take in air, burn fuel with it in a combustion chamber, and accelerate the exhaust rearwards to provide thrust.

Turbojet and turbofan engines use a spinning turbine to drive one or more fans, which provide additional thrust. An afterburner may be used to inject extra fuel into the hot exhaust, especially on military "fast jets". Use of a turbine is not absolutely necessary: other designs include the pulse jet and ramjet. These mechanically simple designs cannot work when stationary, so the aircraft must be launched to flying speed by some other method.

Rotorcraft

Some rotorcraft, such as helicopters, have a powered rotary wing or rotor, where the rotor disc can be angled slightly forward so that a proportion of its lift is directed forwards. The rotor may, like a propeller, be powered by a variety of methods such as a piston engine or turbine. Experiments have also used jet nozzles at the rotor blade tips.

Other types of powered aircraft

Rocket-powered aircraft  have occasionally been experimented with, and the Messerschmitt   Komet  fighter even saw action in the Second World War. Since then, they have been restricted to research aircraft, such as the North American X-15, which traveled up into space where air-breathing engines cannot work (rockets carry their own oxidant). Rockets have more often been used as a supplement to the main power plant, typically for the rocket-assisted take off of heavily loaded aircraft, but also to provide high-speed dash capability in some hybrid designs such as the Saunders-Roe SR.53.

The ornithopter obtains thrust by flapping its wings. It has found practical use in a model hawk used to freeze prey animals into stillness so that they can be captured, and in toy birds.

Aerostats

Lighter-than-air types are characterised by one or more gasbags, typically with a supporting structure of flexible cables or a rigid framework called its hull. Other elements such as engines or a gondola may also be attached to the supporting structure.

Aerodynes

Airframe diagram for anAgustaWestland AW101 helicopter

Heavier-than-air types are characterised by one or more wings and a central fuselage. The fuselage typically also carries a tail orempennage for stability and control, and an undercarriage for takeoff and landing. Engines may be located on the fuselage or wings. On a fixed-wing aircraft the wings are rigidly attached to the fuselage, while on a rotorcraft the wings are attached to a rotating vertical shaft. Smaller designs sometimes use flexible materials for part or all of the structure, held in place either by a rigid frame or by air pressure.

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