An ornithopter (from Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 ornithos "bird"
and pteron "wing") is an aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 that flies
Flight is the process by which an object moves either through an atmosphere or beyond it by generating lift or propulsive thrust, or aerostatically using buoyancy, or by simple ballistic movement....

 by flapping its wing
A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...

s. Designers seek to imitate the flapping-wing flight of bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s, bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...

s, and insects. Though machines may differ in form, they are usually built on the same scale
Scale (ratio)
The scale ratio of some sort of model which represents an original proportionally is the ratio of a linear dimension of the model to the same dimension of the original. Examples include a 3-dimensional scale model of a building or the scale drawings of the elevations or plans of a building. In such...

 as these flying creatures. Manned ornithopters have also been built, and some have been successful. The machines are of two general types: those with engines, and those powered by the muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

s of the pilot
An aviator is a person who flies an aircraft. The first recorded use of the term was in 1887, as a variation of 'aviation', from the Latin avis , coined in 1863 by G. de la Landelle in Aviation Ou Navigation Aérienne...


Early history of the ornithopter

The Sanskrit epic Ramayana
The Ramayana is an ancient Sanskrit epic. It is ascribed to the Hindu sage Valmiki and forms an important part of the Hindu canon , considered to be itihāsa. The Ramayana is one of the two great epics of India and Nepal, the other being the Mahabharata...

 (4th Century BC) describes an ornithopter, the Pushpaka Vimana. The ancient Greek legend of Daedalus
In Greek mythology, Daedalus was a skillful craftsman and artisan.-Family:...

 (Greek demigod engineer) and Icarus
Icarus (mythology)
In Greek mythology, Icarus is the son of the master craftsman Daedalus. The main story told about Icarus is his attempt to escape from Crete by means of wings that his father constructed from feathers and wax...

 (Daedalus's son) and The Chinese Book of Han
Book of Han
The Book of Han, Hanshu or History of the Former Han Dynasty |Fan Ye]] . Various scholars have estimated that the earliest material covered in the book dates back to between 206 and 202 BCE...

(19 AD) both describe the use of feathers to make wings for a person but these are not actually aircrafts. Some early manned flight attempts may have been intended to achieve flapping-wing flight though probably only a glide was actually achieved. These include the flights of the 11th century monk Eilmer of Malmesbury
Eilmer of Malmesbury
Eilmer of Malmesbury was an 11th-century English Benedictine monk best known for his early attempt at a gliding flight using wings.- Life :...

 (recorded in the 12th century) and the 9th century poet Abbas Ibn Firnas
Abbas Ibn Firnas
Abbas Ibn Firnas , also known as Abbas Qasim Ibn Firnas and عباس بن فرناس , was a Muslim Andalusian polymath: an inventor, engineer, aviator, physician, Arabic poet, and Andalusian musician. Of Berber descent, he was born in Izn-Rand Onda, Al-Andalus , and lived in the Emirate of Córdoba...

 (recorded in the 17th century). Roger Bacon
Roger Bacon
Roger Bacon, O.F.M. , also known as Doctor Mirabilis , was an English philosopher and Franciscan friar who placed considerable emphasis on the study of nature through empirical methods...

, writing in 1260, was also among the first to consider a technological means of flight. In 1485, Leonardo da Vinci
Leonardo da Vinci
Leonardo di ser Piero da Vinci was an Italian Renaissance polymath: painter, sculptor, architect, musician, scientist, mathematician, engineer, inventor, anatomist, geologist, cartographer, botanist and writer whose genius, perhaps more than that of any other figure, epitomized the Renaissance...

 began to study the flight of birds. He grasped that humans are too heavy, and not strong enough, to fly using wings simply attached to the arms. Therefore he sketched a device in which the aviator lies down on a plank and works two large, membranous wings using hand levers, foot pedals, and a system of pulleys.
The first ornithopters capable of flight were constructed in France. In 1858 Pierre Jullien's model flew an estimated forty feet. Gustave Trouvé
Gustave Trouvé
Gustave Trouvé was a French electrical engineer of the 19th century. His inventions include:* First outboard motorboat* First electric powered automobile* Gunpowder powered ornithopter in 1870...

's 1870 model flew a distance of 70 metres in a demonstration for the French Academy of Sciences. The wings were flapped by gunpowder
Gunpowder, also known since in the late 19th century as black powder, was the first chemical explosive and the only one known until the mid 1800s. It is a mixture of sulfur, charcoal, and potassium nitrate - with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer...

 charges activating a bourdon tube. Jobert in 1871 used a rubber band
Rubber band
A rubber band is a short length of rubber and latex formed in the shape of a loop and is commonly used to hold multiple objects together...

 to power a small model bird. Alphonse Penaud
Alphonse Pénaud
Alphonse Pénaud , was a 19th-century French pioneer of aviation, inventor of the rubber powered model airplane Planophore and founder of the aviation industry.-Biography:...

, Abel Hureau de Villeneuve
Abel Hureau de Villeneuve
Dr. Abel Hureau de Villeneuve was an aeronautical experimenter, and ran a major French aeronautical society and journal in the late nineteenth century.-Aviation research:In the 1870s, Dr...

, and Victor Tatin
Victor Tatin
Victor Tatin was a French inventor, who created an early airplane, the Aéroplane in 1879. The craft was the first model aeroplane to lift itself by its own power after a run on the ground....

, also made rubber-powered ornithopters during the 1870s. Tatin's ornithopter (now in the US Air & Space Museum) was perhaps the first to use active torsion of the wings, and apparently it served as the basis for a commercial toy offered by Pichancourt
In 1889; Pichancourt developed the L'Oiseau Mechanique which aimed to imitate the motion of a bird's wings in flight.- References :...

 c. 1889.

From 1884 on, Lawrence Hargrave
Lawrence Hargrave
Lawrence Hargrave was an engineer, explorer, astronomer, inventor and aeronautical pioneer.- Early life :Hargrave was born in Greenwich, England, the second son of John Fletcher Hargrave and was educated at Queen Elizabeth's Grammar School, Kirkby Lonsdale, Westmorland...

 built scores of ornithopters powered by rubber bands, springs, steam
Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...

, or compressed air
Compressed air
Compressed air is air which is kept under a certain pressure, usually greater than that of the atmosphere. In Europe, 10 percent of all electricity used by industry is used to produce compressed air, amounting to 80 terawatt hours consumption per year....

. He introduced the use of small flapping wings providing the thrust for a larger fixed wing. This eliminated the need for gear reduction, thereby simplifying the construction. In the 1930s, Alexander Lippisch
Alexander Lippisch
Alexander Martin Lippisch was a German pioneer of aerodynamics. He made important contributions to the understanding of flying wings, delta wings and the ground effect. His most famous design is the Messerschmitt Me 163 rocket-powered interceptor.Lippisch was born in Munich, Kingdom of Bavaria...

 and the NSFK in Germany constructed and successfully flew a series of internal combustion powered ornithopters using a similar overall design, with aerodynamic improvements resulting from methodical study.

Erich von Holst
Erich von Holst
Erich von Holst , was a German behavioral physiologist who was a native of Riga, and was related to historian Hermann Eduard von Holst...

 also working in the 1930s, achieved great efficiency and realism in his work with ornithopters powered by rubber band. This includes perhaps the first success of an ornithopter with a bending wing, intended to more closely imitate the folding wing action of birds although it was not a true variable span wing like birds have.

Manned flight

Manned ornithopters fall into two general categories: Those powered by the muscular effort of the pilot (human-powered ornithopters), and those powered by an engine.

Around 1894, Otto Lilienthal
Otto Lilienthal
Otto Lilienthal was a German pioneer of human aviation who became known as the Glider King. He was the first person to make well-documented, repeated, successful gliding flights. He followed an experimental approach established earlier by Sir George Cayley...

 became famous in Germany for his widely publicized and successful glider flights. Lilienthal also studied bird flight and conducted some related experiments. He constructed an ornithopter, although its complete development was prevented by his untimely death.

In 1929, a man-powered ornithopter designed by Alexander Lippisch
Alexander Lippisch
Alexander Martin Lippisch was a German pioneer of aerodynamics. He made important contributions to the understanding of flying wings, delta wings and the ground effect. His most famous design is the Messerschmitt Me 163 rocket-powered interceptor.Lippisch was born in Munich, Kingdom of Bavaria...

 (designer of the Me163 Komet) flew a distance of 250 to 300 metres after tow launch. Since a tow launch was used, some have questioned whether the aircraft was capable of flying on its own. Lippisch asserted that the aircraft was actually flying, not making an extended glide. (Precise measurement of altitude and velocity over time would be necessary to resolve this question.) Most of the subsequent human-powered ornithopters likewise used a tow launch, and flights were brief simply because human muscle power diminishes rapidly over time.

In 1942, Adalbert Schmid made a much longer flight of a human-powered ornithopter at Munich-Laim. It travelled a distance of 900 metres, maintaining a height of 20 metres throughout most of the flight. Later this same aircraft was fitted with a 3 hp Sachs motorcycle engine. With the engine, it made flights up to 15 minutes in duration. Schmid later constructed a 10 hp ornithopter based on the Grunau-Baby IIa sailplane, which was flown in 1947. The second aircraft had flapping outer wing panels.

In 2005, Yves Rousseau
Yves Rousseau
Yves Rousseau is credited with some ultralight aircraft FAI world records and has received international recognition for his 13 years of work on human-powered ornithopter flight; Rousseau attempted his first human-powered flight with flapping wings in 1995.In 2005, Rousseau was given the Paul...

 was given the Paul Tissandier Diploma, awarded by the FAI
Fédération Aéronautique Internationale
The Fédération Aéronautique Internationale is the world governing body for air sports and aeronautics and astronautics world records. Its head office is in Lausanne, Switzerland. This includes man-carrying aerospace vehicles from balloons to spacecraft, and unmanned aerial vehicles...

 for contributions to the field of aviation. Rousseau attempted his first human-muscle-powered flight with flapping wings in 1995. On 20 April 2006, at his 212th attempt, he succeeded in flying a distance of 64 metres, observed by officials of the Aero Club de France. Unfortunately, on his 213th flight attempt, a gust of wind led to a wing breaking up, causing the pilot to be gravely injured and rendered paraplegic.

A team at the University of Toronto Institute for Aerospace Studies
University of Toronto Institute for Aerospace Studies
The University of Toronto Institute for Aerospace Studies is an advanced research facility for aeronautics and aerospace engineering, located in the Downsview district of Toronto, Ontario, Canada...

, headed by Professor
A professor is a scholarly teacher; the precise meaning of the term varies by country. Literally, professor derives from Latin as a "person who professes" being usually an expert in arts or sciences; a teacher of high rank...

 James DeLaurier
James DeLaurier
James D. DeLaurier is an inventor and professor emeritus of the University of Toronto Institute for Aerospace Studies. He is a leader in design and analysis of lighter than air vehicles and flapping winged aircraft.-Career:...

, worked for several years on an engine-powered, piloted ornithopter. In July 2006, at the Bombardier Airfield at Downsview Park
Downsview Park
Downsview Park is a former Canadian Forces Base in the community of Downsview in Toronto, Canada. It contains about 231.5 hectares of land, of which more than 130 hectares are earmarked for traditional parkland, recreational and cultural amenities...

 in Toronto
Toronto is the provincial capital of Ontario and the largest city in Canada. It is located in Southern Ontario on the northwestern shore of Lake Ontario. A relatively modern city, Toronto's history dates back to the late-18th century, when its land was first purchased by the British monarchy from...

, Professor DeLaurier's machine, the UTIAS Ornithopter No.1
UTIAS Ornithopter No.1
|-See also:*UTIAS Snowbird...

 made a jet-assisted takeoff and 14-second flight. According to DeLaurier, the jet was necessary for sustained flight, but the flapping wings did most of the work.

On August 2, 2010, Todd Reichert of the University of Toronto Institute for Aerospace Studies piloted a human-powered ornithopter named Snowbird. The 32 metre wingspan 42 kilograms (92.6 lb) aircraft was constructed from carbon fibre, balsa, and foam. The pilot sat in a small cockpit suspended below the wings and pumped a bar with his feet to operate a system of wires that flapped the wings up and down. Towed by a car until airborne, it then sustained flight for almost 20 seconds. It flew 145 meters with an average speed of 25.6 km/h (7.1 m/s) Similar tow-launched flights were made in the past, but improved data collection verified that the ornithopter was capable of self-powered flight once aloft.

Applications for unmanned ornithopters

Practical applications capitalize on the resemblance to birds or insects. The Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

 Division of Wildlife has used these machines to help save the endangered
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 Gunnison Sage Grouse
Sage Grouse
The Sage Grouse is the largest grouse in North America, where it is known as the Greater Sage-Grouse. Its range is sagebrush country in the western United States and southern Alberta and Saskatchewan, Canada. A population of smaller birds, known in the U.S. as Gunnison Sage-Grouse, were recently...

. An artificial hawk
The term hawk can be used in several ways:* In strict usage in Australia and Africa, to mean any of the species in the subfamily Accipitrinae, which comprises the genera Accipiter, Micronisus, Melierax, Urotriorchis and Megatriorchis. The large and widespread Accipiter genus includes goshawks,...

 under the control of an operator causes the grouse to remain on the ground so they can be captured for study.

Because ornithopters can be made to resemble birds or insects, they could be used for military applications, such as aerial reconnaissance
Aerial reconnaissance
Aerial reconnaissance is reconnaissance that is conducted using unmanned aerial vehicles or reconnaissance aircraft. Their roles are to collect imagery intelligence, signals intelligence and measurement and signature intelligence...

 without alerting the enemies that they are under surveillance. Several ornithopters have been flown with video cameras on board, some of which can hover and maneuver in small spaces. In 2011, AeroVironment, Inc. announced a remotely piloted ornithopter resembling a large hummingbird for possible spy missions.

AeroVironment, Inc., then led by Paul B. MacCready
Paul MacCready
Paul B. MacCready, Jr. was an American aeronautical engineer. He was the founder of AeroVironment and the designer of the human-powered aircraft that won the Kremer prize...

 (Gossamer Albatross
Gossamer Albatross
-See also:-Further reading:*Allen, Bryan. Winged Victory of "Gossamer Albatross". National Geographic, November 1979, vol. 156, n. 5, p. 640-651...

) developed in the mid-1980s, for the Smithsonian Institution
Smithsonian Institution
The Smithsonian Institution is an educational and research institute and associated museum complex, administered and funded by the government of the United States and by funds from its endowment, contributions, and profits from its retail operations, concessions, licensing activities, and magazines...

, a half-scale radio controlled replica of the giant pterosaur
Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...

, Quetzalcoatlus northropi. It was built to star in the IMAX movie On the Wing. The model had a wingspan
The wingspan of an airplane or a bird, is the distance from one wingtip to the other wingtip. For example, the Boeing 777 has a wingspan of about ; and a Wandering Albatross caught in 1965 had a wingspan of , the official record for a living bird.The term wingspan, more technically extent, is...

 of 5.5 metres (18 feet) and featured a complex, computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

ized autopilot control system, just as the full-size pterosaur relied on its neuromuscular system to make constant adjustments in flight.

Researchers hope to eliminate the motors and gear
A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine....

s of current designs by more closely imitating animal flight muscles. Georgia Tech scientist Robert C. Michelson
Robert C. Michelson
Robert C. Michelson is an American engineer and academic widely known for inventing the entomopter, a biologically inspired flapping-winged aerial robot, and for having established the International Aerial Robotics Competition. He has received degrees in electrical engineering from the Virginia...

 is developing a Reciprocating Chemical Muscle
Reciprocating Chemical Muscle
The Reciprocating Chemical Muscle is a mechanism that takes advantage of the superior energy density of chemical reactions. It is a regenerative device that converts chemical energy into motion through a direct noncombustive chemical reaction.-Function:...

 for use in micro-scale flapping-wing aircraft. Michelson uses the term "entomopter
The Entomopter is a multimode insect-like robot developed by Prof. Robert C. Michelson and his design team from the Georgia Tech Research Institute , University of Cambridge , ETS Labs and others. The name 'Entomopter' is derived from entomo + pteron...

" for this type of ornithopter. SRI International
SRI International
SRI International , founded as Stanford Research Institute, is one of the world's largest contract research institutes. Based in Menlo Park, California, the trustees of Stanford University established it in 1946 as a center of innovation to support economic development in the region. It was later...

 is developing polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

 artificial muscles which may also be used for flapping-wing flight.

In 2002, Krister Wolff and Peter Nordin
Peter Nordin
Peter Nordin is a Swedish computer scientist, entrepreneur and author who has contributed to artificial intelligence, automatic programming, machine learning, and evolutionary robotics.- Studies and early career :...

 of Chalmers University of Technology
Chalmers University of Technology
Chalmers University of Technology , is a Swedish university located in Gothenburg that focuses on research and education in technology, natural science and architecture.-History:...

 in Sweden, built a flapping wing robot that learned flight techniques. The balsa
Ochroma pyramidale, commonly known as the balsa tree , is a species of flowering plant in the mallow family, Malvaceae. It is a large, fast-growing tree that can grow up to tall. It is the source of balsa wood, a very lightweight material with many uses...

Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

 design was driven by machine learning
Machine learning
Machine learning, a branch of artificial intelligence, is a scientific discipline concerned with the design and development of algorithms that allow computers to evolve behaviors based on empirical data, such as from sensor data or databases...

 software technology known as a steady state linear evolutionary algorithm
Evolutionary algorithm
In artificial intelligence, an evolutionary algorithm is a subset of evolutionary computation, a generic population-based metaheuristic optimization algorithm. An EA uses some mechanisms inspired by biological evolution: reproduction, mutation, recombination, and selection...

. Inspired by natural evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

, the software "evolves" in response to feedback on how well it performs a given task. Although confined to a laboratory apparatus, their ornithopter evolved behavior for maximum sustained lift force and horizontal movement.

Since 2002, Prof. Theo Van Holten has been working on an ornithopter which is constructed like a helicopter. The device is called the ornicopter  and was made by constructing the main rotor so that it would have no reaction torque at all.

In 2008, Schiphol Airport started using a real looking mechanical hawk designed by falconer Robert Musters. The radio controlled robot bird is used to scare away birds that could damage the engines of airplanes.

In March 2011, scientists and engineers in Festo have created a robotic SmartBird, based on a seagull's motion. The SmartBird weighs only 450 grams and is controlled by a radio handset.

Ornithopters as a hobby

A hobby is a regular activity or interest that is undertaken for pleasure, typically done during one's leisure time.- Etymology :A hobby horse is a wooden or wickerwork toy made to be ridden just like a real horse...

ists can build and fly their own ornithopters. These range from light-weight models powered by rubber band, to larger models with radio control.

The rubber-band-powered model can be fairly simple in design and construction. Hobbyists compete for the longest flight times with these models. An introductory model can be fairly simple in design and construction, but the advanced competition designs are extremely delicate and challenging to build. Roy White holds the United States national record for indoor rubber-powered, with his flight time of 21 minutes, 44 seconds.

Commercial free-flight rubber-band powered toy
A toy is any object that can be used for play. Toys are associated commonly with children and pets. Playing with toys is often thought to be an enjoyable means of training the young for life in human society. Different materials are used to make toys enjoyable and cuddly to both young and old...

 ornithopters have long been available. The first of these was sold under the name Tim Bird in Paris in 1879. Later models were also sold as Tim Bird (made by G de Ruymbeke, France, since 1969).

Commercial radio controlled designs stem from Percival Spencer's engine-powered Seagulls, developed circa 1958, and Sean Kinkade's work in the late 1990s to present day. The wings are usually driven by an electric motor. Many hobbyists enjoy experimenting with their own new wing designs and mechanisms. The opportunity to interact with real birds in their own domain also adds great enjoyment to this hobby. Birds are often curious and will follow or investigate the model while it is flying. In a few cases, RC birds have been attacked by birds of prey
Bird of prey
Birds of prey are birds that hunt for food primarily on the wing, using their keen senses, especially vision. They are defined as birds that primarily hunt vertebrates, including other birds. Their talons and beaks tend to be relatively large, powerful and adapted for tearing and/or piercing flesh....

, crow
Crows form the genus Corvus in the family Corvidae. Ranging in size from the relatively small pigeon-size jackdaws to the Common Raven of the Holarctic region and Thick-billed Raven of the highlands of Ethiopia, the 40 or so members of this genus occur on all temperate continents and several...

s, and even cats. More recent cheaper models such as the Dragonfly
FlyTech Dragonfly
The Flytech Dragonfly is WowWee's entry into remote-controlled flying toy industry. The Dragonfly has been incorrectly billed as the world's first commercially available RC ornithopter...

 from WowWee have extended the market from dedicated hobbyists to the general toy market,

Some helpful resources for hobbyists include The Ornithopter Design Manual, book written by Nathan Chronister, and The Ornithopter Zone web site, which includes a large amount of information about building and flying these models. To see video examples of a remote control Ornithopter visit the Birds You Fly website.

Ornithopters are also of interest as the subject of one of the events in the nationwide Science Olympiad
Science Olympiad
Science Olympiad is an American elementary, middle, or high school team competition which tests knowledge of various science topics and engineering ability. Over 6,200 teams from 49 U.S. states compete each year. Most teams compete in three levels of competition: regionals, states, and nationals...

 event list. The event ("Flying Bird") entails building a self-propelled ornithopter to exacting specifications, with points awarded for high flight time and low weight. Bonus points are also awarded if the ornithopter happens to look like a real bird.


As demonstrated by birds, flapping wings offer potential advantages in maneuverability and energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 savings compared with fixed-wing aircraft, as well as potentially vertical take-off and landing. It has been suggested that these advantages are greatest at small sizes and low flying speeds.

Unlike airplanes and helicopters, the driving airfoil
An airfoil or aerofoil is the shape of a wing or blade or sail as seen in cross-section....

s of the ornithopter have a flapping or oscillating motion, instead of rotary. As with helicopters, the wings usually have a combined function of providing both lift and thrust. Theoretically, the flapping wing can be set to zero angle of attack
Angle of attack
Angle of attack is a term used in fluid dynamics to describe the angle between a reference line on a lifting body and the vector representing the relative motion between the lifting body and the fluid through which it is moving...

 on the upstroke, so it passes easily through the air. Since typically the flapping airfoils produce both lift and thrust, drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...

-inducing structures are minimized. These two advantages potentially allow a high degree of efficiency.

In propeller
Propeller (aircraft)
Aircraft propellers or airscrews convert rotary motion from piston engines or turboprops to provide propulsive force. They may be fixed or variable pitch. Early aircraft propellers were carved by hand from solid or laminated wood with later propellers being constructed from metal...

- or jet
Jet engine
A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...

-driven aircraft, the propeller creates a relatively narrow stream of relatively fast moving air. The energy carried by the air is lost. The same amount of force can be produced by accelerating a larger mass of air to a smaller velocity, for example by using a larger propeller or adding a bypass fan
The turbofan is a type of airbreathing jet engine that is widely used for aircraft propulsion. A turbofan combines two types of engines, the turbo portion which is a conventional gas turbine engine, and the fan, a propeller-like ducted fan...

 to a jet engine. Use of flapping wings offers even larger displaced air mass, moved at lower velocity, thus improving efficiency.

Wing design

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s inspired Leonardo da Vinci
Leonardo da Vinci
Leonardo di ser Piero da Vinci was an Italian Renaissance polymath: painter, sculptor, architect, musician, scientist, mathematician, engineer, inventor, anatomist, geologist, cartographer, botanist and writer whose genius, perhaps more than that of any other figure, epitomized the Renaissance...

 when he designed his ornithopter in 1490. Leonardo da Vinci was interested in flying during 1488–1514. He never saw his dream of flight take place because his ornithopter was too heavy and required too much energy to produce lift or thrust. In 1929, the human-powered ornithopter constructed by Alexander Lippisch
Alexander Lippisch
Alexander Martin Lippisch was a German pioneer of aerodynamics. He made important contributions to the understanding of flying wings, delta wings and the ground effect. His most famous design is the Messerschmitt Me 163 rocket-powered interceptor.Lippisch was born in Munich, Kingdom of Bavaria...

 was towed into the air and glided around. In 1959, in England, another ornithopter was towed into the air and demonstrated the ornithopter being a birdlike machine. By the 1960s, there were powered unmanned ornithopter flights of various sizes demonstrating how ornithopters flew. In 1991 Harris and DeLaurier
James DeLaurier
James D. DeLaurier is an inventor and professor emeritus of the University of Toronto Institute for Aerospace Studies. He is a leader in design and analysis of lighter than air vehicles and flapping winged aircraft.-Career:...

 flew the first successful engine-powered remotely piloted ornithopter in Toronto, Canada. By 1999, there was an ornithopter design that was designed to take off from a level pavement.

Lift (force)
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...

 is the force that utilises the fluid continuity and Newton's laws
Newton's laws of motion
Newton's laws of motion are three physical laws that form the basis for classical mechanics. They describe the relationship between the forces acting on a body and its motion due to those forces...

 to create a force perpendicular to the fluid flow. It is opposed by weight
In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:...

, which is the force that pulls things towards the ground. Thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....

 is the force that moves things through the air while drag is the force of flight that is an aerodynamic force that reduces speed.

In order to create an effective ornithopter, it had to be able to flap its wings to generate enough power to get off the ground and travel through the air. Efficient flapping of the wing is characterized by pitching angles, lagging plunging displacements by approximately 90 degrees. Flapping wings increase drag and are not as efficient as propeller-powered aircraft. To increase efficiency of the ornithopter, more power is required on the down stroke than on the upstroke. If the wing on the ornithopter was not flexible and flapped at the same angle while moving up and down, it would act like a huge board moving in two dimensions, not producing lift or thrust. The flexibility and move-ability of the wing let it twist and bend to the reactions of the ornithopter while in flight.

The interest in developing a successful powered ornithopter similar to birds and bats, was one many sought after. In order to get around the problem of not having enough energy for sustained flight, the ornithopter would be required to produce enough lift and thrust to travel through the air. Alphonse Pénaud introduced the idea of a powered ornithopter in 1874. His design had limited power and was uncontrollable causing it to be transformed into a toy for children.

The wing design is designed with the spar as far forward of the airfoil but still having acceptable dimensions of strength. Engineers and researchers have experimented with wings that require carbon fiber, plywood, fabric, ribs, and the trailing edge to be stiff, strong, and for the mass to be as low as possible. Any mass located to the aft or empennage, reduce the wings performance and hinder the design of the ornithopter. In order to calculate the performance of the ornithopter, the wings lift is determined by the lift of the wing versus weight, drag and thrust. A smooth aerodynamic surface with a double-surface airfoil is more efficient then a single-surface airfoil to produce more lift.

A variation of ornithopters has the wings and flapping surfaces towards the empennage
The empennage , also known as the tail or tail assembly, of most aircraft gives stability to the aircraft, in a similar way to the feathers on an arrow...

 to increase stabilizing forces and thrust. With different designs, ornithopters do not act like birds or bats in flight. Typically birds and bats have thin and cambered wings to produce lift and thrust. Ornithopters with thinner wings have a limited angle of attack but provide optimum minimum-drag performance in a single value of lift coefficient.

Although hummingbird
Hummingbirds are birds that comprise the family Trochilidae. They are among the smallest of birds, most species measuring in the 7.5–13 cm range. Indeed, the smallest extant bird species is a hummingbird, the 5-cm Bee Hummingbird. They can hover in mid-air by rapidly flapping their wings...

s fly with fully extended wings, an ornithopter would not be able to effectively fly that way. If an ornithopter wing were to fully extend and twist and flap in small movements it would cause a stall but if it were to twist and flap in very large motions, then it would act like a windmill causing an inefficient flying situation.

A team of engineers and researchers called "Fullwing" has created an ornithopter that has an average lift of over 8 pounds, an average thrust of 0.88 pounds, and has a propulsive efficiency of 54%. The wings were tested in a low speed wind tunnel measuring the aerodynamic performance. Discovering that the higher the frequency of the wing beat, the higher the average thrust of the ornithopter.

See also

  • FlyTech Dragonfly
    FlyTech Dragonfly
    The Flytech Dragonfly is WowWee's entry into remote-controlled flying toy industry. The Dragonfly has been incorrectly billed as the world's first commercially available RC ornithopter...

  • Gyroplane
  • Helicopter
    A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...

  • Human-powered aircraft
    Human-powered aircraft
    A human-powered aircraft is an aircraft powered by direct human energy and the force of gravity; the thrust provided by the human may be the only source; however, a hang glider that is partially powered by pilot power is a human-powered aircraft where the flight path can be enhanced more than if...

  • Insectothopter
    The Insectothopter was a miniature unmanned aerial vehicle developed by the United States Central Intelligence Agency's research and development office in the 1970s. The Insectothopter was the size of a dragonfly, and was hand-painted to look like one. It was powered by a small gasoline engine...

  • Micromechanical Flying Insect
    Micromechanical Flying Insect
    The Micromechanical Flying Insect project is research effort to develop a flying robot based on living insects flight techniques, i.e. an ornithopter. The flying robot will be capable of sustained autonomous flight. The design of artificial fly is based on bionics principles and relies on...

  • Nano Hummingbird
    AeroVironment Nano Hummingbird
    The Nano Hummingbird or Nano Air Vehicle is a tiny, remote controlled aircraft built to resemble and fly like a hummingbird, developed in the United States by AeroVironment, Inc. to specifications provided by the Defense Advanced Research Projects Agency...

  • Rotary-wing aircraft
  • STOL
    STOL is an acronym for short take-off and landing, a term used to describe aircraft with very short runway requirements.-Definitions:There is no one accepted definition of STOL and many different definitions have been used by different authorities and nations at various times and for a myriad of...

    A vertical take-off and landing aircraft is one that can hover, take off and land vertically. This classification includes fixed-wing aircraft as well as helicopters and other aircraft with powered rotors, such as cyclogyros/cyclocopters and tiltrotors...

    STOVL is an acronym for short take off and vertical landing.This is the ability of some aircraft to take off from a short runway or take off vertically if it does not have a very heavy payload and land vertically...


Further reading

  • Chronister, Nathan. (1999). The Ornithopter Design Manual. Published by The Ornithopter Zone.
  • Mueller, Thomas J. (2001). "Fixed and flapping wing aerodynamics for micro air vehicle applications". Virginia: American Inst. of Aeronautics and Astronautics. ISBN 1-56347-517-0
  • Azuma, Akira (2006). "The Biokinetics of Flying and Swimming". Virginia: American Institute of Aeronautics and Astronautics 2nd Edition. ISBN 1-56347-781-5.
  • DeLaurier, James D. "The Development and Testing of a Full-Scale Piloted Ornithopter." Canadian Aeronautics and Space Journal. 45. 2 (1999), 72–82. (accessed November 30, 2010).
  • Warrick, Douglas, Bret Tobalske, Donald Powers, and Michael Dickinson. "The Aerodynamics of Hummingbird Flight." American Institute of Aeronautics and Astronautics 1–5. Web. 30 Nov 2010.
  • Crouch, Tom D. Aircraft of the National Air and Space Museum. Fourth ed. Lilienthal Standard Glider. Smithsonian Institution, 1991.
  • Bilstein, Roger E. Flight in America 1900–1983. First ed. Gliders and Airplanes. Baltimore, Maryland: Johns Hopkins University Press, 1984. (pages 8–9)
  • Crouch, Tom D. Wings. A History of Aviation from Kites to the Space Age. First ed. New York: W.W. Norton & Company, Inc., 2003. (pages 44–53)
  • Anderson, John D. A history of aerodynamics and its impact on flying machines. Cambridge: United Kingdom, 1997.

General interest

Specific projects

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