Ornithopter
An ornithopter is an aircraft that flies by flapping its wings. Designers sought to imitate the flapping-wing flight of birds, bats, and insects. Though machines may differ in form, they are usually built on the same scale as flying animals. Larger, crewed ornithopters have also been built and some have been successful. Crewed ornithopters are generally powered either by engines or by the pilot.
Early history
Some early crude flight attempts may have been intended to achieve flapping-wing flight, but probably only a glide was actually achieved. They include the purported flights of the 11th-century Catholic monk Eilmer of Malmesbury and the 9th-century poet Abbas Ibn Firnas. Roger Bacon, writing in 1260, was also among the first to consider a technological means of flight. In 1485, Leonardo da Vinci 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. He, therefore, 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 successful ornithopter was built by a Polish nobleman and scientist of Italian descent, Tytus Liwiusz Boratyni. In 1648, he built a spring-powered prototype that lifted a cat during a test flight. Tytus Boratyni planned to build a manned version called the "Flying Dragon". The project assumed numerous rescue systems, including a parachute. The bottom of the ornithopter's fuselage was to be able to float on water in the event of an accident over the sea or a lake. In order to implement the project, he unsuccessfully applied for funding for research from King Władysław IV Vasa.
In 1841, an ironsmith kalfa, Manojlo, who "came to Belgrade from Vojvodina", attempted flying with a device described as an ornithopter. Refused by the authorities a permit to take off from the belfry of Saint Michael's Cathedral, he clandestinely climbed to the rooftop of the Dumrukhana and took off, landing in a heap of snow, and surviving.
The first ornithopters capable of flight were constructed in France. Jobert in 1871 used a rubber band to power a small model bird. Alphonse Pénaud, Abel Hureau de Villeneuve, and Victor Tatin also made rubber-powered ornithopters during the 1870s. Tatin's ornithopter 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 1889. Gustave Trouvé was the first to use internal combustion, and his 1890 model flew a distance of 80 meters in a demonstration for the French Academy of Sciences. The wings were flapped by gunpowder charges activating a Bourdon tube.
From 1884 on, Lawrence Hargrave built scores of ornithopters powered by rubber bands, springs, steam, or compressed air. He introduced the use of small flapping wings providing the thrust for a larger fixed wing; this innovation eliminated the need for gear reduction, thereby simplifying the construction.
E. P. Frost made ornithopters starting in the 1870s; first models were powered by steam engines, then in the 1900s, an internal-combustion craft large enough for a person was built, though it did not fly.
In the 1930s, Alexander Lippisch and the National Socialist Flyers Corps of Nazi Germany constructed and successfully flew a series of internal combustion-powered ornithopters, using Hargrave's concept of small flapping wings, but with aerodynamic improvements resulting from the methodical study.
Erich von Holst, also working in the 1930s, achieved great efficiency and realism in his work with ornithopters powered by rubber bands. He achieved perhaps the first success of an ornithopter with a bending wing, intended to imitate more closely the folding wing action of birds, although it was not a true variable-span wing such as those of birds.
Around 1960, Percival Spencer successfully flew a series of uncrewed ornithopters using internal combustion engines ranging from displacement, and having wingspans up to. In 1961, Percival Spencer and Jack Stephenson flew the first successful engine-powered, remotely piloted ornithopter, known as the Spencer Orniplane. The Orniplane had a wingspan, weighed, and was powered by a -displacement two-stroke engine. It had a biplane configuration, to reduce oscillation of the fuselage.
Crewed flight
Crewed ornithopters fall into two general categories: Those powered by the muscular effort of the pilot, and those powered by an engine.One early experimenter was the Dutchman Vincent de Groof in the 1860s and 1870s.
Around 1894, Otto Lilienthal, an aviation pioneer, 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 on 9 August 1896 in a glider accident.
In 1929, a man-powered ornithopter designed by Alexander Lippisch flew a distance of 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. 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, maintaining a height of throughout most of the flight. Later this same aircraft was fitted with a Sachs motorcycle engine. With the engine, it made flights up to 15 minutes in duration. Schmid later constructed a ornithopter, based on the Grunau-Baby IIa sailplane, which was flown in 1947. The second aircraft had flapping outer wing panels.
The French engineer René Riout devoted himself for three decades to the realization of flapping wing ornithopters. In 1905 he invented his first models. In 1909 he won the gold medal in the Lépine competition for a reduced model. In 1913 he worked on the development of a model ordered by a pilot, the Dubois-Riout. The tests were stopped in 1916. In 1937, he finalized the Riout 102T Alérion, certainly the most successful piloted flapping wing ornithopter until the second decade of the 21st century. Ultimately, the conclusions of the wind tunnel tests were not favorable to the continuation of the project.
In 2005, Yves Rousseau was given the Paul Tissandier Diploma, awarded by the FAI 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, observed by officials of the Aero Club de France. 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, headed by Professor James DeLaurier, worked for several years on an engine-powered, piloted ornithopter. In July 2006, at the Bombardier Airfield at Downsview Park in Toronto, Professor DeLaurier's machine, the UTIAS Ornithopter No.1 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 same institution piloted a human-powered ornithopter named Snowbird. The wingspan, 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 with an average speed of. 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 uncrewed ornithopters
Because ornithopters can be made to resemble birds or insects, they could be used for military applications such as aerial reconnaissance 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 demonstrated a remotely piloted ornithopter resembling a large hummingbird for possible spy missions.Led by Paul B. MacCready, AeroVironment developed a half-scale radio-controlled model of the giant pterosaur, Quetzalcoatlus northropi, for the Smithsonian Institution in the mid-1980s. It was built to star in the IMAX movie On the Wing. The model had a wingspan and featured a complex computerized autopilot control system, just as the full-sized pterosaur relied on its neuromuscular system to make constant adjustments in flight.
Researchers hope to eliminate the motors and gears of current designs by more closely imitating animal flight muscles. Georgia Tech Research Institute's Robert C. Michelson is developing a reciprocating chemical muscle for use in microscale flapping-wing aircraft. Michelson uses the term "entomopter" for this type of ornithopter. SRI International is developing polymer artificial muscles that may also be used for flapping-wing flight.
In 2002, Krister Wolff and Peter Nordin of Chalmers University of Technology in Sweden, built a flapping-wing robot that learned flight techniques. The balsa-wood design was driven by machine learning software technology known as a steady-state linear evolutionary algorithm. Inspired by natural evolution, 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 that 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.
In 2008, Amsterdam Airport Schiphol started using a realistic-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 2012, RoBird, a spin-off of the University of Twente, started making artificial birds of prey for airports and agricultural and waste-management industries.
Adrian Thomas and Alex Caccia founded Animal Dynamics Ltd in 2015, to develop a mechanical analogue of dragonflies to be used as a drone that will outperform quadcopters. The work is funded by the Defence Science and Technology Laboratory, the research arm of the British Ministry of Defence, and the United States Air Force.