An ornithopter () is an aircraft that flies by flapping its wings. Designers sought to imitate the flapping-wing flight of birds, bats, and insects. The term covers a wide range of possible designs. Ornithopters are typically built on the scale of the animals they emulate, however larger, crewed fliers have also found experimental success. 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 (recorded in the 12th century) and the 9th-century poet Abbas Ibn Firnas (recorded in the 17th century).White, Lynn. "Eilmer of Malmesbury, an Eleventh Century Aviator: A Case Study of Technological Innovation, Its Context and Tradition." Technology and Culture, Volume 2, Issue 2, 1961, pp. 97–111 (97–99 resp. 100–101). 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.Bondaryk P., Gruszczyński J., Kłosowski M., Kopański T. j., Matusiak W., Ruchała P., Rusiecki M., Witkowski R., Historia lotnictwa w Polsce, Carta Blanca, Warsaw 2011.
In 1841, Manojlo, a journeyman ironsmith who "came to Belgrade from Vojvodina", attempted flying with a device described as an ornithopter ("flapping wings like those of a bird"). 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 (import tax head office) 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.Chanute, Octave. 1894, reprinted 1998. Progress in Flying Machines. Dover 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.W. Hudson Shaw and Olaf Ruhen. 1977. Lawrence Hargrave: Explorer, Inventor & Aviation Experimenter. Cassell Australia Ltd. pp. 53–160. 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.Kelly, Maurice. 2006. Steam in the Air. Ben & Sword Books. Pages 49–55 are about Frost.
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.Rubber Band Powered Ornithopters at Ornithopter Zone web site
Around 1960, Percival Spencer successfully flew a series of uncrewed ornithopters using internal combustion engines ranging from displacement, and having wingspans up to .The complete book of model aircraft, spacecraft, and rockets − by Louis H. Hertz, Bonanza Books, 1968. In 1961, Percival Spencer and Jack Stephenson flew the first successful engine-powered, remotely piloted ornithopter, known as the Spencer Orniplane.Video provided by Jack Stephenson: https://www.youtube.com/watch?v=vS4Yz-VcNes 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.RC History Brought Back to Life: Spencer's Ornithopter, by Faye Stilley, Feb 1999 Model Airplane News
Crewed flight
Crewed ornithopters fall into two general categories: Those powered by the muscular effort of the pilot (human-powered ornithopters), 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 (designer of the Messerschmitt Me 163 Komet) 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. (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 , 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.Bruno Lange, Typenhandbuch der deutschen Luftfahrttechnik, Koblenz, 1986.
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.Philippe Ricco, « L'Alérion Riout », L'Aviation Française Magazine, décembre 2005, p. 4-11
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.FAI web site.
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,Dr. James DeLaurier's report on the Flapper's Flight July 8, 2006 the jet was necessary for sustained flight, but the flapping wings did most of the work.University of Toronto ornithopter takes off July 31, 2006
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 .Human-Powered Ornithoper Flight in Flapping Wings: The Ornithopter Zone Newsletter, Fall 2010. 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 (of Gossamer Albatross fame), 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.