HISTORY unmanned

The first ornithopters were flown in France, in the 1870s. Keep in mind that this was almost a hundred years after the invention of the hot air balloon. People were looking for another way to fly, and they drew inspiration from the flight of birds. Bird flight was the example that proved a heavier-than air method of flight could exist. The early experiments with unmanned ornithopters were therefore intended to pave the way for human flight. However, the unmanned ornithopter is a fascinating endeavor in its own right. Today we have found many applications for unmanned aircraft.

The first experimental ornithopters were powered by rubber band, just like some of the models that hobbyists can build today. The first illustration shows an ornithopter that was flown by Jobert in 1971. It was powered by a stretched rubber band turning a crank. In the following year, Jobert built a biplane (four-winged) ornithopter with the twisted rubber band motor more common today. The use of four wings was a clever innovation that reduced the amount of torque needed to flap the wings. The other ornithopters shown here were built by Alphonse Penaud and Hureau de Villeneuve, respectively, in 1872. (These were described by Octave Chanute, in a 1891 article that would become part of his book, Progress in Flying Machines.)

In 1874, Victor Tatin devised a more complicated crank mechanism that actively drove the twisting of the wings. His ornithopter shown here is on exhibit at the National Air & Space Museum in Washington. Most of the mechanism was fashioned from bent wire, and it is quite interesting to examine up close. A similar mechanism was used by Pichancourt in his toy bird, "l'oiseau mécanique". This was perhaps the first commercial venture involving ornithopters.

For a long time, we thought Gustave Trouvé had built the first successful ornithopter. Recently, with the help of biographer Kevin Desmond, we were able to sort things out a bit. In 1870, Trouve made an ornithopter powered by compressed air. I am not sure if it actually flew, and we don't have any pictures of it. The ornithopter shown here was flown in 1890, not 1870 as previously thought. Twelve gunpowder charges were fired successively into a bourdon tube to flap the wings. The ornithopter flew 70 meters in a demonstration to the French Academy of Sciences. Therefore it appears this was not the first ornithopter to fly, but it was the first to use a type of internal combustion engine.

Lawrence Hargrave built a series of ornithopters in the 1890s. They were powered by rubber band, steam, or compressed air. To reduce the torque requirement, he made the flapping wings smaller, and he provided a large fixed wing. The concept would be influential later on, as it didn’t require as much gear reduction and simplified construction.

Alexander Lippisch led a group of aviation students during the 1930s. He and his students built many large ornithopters powered by rubber band and by internal combustion engines. The students competed for the longest flight time with their engine-powered ornithopters, achieving flights over 16 minutes. Lippisch favored the small-flapper design of Hargrave, bringing it up to date with the use of modern airfoils.

Erich von Holst experimented with various bird and dragonfly ornithopter configurations in the 1930s. He used pulleys to increase the torque. His work included experimentation with biplane wing phasing and hinged outer wing panels. Some of his rubber-powered ornithopters achieved a very high level of realism. In some models, the outer wing panels were hinged, to more closely mimic the movement of a bird's wings. Recently Festo’s “SmartBird” ornithopter has used this concept, and I would like readers to notice how it is based on Erich von Holst’s much earlier ornithopter designs.

Ornithopter contests began in the 1930s. A model airplane club called the Chicago Aeronuts was holding various contests for the indoor flying of model airplanes. For some extra challenge, they decided to add ornithopters to the list of events. Ed Lidgard's design shown here could be built from magazine plans, and many of the rubber-band-powered ornithopters built over the subsequent decades followed a similar pattern. Eventually the ornithopter event became part of the national model competition arranged by the Academy of Model Aeronautics.

In the 1980s, it was found that biplane ornithopters had a huge advantage in these indoor flying contests. Another modification was to move the stabilizer to the front of the model, where it could act as a fixed wing, supporting the weight of the fuselage. With these innovations, ornithopter flight times increased from around four minutes, to the current record of 21 minutes, 44 seconds held by Roy White. Successful competition models are extremely lightweight and delicate. Careful adjustments must be made to maximize the flight time without hitting the ceiling. Perhaps as you refine your ornithopter skills, you will be able to log some impressive flight times of your own.

In the 1950s, Percival Spencer constructed a series of engine-driven ornithopters in the shape of a bird. These ornithopters, called the “Spencer Seagulls”, ranged in size from a small 0.02-engine-powered ornithopter to one with an eight-foot wingspan. Spencer is also noted as a pioneer pilot and the designer of the Republic Seabee amphibious airplane. He also designed a toy, called the Wham-O Bird, which introduced thousands of children to the idea of mechanized flapping-wing flight. Spencer collaborated with Jack Stephenson to build the Orniplane. Flown in 1961, this was the first radio-controlled ornithopter. Spencer sought funding to build a manned version. The biplane wing configuration was to provide a smoother ride for the pilot. Reportedly, Spencer's colleague Dale Anderson later converted one of Spencer's Seagull ornithopters to radio control as well.

Spencer’s work was largely unknown until the 1990s. At that point, rediscovery of his simple but effective wing design had a profound influence on the nascent field of RC ornithopters. Around this time, a few people such as Paul MacCready and Horst Räbiger had built some very advanced RC ornithopters. But it was the revival of Spencer’s simple design which led to the first commercially available RC ornithopters.

Another development around 2000 was the “micro air vehicle” ornithopter. This resulted from newly available tiny motors and batteries. The Luna design, which I had developed originally as a rubber-band-powered model, provided the basis for many of these MAV ornithopters, because the scissor wing flapping mechanism made it possible to drive four wings without added complexity. With the addition of radio control, it was found these models could hover and carry small payloads such as cameras.

There are a few interesting threads in ornithopter development which I have not gone into here. This would include the use of airfoiled wings, instead of the membrane wings, and the development of the actively stabilized, robotic ornithopters. You can check out the desktop version of this web site if you would like to learn more.