. Ornithopter

n ornithopter is a machine with flapping wings. Early inventors tried to copy bird flight by designing and building these aircraft, but their designs failed to get off the ground. Small ornithopters have flown as toy models and research experiments.

The principle behind the ornithopter is that the flapping wings provide both lift and propulsion. When people first dreamed of flying, they naturally tried to imitate birds, and some tried strap­ping wings to their arms. In about 1500, Italian artist and inventor, Leonardo da Vinci, made a sketch of a practical-look­ing ornithopter, but it never flew. One of
the first toy airplanes was a model flown at the court of the King of Poland in 1647, by an Italian inventor named Titus Burratini. His model apparently had fixed and flapping wings.

Flapping wings were not the answer for human flight, as glider pioneer Sir George Cayley (1773-1857) realized. Cayley decided that if an aircraft needed wings for lift, some other means must be found for propulsion. The answer was the fixed-wing airplane with a propeller. Cayley never flew a powered plane, however, and people continued to design flapping-wing machines.

A model ornithopter, flown in 1870 by Gustave Trouve (1839-1902), was powered by revolver cartridges. The exploding cartridge forced the wings down, and springs pushed the wings up again. Trouve’s ornithopter apparently flew for 230 feet (70 meters). Another French inventor, Alphonse Penaud (1850-1880), designed an ornithopter as well as model gliders. His models flew well and later inspired Orville and Wilbur Wright. Unfortunately, when his clever designs for flying machines were not taken up by the authorities, Penaud became depressed and committed sui­cide. In the 1890s, Australian Lawrence Hargrave built an ornithopter powered by using steam or compressed air to flap one set of small wings, while relying on large, fixed wings for lift.

A toy ornithopter flies because it is so lightweight. By the 1930s, rubber – powered model “flapping birds” were popular toys. These ornithopters could fly well in calm air for a short period of time. A small ornithopter, made from wood, wire, paper, or plastic, needs only a taut, twisted rubber band for power to make the wings flap. Model ornithopters fly best in the calm air inside a large building-rubber-powered ornithopters have achieved inside flight durations of more than 20 minutes. For outside use, there are radio-controlled ornithopter kits that are usually powered by a small electric motor.

The problem with ornithopters is finding a power plant that will make the wings beat up and down with sufficient

TECH^TALK

HOW AN ORNITHOPTER FLIES

An ornithopter creates all its thrust— and most of its lift—by flapping its wings. The wings beat in a twisting motion rather than directly up and down. They are joined by a center section that is moved up and down by the drive mechanism from the engine. The thrust comes from a low-pressure zone around the lead­ing edge of the wing that generates leading-edge suction. Many toy ornithopters fly nose-up to ensure enough lift. The tail is usually set at a steep angle of incidence, angled up.

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power to generate both lift and propul­sion but is not so heavy that the machine cannot leave the ground. A leading designer of ornithopters is Dr. James Delaurier of the University of Toronto’s Institute for Aerospace Studies in Canada. His team has flown several small flapping-wing designs. In 2006 they successfully flew a larger machine, using a jet-assisted takeoff.

SEE ALSO:

• Aerodynamics • Bird • Cayley,

George • Da Vinci, Leonardo • Wing

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