Early Helicopter Technology

Helicopter flight was probably the first type of flight envisioned by man. The idea dates back to ancient China, where children played with homemade tops of slightly twisted feathers attached to the end of a stick. They would rapidly spin the stick between their hands to generate lift and then release the top into free flight.

In the western world, the ancient Greek mathematician, physicist, and inventor, Archimedes, who lived and worked in the second century B.C.E. perfected the principle of the rotating screw for use as a water pump. When the screw was rotated inside a cylinder, the screw moved the water in front of it. At the same time, the water resisted and pushed back. This resistance also applied to the movement of screws through air—a type of fluid.

The 15^th century Italian Leonardo da Vinci has often been cited as the first person who conceived of a helicopter capable of lifting a person and then experimented with models of his designs. His sketch of the "aerial-screw" or "air gyroscope" showed a device with a helical rotor. The helical surface on his device resembled a helicopter and was made from iron wire and covered with linen surfaces made "airtight with starch."

Leonardo planned to use muscle power to revolve the rotor, although such power would never have been sufficient to operate a helicopter successfully. His notes implied that his models flew, but from his sketch, there was no way to deal with the torque created by the propeller. Although he had undoubtedly identified the concept of a rotary-wing aircraft, the technology needed to create a helicopter had not yet been produced. His drawings date to 1483, but they were first published nearly three centuries later.

A large number of fanciful inventions surfaced between the time of Leonardo and the 20^th century. These helped advance the knowledge of vertical flight, but they all lacked sufficient power to achieve flight and were too bulky and heavy. Serious efforts to create a real helicopter did not occur until the early years of the 20^th century.

In 1754, Mikhail Lomonosov, the "Father of Russian Science," suggested that a coaxial rotor machine could be used to lift meteorological instruments. He developed a small coaxial rotor modeled after the Chinese top, but powered by a wound-up spring that he demonstrated to the Russian Academy of Sciences in July 1754. The device may have climbed and flown freely or it may have been suspended from a string.

J.P. Paucton seems to have been the first European to propose the helicopter as a man-carrying vehicle. In his Theorie de la vis d'Archimedes, he described a man-powered machine called a Pterophere with two airscrews—one to support the machine in flight and the second to provide forward propulsion.

In 1783, the French naturalist Launoy, with the assistance of his mechanic Bienvenu, used a version of the Chinese top in a model consisting of two sets of rotors made of turkey feathers that rotated in opposite directions. This "counter-rotation" solved the problem of torque since the forces created by each rotor cancelled each other out. They demonstrated the model, which resembled Lomonosov's model in principle, in 1784 before the French Academy of Sciences and succeeded in achieving free flight.

George Cayley, who, as a young boy, had been fascinated by the Chinese top, built his earliest vertical-flight model, a twin-rotor helicopter model in 1792 and described it in On Aerial Navigation in 1796. It was very similar to Launoy and Beinvenu's model. By the end of the 18th century, he had constructed several successful vertical-flight models with rotors made of sheets of tin and driven by wound-up clock springs. In a scientific paper published in 1843, Cayley described a relatively large vertical flight aircraft design that he called an Aerial Carriage. However, his device remained only an idea because the only engines available at the time were steam engines, which were much too heavy for successful flight.

The lack of a suitable engine stifled aeronautical progress, but the use of miniature lightweight steam engines met with limited success. In 1842, the Englishman W.H. Phillips constructed a steam-driven vertical flight machine that ejected steam generated by a miniature boiler out of its blade tips. Although impractical to build at full-scale, Phillips' machine marked the first time that a model helicopter had flown powered by an engine rather than by stored energy devices such as wound-up springs. He exhibited his model at the Crystal Palace in London in 1868.

Another idea at this time, documented by Octave Chanute in Progress in Flying Machines, was a model built by Cossus of France in 1845. It had three rotating aerial screws that were moved by steam power. Chanute also mentioned a device by a Mr. Bright that consisted of axles that were suspended beneath a balloon and rotated in opposite directions.

A U.S. Confederate soldier, William Powers, designed an attack helicopter in 1862 that made use of Archimedes' screws powered by a steam engine that was to propel it vertically and forward. He intended to use it to break the Union's siege of the southern ports. He constructed a non-flying model but did not construct a full-size craft.

In France, an association was set up to assemble the many helicopter models and designs that had proliferated during the 1860s. In 1863, the Vicomte Gustave Ponton d'Amecourt built a model helicopter with counter-rotating propellers and a steam engine. He patented it in France and Great Britain and exhibited it at the 1868 London Aeronautical Exposition. This machine failed, but another model using spring propulsion had better luck. He called his machines "helicopteres," which was derived from the Greek adjective "elikoeioas," meaning spiral or winding and the noun "pteron," meaning feather or wing.

In 1870, Alphonse Penaud constructed several model helicoptére that he fashioned after the Chinese top. They had two superimposed screws rotating in opposite directions and set in motion by the force of twisted rubber bands. Some of his models rose to more than 50 feet (15 meters). In 1871, Pomes and De la Pauze designed an apparatus that had a rotor powered by gunpowder, but it was never built.

In 1877, Emmanuel Dieuaide, a former secretary of the French Aeronautical Society, designed a helicopter with counter-rotating rotors. The engine boiler was on the ground and connected to the machine by a flexible tube. Also that year, Melikoff designed and patented a helicopter with a conical-shaped rotor that doubled as a parachute for descent.

In 1878, Castel, a Frenchman, designed and built a helicopter driven by compressed air with eight rotors on two counter-rotating shafts. This model did not work, but a smaller one built by Dandrieux between 1878 and 1879 and driven by elastic bands did.

Also in 1878, Enrico Forlanini, an Italian civil engineer, built another type of flying steam-driven helicopter model powered by a 7.7-pound (3.5-kilogram) engine. This model had two counter-rotating rotors and rose more than 40 feet (12 meters), flying for as much as 20 seconds.

In the 1880s, Thomas Alva Edison experimented with small helicopter models in the United States. He tested several rotor configurations driven by a gun cotton engine, an early form of internal combustion engine. However, a series of explosions that blew up part of his laboratory deterred him. Later, Edison used an electric motor for power, and he was one of the first to realize from his experiments that a large-diameter rotor with low blade area was needed to give good hovering efficiency. Edison's scientific approach to the problems of vertical flight proved that both high aerodynamic efficiency of the rotor and high power from an engine were required for successful vertical flight.

At the end of the nineteenth century, inventors had not solved the inherent aerodynamic and mechanical complexities of building a vertical flight aircraft. The hundreds of failed helicopter inventions had either inadequate power or control or experienced excessive vibration. Some of the better-designed early helicopters managed to hop briefly into the air, but they did not attain sustained flight with control. Steam engines were just too heavy for a full-scale helicopter. Not until the internal combustion engine was invented and became available could inventors develop full-sized models.

A number of technical problems challenged the early developers of helicopters. These included limited knowledge of the aerodynamics of vertical flight, the lack of a suitable engine, the inability to keep the weight of the structure and engine low enough, the problem of excessive vibration, the inability to deal with the torque created by the propellers, and the inability to achieve adequate stability and control.

—Judy Rumerman

References and Sources:

Gablehouse, Charles. Helicopters and Autogiros; A History of Rotating-wing and V/STOL Aviation. Philadelphia: J.B. Lippincott Company, 1969.

Lightbody, Andy and Poyer, Joe. The Illustrated History of Helicopters. Lincolnwood, Ill.: Publications International, 1990.

On-Line References:

Chanute, Octave. Progress in Flying Machines. M N Forney 1894, Lorenz & Herweg 1976, Dover 1997 also at http://hawaii.psychology.msstate.edu/invent/i/Chanute/library/Prog_Contents.html.

"Helicopter." http://www.britannica.com.

"History of Helicopters – an Epic of Man's Desire to Find Freedom in Flight." Hiller Copter-News. http://www.hiller.org/exhibits/copter-news-v3n8/copter-news.html.

Leishman, J. Gordon. "Evolution of Helicopter Flight." http://www.flight100.org/history/helicopter.html.