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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 15th 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."
In
1483, Leonardo da Vinci of Italy sketched the most advanced plans of the
period for an aircraft that was really a helicopter. His theory for "compressing" the air to obtain lift was substantially
similar to that of the modern helicopter.
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 20th 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 20th 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
modelled 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.
Launoy
and Bienvenu designed a version of the Chinese top that consisted of two
sets of rotors
made of turkey feathers that rotated in opposite directions, which solved
the problem of torque.
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.
In
1843, Sir George Cayley of Great Britain drew up plans for this "aerial
carriage"
that used rotors on opposite sides to counteract torque. This
configuration is sometimes still used.
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.
This
1845 design for a primitive helicopter by Cossus appeared in Octave
Chanute's Progress in Flying Machines.
The rotating screws were to be moved by steam power.
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.
Gustave
Ponton D'Amecourt constructed, in 1865, an aerial screw machine that
worked by steam.
It was exhibited at the London Aeronautical Exposition in 1868.
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.
Penaud's flying screw, which the French called a "Helicoptere," consisted
of two superimposed screws
rotating in opposite directions and powered by the force of twisted rubber
bands.
This design inspired by the Wright brothers when they were boys.
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.
The
invention of Dieuaide, at one time secretary of the French Aeronautical
Society,
consisted of two pairs of square vanes set a various angles to the line of
motion so as to
vary the pitch and rotated in opposite directions by gearing. It had a
steam engine.
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.
This
design by Melikoff in 1877 consisted of a screw parachute.
It would be rotated by a gas turbine. It was designed to carry a man.
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.
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