helicopter development in the early 20th century
Cornu in his first helicopter in 1907. Note that he is sitting between the
which rotated in opposite directions to cancel torque.
This helicopter was the first flying machine to have risen from the ground
using rotor blades instead of wings.
At the end of the nineteenth century,
the internal combustion engine became available, making the development of
full-sized vertical-flight craft with adequate power a possibility.
However, other problems remained, particularly those relating to torque,
dissymmetry of lift, and control. Inventors during the next two decades
built many small prototype helicopters that attempted to solve these
problems, but progress came only in small steps.
Gaetano A. Crocco of Italy patented an
early cyclic pitch design in 1906. Crocco recognized that a way to change
the pitch cyclically on the blades was needed if a helicopter was to work
properly in forward flight.
During 1906, the brothers Louis and
Jacques Bréguet began their helicopter experiments and meticulously tested
airfoil shapes under the guidance of Professor Charles Richet. In 1907,
they built the Bréguet-Richet Gyroplane No. 1, one of the first mechanical
devices to actually hover. The gyroplane flew
for one minute on August 24, 1907 (some sources say September 29, 1907) in
what is generally accepted as the first vertical flight. A
45-horsepower (33.5-kilowatt) engine provided just enough power to achieve
vertical flight. However, there was no means of control or stability, and
it needed four men to steady it while it hovered
about 2 feet (0.6 meters) off the ground.
Without a control system, it was not a practical helicopter.
Breguet, one of the foremost helicopter pioneers, built the first
to leave the ground with a pilot in 1907. However, it had no means of
13, 1907, the French bicycle maker Paul Cornu became the first person to
rise vertically in powered free flight.
His helicopter used two counter-rotating rotors to cancel torque.
Some control was achieved by placing auxiliary paddle-like wings below the
rotors, and sticks held by men on the ground stabilized the machine.
Although Cornu achieved a historic first,
rising about one foot (0.6 meter) and hovering for about 20 seconds, the
controls were inadequate, and the craft never developed into a practical
1907, the French inventor Paul Cornu made a helicopter that used two
counter-rotating rotors driven by a 24-hp (18-kW) Antoinette engine.
It lifted its inventor to about five feet (1.5 meters) and remained aloft
In June 1909, Igor Sikorsky built his
first helicopter, the S-1, in Kiev, Russia. The wooden craft weighed 450
pounds (204 kilograms) and had dual coaxial rotors. But the two blades
were inefficient, and the most powerful engine that was available, a
25-horsepower (20 kilowatt) Anzani engine, could not lift its own weight.
The next year, he built the S-2, which weighed only 400 pounds (181
kilograms) and had a three-blade rotor system. This model could rise, but
the engine was too weak to carry a passenger. The machine also shook and
vibrated violently because it needed a stiffer frame. Sikorsky turned to
airplane development, returning to helicopters only in the 1930s after he
emigrated to the United States.
The first vertical flight machine in the
United States seems to have been developed by Emile Berliner and John
Newton Williams. Berliner designed what may have been the first production
rotary aircraft engine, the 36-horsepower (27-kilowatt) Adams-Farwell
engine. In 1908, Williams constructed a coaxial machine for Berliner using
two of these engines. It reportedly lifted both Williams and the machine—a
weight of 610 pounds (277 kilograms)—but was probably steadied from the
ground. Williams later built another craft using a 40-horsepower
(30-kilowatt) Curtiss engine. It hovered at around three feet (0.9 meter),
again steadied from the ground. Berliner also was the first to propose the
auxiliary vertically mounted tail rotor.
Berliner 1921 single-wing rotary-powered helicopter had deflector vanes at
the wing tips.
Handicapped by a heavy 80-hp engine, this early coaxial helicopter built
by Emile Berliner
along with J. Newton Williams, lifted its own weight into the air in 1908.
This helicopter used skid landing gear.
Emile's son, Henry, later designed another craft that flew with some
success carrying a pilot in 1924.
Professor Zhukovskii and his students at
Moscow University may also have constructed a primitive coaxial helicopter
in 1910. Zhukovskii was well known for his theoretical contributions to
aerodynamics and published several papers on the subject of rotating wings
In 1912, the Russian Boris Yuriev built
a 445-pound (202-kilogram) helicopter that had a modern-looking single
rotor and smaller tail rotor and large diameter, high aspect ratio blades.
The tail rotor was needed to counteract the torque generated by the main
rotor but it added weight and like Sikorsky's helicopters, had an
undersized engine. The machine never flew properly. But Yuriev was one of
the first to use a tail rotor and also one of several pioneers to propose
the concept of cyclic pitch for rotor control.
Around 1912, the Danish aviation pioneer
Jacob Christian Ellehammer became interested in vertical flight. He
designed a coaxial helicopter with counter-rotating rotors that were
stacked vertically. Each rotor consisted of a large aluminium ring about 20
feet (six meters) in diameter with six five-foot (1.5-meter) blades
attached to the outside edge of the rotors. A cyclic pitch mechanism was
used to change the pitch of the rotating blades and for control.
Ellehammer made several short hops in the craft.
helicopter, with two superimposed airscrews rotating in opposite
was built by J.C.H. Ellehammer in Denmark in 1912. It flew but never rose
above four feet.
Two Austrians, Stephan Petroczy and
Professor Theodore von Karman, built and flew a coaxial rotor helicopter
during the closing years of World War I. Intended for observation, this
machine included a pilot/observer position above the wooden
counter-rotating rotors, inflated bags for landing gear, and a
quick-opening parachute. Three 120-horsepower (89-kilowatt) rotary engines
provided power. The machine achieved numerous short vertical flights
restrained by cables and reached a height of more than 150 feet (46
Around 1919, Henry Berliner built a
counter-rotating coaxial rotor machine that made brief uncontrolled hops
to a height of about four feet (1.2 meters) while steadied from the
ground. In 1922, he mounted two coaxial counter-rotating rotors on the
wing tips of a Nieuport biplane fuselage. Sets of movable vanes—flat
surfaces mounted under the rotors—provided some control. The craft
reportedly could manoeuvre in all directions and obtained a speed of about
40 miles per hour (64 kilometres per hour). In June 1922, it hovered
around 12 feet (3.3 meters) off the ground and was successfully
demonstrated to the U.S. Army in 1924. The Berliner aircraft are
considered the first rudimentary piloted helicopters developed in the
During the late 1910s and early 1920s,
Louis Brennan of England's Royal Aircraft Establishment worked on a
helicopter with an exceptionally large two-bladed rotor. To deal with the
problem of torque, Brennan used a single rotor and mounted propellers on
the blades themselves. The use of servo-flaps or ailerons inboard of the
propellers achieved control. He took several low-altitude flights, which
ended in October 1925, when the machine crashed.
In the 1920s, the Marquis Raul Pateras
Pescara, an Argentinean working in Europe, achieved one of the first
successful applications of cyclic pitch. He was also the first to
demonstrate that a helicopter with engine failure could still reach the
ground safely by means of autorotation—the phenomenon that caused blades
to turn even without power being applied to them that resulted from the
flow of air as the craft moved through it. His coaxial helicopter had
biplane-type rotors with a total of 20 lifting surfaces. In 1924, Pescara
set a new world record by flying his craft almost one-half mile (0.8
kilometre) in 4 minutes and 11 seconds—a speed of about eight miles per
hour (13 kilometres per hour)—at a height of six feet (1.8 meters).
helicopter, designed by George De Bothezat and Ivan Jerome,
made its first public flight on December 18, 1922, at McCook Field near
A Russian immigrant to the United
States, George de Bothezat, designed and built a four-rotor machine
powered by a 180-horsepower (134-kilowatt) rotary engine under the
sponsorship of the U.S. Army.
It weighed 3,600 pounds (1,633 kilograms),
and the x-shaped structure was more than 60 feet (18.3 meters) wide, with
four huge fan-shaped rotors mounted at each corner. The pilot controlled
individual collective pitch mechanisms for each rotor. De Bothezat flew
the helicopter on its first flight at McCook Field near Dayton, Ohio, in
October 1922. This flight lasted about a minute and a half as the craft
rose six feet (1.8 meters), drifted with the wind, and landed some 500
feet (152 meters) away. Over the next two years, the helicopter made more
than 100 test flights—some rising to 15 feet (4.6 meters) and one with
three passengers clinging to the frame to demonstrate the machine's
stability. The U.S. Army tested the machine and commented favourably on it.
But the Army abandoned it because of its complexity and unreliability and
because de Bothezat was difficult to work with.
helicopter, built by Etiénne Oehmichen, had four lifting airscrews
and five auxiliary propellers.
It set flight records in 1924.
Another French pioneer, Etienne
Oehmichen, began his experiments in 1920 by suspending a balloon above a
twin-rotor helicopter to provide additional lift. A later design had four
lifting airscrews and five auxiliary propellers. On April 14, 1924, he
flew this type of craft, powered by a 180-horsepower (134-kilowatt) Rhone
engine, 1,181 feet (360 meters), establishing the first helicopter
distance record officially recognized by the Federation Aeronautique
Internationale. On May 4, he was the first to fly a helicopter at least
one kilometre (0.6 mile) in a closed circuit in a 5,550-foot
(1.692-kilometer) flight that lasted 14 minutes and rose to 50 feet (15