Helicopter

Helicopter

Overview


A helicopter (informally known as a "chopper") is a type of rotorcraft
Rotorcraft
A rotorcraft or rotary wing aircraft is a heavier-than-air flying machine that uses lift generated by wings, called rotor blades, that revolve around a mast. Several rotor blades mounted to a single mast are referred to as a rotor. The International Civil Aviation Organization defines a rotorcraft...

 in which lift
Lift (force)
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...

 and thrust
Thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....

 are supplied by one or more engine-driven rotor
Helicopter rotor
A helicopter main rotor or rotor system is a type of fan that is used to generate both the aerodynamic lift force that supports the weight of the helicopter, and thrust which counteracts aerodynamic drag in forward flight...

s. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft
Fixed-wing aircraft
A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...

 would usually not be able to take off or land.
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Encyclopedia


A helicopter (informally known as a "chopper") is a type of rotorcraft
Rotorcraft
A rotorcraft or rotary wing aircraft is a heavier-than-air flying machine that uses lift generated by wings, called rotor blades, that revolve around a mast. Several rotor blades mounted to a single mast are referred to as a rotor. The International Civil Aviation Organization defines a rotorcraft...

 in which lift
Lift (force)
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...

 and thrust
Thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....

 are supplied by one or more engine-driven rotor
Helicopter rotor
A helicopter main rotor or rotor system is a type of fan that is used to generate both the aerodynamic lift force that supports the weight of the helicopter, and thrust which counteracts aerodynamic drag in forward flight...

s. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft
Fixed-wing aircraft
A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...

 would usually not be able to take off or land. The capability to efficiently hover for extended periods of time allows a helicopter to accomplish tasks that fixed-wing aircraft and other forms of vertical takeoff and landing
VTOL
A vertical take-off and landing aircraft is one that can hover, take off and land vertically. This classification includes fixed-wing aircraft as well as helicopters and other aircraft with powered rotors, such as cyclogyros/cyclocopters and tiltrotors...

 aircraft cannot perform.

The word helicopter is adapted from the French , coined by Gustave de Ponton d'Amecourt in 1861, which originates from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 helix/helik- = "twisted, curved" and pteron = "wing".

Helicopters were developed and built during the first half-century of flight
Flight
Flight is the process by which an object moves either through an atmosphere or beyond it by generating lift or propulsive thrust, or aerostatically using buoyancy, or by simple ballistic movement....

, with the Focke-Wulf Fw 61
Focke-Wulf Fw 61
|-See also:-References:NotesBibliography* Coates, Steve and Jean-Christophe Carbonel. Helicopters of the Third Reich. Crowborough, UK: Classic Publications Ltd., 2002. ISBN 1-903223-24-5....

 being the first operational helicopter in 1936. Some helicopters reached limited production, but it was not until 1942 that a helicopter designed by Igor Sikorsky
Igor Sikorsky
Igor Sikorsky , born Igor Ivanovich Sikorsky was a Russian American pioneer of aviation in both helicopters and fixed-wing aircraft...

 reached full-scale production
Mass production
Mass production is the production of large amounts of standardized products, including and especially on assembly lines...

, with 131 aircraft built. Though most earlier designs used more than one main rotor, it was the single main rotor with antitorque tail rotor
Tail rotor
The tail rotor, or anti-torque rotor, is a smaller rotor mounted so that it rotates vertically or near-vertically at the end of the tail of a traditional single-rotor helicopter. The tail rotor's position and distance from the center of gravity allow it to develop thrust in the same direction as...

 configuration of this design that would come to be recognized worldwide as the helicopter.

History


The earliest references for vertical flight have come from China. Since around 400 BC, Chinese
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 children have played with bamboo flying toys
Bamboo-copter
The bamboo-copter or bamboo dragonfly is a toy propeller that flies up when its shaft is rapidly spun...

, and the 4th-century AD Daoist book Baopuzi
Baopuzi
The Baopuzi , written by the Jin Dynasty scholar Ge Hong 葛洪 , is divided into esoteric Neipian 內篇 "Inner Chapters" and exoteric Waipian 外篇 "Outer Chapters". The Daoist Inner Chapters discuss topics such as techniques for xian 仙 "immortality; transcendence", Chinese alchemy, elixirs, and demonology...

 (抱朴子 "Master who Embraces Simplicity") reportedly describes some of the ideas inherent to rotary wing aircraft:
It was not until the early 1480s, when Leonardo da Vinci
Leonardo da Vinci
Leonardo di ser Piero da Vinci was an Italian Renaissance polymath: painter, sculptor, architect, musician, scientist, mathematician, engineer, inventor, anatomist, geologist, cartographer, botanist and writer whose genius, perhaps more than that of any other figure, epitomized the Renaissance...

 created a design for a machine that could be described as an "aerial screw", that any recorded advancement was made towards vertical flight. His notes suggested that he built small flying models, but there were no indications for any provision to stop the rotor from making the whole craft rotate. As scientific knowledge increased and became more accepted, men continued to pursue the idea of vertical flight. Many of these later models and machines would more closely resemble the ancient bamboo flying top with spinning wings, rather than Da Vinci's screw.
In July 1754, Mikhail Lomonosov
Mikhail Lomonosov
Mikhail Vasilyevich Lomonosov was a Russian polymath, scientist and writer, who made important contributions to literature, education, and science. Among his discoveries was the atmosphere of Venus. His spheres of science were natural science, chemistry, physics, mineralogy, history, art,...

 demonstrated a small tandem rotor to the Russian Academy of Sciences
Russian Academy of Sciences
The Russian Academy of Sciences consists of the national academy of Russia and a network of scientific research institutes from across the Russian Federation as well as auxiliary scientific and social units like libraries, publishers and hospitals....

. It was powered by a spring and suggested as a method to lift meteorological instruments. In 1783, Christian de Launoy, and his mechanic
Mechanic
A mechanic is a craftsman or technician who uses tools to build or repair machinery.Many mechanics are specialized in a particular field such as auto mechanics, bicycle mechanics, motorcycle mechanics, boiler mechanics, general mechanics, industrial maintenance mechanics , air conditioning and...

, Bienvenu, made a model with a pair of counter-rotating rotors, using turkey
Turkey (bird)
A turkey is a large bird in the genus Meleagris. One species, Meleagris gallopavo, commonly known as the Wild Turkey, is native to the forests of North America. The domestic turkey is a descendant of this species...

 flight feathers as rotor blades, and in 1784, demonstrated it to the French Academy of Sciences
French Academy of Sciences
The French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research...

. Sir George Cayley, influenced by a childhood fascination with the Chinese flying top, grew up to develop a model of feathers, similar to Launoy and Bienvenu, but powered by rubber bands. By the end of the century, he had progressed to using sheets of tin for rotor blades and springs for power. His writings on his experiments and models would become influential on future aviation pioneers. Alphonse Pénaud
Alphonse Pénaud
Alphonse Pénaud , was a 19th-century French pioneer of aviation, inventor of the rubber powered model airplane Planophore and founder of the aviation industry.-Biography:...

 would later develop coaxial rotor model helicopter toys in 1870, also powered by rubber bands. One of these toys, given as a gift by their father, would inspire the Wright brothers
Wright brothers
The Wright brothers, Orville and Wilbur , were two Americans credited with inventing and building the world's first successful airplane and making the first controlled, powered and sustained heavier-than-air human flight, on December 17, 1903...

 to pursue the dream of flight.

In 1861, the word "helicopter" was coined by Gustave de Ponton d'Amécourt, a French inventor who demonstrated a small, steam-powered model. While celebrated as an innovative use of a new metal, aluminum, the model never lifted off the ground. D'Amecourt's linguistic contribution would survive to eventually describe the vertical flight he had envisioned. Steam power was popular with other inventors as well. In 1878 Enrico Forlanini
Enrico Forlanini
Enrico Forlanini was an Italian engineer, inventor and aeronautical pioneer, well known for his works on helicopters, aircraft, hydrofoils and dirigibles. He was born in Milan...

's unmanned helicopter was also powered by a steam engine. It was the first of its type that rose to a height of 12 meters (40 ft), where it hovered for some 20 seconds after a vertical take-off. Emmanuel Dieuaide's steam-powered design featured counter-rotating rotors powered through a hose from a boiler on the ground.

In 1885, Thomas Edison
Thomas Edison
Thomas Alva Edison was an American inventor and businessman. He developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb. In addition, he created the world’s first industrial...

 was given US$1,000 by James Gordon Bennett, Jr.
James Gordon Bennett, Jr.
James Gordon Bennett, Jr. was publisher of the New York Herald, founded by his father, James Gordon Bennett, Sr., who emigrated from Scotland. He was generally known as Gordon Bennett to distinguish him from his father....

, to conduct experiments towards developing flight. Edison built a helicopter and used the paper for a stock ticker to create guncotton, with which he attempted to power an internal combustion engine. The helicopter was damaged by explosions and one of his workers was badly burned. Edison reported that it would take a motor with a ratio of three to four pounds per horsepower produced to be successful, based on his experiments. Ján Bahýľ
Ján Bahýl
Ján Bahýľ was a Slovak inventor and constructor. He was working on several problems from the areas of military science, military construction, engineering etc. Among others, he focused on flying machines. In 1895, he was granted a patent on helicopter.-Biography:Ján Bahýľ was born in Zvolenská...

, a Slovak
Slovaks
The Slovaks, Slovak people, or Slovakians are a West Slavic people that primarily inhabit Slovakia and speak the Slovak language, which is closely related to the Czech language.Most Slovaks today live within the borders of the independent Slovakia...

 inventor, adapted the internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

 to power his helicopter model that reached a height of 0.5 meters (1.6 ft) in 1901. On 5 May 1905, his helicopter reached four meters (13 ft) in altitude and flew for over 1,500 meters (4,900 ft). In 1908, Edison patented his own design for a helicopter powered by a gasoline engine with box kites attached to a mast by cables for a rotor, but it never flew.

First flights


In 1906, two French brothers, Jacques and Louis Breguet, began experimenting with airfoils for helicopters and in 1907, those experiments resulted in the Gyroplane No.1. Although there is some uncertainty about the dates, sometime between 14 August and 29 September 1907, the Gyroplane No. 1 lifted its pilot up into the air about two feet (0.6 m) for a minute. However, the Gyroplane No. 1 proved to be extremely unsteady and required a man at each corner of the airframe to hold it steady. For this reason, the flights of the Gyroplane No. 1 are considered to be the first manned flight of a helicopter, but not a free or untethered flight.

That same year, fellow French inventor Paul Cornu
Paul Cornu
Paul Cornu was a French engineer who manufactured bicycles by trade.French engineer Paul Cornu designed the world's first manned rotary wing aircraft and made the first piloted free flight with it at Lisieux, Calvados, France on November 13, 1907. This first flight lifted Cornu about 30 cm ...

 designed and built a Cornu helicopter
Cornu helicopter
|-References:* *...

 that used two 20-foot (6 m) counter-rotating rotors driven by a 24-hp (18-kW) Antoinette engine. On 13 November 1907, it lifted its inventor to 1 foot (0.3 m) and remained aloft for 20 seconds. Even though this flight did not surpass the flight of the Gyroplane No. 1, it was reported to be the first truly free flight with a pilot.Leishman, Dr. J. Gordon, Technical Fellow of AHS International. "Paper." 64th Annual Forum of the American Helicopter Society International, on the aerodynamic capability of Cornu's design, arguing that the aircraft lacked the power and rotor loading to lift free of the ground in manned flight. Cornu's helicopter would complete a few more flights and achieve a height of nearly 6.5 feet (2 m), but it proved to be unstable and was abandoned.

The Danish inventor Jacob Ellehammer
Jacob Ellehammer
Jacob Christian Hansen Ellehammer was a Danish watchmaker and inventor born in Bakkebølle, Denmark. He is remembered chiefly for his contributions to powered flight....

 built the Ellehammer helicopter in 1912. It consisted of a frame equipped with two counter-rotating discs, each of which was fitted with six vanes around its circumference. After a number of indoor tests, the aircraft was demonstrated outdoors and made a number of free take-offs. Experiments with the helicopter continued until September 1916, when it tipped over during take-off, destroying its rotors.

Early development


In the early 1920s, Argentine Raoul Pateras-Pescara de Castelluccio
Raúl Pateras Pescara
Raúl Pateras Pescara de Castelluccio , marquis of Pateras-Pescara, was an Argentine lawyer and inventor specializing in seaplanes and helicopters, as well as motors, compressors, and the Pescara free-piston engine.-Biography:At the beginning of the 20th century, his family returned from Buenos...

, while working in Europe, demonstrated one of the first successful applications of cyclic pitch. Coaxial, contra-rotating, biplane rotors could be warped to cyclically increase and decrease the lift they produced. The rotor hub could also be tilted forward a few degrees, allowing the aircraft to move forward without a separate propeller to push or pull it. Pateras-Pescara was also able to demonstrate the principle of autorotation
Autorotation
In aviation, autorotation refers to processes in both fixed-wing and rotary-wing aircraft. The term means significantly different things in each context....

. By January 1924, Pescara's helicopter No. 1 was tested but was found underpowered and could not lift its own weight. The British government funded further research by Pescara which resulted in helicopter No. 3, powered by a 250 hp radial engine which could fly for up to ten minutes.

On 14 April 1924 Frenchman Etienne Oehmichen
Etienne Oehmichen
Étienne Oehmichen was a French engineer and helicopter designer....

, set the first helicopter world record recognized by the Fédération Aéronautique Internationale
Fédération Aéronautique Internationale
The Fédération Aéronautique Internationale is the world governing body for air sports and aeronautics and astronautics world records. Its head office is in Lausanne, Switzerland. This includes man-carrying aerospace vehicles from balloons to spacecraft, and unmanned aerial vehicles...

(FAI), flying his helicopter 360 meters (1,181 ft). On 18 April 1924, Pescara beat Oemichen's record, flying for a distance of 736 meters (nearly a half mile) in 4 minutes and 11 seconds (about 8 mph, 13 km/h) maintaining a height of six feet (2 m). Not to be outdone, Oehmichen reclaimed the world record on 4 May when he flew his No. 2 machine again for a 14-minute flight covering 5,550 feet (1.05 mi, 1.69 km) while climbing to a height of 50 feet (15 m). Oehmichen also set the 1 km closed-circuit record at 7 minutes 40 seconds.

In the USA, George de Bothezat
George de Bothezat
George de Bothezat was a Russian American engineer, businessman and pioneer of helicopter flight.-Biography:George Bothezat was born in a family of Bessarabian landlords in 1882. After graduating school in Iași and attending the University of Iaşi he enrolled at the Mechanical Department of...

 built the quadrotor De Bothezat helicopter
De Bothezat helicopter
|-See also:-References:NotesCitationsBibliography* Lambermont, Paul Marcel. Helicopters and autogyros of the world. London: Cassell, 1958....

 for the United States Army Air Service but the Army cancelled the program in 1924, and the aircraft was scrapped.

Meanwhile, Juan de la Cierva
Juan de la Cierva
Juan de la Cierva y Codorníu, 1st Count of De La Cierva was a Spanish civil engineer, pilot and aeronuatical engineer. His most famous accomplishment was the invention in 1920 of the Autogiro, a single-rotor type of aircraft that came to be called autogyro in the English language...

 was developing the first practical rotorcraft in Spain. In 1923, the aircraft that would become the basis for the modern helicopter rotor
Helicopter rotor
A helicopter main rotor or rotor system is a type of fan that is used to generate both the aerodynamic lift force that supports the weight of the helicopter, and thrust which counteracts aerodynamic drag in forward flight...

 began to take shape in the form of an autogyro
Autogyro
An autogyro , also known as gyroplane, gyrocopter, or rotaplane, is a type of rotorcraft which uses an unpowered rotor in autorotation to develop lift, and an engine-powered propeller, similar to that of a fixed-wing aircraft, to provide thrust...

, Cierva's C.4. Cierva had discovered aerodynamic and structural deficiencies in his early designs that could cause his autogyros to flip over after takeoff. The flapping hinges that Cierva designed for the C.4 allowed the rotor to develop lift equally on the left and right halves of the rotor disk. A crash in 1927, led to the development of a drag hinge to relieve further stress on the rotor from its flapping motion. These two developments allowed for a stable rotor system, not only in a hover, but in forward flight.

Albert Gillis von Baumhauer, a Dutch aeronautical engineer, began studying rotorcraft design in 1923. His first prototype "flew" ("hopped" and hovered in reality) on 24 September 1925, with Dutch Army-Air arm Captain Floris Albert van Heijst at the controls. The controls that Captain van Heijst used were Von Baumhauer's inventions, the cyclic and collective
Helicopter flight controls
A helicopter pilot manipulates the helicopter flight controls in order to achieve controlled aerodynamic flight. The changes made to the flight controls are transmitted mechanically to the rotor, producing aerodynamic effects on the helicopter's rotor blades which allow the helicopter to be...

. Patents were granted to von Baumhauer for his cyclic and collective controls by the British ministry of aviation on 31 January 1927, under patent number 265,272.

In 1928, Hungarian aviation engineer Oszkár Asbóth
Oszkár Asbóth
Asboth Oszkár was a Hungarian aviation engineer often credited with the invention of the helicopter...

 constructed a helicopter prototype that took off and landed at least 182 times, with a maximum single flight duration of 53 minutes.

In 1930, the Italian engineer Corradino D'Ascanio
Corradino D'Ascanio
General Corradino D'Ascanio was an Italian aeronautical engineer. D'Ascanio designed the first production helicopter, for Agusta, and designed the first motor scooter for Ferdinando Innocenti...

 built his D'AT3, a coaxial helicopter. His relatively large machine had two, two-bladed, counter-rotating rotors. Control was achieved by using auxiliary wings or servo-tabs on the trailing edges of the blades, a concept that was later adopted by other helicopter designers, including Bleeker and Kaman. Three small propellers mounted to the airframe were used for additional pitch, roll, and yaw control. The D'AT3 held modest FAI speed and altitude records for the time, including altitude (18 m or 59 ft), duration (8 minutes 45 seconds) and distance flown (1,078 m or 3,540 ft).

In the Soviet Union, Boris N. Yuriev and Alexei M. Cheremukhin, two aeronautical engineers working at the Tsentralniy Aerogidrodinamicheskiy Institut
TsAGI
TsAGI is a transliteration of the Russian abbreviation for Центра́льный аэрогидродинами́ческий институ́т or "Tsentralniy Aerogidrodinamicheskiy Institut", the Central Aerohydrodynamic Institute....

 (TsAGI, , Central Aerohydrodynamic Institute), constructed and flew the TsAGI 1-EA single rotor helicopter, which used an open tubing framework, a four blade main rotor, and twin sets of 1.8-meter (6-foot) diameter anti-torque rotors; one set of two at the nose and one set of two at the tail. Powered by two M-2 powerplants, up-rated copies of the Gnome Monosoupape
Gnome Monosoupape
The Monosoupape , was a rotary engine design first introduced in 1913 by Gnome Engine Company...

 rotary radial engine of World War I, the TsAGI 1-EA made several successful low altitude flights. By 14 August 1932, Cheremukhin managed to get the 1-EA up to an unofficial altitude of 605 meters (1,985 ft), shattering d'Ascanio's earlier achievement. As the Soviet Union was not yet a member of the FAI
Fédération Aéronautique Internationale
The Fédération Aéronautique Internationale is the world governing body for air sports and aeronautics and astronautics world records. Its head office is in Lausanne, Switzerland. This includes man-carrying aerospace vehicles from balloons to spacecraft, and unmanned aerial vehicles...

, however, Cheremukhin's record remained unrecognized.

Nicolas Florine
Nicolas Florine
Nicolas Florine, born Nikolay Florin , was an engineer that built the first tandem rotor helicopter to fly freely in Belgium in 1933. He was born in Batoum, Georgia.-External links:*...

, a Russian engineer, built the first twin tandem rotor machine to perform a free flight. It flew in Sint-Genesius-Rode
Sint-Genesius-Rode
Sint-Genesius-Rode is a municipality located in Flanders, one of three regions of Belgium, in the province of Flemish Brabant. The municipality comprises the town of Sint-Genesius-Rode only. On January 1, 2008, the town had a total population of 18,021...

, at the Laboratoire Aérotechnique de Belgique (now von Karman Institute) in April 1933, and attained an altitude of six meters (20 ft) and an endurance of eight minutes. Florine chose a co-rotating configuration because the gyroscopic stability of the rotors would not cancel. Therefore the rotors had to be tilted slightly in opposite directions to counter torque. Using hingeless rotors and co-rotation also minimised the stress on the hull. At the time, it was one of the most stable helicopter in existence.

The Bréguet-Dorand Gyroplane Laboratoire
Gyroplane Laboratoire
-External links:* -See also:...

 was built in 1933. It is coaxial helicopter, contra-rotating. After many ground tests and an accident, it first took flight on 26 June 1935. Within a short time, the aircraft was setting records with pilot Maurice Claisse at the controls. On 14 December 1935, he set a record for closed-circuit flight with a 500-meter (1,600 ft) diameter. The next year, on 26 September 1936, Claisse set a height record of 158 meters (520 ft). And, finally, on 24 November 1936, he set a flight duration record of one hour, two minutes and 5 seconds over a 44 kilometer (27 mi) closed circuit at 44.7 kilometers per hour (27.8 mph). The aircraft was destroyed in 1943 by an Allied airstrike
Airstrike
An air strike is an attack on a specific objective by military aircraft during an offensive mission. Air strikes are commonly delivered from aircraft such as fighters, bombers, ground attack aircraft, attack helicopters, and others...

 at Villacoublay airport.

Birth of an industry


Despite the success of the Gyroplane Laboratoire, the German Focke-Wulf Fw 61
Focke-Wulf Fw 61
|-See also:-References:NotesBibliography* Coates, Steve and Jean-Christophe Carbonel. Helicopters of the Third Reich. Crowborough, UK: Classic Publications Ltd., 2002. ISBN 1-903223-24-5....

, first flown in 1936, would eclipse its accomplishments. The Fw 61 broke all of the helicopter world records in 1937, demonstrating a flight envelope
Flight envelope
In aerodynamics, the flight envelope or performance envelope of an aircraft refers to the capabilities of a design in terms of airspeed and load factor or altitude. The term is somewhat loosely applied, and can also refer to other measurements such as maneuverability...

 that had only previously been achieved by the autogyro. Nazi Germany
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

 would use helicopters in small numbers during World War II for observation, transport, and medical evacuation. The Flettner Fl 282 Kolibri
Flettner Fl 282
|- References :NotesBibliography* Coates, Steve and Jean-Christophe Carbonel. Helicopters of the Third Reich. Crowborough, UK: Classic Publications Ltd., 2002. ISBN 1-903223-24-5....

 synchropter was used in the Mediterranean, while the Focke Achgelis Fa 223 Drache was used in Europe. Extensive bombing by the Allied forces
Allies of World War II
The Allies of World War II were the countries that opposed the Axis powers during the Second World War . Former Axis states contributing to the Allied victory are not considered Allied states...

 prevented Germany from producing any helicopters in large quantities during the war.

In the United States, Igor Sikorsky
Igor Sikorsky
Igor Sikorsky , born Igor Ivanovich Sikorsky was a Russian American pioneer of aviation in both helicopters and fixed-wing aircraft...

 and W. Lawrence LePage were competing to produce the United States military's first helicopter. Prior to the war, LePage had received the patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....

 rights to develop helicopters patterned after the Fw 61, and built the XR-1
Platt-Le Page XR-1
The Platt-LePage XR-1, also known by the company designation PL-3, was an early American twin-rotor helicopter, built by the Platt-LePage Aircraft Company of Eddystone, Pennsylvania. The winner of a United States Army Air Force design competition held in early 1940, the XR-1 was the first...

. Meanwhile, Sikorsky had settled on a simpler, single rotor design, the VS-300, which turned out to be the first practical single lifting-rotor helicopter design and the best-flying one since the Soviet TsAGI 1-EA flown nearly a decade before. After experimenting with configurations to counteract the torque produced by the single main rotor, he settled on a single, smaller rotor mounted vertically on the tailboom.

Developed from the VS-300, Sikorsky's R-4
Sikorsky R-4
The Sikorsky R-4 was a two-place helicopter designed by Igor Sikorsky with a single, three-bladed main rotor and powered by a radial engine. The R-4 was the world's first large-scale mass-produced helicopter and the first helicopter to enter service with the United States Army Air Forces, Navy, and...

 became the first large-scale mass produced helicopter with a production order for 100 aircraft. The R-4 was the only Allied helicopter to see service in World War II, primarily being used for rescue in Burma, Alaska, and other areas with harsh terrain. Total production would reach 131 helicopters before the R-4 was replaced by other Sikorsky helicopters such as the R-5
Sikorsky H-5
The Sikorsky H-5, is a helicopter built by Sikorsky Aircraft Corporation, formerly used by the United States Air Force, and its predecessor, the United States Army Air Forces, as well as the United States Navy and United States Coast Guard The Sikorsky H-5, (aka R-5, S-51, HO3S-1, or Horse) (R-5...

 and the R-6. In all, Sikorsky would produce over 400 helicopters before the end of World War II.

As LePage and Sikorsky were building their helicopters for the military, Bell Aircraft
Bell Aircraft
The Bell Aircraft Corporation was an aircraft manufacturer of the United States, a builder of several types of fighter aircraft for World War II but most famous for the Bell X-1, the first supersonic aircraft, and for the development and production of many important civilian and military helicopters...

 hired Arthur Young
Arthur M. Young
Arthur Middleton Young was an American inventor, helicopter pioneer, cosmologist, philosopher, astrologer and author. Young was the designer of Bell Helicopter's first helicopter, the Model 30, and inventor of the stabilizer bar used on many of Bell's early helicopter designs...

 to help build a helicopter using Young's two-blade teetering rotor design which used a weighted stabilizing bar placed at a 90º angle to the rotor blades. The subsequent Model 30 helicopter showed the design's simplicity and ease of use. The Model 30 was developed into the Bell 47
Bell 47
The Bell 47 is a two-bladed, single engine, light helicopter manufactured by Bell Helicopter. Based on the third Model 30 prototype, Bell's first helicopter designed by Arthur M. Young, the Bell 47 became the first helicopter certified for civilian use on 8 March 1946...

, which became the first helicopter certificated for civilian use in the United States. Produced in several countries, the Bell 47 would stand as the most popular helicopter model for nearly 30 years.

Turbine age


In 1951, at the urging of his contacts at the Department of the Navy, Charles Kaman
Charles Kaman
Charles Huron Kaman was an American aeronautical engineer, businessman, inventor and philanthropist, known for his work in rotary-wing flight and also in musical instrument design via the Kaman Music Corporation.-Biography:...

 modified his K-225
Kaman K-225
-External links:* 1949 Popular Science article on Kaman K-190 and the blade intermesh technology developed by Kaman — ie rare photos* * *...

 helicopter with a new kind of engine, the turboshaft
Turboshaft
A turboshaft engine is a form of gas turbine which is optimized to produce free turbine shaft power, rather than jet thrust...

 engine. This adaptation of the turbine engine provided a large amount of power to the helicopter with a lower weight penalty than piston engines, with their heavy engine blocks and auxiliary components. On 11 December 1951, the Kaman
Kaman Aircraft
Kaman Aircraft is a U.S. aerospace company, with headquarters in Bloomfield, Connecticut. It was founded in 1945 by Charles Kaman. During the first ten years the company operated exclusively as a designer and manufacturer of several helicopters that set world records and achieved many aviation...

 K-225 became the first turbine-powered helicopter in the world. Two years later, on 26 March 1954, a modified Navy HTK-1, another Kaman helicopter, became the first twin-turbine helicopter to fly. However, it was the Sud Aviation
Sud Aviation
Sud-Aviation was a French state-owned aircraft manufacturer, originating from the merger of Sud-Est and Sud-Ouest on March 1, 1957...

 Alouette II that would become the first helicopter to be produced with a turbine-engine.

Reliable helicopters capable of stable hover flight were developed decades after fixed-wing aircraft. This is largely due to higher engine power density requirements than fixed-wing aircraft. Improvements in fuels and engines during the first half of the 20th century were a critical factor in helicopter development. The availability of lightweight turboshaft
Turboshaft
A turboshaft engine is a form of gas turbine which is optimized to produce free turbine shaft power, rather than jet thrust...

 engines in the second half of the 20th century led to the development of larger, faster, and higher-performance helicopters. While smaller and less expensive helicopters still use piston engines, turboshaft engines are the preferred powerplant for helicopters today.

Uses



Due to the operating characteristics of the helicopter—its ability to takeoff and land vertically, and to hover for extended periods of time, as well as the aircraft's handling properties under low airspeed
Airspeed
Airspeed is the speed of an aircraft relative to the air. Among the common conventions for qualifying airspeed are: indicated airspeed , calibrated airspeed , true airspeed , equivalent airspeed and density airspeed....

 conditions—it has been chosen to conduct tasks that were previously not possible with other aircraft, or were time- or work-intensive to accomplish on the ground. Today, helicopter uses include transportation, construction, firefighting, search and rescue, and military uses.



A helicopter used to carry loads connected to long cables or slings is called an aerial crane
Aerial crane
Helicopters used to lift heavy loads are called aerial cranes or skycranes. As aerial cranes, helicopters carry loads connected to long cables or slings in order to place heavy equipment when other methods are not available or economically feasible, or when the job must be accomplished in remote or...

. Aerial cranes are used to place heavy equipment, like radio transmission towers and large air conditioning units, on the tops of tall buildings, or when an item must be raised up in a remote area, such as a radio tower raised on the top of a hill or mountain. Helicopters are used as aerial cranes in the logging industry to lift trees out of terrain where vehicles cannot travel and where environmental concerns prohibit the building of roads. These operations are referred to as longline because of the long, single sling line used to carry the load.

Helitack
Helitack
Helitack refers to "helicopter-delivered fire resources", and is the system of managing and using helicopters and their crews to perform aerial firefighting and other firefighting duties, primarily initial attack on wildfires...

 is the use of helicopters to combat wildland fires
Wildland fire suppression
Wildfire suppression refers to the firefighting tactics used to suppress wildfires. Firefighting efforts in wildland areas requires different techniques, equipment, and training from the more familiar structure fire fighting found in populated areas...

. The helicopters are used for aerial firefighting
Aerial firefighting
Aerial firefighting is the use of aircraft and other aerial resources to combat wildfires. The types of aircraft used include fixed-wing aircraft and helicopters. Smokejumpers and rappellers are also classified as aerial firefighters, delivered to the fire by parachute from a variety of fixed-wing...

 (or water bombing) and may be fitted with tanks or carry helibuckets. Helibuckets, such as the Bambi bucket, are usually filled by submerging the bucket into lakes, rivers, reservoirs, or portable tanks. Tanks fitted onto helicopters are filled from a hose while the helicopter is on the ground or water is siphoned from lakes or reservoirs through a hanging snorkel as the helicopter hovers over the water source. Helitack helicopters are also used to deliver firefighters, who rappel down to inaccessible areas, and to resupply firefighters. Common firefighting helicopters include variants of the Bell 205 and the Erickson S-64 Aircrane helitanker.

Helicopters are used as air ambulance
Air ambulance
An air ambulance is an aircraft used for emergency medical assistance in situations where either a traditional ambulance cannot reach the scene easily or quickly enough, or the patient needs to be transported over a distance or terrain that makes air transportation the most practical transport....

s for emergency medical assistance in situations when an ambulance
Ambulance
An ambulance is a vehicle for transportation of sick or injured people to, from or between places of treatment for an illness or injury, and in some instances will also provide out of hospital medical care to the patient...

 cannot easily or quickly reach the scene. Helicopters are also used when a patient needs to be transported between medical facilities and air transportation is the most practical method for the safety of the patient. Air ambulance helicopters are equipped to provide medical treatment to a patient while in flight. The use of helicopters as an air ambulance is often referred to as MEDEVAC
MEDEVAC
Medical evacuation, often termed Medevac or Medivac, is the timely and efficient movement and en route care provided by medical personnel to the wounded being evacuated from the battlefield or to injured patients being evacuated from the scene of an accident to receiving medical facilities using...

, and patients are referred to as being "airlifted", or "medevaced".

Police departments and other law enforcement agencies use helicopters
Police aircraft
A police aircraft is an airplane, helicopter, powered paraglider, or blimpused in police operations. They are commonly used for traffic control, ground support, search and rescue, high-speed car pursuits, observation, air patrol and riot control...

 to pursue suspects. Since helicopters can achieve a unique aerial view, they are often used in conjunction with police on the ground to report on suspects' locations and movements. They are often mounted with lighting and heat-sensing
Thermographic camera
A thermographic camera or infrared camera is a device that forms an image using infrared radiation, similar to a common camera that forms an image using visible light...

 equipment for night pursuits.

Military forces use attack helicopter
Attack helicopter
An attack helicopter is a military helicopter with the primary role of an attack aircraft, with the capability of engaging targets on the ground, such as enemy infantry and armored vehicles...

s to conduct aerial attacks on ground targets. Such helicopters are mounted with missile launchers and minigun
Minigun
The Minigun is a 7.62 mm, multi-barrel heavy machine gun with a high rate of fire , employing Gatling-style rotating barrels with an external power source...

s. Transport helicopters
Military helicopter
A military helicopter is a helicopter that is either specifically built or converted for use by military forces. A military helicopter's mission is a function of its design or conversion...

 are used to ferry troops and supplies where the lack of an airstrip would make transport via fixed-wing aircraft impossible. The use of transport helicopters to deliver troops as an attack force on an objective is referred to as Air Assault
Air assault
Air assault is the movement of ground-based military forces by vertical take-off and landing aircraft—such as the helicopter—to seize and hold key terrain which has not been fully secured, and to directly engage enemy forces...

. Unmanned Aerial Systems
Unmanned aerial vehicle
An unmanned aerial vehicle , also known as a unmanned aircraft system , remotely piloted aircraft or unmanned aircraft, is a machine which functions either by the remote control of a navigator or pilot or autonomously, that is, as a self-directing entity...

 (UAS) helicopter systems of varying sizes are being developed by companies for military reconnaissance
Reconnaissance
Reconnaissance is the military term for exploring beyond the area occupied by friendly forces to gain information about enemy forces or features of the environment....

 and surveillance
Surveillance aircraft
A surveillance aircraft is an aircraft used for surveillance — collecting information over time. They are operated by military forces and other government agencies in roles such as intelligence gathering, battlefield surveillance, airspace surveillance, observation , border patrol and fishery...

 duties. Naval forces also use helicopters equipped with dipping sonar for anti-submarine warfare
Anti-submarine warfare
Anti-submarine warfare is a branch of naval warfare that uses surface warships, aircraft, or other submarines to find, track and deter, damage or destroy enemy submarines....

, since they can operate from small ships.

Oil companies charter helicopters to move workers and parts quickly to remote drilling sites located out to sea or in remote locations. The speed over boats makes the high operating cost of helicopters cost effective to ensure that oil platform
Oil platform
An oil platform, also referred to as an offshore platform or, somewhat incorrectly, oil rig, is a lаrge structure with facilities to drill wells, to extract and process oil and natural gas, and to temporarily store product until it can be brought to shore for refining and marketing...

s continue to flow. Various companies specialize in this type of operation.

Other uses of helicopters include, but are not limited to:
  • Aerial photography
    Aerial photography
    Aerial photography is the taking of photographs of the ground from an elevated position. The term usually refers to images in which the camera is not supported by a ground-based structure. Cameras may be hand held or mounted, and photographs may be taken by a photographer, triggered remotely or...

  • Motion picture photography
  • Electronic news gathering
    Electronic news gathering
    ENG is a broadcasting industry acronym which stands for electronic news gathering. It can mean anything from a lone broadcast journalist reporter taking a single professional video camera out to shoot a story, to an entire television crew taking a production truck or satellite truck on location...

  • Reflection seismology
    Reflection seismology
    Reflection seismology is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the Earth's subsurface from reflected seismic waves. The method requires a controlled seismic source of energy, such as dynamite/Tovex, a specialized air gun or a...

  • Search and Rescue
    Search and rescue
    Search and rescue is the search for and provision of aid to people who are in distress or imminent danger.The general field of search and rescue includes many specialty sub-fields, mostly based upon terrain considerations...

  • Tourism
    Tourism
    Tourism is travel for recreational, leisure or business purposes. The World Tourism Organization defines tourists as people "traveling to and staying in places outside their usual environment for not more than one consecutive year for leisure, business and other purposes".Tourism has become a...

     or recreation
    Recreation
    Recreation is an activity of leisure, leisure being discretionary time. The "need to do something for recreation" is an essential element of human biology and psychology. Recreational activities are often done for enjoyment, amusement, or pleasure and are considered to be "fun"...

  • Transport
    Transport
    Transport or transportation is the movement of people, cattle, animals and goods from one location to another. Modes of transport include air, rail, road, water, cable, pipeline, and space. The field can be divided into infrastructure, vehicles, and operations...


Rotor system


The rotor system, or more simply rotor, is the rotating part of a helicopter which generates lift
Lift (force)
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...

. A rotor system may be mounted horizontally as main rotors are, providing lift vertically, or it may be mounted vertically, such as a tail rotor, to provide lift horizontally as thrust to counteract torque effect. The rotor consists of a mast, hub and rotor blades.

The mast is a cylindrical metal shaft which extends upwards from and is driven by the transmission. At the top of the mast is the attachment point for the rotor blades called the hub. The rotor blades are then attached to the hub by a number of different methods. Main rotor systems are classified according to how the main rotor blades are attached and move relative to the main rotor hub. There are three basic classifications: hingeless, fully articulated, and teetering, although some modern rotor systems use an engineered combination of these types.

Antitorque configurations


Most helicopters have a single main rotor, but torque created as the engine turns the rotor against its air drag causes the body of the helicopter to turn in the opposite direction to the rotor. To eliminate this effect, some sort of antitorque control must be used. The design that Igor Sikorsky
Igor Sikorsky
Igor Sikorsky , born Igor Ivanovich Sikorsky was a Russian American pioneer of aviation in both helicopters and fixed-wing aircraft...

 settled on for his VS-300
Vought-Sikorsky 300
|-See also:-References:NotesBibliography* Chiles, James R. The God Machine: From Boomerangs to Black Hawks: The Story of the Helicopter. New York: Bantam, 2008. ISBN 978-0553383522....

 was a smaller rotor mounted vertically on the tail. The tail rotor pushes or pulls against the tail to counter the torque effect, and has become the recognized convention for helicopter design. Some helicopters utilize alternate antitorque controls in place of the tail rotor, such as the ducted fan
Ducted fan
A ducted fan is a propulsion arrangement whereby a fan, which is a type of propeller, is mounted within a cylindrical shroud or duct. The duct reduces losses in thrust from the tip vortices of the fan, and varying the cross-section of the duct allows the designer to advantageously affect the...

 (called Fenestron
Fenestron
A Fenestron is a shrouded tail rotor of a helicopter that is essentially a ducted fan. The housing is integral with the tail skin, and, like the conventional tail rotor it replaces, is intended to counteract the torque of the main rotor...

 or FANTAIL), and NOTAR
NOTAR
NOTAR is the name of a helicopter anti-torque system which replaces the use of a tail rotor. Developed by McDonnell Douglas Helicopter Systems , the name is an acronym derived from the phrase NO TAil Rotor...

. NOTAR provides antitorque similar to the way a wing develops lift, through the use of a Coandă effect
Coanda effect
The Coandă effect is the tendency of a fluid jet to be attracted to a nearby surface. The principle was named after Romanian aerodynamics pioneer Henri Coandă, who was the first to recognize the practical application of the phenomenon in aircraft development....

 on the tailboom.

The use of two or more horizontal rotors turning in opposite directions is another configuration used to counteract the effects of torque on the aircraft without relying on an antitorque tail rotor. This allows the power normally required to drive the tail rotor to be applied to the main rotors, increasing the aircraft's lifting capacity. Primarily, there are three common configurations that use the counter-rotating effect to benefit the rotorcraft. Tandem rotors are two rotors with one mounted behind the other. Coaxial rotors are two rotors that are mounted one above the other with the same axis. Intermeshing rotors
Intermeshing rotors
Intermeshing rotors on a helicopter are a set of two rotors turning in opposite directions, with each rotor mast mounted on the helicopter with a slight angle to the other, in a transversely symmetrical manner, so that the blades intermesh without colliding. The arrangement allows the helicopter to...

 are two rotors that are mounted close to each other at a sufficient angle to allow the rotors to intermesh over the top of the aircraft. Transverse rotors is another configuration found on tiltrotor
Tiltrotor
A tiltrotor is an aircraft which uses a pair or more of powered rotors mounted on rotating shafts or nacelles at the end of a fixed wing for lift and propulsion, and combines the vertical lift capability of a helicopter with the speed and range of a conventional fixed-wing aircraft...

s and some earlier helicopters, where the pair of rotors are mounted at each end of the wings or outrigger structures. Tip jet designs permit the rotor to push itself through the air, and avoid generating torque.

Engines


The number, size and type of engine used on a helicopter determines the size, function and capability of that helicopter design. The earliest helicopter engines were simple mechanical devices, such as rubber bands or spindles, which relegated the size of helicopters to toys and small models. For a half century before the first airplane flight, steam engines were used to forward the development of the understanding of helicopter aerodynamics, but the limited power did not allow for manned flight. The introduction of the internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

 at the end of the 19th century became the watershed for helicopter development as engines began to be developed and produced that were powerful enough to allow for helicopters able to lift humans.

Early helicopter designs utilized custom-built engines or rotary engine
Rotary engine
The rotary engine was an early type of internal-combustion engine, usually designed with an odd number of cylinders per row in a radial configuration, in which the crankshaft remained stationary and the entire cylinder block rotated around it...

s designed for airplanes, but these were soon replaced by more powerful automobile engines and radial engines. The single, most-limiting factor of helicopter development during the first half of the 20th century was that the amount of power produced by an engine was not able to overcome the engine's weight in vertical flight. This was overcome in early successful helicopters by using the smallest engines available. When the compact, flat engine
Flat engine
A flat engine is an internal combustion engine with multiple pistons that move in a horizontal plane. Typically, the layout has cylinders arranged in two banks on either side of a single crankshaft and is sometimes known as the boxer, or horizontally opposed engine. The concept was patented in 1896...

 was developed, the helicopter industry found a lighter-weight powerplant easily adapted to small helicopters, although radial engines continued to be used for larger helicopters.

Turbine engines revolutionized the aviation industry, and the turboshaft
Turboshaft
A turboshaft engine is a form of gas turbine which is optimized to produce free turbine shaft power, rather than jet thrust...

 engine finally gave helicopters an engine with a large amount of power and a low weight penalty. The turboshaft engine was able to be scaled to the size of the helicopter being designed, so that all but the lightest of helicopter models are powered by turbine engines today.

Special jet engines developed to drive the rotor from the rotor tips are referred to as tip jets. Tip jets powered by a remote compressor are referred to as cold tip jets, while those powered by combustion exhaust are referred to as hot tip jets. An example of a cold jet helicopter is the Sud-Ouest Djinn
Sud-Ouest Djinn
|-See also:-References:* The Illustrated Encyclopedia of Aircraft , 1985, Orbis Publishing, Page 2975- External links :* rare photo of the single seat SO.1220 that tested the power concept -- ie bottom of page 128**...

, and an example of the hot tip jet helicopter is the YH-32 Hornet
YH-32 Hornet
|-See also:-References:* Display information at Museum of Flight in Seattle, Washington* "The First 100 Years of Aviation"-External links:* * *...

.

Some radio-controlled helicopter
Radio-controlled helicopter
Radio-controlled helicopters are model aircraft which are distinct from RC airplanes because of the differences in construction, aerodynamics, and flight training...

s and smaller, helicopter-type unmanned aerial vehicle
Unmanned aerial vehicle
An unmanned aerial vehicle , also known as a unmanned aircraft system , remotely piloted aircraft or unmanned aircraft, is a machine which functions either by the remote control of a navigator or pilot or autonomously, that is, as a self-directing entity...

s, use electric motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

s. Radio-controlled helicopters may also have piston engines that use fuels other than gasoline, such as Nitromethane. Some turbine engines commonly used in helicopters can also use biodiesel instead of jet fuel.

Flight controls




A helicopter has four flight control inputs. These are the cyclic, the collective, the anti-torque pedals, and the throttle. The cyclic control is usually located between the pilot's legs and is commonly called the cyclic stick or just cyclic. On most helicopters, the cyclic is similar to a joystick. However, the Robinson R22
Robinson R22
The Robinson R22 is a two-bladed, single-engine light utility helicopter manufactured by Robinson Helicopter. The two-seat R22 was designed in 1973 by Frank Robinson and has been in production since 1979.-Development:...

 and Robinson R44
Robinson R44
|-See also:-External links:* * * * * *...

 have a unique teetering bar cyclic control system and a few helicopters have a cyclic control that descends into the cockpit from overhead.

The control is called the cyclic because it changes the pitch
Blade pitch
Blade pitch or simply pitch refers to turning the angle of attack of the blades of a propeller or helicopter rotor into or out of the wind to control the production or absorption of power. Wind turbines use this to adjust the rotation speed and the generated power...

 of the rotor blades cyclically. The result is to tilt the rotor disk in a particular direction, resulting in the helicopter moving in that direction. If the pilot pushes the cyclic forward, the rotor disk tilts forward, and the rotor produces a thrust in the forward direction. If the pilot pushes the cyclic to the side, the rotor disk tilts to that side and produces thrust in that direction, causing the helicopter to hover sideways.

The collective pitch control or collective is located on the left side of the pilot's seat with a settable friction control to prevent inadvertent movement. The collective changes the pitch angle of all the main rotor blades collectively (i.e. all at the same time) and independently of their position. Therefore, if a collective input is made, all the blades change equally, and the result is the helicopter increasing or decreasing in altitude.

The anti-torque pedals are located in the same position as the rudder
Rudder
A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...

 pedals in a fixed-wing aircraft, and serve a similar purpose, namely to control the direction in which the nose of the aircraft is pointed. Application of the pedal in a given direction changes the pitch of the tail rotor blades, increasing or reducing the thrust produced by the tail rotor and causing the nose to yaw
Flight dynamics
Flight dynamics is the science of air vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as pitch, roll and yaw .Aerospace engineers develop control systems for...

 in the direction of the applied pedal. The pedals mechanically change the pitch of the tail rotor altering the amount of thrust produced.

Helicopter rotors are designed to operate in a narrow range of RPM
Revolutions per minute
Revolutions per minute is a measure of the frequency of a rotation. It annotates the number of full rotations completed in one minute around a fixed axis...

. The throttle controls the power produced by the engine, which is connected to the rotor by a fixed ratio transmission. The purpose of the throttle is to maintain enough engine power to keep the rotor RPM within allowable limits in order to keep the rotor producing enough lift for flight. In single-engine helicopters, the throttle control is a motorcycle-style twist grip mounted on the collective control, while dual-engine helicopters have a power lever for each engine.

A Swashplate
Swashplate (helicopter)
A swashplate is a device that translates input via the helicopter flight controls into motion of the main rotor blades. Because the main rotor blades are spinning, the swashplate is used to transmit three of the pilot's commands from the non-rotating fuselage to the rotating rotor hub and...

 transmits the pilot commands to the main rotor blades for articulated rotors.

Flight conditions


There are three basic flight conditions for a helicopter: hover, forward flight
Flight
Flight is the process by which an object moves either through an atmosphere or beyond it by generating lift or propulsive thrust, or aerostatically using buoyancy, or by simple ballistic movement....

 and the transition between the two.

  • Hover
Hovering is the most challenging part of flying a helicopter. This is because a helicopter generates its own gusty air while in a hover, which acts against the fuselage
Fuselage
The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...

 and flight control surfaces. The end result is constant control inputs and corrections by the pilot to keep the helicopter where it is required to be. Despite the complexity of the task, the control inputs in a hover are simple. The cyclic is used to eliminate drift in the horizontal plane, that is to control forward and back, right and left. The collective is used to maintain altitude. The pedals are used to control nose direction or heading
Course (navigation)
In navigation, a vehicle's course is the angle that the intended path of the vehicle makes with a fixed reference object . Typically course is measured in degrees from 0° clockwise to 360° in compass convention . Course is customarily expressed in three digits, using preliminary zeros if needed,...

. It is the interaction of these controls that makes hovering so difficult, since an adjustment in any one control requires an adjustment of the other two, creating a cycle of constant correction.

  • Transition from hover to forward flight
As a helicopter moves from hover to forward flight it enters a state called Translational lift
Translational lift
Translational lift is a transitional state present as a helicopter moves from hover to forward flight...

 which provides extra lift without increasing power. This state, most typically, occurs when the airspeed reaches approximately 16-24 knots, and may be necessary for a helicopter to obtain flight.

  • Forward flight
In forward flight a helicopter's flight controls behave more like that in a fixed-wing aircraft. Displacing the cyclic forward will cause the nose to pitch down, with a resultant increase in airspeed and loss of altitude. Aft cyclic will cause the nose to pitch up, slowing the helicopter and causing it to climb. Increasing collective (power) while maintaining a constant airspeed will induce a climb while decreasing collective will cause a descent. Coordinating these two inputs, down collective plus aft cyclic or up collective plus forward cyclic, will result in airspeed changes while maintaining a constant altitude. The pedals serve the same function in both a helicopter and a fixed-wing aircraft, to maintain balanced flight. This is done by applying a pedal input in whichever direction is necessary to center the ball in the turn and bank indicator
Turn and bank indicator
In aviation, the turn and bank indicator shows the rate of turn and the coordination of the turn. The rate of turn is indicated from a rate gyroscopically and the coordination of the turn is shown by either a pendulum or a heavy ball mounted in a curved sealed glass tube. No pitch information is...

.

Limitations




The main limitation of the helicopter is its low speed. There are several reasons a helicopter cannot fly as fast as a fixed wing aircraft. When the helicopter is hovering, the outer tips of the rotor travel at a speed determined by the length of the blade and the RPM. In a moving helicopter, however, the speed of the blades relative to the air depends on the speed of the helicopter as well as on their rotational velocity. The airspeed of the advancing rotor blade is much higher than that of the helicopter itself. It is possible for this blade to exceed the speed of sound
Speed of sound
The speed of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic medium. In dry air at , the speed of sound is . This is , or about one kilometer in three seconds or approximately one mile in five seconds....

, and thus produce vastly increased drag and vibration. See Wave drag
Wave drag
In aeronautics, wave drag is a component of the drag on aircraft, blade tips and projectiles moving at transonic and supersonic speeds, due to the presence of shock waves. Wave drag is independent of viscous effects.- Overview :...

.

Because the advancing blade has higher airspeed than the retreating blade and generates a dissymmetry of lift
Dissymmetry of lift
Dissymmetry of lift in rotorcraft aerodynamics refers to an uneven amount of lift on opposite sides of the rotor disc. It is a phenomenon that affects single-rotor helicopters in lateral flight, whether the direction of flight be forwards, sideways or in reverse.The dissymmetry is caused by...

, rotor blades are designed to "flap" – lift and twist in such a way that the advancing blade flaps up and develops a smaller angle of attack. Conversely, the retreating blade flaps down, develops a higher angle of attack, and generates more lift. At high speeds, the force on the rotors is such that they "flap" excessively and the retreating blade can reach too high an angle and stall. For this reason, the maximum safe forward airspeed of a helicopter is given a design rating called VNE, Velocity, Never Exceed. In addition it is possible for the helicopter to fly at an airspeed where an excessive amount of the retreating blade stalls which results in high vibration, pitch -up, and roll into the retreating blade.

During the closing years of the 20th century designers began working on helicopter noise reduction
Helicopter noise reduction
Helicopter noise reduction is a topic of research into designing helicopters which can be operated more quietly, reducing the public-relations problems with night-flying or expanding an airport...

. Urban communities have often expressed great dislike of noisy aircraft, and police and passenger helicopters can be unpopular. The redesigns followed the closure of some city heliports and government action to constrain flight paths in national parks and other places of natural beauty.

Helicopters also vibrate; an unadjusted helicopter can easily vibrate so much that it will shake itself apart. To reduce vibration, all helicopters have rotor adjustments for height and weight. Blade height is adjusted by changing the pitch of the blade. Weight is adjusted by adding or removing weights on the rotor head and/or at the blade end caps. Most also have vibration dampers for height and pitch. Some also use mechanical feedback systems to sense and counter vibration. Usually the feedback system uses a mass as a "stable reference" and a linkage from the mass operates a flap to adjust the rotor's angle of attack
Angle of attack
Angle of attack is a term used in fluid dynamics to describe the angle between a reference line on a lifting body and the vector representing the relative motion between the lifting body and the fluid through which it is moving...

 to counter the vibration. Adjustment is difficult in part because measurement of the vibration is hard, usually requiring sophisticated accelerometers mounted throughout the airframe and gearboxes. The most common blade vibration adjustment measurement system is to use a stroboscopic flash lamp, and observe painted markings or coloured reflectors on the underside of the rotor blades. The traditional low-tech system is to mount coloured chalk on the rotor tips, and see how they mark a linen sheet. Gearbox vibration most often requires a gearbox overhaul or replacement. Gearbox or drive train vibrations can be extremely harmful to a pilot. The most severe being pain, numbness, loss of tactile discrimination and dexterity.

Hazards


As with any moving vehicle, unsafe operation could result in loss of control, structural damage, or fatality. The following is a list of some of the potential hazards for helicopters:
  • Settling with power
    Settling with power
    In helicopter flight, it is possible for the rotors to descend into their own downwash, a cone of turbulent air previously forced downward in the generation of lift. As turbulent air does not have the same physical properties as still or clean air, the rotors produce less lift and the aircraft may...

    , also known as a vortex ring
    Vortex ring
    A vortex ring, also called a toroidal vortex, is a region of rotating fluid moving through the same or different fluid where the flow pattern takes on a toroidal shape. The movement of the fluid is about the poloidal or circular axis of the doughnut, in a twisting vortex motion...

     state, is when the aircraft is unable to arrest its descent due to the rotor's downwash interfering with the aerodynamics of the rotor.
  • Retreating blade stall
    Retreating blade stall
    Retreating blade stall is a hazardous flight condition in helicopters and other rotary wing aircraft, where the rotor blade rotating away from the direction of flight stalls. The stall is due to low relative airspeed and/or excessive angle of attack...

     is experienced during high speed flight and is the most common limiting factor of a helicopter's forward speed.
  • Ground resonance
    Ground resonance
    Ground resonance is a hazardous condition that can occur any time the rotor of a helicopter or gyroplane is turning while the aircraft is on the ground...

     affects helicopters with fully articulated rotor systems having a natural lead-lag frequency less than the blade rotation frequency.
  • Low-G condition
    Low-G condition
    Low-g condition is a phase of aerodynamic flight where the airframe is temporarily unloaded. The pilot—and the airframe—feel temporarily "weightless" because the aircraft is in free-fall or decelerating vertically at the top of a climb. It may also occur during an excessively rapid...

     affects helicopters with two-bladed main rotors, particularly lightweight helicopters.
  • Dynamic rollover
    Dynamic rollover
    A helicopter is susceptible to a lateral rolling tendency,called dynamic rollover, when lifting off the surface.For dynamic rollover to occur, some factor has to firstcause the helicopter to roll or pivot around a skid, or...

     in which the helicopter pivots around one of the skids and 'pulls' itself onto its side.
  • Powertrain
    Powertrain
    In a motor vehicle, the term powertrain or powerplant refers to the group of components that generate power and deliver it to the road surface, water, or air. This includes the engine, transmission, drive shafts, differentials, and the final drive...

     failures, especially those that occur within the shaded area of the height-velocity diagram
    Height-velocity diagram
    The Height-Velocity diagram or H/V curve is a graph charting the safe/unsafe flight profiles relevant to a specific helicopter. As operation outside the safe area of the chart can be fatal in the event of a power or transmission failure it is sometimes referred to as the dead man's curve or Coffin...

    .
  • Tail rotor failures which occur from either a mechanical malfunction of the tail rotor control system or a loss of tail rotor thrust authority, called Loss of Tail-rotor Effectiveness (LTE).
  • Brownout
    Brownout (aviation)
    In aviation, a brownout is an in-flight visibility restriction due to dust or sand in the air.In a brownout, the pilot cannot see nearby objects which provide the outside visual references necessary to control the aircraft near the ground. This can cause spatial disorientation and loss of...

     in dusty conditions or whiteout
    Whiteout (weather)
    Whiteout is a weather condition in which visibility and contrast are severely reduced by snow or sand. The horizon disappears completely and there are no reference points at all, leaving the individual with a distorted orientation...

     in snowy conditions.
  • Low Rotor RPM, or rotor droop, in which the engine cannot drive the blades at sufficient RPM to maintain flight.
  • Rotor Overspeed, which can over-stress the rotor hub pitch bearings (Brinelling) and, if severe enough, cause blade separation from the aircraft.
  • Wire and tree strikes due to low altitude operations and take-offs and landings in remote locations.
  • Controlled flight into terrain
    Controlled flight into terrain
    Controlled flight into terrain describes an accident in which an airworthy aircraft, under pilot control, is unintentionally flown into the ground, a mountain, water, or an obstacle. The term was coined by engineers at Boeing in the late 1970s...

     in which the aircraft is flown into the ground unintentionally due to lack of situational awareness.

Deadliest crashes

  1. 2002: a Mil Mi-26
    Mil Mi-26
    The Mil Mi-26 is a Soviet/Russian heavy transport helicopter. In service with civilian and military operators, it is the largest and most powerful helicopter ever to have gone into production.-Design and development:...

     was shot down over Chechnya
    Chechnya
    The Chechen Republic , commonly referred to as Chechnya , also spelled Chechnia or Chechenia, sometimes referred to as Ichkeria , is a federal subject of Russia . It is located in the southeastern part of Europe in the Northern Caucasus mountains. The capital of the republic is the city of Grozny...

    ; 127 killed.
  2. 1997: two Israeli Sikorsky CH-53 Sea Stallions collided over Israel
    1997 Israeli helicopter disaster
    The 1997 Israeli helicopter disaster occurred on 4 February 1997. 73 IDF soldiers were killed when two Sikorsky CH-53 Sea Stallion Yas'ur 2000 helicopters, 357 and 903, collided over She'ar Yashuv in northern Israel. The helicopters were supposed to have crossed the border into Israel's "security...

    ; 73 killed.
  3. December 14, 1992: despite being heavily escorted, a Russian Army Mil Mi-8
    Mil Mi-8
    The Mil Mi-8 is a medium twin-turbine transport helicopter that can also act as a gunship. The Mi-8 is the world's most-produced helicopter, and is used by over 50 countries. Russia is the largest operator of the Mi-8/Mi-17 helicopter....

     was shot down by Georgian forces in Abkhazia using SA-14 MANPADs, with the loss of three crew members and 58 passengers composed of mainly Russian refugees.
  4. October 4, 1993: Russian forces shot down a Georgian Mi-8 transporting 60 refugees from eastern Abkhazia; all on board were killed.
  5. May 10, 1977: an Israeli CH-53 crashed
    1977 Israeli CH-53 crash
    On May 10, 1977, an Israeli Air Force Sikorsky CH-53 Yas'ur helicopter crashed during an exercise in the Jordan Valley, killing all 54 on board . The disaster became known as Ason Hanun-dalet, or "Disaster of the 54".-External links:*...

     near Yitav
    Yitav
    Yitav is an Israeli settlement and moshav shitufi in the southern Jordan Valley of the West Bank. Located just north of Jericho and west of the Palestinian village of al-Auja, it falls under the jurisdiction of Bik'at HaYarden Regional Council...

     in the Jordan Valley
    Jordan Valley (Middle East)
    The Jordan Valley forms part of the larger Jordan Rift Valley. It is 120 kilometers long and 15 kilometers wide, where it runs from Lake Tiberias in the north to northern Dead Sea in the south. It runs for an additional 155 kilometer south of the Dead Sea to Aqaba, an area also known as Wadi...

    ; 54 killed.
  6. September 11, 1982: a U.S. Army Boeing CH-47 Chinook crashed at an air show in Mannheim, Germany; 46 killed.
  7. 1986: a Boeing 234LR Chinook operated by British International Helicopters
    British International Helicopters
    British International Helicopter Services Limited is an airline based at Penzance heliport, in Cornwall, England, United Kingdom, with headquarters located at Sherborne, Dorset. It operates seasonal and year round domestic scheduled services to the Isles of Scilly. Its main base is Penzance...

     crashed in the Shetland Islands
    Shetland Islands
    Shetland is a subarctic archipelago of Scotland that lies north and east of mainland Great Britain. The islands lie some to the northeast of Orkney and southeast of the Faroe Islands and form part of the division between the Atlantic Ocean to the west and the North Sea to the east. The total...

    ; 45 killed.
  8. 1992 Azerbaijani Mil Mi-8 shootdown
    1992 Azerbaijani Mil Mi-8 shootdown
    On January 28, 1992 the Azerbaijani transport helicopter Mil Mi-8 was reportedly shot down by a heat-seeking missile near the Azerbaijani town of Shusha....

    : 44 killed.
  9. 2009 Pakistan Army Mil Mi-17 crash
    2009 Pakistan Army Mil Mi-17 crash
    A Russian-made Mil Mi-17 transport helicopter of the Pakistan Army crashed in the FATA, in Orakzai Agency on July 3, 2009. According to a source within the Army the crash was due to a technical fault. Some sources report that local people are saying it was due to militant activity...

    : 41 killed.
  10. 2011: a CH-47 Chinook was shot down in Afghanistan: 38 killed.
  11. January 26, 2005: An USMC Sikorsky CH-53E Super Stallion crashed near Ar Rutbah, Iraq
    Iraq
    Iraq ; officially the Republic of Iraq is a country in Western Asia spanning most of the northwestern end of the Zagros mountain range, the eastern part of the Syrian Desert and the northern part of the Arabian Desert....

     killing all 31 service members on board.

World records


Record type Record Helicopter Pilot(s) Date Location Note Reference
Speed 400.87 km/h Westland Lynx
Westland Lynx
The Westland Lynx is a British multi-purpose military helicopter designed and built by Westland Helicopters at its factory in Yeovil. Originally intended as a utility craft for both civil and naval usage, military interest led to the development of both battlefield and naval variants...

 
John Trevor Egginton (UK) 11 August 1986 England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, UK
Distance without landing 3,561.55 km Hughes YOH-6A  Robert G. Ferry (USA) 6 April 1966 USA 
Around-the-world speed 136.7 km/h Agusta A109S Grand  Scott Kasprowicz (USA) August 2008 From and to New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

 
via Europe, Russia, Alaska, Canada
No in-flight refueling
Highest level flight altitude 11,010 m Sikorsky CH-54 Tarhe  James K. Church 4 Nov 1971 USA 
Altitude with 40-tonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...

 payload 
2,255 m Mil V-12  Vasily Kolochenko, et al. 6 Aug 1969 Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 


See also



  • Autogyro
    Autogyro
    An autogyro , also known as gyroplane, gyrocopter, or rotaplane, is a type of rotorcraft which uses an unpowered rotor in autorotation to develop lift, and an engine-powered propeller, similar to that of a fixed-wing aircraft, to provide thrust...

  • Autorotation (helicopter)
    Autorotation (helicopter)
    Autorotation is the state of flight where the main rotor system of a helicopter is being turned by the action of air moving up through the rotor rather than engine power driving the rotor...

  • Backpack helicopter
    Backpack helicopter
    A backpack helicopter is a helicopter motor and rotor and controls assembly that can be strapped to a person's back, so that he can walk about on the ground wearing it, and can use it to fly. Its harness, like a parachute harness, should have a strap between the legs, so that the pilot does not...

  • Helicopter dynamics
    Helicopter dynamics
    Helicopter dynamics is a field within aerospace engineering concerned with theoretical and practical aspects of helicopter flight. Its purpose is the knowledge of forces and torques which appear in helicopter flight.-History:...

  • Helicopter manufacturers
    Helicopter manufacturers
    It is useful to think of helicopter manufacturers as falling into two categories, those that can design, certify and manufacture new helicopter designs from scratch and those that can only manufacture extant designs under license...

  • Cyclogyro
    Cyclogyro
    The cyclogyro, or cyclocopter, is an aircraft design that uses Cycloidal Rotors which consist of airfoils rotating around a horizontal axis for both lift and thrust...

  • Disk loading
    Disk loading
    In fluid dynamics, disk loading or disc loading is the average pressure change across an actuator disk, such as an airscrew. Airscrews with a relatively low disk loading are typically called rotors, including helicopter main rotors and tail rotors; propellers typically have a higher disk...

  • Gyrodyne
  • Heliport
    Heliport
    A heliport is a small airport suitable only for use by helicopters. Heliports typically contain one or more helipads and may have limited facilities such as fuel, lighting, a windsock, or even hangars...

  • Jesus nut
    Jesus nut
    Jesus nut or Jesus pin are colloquialisms for the main rotor retaining nut that holds the main rotor to the mast of some helicopters, such as the UH-1 Iroquois helicopter. The term may have been coined by American soldiers in Vietnam; the Vietnam War was the first war to feature large numbers of...

    , the top central big nut that holds the rotor on
  • List of rotorcraft
  • Miniature helicopter
    Miniature helicopter
    Miniature helicopters are remotely controlled helicopters with a weight ranging from hundred grams to a few grams. Most in production are toys aimed at hobbyists and enthusiasts. In addition there are many companies making prototypes for military and security applications...

  • Monocopter
    Monocopter
    A monocopter or gyropter is a rotorcraft that uses a single rotating blade. The concept is similar to the whirling helicopter seeds that fall from some trees. The name gyropter is sometimes applied to monocopters in which the entire aircraft rotates about its center of mass as it flies...

  • Radio-controlled helicopter
    Radio-controlled helicopter
    Radio-controlled helicopters are model aircraft which are distinct from RC airplanes because of the differences in construction, aerodynamics, and flight training...

  • Transverse Flow Effect
    Transverse flow effect
    Transverse flow effect is an aerodynamic effect encountered when a helicopter moves through the air.In a hover, the air above the rotor disk is being pulled down from above and is equally distributed around the rotor disk...

  • Unmanned aerial vehicle
    Unmanned aerial vehicle
    An unmanned aerial vehicle , also known as a unmanned aircraft system , remotely piloted aircraft or unmanned aircraft, is a machine which functions either by the remote control of a navigator or pilot or autonomously, that is, as a self-directing entity...

  • VTOL
    VTOL
    A vertical take-off and landing aircraft is one that can hover, take off and land vertically. This classification includes fixed-wing aircraft as well as helicopters and other aircraft with powered rotors, such as cyclogyros/cyclocopters and tiltrotors...

    , vertical take-off and landing aircraft


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