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{{Short description|Type of rotorcraft}}
{{Other uses}}
{{pp-move}}
{{pp-vandalism|small=yes}}
{{Use dmy dates|date=September 2019}}
{{Use British English|date=February 2014}}
[[File:LAPD Bell 206 Jetranger.jpg|thumb|A [[Bell 206]] helicopter operated by the [[Los Angeles Police Department]] [[LAPD Air Support Division|Air Support Division]]]]
[[File:150610-Z-II459-035 (18071389214).jpg|thumb|Cabin view looking out from a helicopter in flight]]
[[File:RCAF Bell CH-146 5D3 4156 (43790685721).jpg|thumb|Bell 412CF looking forward from the tail, showing its twin turbine engine exhausts]]
[[File:Hiller YROE-1.jpg|thumb|1956 Hiller YROE-1 one-man "Rotorcycle" being tested at NASA Ames Research Center]]
A '''helicopter''' is a type of [[rotorcraft]] in which [[Lift (force)|lift]] and [[thrust]] are supplied by horizontally spinning [[Helicopter rotor|rotor]]s. This allows the helicopter to [[VTOL|take off and land vertically]], to [[hover (helicopter)|hover]], and to fly forward, backward and laterally. These attributes allow helicopters to be used in congested or isolated areas where [[fixed-wing aircraft]] and many forms of short take-off and landing ([[STOL]]) or short take-off and vertical landing ([[STOVL]]) aircraft cannot perform without a [[runway]].
The [[Focke-Wulf Fw 61]] was the first successful, practical, and fully controllable helicopter in 1936, while in 1942, the [[Sikorsky R-4]] became the first helicopter to reach full-scale [[mass production|production]]. Starting in 1939 and through 1943, Igor Sikorsky worked on the development of the [[Vought-Sikorsky VS-300|VS-300]], which over four iterations, became the basis for modern helicopters with a single main rotor and a single tail rotor.
Although most earlier designs used more than one main rotor, the configuration of a single [[main rotor]] accompanied by a vertical anti-torque [[tail rotor]] (i.e. ''unicopter'', not to be confused with the single-blade [[monocopter]]) has become the most common helicopter configuration. However, twin-rotor helicopters (bicopters), in either [[tandem rotors|tandem]] or [[transverse rotors]] configurations, are sometimes in use due to their greater payload capacity than the monorotor design, and [[coaxial rotors|coaxial-rotor]], [[tiltrotor]] and [[compound helicopter]]s are also all flying today. Four-rotor helicopters ([[quadcopter]]s) were pioneered [[Breguet-Richet Gyroplane|as early as 1907]] in France, and along with other types of [[multicopter]]s, have been developed mainly for specialized applications such as commercial [[unmanned aerial vehicle]]s (drones) due to the rapid expansion of [[drone racing]] and [[aerial photography]] [[market (economics)|market]]s in the early 21st century, as well as recently [[weapon]]ized utilities such as [[artillery spotting]], [[aerial bomb]]ing and [[loitering munition|suicide attack]]s.
==Etymology==
The English word ''helicopter'' is adapted from the French word {{lang|fr|hélicoptère}}, coined by Gustave Ponton d'Amécourt in 1861, which originates from the [[Greek language|Greek]] ''{{Transliteration|el|helix}}'' ({{lang|grc|ἕλιξ}}), ''genitive'' ''helikos'' (ἕλῐκος), "helix, spiral, whirl, convolution"<ref>[[Genitive case|GEN]] {{lang|grc|[[:en:wikt:ἕλιξ#Inflection|ἕλικος]]}} ''helikos'' (the [[kappa|κ]] being [[Romanization of Greek|romanised]] as a ''[[c]]''); see {{LSJ|e(/lic2|ἕλιξ}} and {{LSJ|e(/lic1|ἕλιξ (as an adjective)|ref}}.</ref> and ''{{Transliteration|el|pteron}}'' ({{lang|grc|πτερόν}}) "wing".<ref>{{LSJ|ptero/n|πτερόν|shortref}}.</ref><ref>{{OEtymD|helicopter}}</ref> In a process of [[rebracketing]], the word is often (erroneously, from an etymological point of view) perceived by English speakers as consisting of ''heli-'' and ''-copter'', leading to words like ''helipad'' and ''quadcopter''.<ref>{{cite web |title=helicopter |url=http://www.thefreedictionary.com/helicopter |url-status=live |archive-url=https://web.archive.org/web/20141031002044/http://www.thefreedictionary.com/helicopter |archive-date=31 October 2014 |access-date=30 October 2014 |website=[[The Free Dictionary]]}}</ref><ref>Cottez 1980, p. 181.</ref> English language nicknames for "helicopter" include "chopper", "copter", "heli", and "whirlybird". In the [[United States]] military, the common slang is "helo" pronounced /ˈhiː.loʊ/.
==
[[File:Rotor Antitorque System.svg|thumb|Main and anti-torque rotors]]
A helicopter is a type of [[rotorcraft]] in which lift and thrust are supplied by one or more horizontally-spinning rotors.<ref>{{Cite web|url=https://www.nasa.gov/learning-resources/for-kids-and-students/what-is-a-helicopter-2-grades-5-8/|title=What Is a Helicopter? (Grades 5-8) NASA|date=21 May 2014|access-date=18 November 2024|archive-date=14 September 2024|archive-url=https://web.archive.org/web/20240914061240/https://www.nasa.gov/learning-resources/for-kids-and-students/what-is-a-helicopter-2-grades-5-8/|url-status=live}}</ref> By contrast the [[autogyro]] (or gyroplane) and [[gyrodyne]] have a free-spinning rotor for all or part of the flight envelope, relying on a separate thrust system to propel the craft forwards, so that the airflow sets the rotor spinning to provide lift. The compound helicopter also has a separate thrust system, but continues to supply power to the rotor throughout normal flight.{{citation needed|date=December 2023}} U.S. federal regulations state that "helicopter" means a rotorcraft that, for its horizontal motion, depends principally on its engine-driven rotors.<ref>[https://www.ecfr.gov/current/title-14/chapter-I/subchapter-A/part-1 ] (Definitions and Abbreviations) of Subchapter A of Chapter I of Title 14 of the U.S. Code of Federal Regulations </ref>
===Rotor system===
{{main|Helicopter rotor}}
The rotor system, or more simply ''rotor'', is the rotating part of a helicopter that generates [[lift (force)|lift]]. 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 horizontal thrust to counteract torque from the main rotors. The rotor consists of a mast, hub and rotor blades.{{Citation needed|date=December 2023}}
The mast is a cylindrical metal shaft that extends upwards from the transmission. At the top of the mast is the attachment point for the rotor blades called the hub. Main rotor systems are classified according to how the rotor blades are attached and move relative to the hub. There are three basic types: hingeless, fully articulated, and teetering; although some modern rotor systems use a combination of these.{{citation needed|date=December 2023}}
===Anti-torque===
{{see|Tail rotor}}
[[File:Igor Sikorsky 300.jpg|thumb|Sikorsky's V-300, 1937]]
Most helicopters have a single main rotor, but torque created by its [[aerodynamic drag]] must be countered by an opposed torque. The design that [[Igor Sikorsky]] settled on for his [[Vought-Sikorsky 300|VS-300]] was a smaller tail rotor. The tail rotor pushes or pulls against the tail to counter the torque effect, and this has become the most common configuration for helicopter design, usually at the end of a ''tail boom''.{{citation needed|date=December 2023}}
Some helicopters use other anti-torque controls instead of the tail rotor, such as the [[ducted fan]] (called ''[[Fenestron]]'' or ''FANTAIL'') and [[NOTAR]]. NOTAR provides anti-torque similar to the way a wing develops lift through the use of the [[Coandă effect]] on the tail boom.<ref name="Frawley Civil">Frawley 2003, p. 151.</ref>
[[File:Belgium Police 520N (cropped).jpg|thumb|[[MD Helicopters MD 500|MD 520N]] [[NOTAR]]]]
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 anti-torque tail rotor. This allows the power normally required to be diverted for the tail rotor to be applied fully to the main rotors, increasing the aircraft's power efficiency and lifting capacity. There are several common configurations that use the counter-rotating effect to benefit the rotorcraft:
* [[Tandem rotors]] are two counter-rotating rotors with one mounted behind the other.<ref>{{Cite web |date=2014-02-18 |title=FM 1-514 Chptr 3 – Rotor System Operation |url=http://www.cavalrypilot.com/fm1-514/Ch3.htm |access-date=2024-05-03 |archive-url=https://web.archive.org/web/20140218111928/http://www.cavalrypilot.com/fm1-514/Ch3.htm |archive-date=18 February 2014 }}</ref>
* [[Transverse rotors]] are pair of counter-rotating rotors transversely mounted at the ends of fixed wings or outrigger structures. Now used on [[tiltrotor]]s, some early model helicopters had used them.
* [[Coaxial rotors]] are two counter-rotating rotors mounted one above the other with the same axis.
* [[Intermeshing rotors]] are two counter-rotating rotors mounted close to each other at a sufficient angle to let the rotors intermesh over the top of the aircraft without colliding. An aircraft utilizing this is known as a '''synchropter'''.
* [[Multirotor]]s make use of three or more rotors. Specific terms are also used depending on the exact amount of rotors, such as '''tricopter''', '''[[quadcopter]]''', '''hexacopter''' and '''octocopter''' for three rotors, four rotors, six rotors and eight rotors respectively, of which quadcopter is the most common. Multirotors are primarily used on [[unmanned aerial vehicle|drones]] and use on aircraft with a human pilot is rare.{{citation needed|date=December 2023}}
[[Tip jet]] designs let the rotor push itself through the air and avoid generating torque.<ref>{{cite web |url= http://www.aerospaceweb.org/question/helicopters/q0034.shtml |title= Helicopter Yaw Control Methods |work= aerospaceweb.org |access-date= 1 April 2015 |archive-url= https://web.archive.org/web/20150919123404/http://www.aerospaceweb.org/question/helicopters/q0034.shtml |archive-date= 19 September 2015 |url-status= live}}</ref>
===Engines===
{{main|Aircraft engine|Turboshaft}}
[[File:Sikorsky H-34 engine AAT.JPG|thumb|left|H-34 with a radial piston engine in the nose]]
[[File:CH-53G engine.jpg|thumb|Turbine engine of a [[Sikorsky CH-53 Sea Stallion|CH-53 Sea Stallion]]]]
The number, size and type of engine(s) 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]] 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.{{citation needed|date=September 2008}}
Early helicopter designs utilized custom-built engines or [[rotary engine]]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]] 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.{{citation needed|date=September 2008}}
Turbine engines revolutionized the aviation industry; and the turboshaft engine for helicopter use, pioneered in December 1951 by the aforementioned Kaman K-225, finally gave helicopters an engine with a large amount of power and a low weight penalty. Turboshafts are also more reliable than piston engines, especially when producing the sustained high levels of power required by a helicopter. 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.{{citation needed|date=September 2008}}
Special jet engines developed to drive the rotor from the rotor tips are referred to as [[tip jet]]s. 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]], and an example of the hot tip jet helicopter is the [[YH-32 Hornet]].{{citation needed|date=September 2008}}
Some [[radio-controlled helicopter]]s and smaller, helicopter-type [[unmanned aerial vehicle]]s, use [[electric motor]]s or motorcycle engines.<ref name=H2R>{{cite web |title=Kawasaki successfully tests the Ninja H2R-powered unmanned helicopter |url=https://uasweekly.com/2020/10/29/kawasaki-successfully-tests-the-ninja-h2r-powered-unmanned-helicopter/ |website=UASweekly.com |date=29 October 2020 |access-date=31 October 2020 |archive-date=1 November 2020 |archive-url=https://web.archive.org/web/20201101045209/https://uasweekly.com/2020/10/29/kawasaki-successfully-tests-the-ninja-h2r-powered-unmanned-helicopter/ |url-status=live }}</ref> Radio-controlled helicopters may also have [[piston engine]]s that use fuels other than gasoline, such as [[Nitromethane#Use as an engine fuel|nitromethane]]. Some turbine engines commonly used in helicopters can also use biodiesel instead of jet fuel.<ref>[https://web.archive.org/web/20080928153738/http://www.businessweek.com/autos/content/nov2006/bw20061102_790939.htm?chan=top+news_top+news+index_autos "Jay Leno's EcoJet Concept"]. ''[[businessweek]].com'', 2 November 2006. Retrieved 12 December 2010.</ref><ref>Skinner, Tony. [https://archive.today/20130421063845/http://www.shephard.co.uk/news/rotorhub/eurosatory-2010-industry-celebrates-first-helicopter-biofuel-flight/6577/ "Eurosatory 2010: Industry celebrates first helicopter biofuel flight"]. ''shephard.co.uk'', 17 June 2010. Retrieved 12 December 2010.</ref>
There are also [[human-powered helicopter]]s.
===Transmission===
The [[transmission (mechanical device)|transmission]] is a mechanical system that transmits power from the engine(s) to the rotors. The transmission is a system of [[gears]], [[Bearing (mechanical)|bearing]]s, [[clutch]]es and [[Drive shaft|shaft]]s that performs several functions (1) Translates the alignment of the [[drive shaft]] to match the alignment of the rotor shafts; (2) Reduces the RPM of the drive shaft to the lower RPMs of the rotors; and (3) Enables the engine to engage or disengage from the rotors. For helicopters with tail rotors, the transmission [[drivetrain]] forks into two paths: one leading to the main rotor, and one leading to the tail rotor.<ref name="HRFch4">''Helicopter Flying Handbook'', FAA, 2024, Chaper 4 "Helicopter Components, Sections, and Systems" https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/helicopter_flying_handbook</ref>{{rp|4-10 to 4-13}}<ref>''Helicopter Instructor's Handbook'', FAA, 2014, ISBN 9781629141442, 1629141445</ref><ref>Bailey, Norman (2014) 'Helicopter Pilot's Manual'' Crowood, ISBN 9781847979230, 1847979238</ref>
The drive shafts of helicopter engines are typically not aligned with the rotor shafts, so the transmission must translate the alignment of the drive shaft to match the shafts of the rotors. Many engine drive shafts are aligned horizontally, yet the main rotor shaft ("mast") is usually vertical, and the tail rotor shaft is often perpendicular to the engine's drive shaft. The transmission contains a series of gears, usually [[bevel gear]]s, that translate the alignment of the drive shaft to the alignment of the rotor shafts.<ref name="HRFch4"/>{{rp|4-12}}<ref>''Bevel Gear Fundamentals and Applications'', Jan Klingelnberg, 2015, Springer Berlin Heidelberg, ISBN 9783662438930, 3662438933</ref>
The transmission also reduces the RPMs of the engine to the lower RPMs required by the rotors. The output drive shaft of the engine, before any gearing is applied, is typically between 3,000 and 50,000 RPM ([[Gas turbine|turbine engine]]s typically have higher RPM than [[piston engine]]s). The main rotor typically rotates between 300 and 600 RPM. The tail rotor, if present, usually rotates between 1,000 and 5,000 RPM. (The RPMs of a given model of helicopter are usually fixed {{em-dash}} the RPM ranges listed above represent a variety of helicopter models).<ref name=newman/> The transmission contains a series of [[reduction gear]]s to reduce the engine RPM to the rotor RPMs. Several types of reduction gears may be used, including bevel gears, [[planetary gear]]s, [[helical gear]]s, and [[spur gear]]s. Most transmissions contain several reduction gears: the engine itself may contain reduction gears (often spur gears) between the engine's internal shaft and the output drive shaft; the main rotor may have a reduction gear at its base (typically a planetary gear); and there may be reduction gears at the tail rotor, and on the shaft leading to the tail rotor.<ref name="HRFch4"/>{{rp|4-11}}
The transmission often includes one or more [[clutch]]es, which permit the rotors to engage or disengage from the engine. A clutch is required so the engine can start up and gain speed before taking the load of the rotors. A clutch is also required in the case of engine failure: in that situation, the rotors must disengage from the engine so that the rotors can continue spinning and perform [[autorotation]]. Helicopter clutches are usually [[freewheel]] clutches relying on centrifugal forces ([[sprag clutch]]s are commonly used), but [[belt drive]] clutches are also used.<ref name="HRFch4"/>{{rp|4-7, 4-12 to 4-13}}
===Flight controls===
{{main|Helicopter flight controls}}
[[File:Helicopter controls layout.svg|thumb|Controls from a [[Bell 206]]]]
A helicopter has four flight control inputs. These are the cyclic, the collective, the anti-torque foot 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'' or ''stick'' and moves forwards and backwards and side to side. On most helicopters, the cyclic is similar to a [[joystick]]. However, the [[Robinson R22]], [[Robinson R44]] and [[Robinson R66]] have a unique teetering-bar cyclic control system and a few helicopters have a cyclic control that descends into the cockpit from overhead.{{citation needed|date=December 2023}}
The cyclic is called the cyclic because it cyclically changes the pitch of the main rotor blades. In a forward flight state, as the blades rotate, the blade rotating forward will see higher speed and a corresponding increase in lift compared to the retreating blade. As such, the angle of attack of the forward rotating blade has to be lower than the retreating blade or the helicopter will roll to the retreating blade side. This happens cyclically as the blades rotate through a complete rotation leading to the naming of this control as the cyclic. The cyclic controls this differential angle.
The cyclic controls the tilt of the rotor. In hover, the cyclic controls motion of the helicopter over the ground. In flight, the cyclic controls the pitch and roll of the helicopter.
In a hover, 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 move sideways.{{citation needed|date=December 2023}}
Because of [[precession]], the cyclic moves the [[Swashplate (helicopter)|swashplate]] 90 degrees before the desired main rotor tilt. This can be seen when the rotor is stopped. With the blades aligned fore/aft, moving the cyclic forward does not change the blade angle but moving the cyclic to the side will change the blade angle.
In flight, the cyclic acts like the stick in an airplane. Moving the cyclic forward pitches the nose down for more speed. Moving the cyclic aft lifts the nose to slow the aircraft. Moving the cyclic to the side rolls the helicopter in that direction which generally leads to turning in that direction, assuming coordinated flight.
The collective pitch control or ''collective'' is located on the left side of the pilot's seat with an adjustable friction control to prevent inadvertent movement freeing the pilot's left hand for other uses. The collective changes the pitch angle of all the main rotor blades collectively (i.e. all at the same time) and independently of their rotational position. Therefore, if an up collective input is made, all the blades increase angle of attack equally, and the result is additional lift (power) to the main rotor system which can increase helicopter speed or altitude.{{citation needed|date=December 2023}} Lowering the collective results in less lift from the main rotor system.
A [[Swashplate (helicopter)|swashplate]] controls the collective and cyclic pitch of the main blades. The swashplate moves up and down, along the main shaft, to change the pitch of the blades. The stick is connected to the swash plate through the collective and cyclic systems allowing both systems to independently control the angle of the blades.
The anti-torque pedals are located in the same position as the [[rudder]] pedals in a fixed-wing aircraft, and serve a similar purpose, namely to control the [[flight dynamics|yaw]] or 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 in the direction of the applied pedal. The pedals mechanically change the pitch of the tail rotor altering the amount of thrust produced.{{citation needed|date=December 2023}} Helicopters do not exhibit [[adverse yaw]] as seen in airplanes and the pedals are not generally required when turning in forward flight. Use of the pedals is closely related to the collective in hover. For example, increasing collective increases aerodynamic drag on the main rotor system causing a yaw of the helicopter. The pedals are used to counter that yaw.
Both the cyclic and collective can have a wide variety of toggles and switches available to the pilot to control such things as aerodynamic trim, engine speed trim, radio and intercom, hook release, water release, etc. This allows the pilot to control these functions without removing their hands from the controls.
Helicopter rotors are designed to operate in a narrow range of [[Revolutions per minute|RPM]].<ref name=crouch>Croucher, Phil. [https://books.google.com/books?id=AovdKRWSqJAC&q=%22Professional+Helicopter+Pilot+Studies%22 Professional helicopter pilot studies] {{Webarchive |url=https://web.archive.org/web/20151127020431/https://books.google.com/books?id=AovdKRWSqJAC&printsec=frontcover&dq=%22Professional+Helicopter+Pilot+Studies%22&hl=da&ei=LYZ4TdmcDMjRsgbj56TyBw&sa=X&oi=book_result&ct=result&resnum=1&ved=0CD8Q6AEwAA#v=onepage&q&f=true |date=27 November 2015}} page 2-11. {{ISBN|978-0-9780269-0-5}}. Quote: [Rotor speed] "is constant in a helicopter".</ref><ref name="hawkRpm">Johnson, Pam. [http://www.michaeljohnsonmp.com/pdf/Pacific_wings_P42-49_Delta_v4_-_bill_whitney.pdf Delta D2] {{webarchive |url=https://web.archive.org/web/20110216035206/http://www.michaeljohnsonmp.com/pdf/Pacific_wings_P42-49_Delta_v4_-_bill_whitney.pdf |date=16 February 2011}} page 44 ''Pacific Wings''. Retrieved 2 January 2010</ref><ref>[http://www.helicoptervietnam.com/history.htm "Helicopters"]. {{Webarchive |url=https://web.archive.org/web/20110711161634/http://www.helicoptervietnam.com/history.htm |date=11 July 2011}} ''Helicopter Vietnam''. Retrieved: 16 February 2011.</ref><ref>The [[Sikorsky UH-60 Black Hawk|UH-60]] permits 95–101% rotor RPM [http://www.usarmyaviation.com/studyguides/index.php?folder=Documents/UH-60BlackhawkSpecific&download=Uh60limits.doc UH-60 limits] {{Webarchive |url=https://web.archive.org/web/20160818162950/http://www.usarmyaviation.com/studyguides/index.php?folder=Documents%2FUH-60BlackhawkSpecific&download=Uh60limits.doc |date=18 August 2016}} ''[[US Army Aviation]]''. Retrieved 2 January 2010</ref><ref name="newman">John M. Seddon, Simon Newman. [https://books.google.com/books?id=X_X3nOODGLgC Basic Helicopter Aerodynamics] {{Webarchive|url=https://web.archive.org/web/20160430134549/https://books.google.com/books?id=X_X3nOODGLgC&printsec=frontcover&hl=da|date=30 April 2016}} p. 216, ''[[John Wiley and Sons]]'', 2011. Retrieved 25 February 2012. {{ISBN|1-119-99410-1}}. Quote: "The rotor is best served by rotating at a constant rotor speed"</ref> 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 so that the rotor produces enough lift for flight. The throttle control is a motorcycle-style [[twist grip]] mounted on the collective control.
===Compound helicopter===
[[File:NH-3A NAN8-65.jpg|left|thumb|The NH-3A was experimental version of the Sea King with wings and jets.]]
A compound helicopter has an additional system for thrust and, typically, small stub [[fixed wing]]s. This offloads the rotor in cruise, which allows its rotation to be [[slowed rotor|slowed down]], thus increasing the maximum speed of the aircraft. The [[Lockheed AH-56A Cheyenne]] diverted up to 90% of its engine power to a [[pusher propeller]] during forward flight.<ref>Kenneth Munson; ''Helicopters: And Other Rotorcraft since 1907'', Blandford, revised edition 1973, pp. 55, 144-5.</ref>
==Flight==
There are three basic flight conditions for a helicopter: hover, forward [[flight]] and the transition between the two.
===Hover===
[[File:Advanced Helicopter Rescue School (cropped).jpg|thumb|An [[Eurocopter MH-65 Dolphin|HH-65 Dolphin]] holding a hover while conducting [[Winch#Aircraft use|rescue hoist]] training]]
Hovering is the most challenging part of flying a helicopter. Required are constant control inputs and corrections by the pilot to keep the helicopter where it is required to be.<ref name=lombar>{{cite news |first=Frank |last=Lombardi |url=http://accessintelligence.imirus.com/Mpowered/book/vrw15/i452/p48 |title=Under the big top |page=48 |work=Rotor & Wing |date=April 2015 |access-date=12 April 2015 |archive-url=https://web.archive.org/web/20150413003001/http://accessintelligence.imirus.com/Mpowered/book/vrw15/i452/p48 |archive-date=13 April 2015 |url-status=live}}</ref> 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 [[Course (navigation)|heading]]. 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.{{citation needed|date=December 2023}} In addition, the center of lift of the main rotor system is significantly above the center of gravity (CG) of the helicopter. Thus, any lateral perturbation of the helicopter in a hover will tend to increase as the rotor lift will increasingly roll or pitch the helicopter in a positive-feedback rotor-lift versus helicopter CG situation. The lateral motion of the helicopter lags behind the roll induced by the rotor lift side vector which will lead an inexperienced pilot into a pilot induced oscillation (PIO) and eventual loss of control.
===Transition from hover to forward flight===
A hovering helicopter is surrounded by a [[vortex ring state|vortex]] of air pushing the helicopter down. This can be a hover in ground effect or out of ground effect. Thus, when in a hover, the engine needs to provide enough power to both counter helicopter weight as well as counter this downward flow of air into the rotor system. As a helicopter moves from hover to forward flight it flies out of this downward flowing vortex and enters a state called [[translational lift]] which provides extra lift without increasing power. This state, most typically, occurs when the airspeed reaches approximately {{convert|16-24|knot|}}, and may be necessary for a helicopter to obtain flight.{{citation needed|date=December 2023}} A maneuver called a running take off involves sliding the helicopter on the ground at increasing speed until sufficient lift is achieved for flight.
===Forward flight===
In forward flight a helicopter's flight controls behave more like those of a fixed-wing aircraft. Applying forward pressure on the cyclic 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. Helicopters do not exhibit adverse [[adverse yaw|yaw]] and the pedals are not generally needed for forward flight, even when turning.
===Autorotation===
If the engine fails or is disconnected from the rotor system, the helicopter will enter an [[autorotation]], where the helicopter's main rotor turns due to air moving up through the rotor, instead of engine power driving the rotor.
==Uses==
[[File:Kfd-205-N408KC-050428-26cr.jpg|thumb|left|A [[Bell 204/205|Bell 205]] dropping water onto a fire]]
Due to the operating characteristics of the helicopter—its ability to take off and land vertically, and to hover for extended periods of time, as well as the aircraft's handling properties under low [[airspeed]] conditions—it has proved advantageous 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 [[transport]]ation of people and cargo, military uses, construction, firefighting, [[search and rescue]], [[tourism]], medical transport, law enforcement, agriculture, [[Electronic news gathering|news]] and [[Motion picture photography|media]], and [[Aerial photography|aerial observation]], among others.<ref>{{cite web |url=http://www.heliventuresnc.com/new-helicopter-pilot-resources/helicopter-career-info/ |title=Helicopter Pilot Training Schools, Careers – Heliventures|work=heliventuresnc.com |access-date=1 April 2015 |archive-url=https://web.archive.org/web/20150402071307/http://www.heliventuresnc.com/new-helicopter-pilot-resources/helicopter-career-info/ |archive-date=2 April 2015 |url-status=live}}</ref>
[[File:KPRC - IAH (cropped).jpg|thumb|[[KPRC-TV|KPRC]]'s [[Bell 206]] providing aerial news coverage]]
A helicopter used to carry loads connected to long cables or slings is called an [[aerial crane]]. 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 [[Heli-logging|logging industry]] to lift trees out of terrain where vehicles cannot travel and where environmental concerns prohibit the building of roads.<ref>Day, Dwayne A. [http://www.centennialofflight.net/essay/Rotary/skycranes/HE13.htm "Skycranes"] {{Webarchive |url=https://web.archive.org/web/20140204054636/http://www.centennialofflight.net/essay/Rotary/skycranes/HE13.htm |date=4 February 2014}}. Centennial of Flight Commission. Retrieved 1 October 2008.</ref> These operations are referred to as longline because of the long, single sling line used to carry the load.<ref>Webster, L.F. ''The Wiley Dictionary of Civil Engineering and Construction''. New York: Wiley, 1997. {{ISBN|0-471-18115-3}}.</ref> In military service helicopters are often useful for delivery of outsized slung loads that would not fit inside ordinary cargo aircraft: artillery pieces, large machinery (field radars, communications gear, electrical generators), or pallets of bulk cargo. In military operations these payloads are often delivered to remote locations made inaccessible by mountainous or riverine terrain, or naval vessels at sea.{{citation needed|date=December 2023}}
[[File:Inbound Choppers in Afghanistan 2008.jpg|thumb|left|Soldiers await pickup from CH-47 helicopters]]
In [[electronic news gathering]], helicopters have provided aerial views of some major news stories, and have been doing so, from the late 1960s. Helicopters have also been used in films, both in front and behind the camera.<ref>{{cite web |date= |title=Rotary inaction |url=http://www.rotaryaction.com/index.html |archive-url=https://web.archive.org/web/20141007195754/http://www.rotaryaction.com/index.html |archive-date=7 October 2014 |accessdate=27 October 2021 |publisher=rotaryaction.com}}</ref>
The largest single non-combat helicopter operation in history was the disaster management operation following the [[Chernobyl disaster|1986 Chernobyl nuclear disaster]]. Hundreds of pilots were involved in [[airdrop]] and observation missions, making dozens of sorties a day for several months.{{citation needed|date=December 2023}}
[[File:Flickr - The U.S. Army - www.Army.mil (193).jpg|thumb|Chinook interior with passengers in seats]]
"[[Helitack]]" is the use of helicopters to combat [[Wildland fire suppression|wildland fires]].<ref name=usfs1>Butler, Bret W. et al. [http://www.fs.fed.us/rm/pubs/rmrs_rp009/appA.html "Appendix A: Glossary: Fire Behavior Associated with the 1994 South Canyon Fire on Storm King Mountain, Colorado research paper"]. {{Webarchive |url=https://web.archive.org/web/20081002035033/http://www.fs.fed.us/rm/pubs/rmrs_rp009/appA.html |date=2 October 2008}} ''U.S. Dept. of Agriculture, Forest Service'', September 1998. Retrieved 2 November 2008.</ref> The helicopters are used for [[aerial firefighting]] (water bombing) and may be fitted with tanks or carry [[Helicopter bucket|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 [[Sikorsky S-64|Erickson S-64]] Aircrane helitanker.{{citation needed|date=December 2023}}
[[File:48th Rescue Squadron - HH-60 Pave Hawk - 2010.jpg|thumb|left|Exercises with a helicopter to rescue someone in water]]
Helicopters are used as [[air ambulance]]s for [[Emergency medical services|emergency medical assistance]] in situations when an [[ambulance]] cannot easily or quickly reach the scene, or cannot transport the patient to a medical facility in time. Helicopters are also used when patients need to be transported between medical facilities and air transportation is the most practical method. An air ambulance helicopter is equipped to stabilize and provide limited medical treatment to a patient while in flight. The use of helicopters as air ambulances is often referred to as "[[MEDEVAC]]", and patients are referred to as being "airlifted", or "medevaced". This use was pioneered in the [[Korean War]], when time to reach a medical facility was reduced to three hours from the eight hours needed in [[World War II]], and further reduced to two hours by the [[Vietnam War]].<ref>Kay, Marcia Hillary. "[http://www.aviationtoday.com/rw/commercial/eng/40-Years-Retrospective-Its-Been-a-Wild-Ride_14518.html 40 Years Retrospective: It's Been a Wild Ride]" ''Rotor & Wing'', August 2007. Accessed: 8 June 2014. {{webarchive |url=https://web.archive.org/web/20140608203922/http://www.aviationtoday.com/rw/commercial/eng/40-Years-Retrospective-Its-Been-a-Wild-Ride_14518.html |date=8 June 2014}}.</ref> In naval service a prime function of rescue helicopters is to promptly retrieve downed aircrew involved in crashes occurring upon launch or recovery aboard aircraft carriers. In past years this function was performed by destroyers escorting the carrier, but since then helicopters have proved vastly more effective.{{citation needed|date=December 2023}}
Police departments and other law enforcement agencies [[Police aviation|use helicopters]] to pursue suspects and patrol the skies. 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 [[Thermographic camera|heat-sensing]] equipment for night pursuits.
[[File:MIL24 HIND HELICOPTER GUNSHIP AT THE LUFTWAFFEN MUSEUM RAF GATOW BERLIN GERMANY JUNE 2013 (9040808927).jpg|thumb|The Mil-24 'Hind' is a well-known military attack helicopter]]
Military forces use [[attack helicopter]]s to conduct aerial attacks on ground targets. Such helicopters are mounted with [[missile launchers]] and [[minigun]]s. [[Military helicopter|Transport helicopters]] 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]]". [[Unmanned aerial vehicle|Unmanned aerial systems]] (UAS) helicopter systems of varying sizes are developed by companies for military [[reconnaissance]] and [[surveillance aircraft|surveillance]] duties. Naval forces also use helicopters equipped with [[Variable depth sonar|dipping sonar]] for [[anti-submarine warfare]], since they can operate from small ships.{{citation needed|date=December 2023}}
Oil companies charter helicopters to move workers and parts quickly to remote drilling sites located at sea or in remote locations. The speed advantage over boats makes the high operating cost of helicopters cost-effective in ensuring that [[oil platform]]s continue to operate. Various companies specialize in this type of operation.{{citation needed|date=December 2023}}
[[NASA]] developed ''[[Ingenuity (helicopter)|Ingenuity]]'', a {{convert|1.8|kg|abbr=on}} helicopter used to survey [[Mars]] (along with a rover). It began service in February 2021 and was retired due to sustained rotor blade damage in January 2024 after 73 sorties. As the Martian atmosphere is 100 times thinner than Earth's, its two blades spin at close to 3,000 revolutions a minute, approximately 10 times faster than that of a terrestrial helicopter.<ref name="Martian helicopter">{{Cite web |url=https://www.bbc.com/news/world-us-canada-44090509?ocid=socialflow_twitter&ns_source=twitter&ns_mchannel=social&ns_campaign=bbcnews |title=Nasa will send helicopter to Mars to test otherworldly flight |last=n/a |first=n/a |date=11 May 2018 |website=BBC |access-date=2018-05-11 |archive-url=https://web.archive.org/web/20180706152705/https://www.bbc.com/news/world-us-canada-44090509?ocid=socialflow_twitter&ns_source=twitter&ns_mchannel=social&ns_campaign=bbcnews |archive-date=6 July 2018 |url-status=live}}</ref>
===Market===
[[File:SH3H HS15 CVW15 1995.JPEG|thumb|Helicopter Anti-Submarine Squadron HS-12 "Wyverns" flying SH-3H Sea Kings in formation, 1985. Military helicopters are a significant part of the helicopter market]]
In 2017, 926 civil helicopters were shipped for $3.68 billion, led by [[Airbus Helicopters]] with $1.87 billion for 369 rotorcraft, [[Leonardo Helicopters]] with $806 million for 102 (first three-quarters only), [[Bell Helicopter]] with $696 million for 132, then [[Robinson Helicopter]] with $161 million for 305.<ref>{{cite news |url= https://gama.aero/wp-content/uploads/memos/63185_GAMA_2017_Year_End_Report.pdf |title= GAMA General Aviation Shipment Report 2017 |publisher= General Aviation Manufacturers Association |date= 21 February 2018 |access-date= 4 March 2018 |archive-url= https://web.archive.org/web/20180304173428/https://gama.aero/wp-content/uploads/memos/63185_GAMA_2017_Year_End_Report.pdf |archive-date= 4 March 2018 |url-status= dead}}</ref>
By October 2018, the in-service and stored helicopter fleet of 38,570 with civil or government operators was led Robinson Helicopter with 24.7% followed by Airbus Helicopters with 24.4%, then Bell with 20.5 and Leonardo with 8.4%, [[Russian Helicopters]] with 7.7%, [[Sikorsky Aircraft]] with 7.2%, [[MD Helicopters]] with 3.4% and other with 2.2%.<!--<ref name=Flight17oct2018>-->
The most widespread model is the piston [[Robinson R44]] with 5,600, then the H125/[[AS350]] with 3,600 units, followed by the [[Bell 206]] with 3,400.<!--<ref name=Flight17oct2018>-->
Most were in North America with 34.3% then in Europe with 28.0% followed by Asia-Pacific with 18.6%, Latin America with 11.6%, Africa with 5.3% and Middle East with 1.7%.<ref name=Flight17oct2018>{{cite news |url= https://www.flightglobal.com/news/articles/analysis-helicopter-market-report-q3-2018-452784/ |title= Helicopter market report Q3 2018 |date= 17 October 2018 |work= Flightglobal |access-date= 18 October 2018 |archive-url= https://web.archive.org/web/20181018122616/https://www.flightglobal.com/news/articles/analysis-helicopter-market-report-q3-2018-452784/ |archive-date= 18 October 2018 |url-status= live}}</ref>
==History==
===Early design===
{{see also|Bamboo-copter|Science and inventions of Leonardo da Vinci|Leonardo's aerial screw}}
[[File:Leonardo da Vinci helicopter.jpg|thumb|left|[[Leonardo's aerial screw|Leonardo's "aerial screw"]]]]
The earliest references for vertical flight came from China. Since around 400 BC,<ref name="Gordon">Leishman, J. Gordon. ''Principles of Helicopter Aerodynamics''. Cambridge aerospace series, 18. Cambridge: [[Cambridge University Press]], 2006. {{ISBN|978-0-521-85860-1}}. {{cite web |url=http://terpconnect.umd.edu/~leishman/Aero/history.html |title=A History of Helicopter Flight |access-date=15 July 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140713201846/http://terpconnect.umd.edu/~leishman/Aero/history.html |archive-date=13 July 2014}} Web extract</ref> Chinese children have played with [[Bamboo-copter|bamboo flying toys]] (or Chinese top).<ref>[http://www.aerospaceweb.org/design/helicopter/history.shtml "Early Helicopter History"]. {{Webarchive |url=https://web.archive.org/web/20041205132718/http://www.aerospaceweb.org/design/helicopter/history.shtml |date=5 December 2004}} ''Aerospaceweb.org''. Retrieved: 12 December 2010</ref><ref name="Taking Flight: Inventing the Aerial Age, from Antiquity Through the First World War">{{cite book |title=Taking Flight: Inventing the Aerial Age, from Antiquity Through the First World War |url=https://books.google.com/books?id=YRqV_PayIKIC&pg=PA22 |date=8 May 2003 |publisher=Oxford University Press|isbn=978-0-19-516035-2|pages=22–23}}</ref><ref name="china-1">{{cite web |last=Goebel |first=Greg |url=http://www.vectorsite.net/avheli_1.html |title=The Invention of the Helicopter |access-date=11 November 2008 |url-status=usurped |archive-url=https://web.archive.org/web/20110629140626/http://www.vectorsite.net/avheli_1.html |archive-date=29 June 2011 |website=VectorSite.net}}</ref> This bamboo-copter is spun by rolling a stick attached to a rotor. The spinning creates lift, and the toy flies when released.<ref name="Gordon"/> The 4th-century AD [[Daoist]] book ''[[Baopuzi]]'' by [[Ge Hong]] ({{lang|zh|抱朴子}} "Master who Embraces Simplicity") reportedly describes some of the ideas inherent to rotary wing aircraft.<ref name="china-2">Fay, John. [http://www.helis.com/pioneers/1.php "Helicopter Pioneers – Evolution of Rotary Wing Aircraft"]. {{Webarchive |url=https://web.archive.org/web/20061107114307/http://www.helis.com/pioneers/1.php |date=7 November 2006}} ''Helicopter History Site''. Retrieved: 28 November 2007</ref>
Designs similar to the Chinese helicopter toy appeared in some Renaissance paintings and other works.<ref>[[Donald F. Lach]]. (1977). [https://books.google.com/books?id=N0xD7BYXv_YC ''Asia in the making of Europe. Volume II, A Century of Wonder''] {{Webarchive |url=https://web.archive.org/web/20150915152103/https://books.google.com/books?id=N0xD7BYXv_YC |date=15 September 2015}}. p. 403</ref> In the 18th and early 19th centuries Western scientists developed flying machines based on the Chinese toy.<ref name="Leishman 2006, p. 8"/>
It was not until the early 1480s, when Italian polymath [[Leonardo da Vinci]] created a design for a machine that could be described as an "[[Leonardo's aerial screw|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 craft rotate.<ref name="flight-1">Rumerman, Judy. [http://www.centennialofflight.net/essay/Rotary/early_helicopters/HE1.htm "Early Helicopter Technology"]. {{Webarchive |url=https://web.archive.org/web/20140220023307/http://www.centennialofflight.net/essay/Rotary/early_helicopters/HE1.htm |date=20 February 2014}} ''Centennial of Flight Commission'', 2003. Retrieved 12 December 2010</ref><ref name="aerial screw">Pilotfriend.com [http://www.pilotfriend.com/photo_albums/helicopters/Leonardo%20Da%20Vinci's%20Helical%20Air%20Screw.htm "Leonardo da Vinci's Helical Air Screw"]. {{Webarchive |url=https://web.archive.org/web/20150924073521/http://www.pilotfriend.com/photo_albums/helicopters/Leonardo%20Da%20Vinci%27s%20Helical%20Air%20Screw.htm |date=24 September 2015}} ''Pilotfriend.com''. Retrieved 12 December 2010</ref> As scientific knowledge increased and became more accepted, people continued to pursue the idea of vertical flight.{{citation needed|date=December 2023}}
In July 1754, Russian [[Mikhail Lomonosov]] had developed a small coaxial modeled after the Chinese top but powered by a wound-up spring device<ref name="Leishman 2006, p. 8">Leishman, J. Gordon (2006). [https://books.google.com/books?id=nMV-TkaX-9cC&dq=Principles%20of%20Helicopter%20Aerodynamics&pg=PP1 Principles of Helicopter Aerodynamics] {{Webarchive |url=https://web.archive.org/web/20150925024931/https://books.google.com/books?id=nMV-TkaX-9cC&lpg=PP1&dq=Principles%20of%20Helicopter%20Aerodynamics |date=25 September 2015}}. Cambridge University Press. p. 8. {{ISBN|0-521-85860-7}}</ref> and demonstrated it to the [[Russian Academy of Sciences]]. It was powered by a spring, and was suggested as a method to lift [[meteorological]] instruments. In 1783, [[Christian de Launoy]], and his [[mechanic]], Bienvenu, used a coaxial version of the Chinese top in a model consisting of contrarotating [[Turkey (bird)|turkey]] flight feathers<ref name="Leishman 2006, p. 8"/> as rotor blades, and in 1784, demonstrated it to the [[French Academy of Sciences]]. [[Sir George Cayley]], influenced by a childhood fascination with the Chinese flying top, developed a model of feathers, similar to that of 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.<ref name="flight-1"/> [[Alphonse Pénaud]] 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]] to pursue the dream of flight.<ref>{{Cite web |url=https://www.loc.gov/teachers/classroommaterials/primarysourcesets/flight/pdf/teacher_guide.pdf |title=The Inventive Wright Brothers |website=[[Library of Congress]] |access-date=29 December 2017 |archive-url= https://web.archive.org/web/20171018101652/http://www.loc.gov/teachers/classroommaterials/primarysourcesets/flight/pdf/teacher_guide.pdf |archive-date=18 October 2017 |url-status=live}}</ref>
[[File:Elicottero sperimentale Enrico Forlanini 1877 Museo scienza e tecnologia Milano.jpg|thumb|Experimental helicopter by [[Enrico Forlanini]] (1877), exposed at the [[Museo nazionale della scienza e della tecnologia Leonardo da Vinci]] of [[Milan]], [[Italy]]]]
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 1877, the Italian engineer, inventor and aeronautical pioneer [[Enrico Forlanini]] developed an unmanned helicopter powered by a [[steam engine]]. It rose to a height of {{convert|13|m|ft|abbr=off|sp=us}}, where it remained for 20 seconds, after a vertical take-off from a park in [[Milan]].<ref name=imss>{{cite web|url=http://www.imss.fi.it/milleanni/cronologia/biografie/forlanie.html|title=Enrico Forlanini|publisher=Mille anni di scienza in Italia|access-date=13 March 2024|language=it|archive-date=18 January 2020|archive-url=https://web.archive.org/web/20200118124028/http://www.imss.fi.it/milleanni/cronologia/biografie/forlanie.html|url-status=live}}</ref> Milan has dedicated its city airport to Enrico Forlanini, also named [[Linate Airport]],<ref>{{cite web|url=https://www.milanolinate-airport.com/it/legal/airport-regulations/aeroporto-linate|title=L'aeroporto di Milano Linate|publisher=Aeroporto di Milano Linate|access-date=13 March 2024|language=it|archive-date=12 March 2024|archive-url=https://web.archive.org/web/20240312232355/https://www.milanolinate-airport.com/it/legal/airport-regulations/aeroporto-linate|url-status=live}}</ref> as well as the nearby park, the Parco Forlanini.<ref>{{cite web|url=https://www.comune.milano.it/aree-tematiche/verde/verde-pubblico/parchi-cittadini/parco-enrico-forlanini|title=Scheda del Parco Forlanini|publisher=Comune di Milano|access-date=13 March 2024|language=it|archive-date=21 April 2024|archive-url=https://web.archive.org/web/20240421204101/https://www.comune.milano.it/aree-tematiche/verde/verde-pubblico/parchi-cittadini/parco-enrico-forlanini|url-status=live}}</ref> Emmanuel Dieuaide's steam-powered design featured counter-rotating rotors powered through a hose from a boiler on the ground.<ref name="flight-1" /> In 1887 Parisian inventor, [[Gustave Trouvé]], built and flew a tethered electric model helicopter.{{citation needed|date=May 2015}}
In July 1901, the maiden flight of [[Hermann Ganswindt]]'s helicopter took place in Berlin-Schöneberg; this was probably the first [[Aircraft#Heavier than air|heavier-than-air]] motor-driven flight carrying humans. A movie covering the event was taken by [[Max Skladanowsky]], but it remains [[lost film|lost]].<ref>{{cite web |url=http://helikopterhysteriezwo.blogspot.jp/2012/06/moments-in-helicopter-history-9.html |title=Moments in Helicopter History (9) – Hermann Ganswindt|website=helikopterhysteriezwo.blogspot.jp |access-date=23 May 2016 |archive-url=https://web.archive.org/web/20160810221946/http://helikopterhysteriezwo.blogspot.jp/2012/06/moments-in-helicopter-history-9.html |archive-date=10 August 2016 |url-status=live}}</ref>
In 1885, [[Thomas Edison]] was given US$1,000 (equivalent to ${{inflation|US|1000|1885|r=-3|fmt=c}} today) by [[James Gordon Bennett, Jr.]], 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.<ref>Bryan, George S. ''Edison: the Man and His Work''. New York: Garden City Publishers, 1926. p. 249</ref> [[Ján Bahýľ]], a [[Slovaks|Slovak]] inventor, adapted the [[internal combustion engine]] to power his helicopter model that reached a height of {{convert|0.5|m|ft|abbr=off|sp=us}} in 1901. On 5 May 1905, his helicopter reached {{convert|4|m|ft|abbr=off|sp=us}} in altitude and flew for over {{convert|1500|m|ft|abbr=off|sp=us}}.<ref>[http://www.helis.com/pioneers/1900.php "Pioneers – 1900/1930"]. {{Webarchive |url=https://web.archive.org/web/20070504045019/http://www.helis.com/pioneers/1900.php |date=4 May 2007}} ''Helicopter History Site''. Retrieved: 3 May 2007</ref> 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,<ref name="us970616">{{cite web |url=https://www.google.de/patents/US970616 |title=Patent US970616 – Flying-machine. |access-date=30 March 2016 |archive-url=https://web.archive.org/web/20160413071048/https://www.google.de/patents/US970616 |archive-date=13 April 2016 |url-status=live}}</ref> but it never flew.<ref>Dowd, George L. "Flops of famous inventors". ''[[Popular Science]]'', December 1930</ref>
===First flights===
In 1906, two French brothers, Jacques and [[Louis Breguet]], began experimenting with airfoils for helicopters. In 1907, those experiments resulted in the [[Breguet-Richet Gyroplane|''Gyroplane No.1'']], possibly as the earliest known example of a quadcopter. Although there is some uncertainty about the date, sometime between 14 August and 29 September 1907, the Gyroplane No. 1 lifted its pilot into the air about {{convert|2|ft|m|sigfig=1|order=flip}} for a minute.<ref name="Munson">Munson 1968.</ref><ref name="Hirschberg">Hirschberg, Michael J. and David K. Dailey, [http://vtol.org/History.htm "Sikorsky"] {{webarchive|url=https://web.archive.org/web/20071218045128/http://www.vtol.org/History.htm|date=18 December 2007}}. ''US and Russian Helicopter Development in the 20th Century'', [[American Helicopter Society]], International. 7 July 2000.</ref> The Gyroplane No.{{nbsp}}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.{{nbsp}}1 are considered to be the first manned flight of a helicopter, but not a free or untethered flight.{{citation needed|date=December 2023}}
[[File:HE2G8.jpg|thumb|left|upright=1.2|Paul Cornu's helicopter, 1907]]
That same year, fellow French inventor [[Paul Cornu]] designed and built the [[Cornu helicopter]] which used two {{convert|20|ft|m|sigfig=2|adj=on|order=flip}} counter-rotating rotors driven by a {{convert|24|hp|kW|abbr=on|sigfig=2}} [[Antoinette (manufacturer)|Antoinette]] engine. On 13 November 1907, it lifted its inventor to {{convert|1|ft|m|sigfig=1|order=flip}} 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.<ref group=n>Leishman, J. Gordon, Technical Fellow of AHS International. [http://helicopter-history.org/Cornu/Cornu_LJpaper.pdf "Paper"]. {{Webarchive |url=https://web.archive.org/web/20081001201210/http://helicopter-history.org/Cornu/Cornu_LJpaper.pdf |date=1 October 2008}} 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.</ref> Cornu's helicopter completed a few more flights and achieved a height of nearly {{convert|6.5|ft|m|sigfig=2|order=flip}}, but it proved to be unstable and was abandoned.<ref name="Munson"/>
In 1909, J. Newton Williams of Derby, Connecticut, and [[Emile Berliner]] of Washington, D.C., flew a helicopter "on three occasions" at Berliner's lab in Washington's [[Brightwood (Washington, D.C.)|Brightwood]] neighborhood.<ref>{{Cite web |date=July 1, 1909 |title=Helicoptre Lifts Itself and Man |url=https://news.google.com/newspapers?id=MbJIAAAAIBAJ&sjid=koEMAAAAIBAJ&pg=4676,522421&dq=brightwood+washington+-coxey&hl=en |access-date=2022-11-23 |website=Youngstown Vindicator}}</ref>
In 1911, Slovenian philosopher and economist Ivan Slokar patented a helicopter configuration.<ref>{{cite web |url=http://www.slovenska-biografija.si/oseba/sbi584468/ |title=Slokar, Ivan (1884–1970) |author=Slovenska akademija znanosti in umetnosti |access-date=30 March 2016 |archive-url=https://web.archive.org/web/20160304111720/http://www.slovenska-biografija.si/oseba/sbi584468/ |archive-date=4 March 2016 |url-status=live}}</ref><ref>{{cite web |url=http://www.ajdovscina.si/ajdovscina/zgodovina/pomembne_osebnosti/2015082013191757/%20Ivan%20Slokar%20-%20letalski%20izumitelj,%20gospodarstvenik,%20jezikoslovec%20(1884%20-%201970)/ |title=Ivan Slokar – letalski izumitelj, gospodarstvenik, jezikoslovec (1884–1970) |author=Občina Ajdovščina |access-date=30 March 2016 |archive-url=https://web.archive.org/web/20160304090149/http://www.ajdovscina.si/ajdovscina/zgodovina/pomembne_osebnosti/2015082013191757/%20Ivan%20Slokar%20-%20letalski%20izumitelj,%20gospodarstvenik,%20jezikoslovec%20(1884%20-%201970)/ |archive-date=4 March 2016 |url-status=live}}</ref><ref>{{cite book |title=Sto slovenskih znanstvenikov, zdravnikov in tehnikov (Open Library) |ol = 19750086M}}</ref>
The Danish inventor [[Jacob Ellehammer]] 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 indoor tests, the aircraft was demonstrated outdoors and made several free take-offs. Experiments with the helicopter continued until September 1916, when it tipped over during take-off, destroying its rotors.<ref>Taylor, Michael J. H. ''Jane's Encyclopedia of Aviation'', p. 348. London: Studio Editions, 1989.</ref>
During [[World War I]], [[Austria-Hungary]] developed the [[Petróczy-Kármán-Žurovec|PKZ]], an experimental helicopter prototype, with two aircraft built.{{citation needed|date=December 2023}}
===Early development===
[[File:Bits & Pieces - BP374 - Test flight of Pescara's helicopter - 1922 - EYE FLM7760 - OB105716.ogv|thumb|Silent film of a test flight of Pescara's helicopter, 1922. [[EYE Film Institute Netherlands]].]]
In the early 1920s, Argentine [[Raúl Pateras Pescara|Raúl Pateras-Pescara de Castelluccio]], while working in Europe, demonstrated one of the first successful applications of cyclic pitch.<ref name="Munson"/> 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]]. By January 1924, Pescara's helicopter No.{{nbsp}}1 was tested but was found to be underpowered and could not lift its own weight. His 2F fared better and set a record.<ref name=PPdist>"[http://www.fai.org/fai-record-file/?recordId=13094 FAI Record ID #13094 – Straight distance. Class E former G (Helicopters), piston ] {{webarchive |url=https://web.archive.org/web/20141006093603/http://www.fai.org/fai-record-file/?recordId=13094 |date=6 October 2014}}" ''Fédération Aéronautique Internationale''. Retrieved: 21 September 2014.</ref> The British government funded further research by Pescara which resulted in helicopter No. 3, powered by a {{convert|250|hp|adj=on}} radial engine which could fly for up to ten minutes.<ref>{{cite magazine|magazine=Popular Science |publisher=Bonnier Corporation |title=New Helicopter Rises in Vertical Flight |url=https://books.google.com/books?id=9ycDAAAAMBAJ&pg=PA70 |date=March 1931 |page=70}}</ref><ref>{{cite magazine|magazine=[[Popular Mechanics]] |title=Helicopter with Six Blades Succeeds in Tests |url=https://books.google.com/books?id=S-QDAAAAMBAJ&pg=PA460 |date=March 1931 |publisher=Hearst Magazines|page=460}}</ref>
In March 1923 ''[[Time (magazine)|Time]]'' magazine reported Thomas Edison sent [[George de Bothezat]] a congratulations for a successful helicopter test flight. Edison wrote, "So far as I know, you have produced the first successful helicopter." The helicopter was tested at [[McCook Field|McCook's Field]] and remained airborne for 2 minutes and 45 seconds at a height of 15 feet.<ref>{{cite magazine |author=<!--Staff writer(s); no by-line.--> |title=A Successful Helicopter |url=https://time.com/vault/issue/1923-03-03/page/23/ |magazine=[[Time (magazine)|Time]] |page=23 |date=March 3, 1923 |access-date=March 2, 2021}}</ref>
On 14 April 1924, Frenchman [[Étienne Oehmichen]] set the first helicopter world record recognized by the ''[[Fédération Aéronautique Internationale]]'' (FAI), flying his [[quadcopter|quadrotor helicopter]] {{convert|360|m|ft|sp=us}}.<ref name=EOdist1>"[http://www.fai.org/fai-record-file/?recordId=13093 FAI Record ID #13093 – Straight distance. Class E former G (Helicopters), piston ] {{webarchive |url=https://web.archive.org/web/20160305020606/http://www.fai.org/fai-record-file/?recordId=13093 |date=5 March 2016}}" ''Fédération Aéronautique Internationale''. Retrieved: 21 September 2014.</ref> On 18{{nbsp}}April 1924, Pescara beat Oemichen's record, flying for a distance of {{convert|736|m|sp=us}}<ref name=PPdist/> (nearly {{convert|.5|mi|order=flip|sp=us|disp=or}}) in 4 minutes and 11 seconds (about {{convert|8|mph|km/h|abbr=on|order=flip|disp=or}}), maintaining a height of {{convert|6|ft|m|abbr=off|sp=us|order=flip}}.<ref name="flight-2">Rumerman, Judy. [http://www.centennialofflight.net/essay/Rotary/early_20th_century/HE2.htm "Helicopter Development in the Early Twentieth Century"] {{Webarchive |url=https://web.archive.org/web/20140220014341/http://www.centennialofflight.net/essay/Rotary/early_20th_century/HE2.htm |date=20 February 2014}}. Centennial of Flight Commission. Retrieved 28 November 2007.</ref> On 4{{nbsp}}May, Oehmichen completed the first {{convert|1|km|adj=on|spell=in|sp=us}} closed-circuit helicopter flight in 7 minutes 40 seconds with his No. 2 machine.<ref name="Munson"/><ref>[http://www.cs.uni-salzburg.at/~rtrummer/documents/PhDThesis.pdf The JAviator Quadrotor]{{dead link|date=September 2024|fix-attempted=yes}} – Rainer K. L. Trummer, University of Salzburg, Austria, 2010, p. 21</ref>
In the US, [[George de Bothezat]] built the quadrotor helicopter [[de Bothezat helicopter]] for the United States Army Air Service but the Army cancelled the program in 1924, and the aircraft was scrapped.{{citation needed|date=February 2013}}
[[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,<ref>Relly Victoria Petrescu and Florian Ioon Petrescu ''The Aviation History'', p. 74. USA, 2013, {{ISBN|978-3-8482-6639-5}}.</ref> with Dutch Army-Air arm Captain Floris Albert van Heijst at the controls. The controls that van Heijst used were von Baumhauer's inventions, the [[Helicopter flight controls|cyclic and collective]].<ref name="Vodegel">H.J.G.C. Vodegel and K.P. Jessurun. ''A Historical Review of Two Helicopters Designed in the Netherlands''. 21st European Rotocraft Forum, 1995, Saint Petersburg, Russia. [http://www.lr.tudelft.nl/fileadmin/Faculteit/LR/Organisatie/Afdelingen_en_Leerstoelen/Afdeling_AEWE/Wind_Energy/Research/Publications/Publications_1995 web extract]{{dead link |date=November 2017 |bot=InternetArchiveBot |fix-attempted=yes}}</ref><ref name="Voogt">Alex de Voogt. ''The Transmission of Helicopter Technology, 1920-1939: Exchanges with von Baumhauer''. Int. j. for the history of eng. & tech., Vol. 83 No. 1, January 2013, 119–40. [https://www.academia.edu/2543089 web extract] {{Webarchive|url=https://web.archive.org/web/20211025160637/https://www.academia.edu/2543089 |date=25 October 2021 }}</ref> Patents were granted to von Baumhauer for his cyclic and collective controls by the British ministry of aviation on 31{{nbsp}}January 1927, under patent number 265,272.{{citation needed|date=February 2013}}
In 1927,<ref>{{Cite web |url=http://siris-thesauri.si.edu/ipac20/ipac.jsp?session=11P8B0B391935.82&profile=planes&uri=link=3100019~!26176~!3100001~!3100002&aspect=subtab13&menu=search&ri=2&source=~!sithesauri&term=Zaschka&index= |title=Smithsonian National Air and Space Museum Washington: ''Zaschka Helicopter (1927)'' |access-date=11 November 2016 |archive-url=https://web.archive.org/web/20160529045002/http://siris-thesauri.si.edu/ipac20/ipac.jsp?session=11P8B0B391935.82&profile=planes&uri=link=3100019~!26176~!3100001~!3100002&aspect=subtab13&menu=search&ri=2&source=~!sithesauri&term=Zaschka&index= |archive-date=29 May 2016 |url-status=dead }}</ref> [[Engelbert Zaschka]] from Germany built a helicopter, equipped with two rotors, in which a [[gyroscope]] was used to increase stability and serves as an energy accumulator for a [[gliding]] flight to make a landing. Zaschka's aircraft, the first helicopter, which ever worked so successfully in miniature, not only rises and descends vertically, but is able to remain stationary at any height.<ref>{{Cite news |title=German Plane Promises New Stunts in Air, The Bee. Danville, Virginia, USA, June 25, 1927, p. 16}}</ref><ref>{{Citation |author=Zaschka, Engelbert |title=<sup>HD</sup> Engelbert Zaschka – ein Universalgenie und Erfinder: Musik, Fahrzeuge & Flugzeuge [SWR-Doku 2016] |work= The Zaschka Innovation |date=18 May 2016 |url=https://www.youtube.com/watch?v=0bjcyA-dF7E |via= Youtube.com |access-date=11 November 2016 |archive-url=https://web.archive.org/web/20161106002447/https://www.youtube.com/watch?v=0bjcyA-dF7E |archive-date=6 November 2016 |url-status=live}}</ref>
In 1928, Hungarian aviation engineer [[Oszkár Asbóth]] constructed a helicopter prototype that took off and landed at least 182 times, with a maximum single flight duration of 53 minutes.<ref>[http://paperspast.natlib.govt.nz/cgi-bin/paperspast?a=d&d=EP19350427.2.86 "Asboth Helicopter"]. {{Webarchive |url=https://web.archive.org/web/20111125201220/http://paperspast.natlib.govt.nz/cgi-bin/paperspast?a=d&d=EP19350427.2.86 |date=25 November 2011}} ''The Evening Post (New Zealand)'', 27 April 1935.</ref><ref>{{YouTube|id=A8bfOKaiScM |title=The first Hungarian helicopter (1929)}} Retrieved: 12 December 2010.</ref>
In 1930, the Italian engineer [[Corradino D'Ascanio]] 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,<ref name="spenser">Spenser 1998</ref> 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).<ref name="spenser"/><ref name=CDAdist>"[http://www.fai.org/fai-record-file/?recordId=13059 FAI Record ID #13086 – Straight distance. Class E former G (Helicopters), piston] {{webarchive |url=https://web.archive.org/web/20151222155348/http://www.fai.org/fai-record-file/?recordId=13059 |date=22 December 2015}}" ''Fédération Aéronautique Internationale''. Retrieved: 21 September 2014.</ref>
====First practical rotorcraft====
[[File:Juan de la Cierva C.6 autogyro.jpg|thumb|A Cierva autogyro in the 1920s, one of the predecessors to helicopters]]
Spanish aeronautical engineer and pilot [[Juan de la Cierva]] invented the [[autogyro]] in the early 1920s, becoming the first practical rotorcraft.<ref>Wayne Johnson, Rotorcraft Aeromechanics, Cambridge University Press, p. 19 (2013)</ref> In 1928, de la Cierva successfully flew an autogyro across the English Channel, from London to Paris.<ref>"Channel Flight By Autogiro. Spanish Airman's Success". ''The Times'' (45002). London. 19 September 1928. col F, p. 14.</ref> In 1934, an autogyro became the first rotorcraft to successfully take off and land on the deck of a ship.<ref>"The first [[Spanish seaplane carrier Dédalo|Dedalo]] was an aircraft transportation ship and the first in the world from which an autogyro took off and landed." Naval Ship Systems Command, US: Naval Ship Systems Command technical news.1966, v. 15–16, p. 40</ref> That same year, the autogyro was employed by the Spanish military during the [[Asturias revolt]], becoming the first military deployment of a rotocraft. Autogyros were also employed in [[New Jersey]] and [[Pennsylvania]] for delivering mail and newspapers prior to the invention of the helicopter.<ref>Pulle, Matt (5 July 2007). "Blade Runner". Dallas Observer. 27 (27). Dallas, Tx. pp. 19–27.</ref> Though lacking true vertical flight capability, work on the autogyro forms the basis for helicopter analysis.<ref>Johnson, Wayne. ''Rotorcraft Aeromechanics'', p. 21. Cambridge University Press, 2013.</ref>
====Single lift-rotor success====
In the Soviet Union, Boris N. Yuriev and Alexei M. Cheremukhin, two aeronautical engineers working at the ''[[Central Aerohydrodynamic Institute|Tsentralniy Aerogidrodinamicheskiy Institut]]'' (TsAGI or the Central Aerohydrodynamic Institute), constructed and flew the TsAGI 1-EA single lift-rotor helicopter, which used an open tubing framework, a four-blade main lift rotor, and twin sets of {{convert|1.8|m|ft|abbr=off|sp=us|adj=on}} diameter, two-bladed 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#Variants|Gnome ''Monosoupape'' 9 Type B-2]] 100 CV output [[rotary engine]] of World War I, the TsAGI 1-EA made several low altitude flights.<ref>{{cite AV media |url=https://www.youtube.com/watch?v=rx565dqF-5M |title=Cheryomukhin TsAGI 1-EA (ЦАГИ 1-ЭА) first Soviet helicopter |date=30 April 2012 |access-date=30 March 2016|via=YouTube |archive-url=https://web.archive.org/web/20160829004008/https://www.youtube.com/watch?v=rx565dqF-5M |archive-date=29 August 2016 |url-status=live}}</ref> By 14 August 1932, Cheremukhin managed to get the 1-EA up to an unofficial altitude of {{convert|605|m|ft|abbr=off|sp=us}}, shattering d'Ascanio's earlier achievement. As the Soviet Union was not yet a member of the [[Fédération Aéronautique Internationale|FAI]], however, Cheremukhin's record remained unrecognized.<ref>Savine, Alexandre. [http://www.ctrl-c.liu.se/misc/ram/1-ea.html "TsAGI 1-EA"]. {{Webarchive |url=https://web.archive.org/web/20090126202112/http://www.ctrl-c.liu.se/misc/ram/1-ea.html |date=26 January 2009}} ''ctrl-c.liu.se'', 24 March 1997. Retrieved 12 December 2010.</ref>
[[Nicolas Florine]], a Russian engineer, built the first twin tandem rotor machine to perform a free flight. It flew in [[Sint-Genesius-Rode]], at the ''Laboratoire Aérotechnique de Belgique'' (now [[von Karman Institute]]) in April 1933, and attained an altitude of {{convert|6|m|ft|abbr=off|sp=us|spell=in}} 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 helicopters in existence.<ref name="art-helicopter">Watkinson 2004, p. 358.</ref>
The Bréguet-Dorand ''[[Gyroplane Laboratoire]]'' was built in 1933. It was a 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 {{convert|500|m|ft|abbr=off|sp=us|adj=on}} diameter.<ref name=GLdist>"[http://www.fai.org/fai-record-file/?recordId=13059 FAI Record ID #13059 – Straight distance. Class E former G (Helicopters), piston] {{webarchive |url=https://web.archive.org/web/20151222155348/http://www.fai.org/fai-record-file/?recordId=13059 |date=22 December 2015}}" ''[[Fédération Aéronautique Internationale]]''. Retrieved: 21 September 2014.</ref> The next year, on 26 September 1936, Claisse set a height record of {{convert|158|m|ft|abbr=off|sp=us}}.<ref name=GLalt>"[http://www.fai.org/fai-record-file/?recordId=13084 FAI Record ID #13084 – Altitude. Class E former G (Helicopters), piston] {{webarchive |url=https://web.archive.org/web/20150207050742/http://www.fai.org/fai-record-file/?recordId=13084 |date=7 February 2015}}" ''Fédération Aéronautique Internationale''. Retrieved: 21 September 2014.</ref> And, finally, on 24 November 1936, he set a flight duration record of one hour, two minutes and 50 seconds<ref name=GLdur>"[http://www.fai.org/fai-record-file/?recordId=13062 FAI Record ID #13062 – Duration in closed circuit. Class E former G (Helicopters), piston] {{webarchive |url=https://web.archive.org/web/20160307032252/http://www.fai.org/fai-record-file/?recordId=13062 |date=7 March 2016}}" ''Fédération Aéronautique Internationale''. Retrieved: 21 September 2014.</ref> over a {{convert|44|km|mi|abbr=off|sp=us}} closed circuit at 44.7 kilometres per hour (27.8 mph). The aircraft was destroyed in 1943 by an [[Allies of World War II|Allied]] [[airstrike]] at [[Villacoublay]] airport.<ref>Day, Dwayne A. "[http://www.centennialofflight.net/essay/Rotary/Breguet/HE7.htm Jacques Bréguet—Gyroplane-Laboratoire] {{Webarchive |url=https://web.archive.org/web/20140224132413/http://www.centennialofflight.net/essay/Rotary/Breguet/HE7.htm |date=24 February 2014}}". Paragraph 10. Centennial of Flight. Retrieved 24 September 2015.</ref>
====American single-rotor beginnings====
American inventor [[Arthur M. Young]] started work on model helicopters in 1928 using converted electric hover motors to drive the rotor head. Young invented the [[stabilizer bar (helicopter)|stabilizer bar]] and patented it shortly after. A mutual friend introduced Young to Lawrence Dale, who once seeing his work asked him to join the Bell Aircraft company. When Young arrived at Bell in 1941, he signed his patent over and began work on the helicopter. His budget was US$250,000 (equivalent to ${{inflation|US|.250|1941|r=1|fmt=c}} million today) to build two working helicopters. In just six months they completed the first Bell Model 1, which spawned the [[Bell Model 30]], later succeeded by the Bell 47.<ref>{{cite web |title=American airplanes:Bell |url=http://www.aerofiles.com/_bell.html |date=20 April 2009 |publisher=aerofiles.com |access-date=23 December 2009 |archive-url= https://web.archive.org/web/20100102011047/http://aerofiles.com/_bell.html |archive-date= 2 January 2010 |url-status= live}}</ref>
===Birth of an industry===
[[File:Fw 61 V.JPG|left|thumb|[[Focke-Wulf Fw 61]], the first successful helicopter]]
[[Heinrich Focke]] at Focke-Wulf had purchased a license from [[Cierva Autogiro Company]], which according to [[Frank Kingston Smith Sr.]], included "the fully controllable cyclic/collective pitch hub system". In return, Cierva Autogiro received a cross-license to build the Focke-Achgelis helicopters. Focke designed the world's first practical helicopter, the [[Helicopter rotor#Transverse|transverse twin-rotor]] [[Focke-Wulf Fw 61]], which first flew in June 1936. It was demonstrated by [[Hanna Reitsch]] in February 1938 inside the [[Deutschlandhalle]] in [[Berlin]].<ref>{{Cite web |last1=Wall |first1=Berend G. van der |last2=Harris |first2=Franklin D. |date=September 2022 |title=Henrich Focke — Inventor of the First Successful Helicopter |url=https://ntrs.nasa.gov/api/citations/20220014586/downloads/1582_van%20der%20Wall_Harris-Focke%20CR-20220014586_Final_092722.pdf |access-date=June 1, 2024 |website=ntrs.nasa.gov |archive-date=30 March 2023 |archive-url=https://web.archive.org/web/20230330172154/https://ntrs.nasa.gov/api/citations/20220014586/downloads/1582_van%20der%20Wall_Harris-Focke%20CR-20220014586_Final_092722.pdf |url-status=live }}</ref> The Fw 61 set a number of FAI records from 1937 to 1939, including: maximum altitude of {{Convert|3427|m|ft}}, maximum distance of {{Convert|230|km|mi}}, and maximum speed of {{convert|124|km/h|mph}}.<ref>{{Cite journal |last=Hirschberg |first=Michael J. |date=1999 |title=A Perspective on the First Century of Vertical Flight |url=https://www.jstor.org/stable/44729509 |journal=SAE Transactions |volume=108 |pages=1120 |jstor=44729509 |issn=0096-736X |access-date=1 June 2024 |archive-date=31 May 2024 |archive-url=https://web.archive.org/web/20240531164507/https://www.jstor.org/stable/44729509 |url-status=live }}</ref> Autogiro development was now being bypassed by a focus on helicopters.<ref name="fs">{{cite book |last1= Smith |first1= Frank |title= Legacy of Wings; The Harold F. Pitcairn Story |date= 1981 |publisher= Jason Aronson, Inc. |___location= New York |isbn=0876684851 |pages=253–254}}</ref>
During World War II, [[Nazi Germany]] used helicopters in small numbers for observation, transport, and medical evacuation. The [[Flettner Fl 282]] ''Kolibri'' [[synchropter]]—using the same basic configuration as [[Anton Flettner]]'s own pioneering [[Flettner Fl 265|Fl 265]]—was used in the [[Baltic Sea|Baltic]], [[Mediterranean Sea|Mediterranean]], and [[Aegean Sea|Aegean]] Seas.<ref>{{Cite web |title=World War II German Helicopters – Flettner Fl 265 and Fl 282 |url=https://www.defensemedianetwork.com/stories/nazi-rotors-german-helicopter-development-1932-1945-flettner/ |access-date=2024-05-31 |website=Defense Media Network |language=en-US |archive-date=31 May 2024 |archive-url=https://web.archive.org/web/20240531232634/https://www.defensemedianetwork.com/stories/nazi-rotors-german-helicopter-development-1932-1945-flettner/ |url-status=live }}</ref> The [[Focke-Achgelis Fa 223 Drache]], like the Fw 61, used two transverse rotors, and was the largest rotorcraft of the war.<ref>{{Cite web |title=Focke-Achgelis Fa 330A-1 Bachstelze (Water Wagtail) {{!}} National Air and Space Museum |url=https://airandspace.si.edu/collection-objects/focke-achgelis-fa-330a-1-bachstelze-water-wagtail/nasm_A19540016000 |access-date=2024-05-31 |website=airandspace.si.edu |language=en}}</ref> [[Strategic bombing during World War II|Extensive bombing]] by the [[Allies of World War II|Allied forces]] prevented Germany from producing helicopters in large quantities during the war.
[[File:Sikorsky R-4 USAAF.jpg|thumb|The [[Sikorsky R-4]] became the first mass-produced helicopter in the early 1940s, and was capable of vertical takeoff. It performed the first [[medevac]] flights during WW2.]]
In the United States, Russian-born engineer [[Igor Sikorsky]] and [[Wynn Laurence LePage]] competed to produce the U.S. military's first helicopter. LePage received the [[patent]] rights to develop helicopters patterned after the Fw 61, and built the [[Platt-Le Page XR-1|XR-1]]<ref name="Francillon">Francillon 1997</ref> in 1941. Meanwhile, Sikorsky settled on a simpler, single-rotor design, the [[VS-300]] of 1939, which turned out to be the first practical single lifting-rotor helicopter design. After experimenting with configurations to counteract the torque produced by the single main rotor, Sikorsky settled on a single, smaller rotor mounted on the tail boom.{{citation needed|date=December 2023}}
Developed from the VS-300, Sikorsky's [[Sikorsky R-4|R-4]] of 1942 was the first large-scale mass-produced helicopter, with a production order for 100 aircraft. The R-4 was the only Allied helicopter to serve in World War II, used primarily for [[search and rescue]] (by the [[USAAF]] [[1st Special Operations Wing#1st Air Commando Group|1st Air Commando Group]]) in the [[Burma campaign]];<ref>{{Cite web|url=https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/195868/sikorsky-r-4b-hoverfly/|archive-url=https://web.archive.org/web/20131203125840/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=518|url-status=live|title=Sikorsky R-4B Hoverfly|archive-date=3 December 2013}}</ref> in Alaska; and in other areas with harsh terrain. Total production reached 131 helicopters before the R-4 was replaced by other Sikorsky helicopters such as the [[Sikorsky H-5|R-5]] and the [[Sikorsky R-6|R-6]]. In all, Sikorsky produced over 400 helicopters before the end of World War II.<ref name="Day">Day, Dwayne A. [http://www.centennialofflight.net/essay/Rotary/Sikorsky_VS300/HE8.htm "Igor Sikorsky – VS 300"]. {{Webarchive |url=https://web.archive.org/web/20140220013543/http://www.centennialofflight.net/essay/Rotary/Sikorsky_VS300/HE8.htm |date=20 February 2014}} ''Centennial of Flight Commission'', 2003. Retrieved 9 December 2007.</ref>
While LePage and Sikorsky built their helicopters for the military, [[Bell Aircraft]] hired [[Arthur M. Young|Arthur Young]] to help build a helicopter using Young's two-blade [[teetering rotor]] design, which used a weighted [[stabilizer bar (helicopter)|stabilizer bar]] placed at a 90° angle to the rotor blades. The subsequent [[Bell 30|Model 30]] helicopter of 1943 showed the design's simplicity and ease of use. The Model 30 was developed into the [[Bell 47]] of 1945, which became the first helicopter certified for civilian use in the United States (March 1946). Produced in several countries, the Bell 47 was the most popular helicopter model for nearly 30 years.{{citation needed|date=December 2023}}
===Turbine age===
{{see also|Gas turbine|turboshaft}}
[[File:C-GAWW CZNL 2-13-2008 AerospatialeSA315B (cropped).jpg|thumb|A turbine powered helicopter with its engine visible]]
In 1951, at the urging of his contacts at the Department of the Navy, [[Charles Kaman]] modified his [[Kaman K-225|K-225]] [[synchropter]]—a design for a twin-rotor helicopter concept first pioneered by [[Anton Flettner]] in 1939, with the aforementioned [[Flettner Fl 265|Fl 265]] piston-engined design in Germany—with a new kind of engine, the [[turboshaft]] engine. This adaptation of the [[gas turbine|turbine engine]] provided a large amount of power to Kaman's helicopter with a lower weight penalty than piston engines, with their heavy engine blocks and auxiliary components. On 11{{nbsp}}December 1951, the [[Kaman Aircraft|Kaman]] 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.<ref>[https://books.google.com/books?id=Zt4DAAAAMBAJ&dq=1954+Popular+Mechanics+January&pg=PA139 "Twin Turborotor Helicopter"]. {{Webarchive |url=https://web.archive.org/web/20150915141300/https://books.google.com/books?id=Zt4DAAAAMBAJ&pg=PA139&dq=1954+Popular+Mechanics+January&hl=en&sa=X&ei=twghT4yjN4_tggfElaX9CA&ved=0CEAQ6AEwBA#v=onepage&q=1954%20Popular%20Mechanics%20January&f=true |date=15 September 2015}} ''Popular Mechanics'', August 1954, p. 139.</ref> However, it was the [[Sud Aviation]] [[Aérospatiale Alouette II|Alouette II]] that would become the first helicopter to be produced with a turbine-engine.<ref name="Connor-1">{{cite web |last1=Connor|first1=R.D |first2=R.E. |last2=Lee |title=Kaman K-225 |publisher=[[Smithsonian National Air and Space Museum]] |date=27 July 2001 |access-date=9 December 2007 |url=http://www.nasm.si.edu/research/aero/aircraft/kamen_k225.htm |archive-url=https://web.archive.org/web/20080101194948/http://www.nasm.si.edu/research/aero/aircraft/kamen_k225.htm |archive-date=1 January 2008}}</ref>
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]] 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.{{citation needed|date=December 2023}}
==Safety==
===Maximum speed limit===
[[File:Russian Air Force Kamov Ka-50.jpg|thumb|A [[Russian Air Force]] [[Kamov Ka-50]] using a coaxial rotor system]]
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 rotational speed. 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 speed. 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]], and thus produce vastly increased [[wave drag|drag]] and vibration.{{citation needed|date=December 2023}}
At the same time, the advancing blade creates more lift traveling forward, the retreating blade produces less lift. If the aircraft were to accelerate to the air speed that the blade tips are spinning, the retreating blade passes through air moving at the same speed of the blade and produces no lift at all, resulting in very high torque stresses on the central shaft that can tip down the retreating-blade side of the vehicle, and cause a loss of control. Dual counter-rotating blades prevent this situation due to having two advancing and two retreating blades with balanced forces.{{citation needed|date=December 2023}}
[[File:British Lynx landing on Kearsarge.jpg|thumb|left|The Lynx helicopter is noted for its speed]]
Because the advancing blade has higher airspeed than the retreating blade and generates a [[dissymmetry of lift]], 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|V<sub>NE</sub>]], ''velocity, never exceed''.<ref>''Rotorcraft Flying Handbook'' 2007, pp. 3–7.</ref> 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.{{citation needed|date=December 2023}}
===Noise===
At the end of the 20th century, designers began working on [[helicopter noise reduction]]. Urban communities have often expressed great dislike of noisy aviation or noisy aircraft, and police and passenger helicopters can be unpopular because of the sound. The redesigns followed the closure of some city [[heliport]]s and government action to constrain flight paths in [[national parks]] and other places of natural beauty.{{citation needed|date=December 2023}}
===Vibration===
[[File:Future SMART Rotor Blades.jpg|thumb|NASA experiment for piezoelectric rotor blades to potentially reduce the noise and vibration]]
To reduce vibration, all helicopters have rotor adjustments for height and weight. A maladjusted helicopter can easily vibrate so much that it will shake itself apart. 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]] to counter the vibration. Adjustment can be 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. [[Health and usage monitoring systems|Health and Usage Monitoring Systems]] (HUMS) provide vibration monitoring and rotor track and balance solutions to limit vibration.<ref>{{Cite web |title=HUMS: Not Just for Heavy Iron Anymore |url=https://www.rotor.org/resource?ArtMID=493&ArticleID=7434 |access-date=2020-12-03 |website=Helicopter Association International |language=en-US |archive-date=19 September 2020 |archive-url=https://web.archive.org/web/20200919213805/https://www.rotor.org/resource?ArtMID=493&ArticleID=7434 |url-status=dead }}</ref> 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 effects are pain, numbness, and loss of tactile discrimination or dexterity.{{citation needed|date=December 2023}}
===Loss of tail-rotor effectiveness===
For a standard helicopter with a single main rotor, the tips of the main rotor blades produce a vortex ring in the air, which is a spiraling and circularly rotating airflow. As the craft moves forward, these vortices trail off behind the craft.{{citation needed|date=December 2023}}
When hovering with a forward diagonal crosswind, or moving in a forward diagonal direction, the spinning vortices trailing off the main rotor blades will align with the rotation of the tail rotor and cause an instability in flight control.<ref>[http://www.dynamicflight.com/aerodynamics/loss_tail_eff/ Loss of Tail Rotor Effectiveness] {{Webarchive |url=https://web.archive.org/web/20160604164023/http://www.dynamicflight.com/aerodynamics/loss_tail_eff/ |date=4 June 2016}}, Dynamic Flight Inc. Accessed 11 May 2016.</ref>
When the trailing vortices colliding with the tail rotor are rotating in the same direction, this causes a loss of thrust from the tail rotor. When the trailing vortices rotate in the opposite direction of the tail rotor, thrust is increased. Use of the foot pedals is required to adjust the tail rotor's angle of attack, to compensate for these instabilities.{{citation needed|date=December 2023}}
These issues are due to the exposed tail rotor cutting through open air around the rear of the vehicle. This issue disappears when the tail is instead ducted, using an internal impeller enclosed in the tail and a jet of high pressure air sideways out of the tail, as the main rotor vortices can not impact the operation of an internal impeller.{{citation needed|date=December 2023}}
===Critical wind azimuth===
For a standard helicopter with a single main rotor, maintaining steady flight with a crosswind presents an additional flight control problem, where strong crosswinds from certain angles will increase or decrease lift from the main rotors. This effect is also triggered in a no-wind condition when moving the craft diagonally in various directions, depending on the direction of main rotor rotation.<ref>[http://www.helicopterflight.net/pedalturns.php Helicopter pedal turns, LTE and the Critical Wind Azimuth] {{Webarchive |url=https://web.archive.org/web/20160604114600/http://www.helicopterflight.net/pedalturns.php |date=4 June 2016}}, Helicopter Flight Inc, Accessed 11 May 2016.</ref>
This can lead to a loss of control and a crash or hard landing when operating at low altitudes, due to the sudden unexpected loss of lift, and insufficient time and distance available to recover.{{citation needed|date=December 2023}}
===Transmission===
Conventional rotary-wing aircraft use a set of complex mechanical gearboxes to convert the high rotation speed of gas turbines into the low speed required to drive main and tail rotors. Unlike powerplants, mechanical gearboxes cannot be duplicated (for redundancy) and have always been a major weak point in helicopter reliability. In-flight catastrophic gear failures often result in gearbox jamming and subsequent fatalities, whereas loss of lubrication can trigger onboard fire.{{citation needed|date=May 2013}} Another weakness of mechanical gearboxes is their transient power limitation, due to structural fatigue limits. Recent EASA studies point to engines and transmissions as prime cause of crashes just after pilot errors.<ref>{{cite web |url=https://www.easa.europa.eu/communications/docs/annual-safety-review/2011/EASA-Annual-Safety-Review-2011.pdf |title=EASA-Annual-Safety-Review-2011 |access-date=18 May 2013 |archive-url=https://web.archive.org/web/20140324201049/https://www.easa.europa.eu/communications/docs/annual-safety-review/2011/EASA-Annual-Safety-Review-2011.pdf |archive-date=24 March 2014 |url-status=live}}</ref>
By contrast, electromagnetic transmissions do not use any parts in contact; hence lubrication can be drastically simplified, or eliminated. Their inherent redundancy offers good resilience to single point of failure. The absence of gears enables high power transient without impact on service life. The concept of electric propulsion applied to helicopter and electromagnetic drive was brought to reality by [[Pascal Chretien]] who designed, built and flew world's first man-carrying, free-flying electric helicopter. The concept was taken from the conceptual [[computer-aided design]] model on 10 September 2010 to the first testing at 30% power on 1 March 2011 – less than six months. The aircraft first flew on 12 August 2011. All development was conducted in Venelles, France.<ref>{{cite web |url=http://www.idtechex.com/events/presentations/challenges-of-aircraft-hybridization-003998.asp |title=Challenges of Aircraft Hybridization |publisher=IDTechEx |access-date=29 April 2013 |archive-url=https://web.archive.org/web/20140324185730/http://www.idtechex.com/events/presentations/challenges-of-aircraft-hybridization-003998.asp |archive-date=24 March 2014 |url-status=live}}</ref><ref>{{cite web |url=https://vtol.org/store/product/vertiflite-marchapril-2012-6058.cfm |title=Vertiflite, March/April 2012 – AHS Online Store |publisher=Vtol.org |access-date=28 April 2013 |archive-url=https://web.archive.org/web/20140324191016/https://vtol.org/store/product/vertiflite-marchapril-2012-6058.cfm |archive-date=24 March 2014 |url-status=live}}</ref>
===Hazards===
[[File:Helicopter crash 2011 zuoz.jpg|thumb|A [[Eurocopter AS350 Écureuil|Eurocopter AS350]], destroyed after its main rotor struck the side of a mountain while at low altitude]]
As with any moving vehicle, unsafe operation could result in loss of control, structural damage, or loss of life. The following is a list of some of the potential hazards for helicopters:
* [[Settling with power]] is when the aircraft has insufficient power to arrest its descent. This hazard can develop into vortex ring state if not corrected early.<ref name="dtic.mil">{{Cite web |url=http://apps.dtic.mil/dtic/tr/fulltext/u2/a526709.pdf |title=Model for Vortex Ring State Influence on Rotorcraft Flight Dynamics |access-date=22 February 2014 |archive-url=https://web.archive.org/web/20140225210121/http://www.dtic.mil/dtic/tr/fulltext/u2/a526709.pdf |archive-date=25 February 2014 |url-status=live}}</ref>
* [[Vortex ring]] state is a hazard induced by a combination of low airspeed, high power setting, and high descent rate. Rotor-tip vortices circulate from the high pressure air below the rotor disk to low pressure air above the disk, so that the helicopter settles into its own descending airflow.<ref name="dtic.mil"/> Adding more power increases the rate of air circulation and aggravates the situation. It is sometimes confused with settling with power, but they are aerodynamically different.
* [[Retreating blade stall]] is experienced during high speed flight and is the most common limiting factor of a helicopter's forward speed.
* [[Ground resonance]] is a self-reinforcing vibration that occurs when the lead/lag spacing of the blades of an [[Helicopter rotor#Fully articulated|articulated rotor system]] becomes irregular.
* [[Low-G condition]] is an abrupt change from a positive G-force state to a negative G-force state that results in loss of lift (unloaded disc) and subsequent roll over. If aft cyclic is applied while the disc is unloaded, the main rotor could strike the tail causing catastrophic failure.<ref>{{cite web |url=http://www.robinsonheli.com/service_library/safety_notices/rhc_sn11.pdf |title=Safety Notice SN-11 |date=October 1982 |publisher=[[Robinson Helicopter Company]] |access-date=22 February 2014 |url-status=dead |archive-url=https://web.archive.org/web/20130811223224/http://robinsonheli.com/service_library/safety_notices/rhc_sn11.pdf |archive-date=11 August 2013 |df=dmy-all}}</ref>
* [[Dynamic rollover]] in which the helicopter pivots around one of the skids and 'pulls' itself onto its side (almost like a fixed-wing aircraft [[Ground loop (aviation)|ground loop]]).
* [[Powertrain]] failures, especially those that occur within the shaded area of the [[height-velocity diagram]].
* 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 (aviation)|Brownout]] in dusty conditions or [[whiteout (weather)|whiteout]] in snowy conditions.
* Low rotor RPM, is when 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.<ref>[http://www.kauaihelicoptertoursafety.com "Helicopter Accidents in Hawaii"]. {{Webarchive |url=https://web.archive.org/web/20160110060633/http://kauaihelicoptertoursafety.com/ |date=10 January 2016}} ''kauaihelicoptertoursafety.com''. Retrieved: 12 December 2010.</ref>
* [[Controlled flight into terrain]] in which the aircraft is flown into the ground unintentionally due to a lack of situational awareness.
* Mast bumping in some helicopters<ref>FAA RFH, page 11-10</ref>
===List of fatal crashes===
{| class="wikitable sortable"
|+ Deadliest helicopter crashes by death toll
|-
!Date !!Operator !!Aircraft !!Event and ___location !!Death toll
|-
|19 August 2002 ||Russia ||[[Mil Mi-26]] ||[[2002 Khankala Mi-26 crash|Shot down over Chechnya]] || 127<ref>{{cite web |url=https://www.theguardian.com/world/2004/apr/30/russia.chechnya |title=Chechen gets life for killing 127 Russian soldiers |publisher=theguardian.com |date=30 April 2004 |accessdate=12 November 2021 |archive-date=22 January 2018 |archive-url=https://web.archive.org/web/20180122181633/https://www.theguardian.com/world/2004/apr/30/russia.chechnya |url-status=live }}</ref>
|-
|9 December 1982 ||Nicaragua ||[[Mil Mi-8]]
|Shot down by Sandinistan rebels while carrying 88 people. All 84 passengers were killed and all four crew members survived.<ref name="1982 Nicaragua Mi-8 crash">{{cite web |title=Accident Details (1982 Nicaragua Mi-8 crash) |url=http://www.planecrashinfo.com/1982/1982-64.htm |publisher=PlaneCrashInfo.com |access-date=13 April 2018 |archive-url=https://web.archive.org/web/20171129175458/http://planecrashinfo.com/1982/1982-64.htm |archive-date=29 November 2017 |url-status=dead }}</ref>
|84
|-
|4 February 1997 ||Israel ||[[Sikorsky CH-53 Sea Stallion]] (x2) ||[[1997 Israeli helicopter disaster|Collision over Israel]] ||73
|-
|14 December 1992 ||Russia (Russian Air Force) ||Mil Mi-8
|Shot down by Georgian forces in Abkhazia using [[SA-14]] MANPADs, despite heavy escort. Three crew and 58 passengers, composed of mainly Russian refugees.<ref name="acig.org">{{cite web |last=Cooper |first=Tom |title=Georgia and Abkhazia, 1992–1993: the War of Datchas. |publisher=acig.org |date=29 September 2003 |url=http://www.acig.org/artman/publish/article_282.shtml |access-date=12 December 2010 |archive-url=https://web.archive.org/web/20080303054854/http://www.acig.org/artman/publish/article_282.shtml |archive-date=3 March 2008 |url-status=usurped}}</ref>
|61
|-
|4 October 1993 ||Georgia ||Mil Mi-8
|Shot down when transporting 60 refugees from eastern Abkhazia; all on board were killed.<ref name="acig.org"/>{{Failed verification|date=May 2021}}
|60
|-
|10 May 1977 ||Israel ||CH-53 ||[[1977 Israeli CH-53 crash|Crash]] near [[Yitav]] in the [[Jordan Valley (Middle East)|Jordan Valley]] ||54
|-
|8 January 1968
|United States
|[[Sikorsky CH-53 Sea Stallion|Sikorsky CH-53A Sea Stallion]], USMC
|Crash near [[Đông Hà Combat Base]] in [[South Vietnam]]. All five crew and 41 passengers were killed.
|46<ref>{{cite web|url=https://aviation-safety.net/wikibase/wiki.php?id=76027|title=ASN Wikibase Occurrence #76027|publisher=Aviation Safety Network|access-date=4 October 2017|archive-date=4 October 2017|archive-url=https://web.archive.org/web/20171004135725/https://aviation-safety.net/wikibase/wiki.php?id=76027|url-status=live}}</ref>
|-
|11 July 1972
|United States
|[[Sikorsky CH-53 Sea Stallion|Sikorsky CH-53D Sea Stallion]], USMC
|Shot down by missile near [[Quảng Trị]] in South Vietnam. Six U.S. Marines and 50 Vietnamese Marines on board. Three U.S. Marines and 43 Vietnamese Marines were killed.
|46<ref>{{cite news |title=Incident Date 19720711 HMM-165 CH-53D 156658+ – Hostile Fire |publisher=Marine Corps Combat Helicopter Association (via popasmoke) |url=http://www.popasmoke.com/kia/conflicts/usmc-reserve/incidents/19720711 |access-date=9 February 2020}}</ref>
|-
|11 September 1982||United States ||[[Boeing CH-47 Chinook]], [[U.S. Army]]||Crash at an air show in [[Mannheim]], then located in [[West Germany]]. ||46<ref>{{cite news |title=Crash Death, 3rd in 8 Years, Not Expected to Halt Future Shows |work=[[Los Angeles Times]] |date=3 May 1993 |url=https://www.latimes.com/archives/la-xpm-1993-05-03-mn-30665-story.html |access-date=12 December 2010 |archive-url=https://web.archive.org/web/20101206162405/http://articles.latimes.com/1993-05-03/news/mn-30665_1_paris-air-show |archive-date=6 December 2010 |url-status=live}}</ref>
|-
|6 November 1986||[[British International Helicopters]]||[[Boeing CH-47 Chinook|Boeing 234LR Chinook]]
|[[1986 British International Helicopters Chinook crash|Crash]] in the [[Shetland Islands]]||45
|-
|28 January 1992 ||Azerbaijan ||Mil Mi-8 ||[[1992 Azerbaijani Mil Mi-8 shootdown|Shootdown]] ||44
|-
|3 July 2009 ||Pakistan (Pakistan Army)|| Mil Mi-17 ||[[2009 Pakistan Army Mil Mi-17 crash|Crash]] ||41
|-
|6 August 2011 ||United States ||CH-47 Chinook
||[[2011 Chinook shootdown in Afghanistan|Shootdown]], Afghanistan ||38<ref>{{cite news |title=31 U.S. troops, 7 Afghans killed as insurgents down NATO chopper |newspaper=Los Angeles Times |date=6 August 2011 |url=http://www.latimes.com/news/nationworld/world/la-fgw-afghan-chopper-20110807,0,7157351.story |access-date=6 August 2011 |archive-url=https://web.archive.org/web/20110807062653/http://www.latimes.com/news/nationworld/world/la-fgw-afghan-chopper-20110807,0,7157351.story |archive-date=7 August 2011 |url-status=live}}</ref>
|-
|18 August 1971
|United States
|CH-47 Chinook, U.S. Army
|Crash near [[Pegnitz (town)|Pegnitz]], then located in West Germany. All four crew and 33 passengers were killed.
|37<ref>{{cite web|url=https://www.dvidshub.net/news/139975/2nd-battalion-4th-infantry-regiment-honors-33-their-own|title=2nd Battalion, 4th Infantry Regiment honors 33 of their own|publisher=dvids|access-date=10 February 2020|archive-date=12 August 2020|archive-url=https://web.archive.org/web/20200812012422/https://www.dvidshub.net/news/139975/2nd-battalion-4th-infantry-regiment-honors-33-their-own|url-status=live}}</ref>
|-
|26 January 2005 ||United States ||[[Sikorsky CH-53E Super Stallion]], USMC ||[[2005 Al-Anbar CH-53E crash|Crash landed]] near [[Ar Rutbah]], [[Iraq]]||31<ref>{{cite news |title=Incident Date 050126 HMH-361 CH-53D – BuNo unknown – incident not yet classified – near Ar Rutbah, Iraq. |publisher=Marine Corps Combat Helicopter Association (via popasmoke) |date=20 November 2007 |url=http://www.popasmoke.com/kia/incidents.php?incident_id=278&conflict_id=32 |access-date=12 December 2010 |archive-url=https://web.archive.org/web/20100702061200/http://www.popasmoke.com/kia/incidents.php?incident_id=278&conflict_id=32 |archive-date=2 July 2010 |url-status=live}}</ref>
|-
|}
==World records==
<!-- for readability, this section is best left in list form -->
{| class="wikitable sortable" style="margin: 1em auto;"
|-
! Record type !! Record !! Helicopter !! Pilot(s) !! Date !! Location !! Note !! Ref.
|-
| Speed || {{convert|400.87|km/h|abbr=on}}|| [[Westland Lynx]] || John Trevor Egginton (UK) || 11 August 1986 || UK || ||<ref>{{cite web |url=http://www.fai.org/fai-record-file/?recordId=11659 |title=Record File n°11659 |work=[[Fédération Aéronautique Internationale]] |access-date=5 June 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131203033038/http://www.fai.org/fai-record-file/?recordId=11659 |archive-date=3 December 2013 |df=dmy-all}}</ref>
|-
| Distance without landing || {{convert|3561.55|km|abbr=on}}|| [[Hughes OH-6 Cayuse|Hughes YOH-6A]] || Robert G. Ferry (USA) || 6 April 1966 || United States || ||<ref>{{cite web |url=http://www.fai.org/fai-record-file/?recordId=784 |title=Record File n°784 |work=[[Fédération Aéronautique Internationale]] |access-date=5 June 2013 |url-status=dead |archive-url=https://web.archive.org/web/20150105132908/http://www.fai.org/fai-record-file/?recordId=784 |archive-date=5 January 2015 |df=dmy-all}}</ref>
|-
| Around-the-world speed || {{convert|136.7|km/h|abbr=on}}|| [[AgustaWestland AW109|Agusta A109S Grand]] || Scott Kasprowicz (USA) || 18 August 2008 || From and to [[New York City]] <br />via Europe, Russia, Alaska, Canada || No in-flight refueling ||<ref>{{cite web |url=http://www.fai.org/fai-record-file/?recordId=15171 |title=Record File n°15171 |work=[[Fédération Aéronautique Internationale]] |access-date=5 June 2013 |url-status=dead |archive-url=https://web.archive.org/web/20150105140347/http://www.fai.org/fai-record-file/?recordId=15171 |archive-date=5 January 2015 |df=dmy-all}}</ref>
|-
| Highest altitude without payload || {{convert|12442|m|abbr=on}}|| [[Aerospatiale Lama]] || [[Jean Boulet]] (France) || 21 June 1972 || [[France]] || || <ref>{{cite web |url=http://www.fai.org/fai-record-file/?recordId=754 |title=Record File n°754 |work=[[Fédération Aéronautique Internationale]] |access-date=10 September 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131203031025/http://www.fai.org/fai-record-file/?recordId=754 |archive-date=3 December 2013 |df=dmy-all}}</ref>
|-
| Highest level flight altitude || {{convert|11010|m|abbr=on}}|| [[Sikorsky CH-54 Tarhe]] || James K. Church || 4 November 1971 || United States || ||<ref>{{cite web |url=http://www.fai.org/fai-record-file/?recordId=9918 |title=Record File n°9918 |work=[[Fédération Aéronautique Internationale]] |access-date=5 June 2013 |url-status=dead |archive-url=https://web.archive.org/web/20150105140344/http://www.fai.org/fai-record-file/?recordId=9918 |archive-date=5 January 2015 |df=dmy-all}}</ref>
|-
| Altitude with 40-[[tonne]] [[Payload (air and space craft)|payload]] || {{convert|2255|m|abbr=on}}|| [[Mil V-12]] || Vasily Kolochenko, et al. || 6 August 1969 || [[Soviet Union|USSR]] || ||<ref>{{cite web |url=http://www.fai.org/fai-record-file/?recordId=9917 |title=Record File n°9917 |work=[[Fédération Aéronautique Internationale]] |access-date=5 June 2013 |url-status=dead |archive-url=https://web.archive.org/web/20150105134839/http://www.fai.org/fai-record-file/?recordId=9917 |archive-date=5 January 2015 |df=dmy-all}}</ref>
|-
| Highest takeoff (turbine) || {{convert|8848|m|abbr=on}}|| [[Eurocopter AS350]] || Didier Delsalle || 14 May 2005 || [[Nepal]] || Mount Everest ||<ref>{{cite web |url=http://www.fai.org/fai-record-file/?recordId=11597 |title=Record File n°11597 |work=[[Fédération Aéronautique Internationale]] |access-date=17 August 2012 |url-status=dead |archive-url=https://web.archive.org/web/20150105141219/http://www.fai.org/fai-record-file/?recordId=11597 |archive-date=5 January 2015 |df=dmy-all}}</ref>
|-
| Highest takeoff (piston) || {{convert|4300.7|m|abbr=on}}|| [[Robinson R44]] || Mark Young || 12 October 2009 || United States || Pike's Peak, Colorado||<ref>{{cite web |url=http://www.fai.org/fai-record-file/?recordId=15629 |title=Record File n°15629 |work=[[Fédération Aéronautique Internationale]] |access-date=17 August 2012 |url-status=dead |archive-url=https://web.archive.org/web/20150105141222/http://www.fai.org/fai-record-file/?recordId=15629 |archive-date=5 January 2015 |df=dmy-all}}</ref>
|-
| First manned electric flight|| Purely electric hover|| [[Solution F/Chretien Helicopter|Solution F Prototype]] || Pascal Chretien || 12 August 2011 || [[France]] || Venelles ||<ref>{{cite web |url=http://www.guinnessworldrecords.com/world-records/9000/First-electric-helicopter |title=First electric helicopter |work=[[Guinness World Record]] |date=4 August 2011 |access-date=4 August 2011 |archive-url=https://web.archive.org/web/20140417005553/http://www.guinnessworldrecords.com/world-records/9000/First-electric-helicopter/ |archive-date=17 April 2014 |url-status=live}}</ref>
|-
| Longest human-powered lift || Pedalling, lift 64 s endurance, 3.3 m height; diagonal width: 46.9 m || [[AeroVelo Atlas]], 4 rotors || Todd Reichert || 13 June 2013 || [[Canada]] || Indoor soccer stadium; [[Igor I. Sikorsky Human Powered Helicopter Competition|Igor I. Sikorsky Competition]] winner ||<ref>{{cite web |url=http://road.cc/content/news/87980-video-canadians-win-long-unclaimed-250000-prize-pedal-powered-helicopter |title=Video: Canadians win long-unclaimed $250,000 prize for pedal-powered helicopter |date=22 July 2013 |work=John Stevenson |access-date=6 February 2014 |archive-url=https://web.archive.org/web/20140307234210/http://road.cc/content/news/87980-video-canadians-win-long-unclaimed-250000-prize-pedal-powered-helicopter |archive-date=7 March 2014 |url-status=live}}</ref>
|}
==See also==
{{Portal|Aviation}}
[[File:RAF Merlin HC3A Helicopter of No28 Sqn MOD 45154033.jpg|thumb|RAF Merlin HC3A Helicopter]]
{{Columns-list|colwidth=30em|
* [[Attack helicopter]]
* [[Backpack helicopter]]
* [[Cyclogyro]]
* [[Disk loading]]
* [[Helicopter dynamics]]
* [[Helicopter height–velocity diagram]]
* [[Helicopter manufacturer]]
* [[Helicopter Underwater Escape Training]]
* [[Jesus nut]], the top central big nut that holds the rotor on<!-- NOTE: this is a legitimate term — read linked article for description -->
* [[List of helicopter airlines]]
* [[List of rotorcraft]]
* [[Transverse flow effect]]
* [[Utility helicopter]]
* [[Wire strike protection system]]
* [[Tiltrotor]]
}}
==References==
==
{{Reflist|group=n}}
===Footnotes===
{{Reflist}}
===Bibliography===
{{refbegin}}
* Chiles, James R. ''The God Machine: From Boomerangs to Black Hawks: The Story of the Helicopter''. New York: Bantam Books, 2007. {{ISBN|0-553-80447-2}}.
* Cottez, Henri. ''Dictionnaire des structures du vocabulaire savant''. Paris: Les Usuels du Robert. 1980. {{ISBN|0-85177-827-5}}.
* Francillon, René J. ''McDonnell Douglas Aircraft since 1920: Volume II''. London: Putnam, 1997. {{ISBN|0-85177-827-5}}.
* Frawley, Gerard. ''The International Directory of Civil Aircraft, 2003–2004''. Fyshwick, Canberra, Act, Australia: Aerospace Publications Pty Ltd., 2003, p. 155. {{ISBN|1-875671-58-7}}.
* Munson, Kenneth. ''Helicopters and other Rotorcraft since 1907''. London: Blandford Publishing, 1968. {{ISBN|978-0-7137-0493-8}}.
* [http://www.faa.gov/library/manuals/aircraft/ ''Rotorcraft Flying Handbook'']. Washington: Skyhorse Publishing, Inc., 2007. {{ISBN|1-60239-060-6}}.
* [https://web.archive.org/web/20110606223247/http://www.faa.gov/library/manuals/aircraft/media/faa-h-8083-21.pdf ''Rotorcraft Flying Handbook: FAA Manual H-8083-21'']. Washington, D.C.: Federal Aviation Administration (Flight Standards Division), U.S. Dept. of Transportation, 2001. {{ISBN|1-56027-404-2}}.
* Thicknesse, P. ''Military Rotorcraft'' (Brassey's World Military Technology series). London: Brassey's, 2000. {{ISBN|1-85753-325-9}}.
* Watkinson, John. Art of the Helicopter. Oxford: Elsevier Butterworth-Heinemann, 2004. {{ISBN|0-7506-5715-4}}
* Wragg, David W. ''Helicopters at War: A Pictorial History''. London: R. Hale, 1983. {{ISBN|0-7090-0858-9}}.
* [[Engelbert Zaschka|Zaschka, Engelbert]]. ''Drehflügelflugzeuge. Trag- und Hubschrauber''. Berlin-Charlottenburg: C. J. E. Volckmann Nachf. E. Wette, 1936. {{OCLC|20483709}}.
{{refend}}
==External links==
{{Commons category|Helicopters}}
{{Wiktionary|helicopter}}
* [http://www.helicopterpage.com "Helicopterpage.com – How Helicopters Work"] Complete site explaining different aspects of helicopters and how they work.
* [https://books.google.com/books?id=IikDAAAAMBAJ&dq=Popular+Science+1932+plane&pg=PA13 "Planes That Go Straight Up"]. 1935 article about early development and research into helicopters.
* [https://books.google.com/books?id=EikDAAAAMBAJ&pg=PA58 "Flights — of the Imagination"]. 1918 article on helicopter design concepts.
* [https://books.google.com/books?id=lNsDAAAAMBAJ&dq=Popular+Science+1936+plane+%22Popular+Mechanics%22&pg=PA577 "Twin Windmill Blades Fly Wingless Ship"] ''Popular Mechanics'', April 1936
* [https://www.youtube.com/watch?v=rx565dqF-5M&t=103s Silent (Russian-language intertitled) video about the Cheremukhin/Yuriev TsAGI 1-EA pioneer helicopter]
* [http://www.vtol.org American Helicopter Society]
* {{cite news |url= http://aviationweek.com/vertical-flight/how-helicopter-has-developed |title= How The Helicopter Has Developed |at= Getting from idea to reality took far longer for the helicopter than for the fixed-wing aircraft |date= 17 June 2016 |author= Graham Warwick |work= Aviation Week & Space Technology}}
{{Aircraft types (by method of thrust and lift)}}
{{Gyrodyne}}
{{
[[Category:Helicopters| ]]
[[Category:Aircraft configurations]]
[[Category:Articles containing video clips]]
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