A helicopter or helicopters is a vertical takeoff and landing aircraft , the engine power to one or more nearly horizontally disposed rotors for lift and propulsion transmits. These work as spinning wings or wings. Helicopters are thus among the rotary wing aircraft and are by far the most important representatives of this large group of aircraft. “Rotary wing” is also the analogous translation of the word helicopter, or heli for short , which is made up of ancient Greek ἕλιξ hélix ( Gen. ἕλικος hélikos ) “winding, spiral, screw” and πτερόν pterón “wing”.
The definition of the term helicopter is variable. In the broadest sense, helicopters and rotary wing aircraft are treated as synonyms. Usually, however, rotary wing aircraft without a powered main rotor, such as gyroscopes with their own propulsion rotors , are not counted among the helicopters. In the case of aircrafts that combine the properties of these two aircraft, the classification to the helicopters is inconsistent. Helicopters that also have rigid wings are called composite helicopters . Convertible aircraft do not count among the helicopters.
The principle of helical buoyancy was already known to the ancient Chinese, who had already used it 2,500 years ago in the “ flying top ” toy . Leonardo da Vinci had made sketches of a helicopter in his “ Paris Manuscripts ” around 1487–1490 , but it was not until the 20th century that this idea was technically implemented. Helicopter development pioneers include a. Jakob Degen , Étienne Œhmichen , Raúl Pateras Pescara , Oszkár Asbóth , Juan de la Cierva , Engelbert Zaschka , Louis Charles Breguet , Alberto Santos Dumont , Henrich Focke , Anton Flettner and Igor Sikorski .
As early as the 14th century, a toy called the "Chinese air top" was known in Europe and is still produced in a modified form today. It was a rotor-like structure made of raised bird feathers, which, when rotated, could soar vertically into the air like a helicopter. Leonardo da Vinci dealt with the helicopter in the 15th century and drew an aircraft that was to receive a drive in the manner of the Archimedean water screw. 1768 the French mathematician designed Alexis Jean-Pierre Paucton the first concept, Pterophore called for a human-powered helicopter with two separate for lift and thrust rotors competent. In 1783 the French naturalist Christian de Launoy and his mechanic Bienvenu built a coaxial version of the Chinese air gyro. The British engineer George Cayley designed a similar construction .
In the 18th and 19th centuries there were a multitude of ideas for helicopter-like aircraft. So designed Mikhail Lomonosov , a model helicopter with coaxial rotors for atmospheric research. The Austrian master watchmaker Jakob Degen also experimented with coaxial models and used a clockwork as a drive. Around 1825 the Englishman David Mayer built a muscle-powered helicopter, and in 1828 the Italian Vittorio Sarti designed a helicopter with two three-bladed propellers. The American Robert Taylor completed his construction of the collective pitch control system in 1842 and offered it to the aviation pioneer Sir George Cayley . This adopted the Taylor concept for an aircraft with two side-mounted coaxial rotors and two propellers for propulsion. A steam engine was supposed to serve as the drive, but it turned out to be too heavy and doomed the project to failure. In 1861 Gustave de Ponton d'Amecourt received a patent for a coaxial rotor concept. Both were obviously aware of the need for torque compensation, which they took into account by using two main rotors rotating in opposite directions. In 1869, the Russian engineer Alexander Nikolajewitsch Lodygin submitted a concept for a helicopter with an electric motor to the Ministry of War. The model was already equipped with a main and a tail rotor. Around 1870 Alphonse Pénaud built coaxial helicopters with rubber band drives as children's toys. One of his toy airplanes is said to have inspired the Wright brothers. In 1874, Fritz and Wilhelm von Achenbach sketched a rotary wing aircraft with a main and tail rotor (the most common helicopter configuration today) that was to be powered by a steam engine. In 1877, the Italian Enrico Forlanini built a small unmanned 3.5 kg helicopter with steam drive and two coaxial rotors rotating in opposite directions . That summer he demonstrated this aircraft in a public park in Milan, flying for about 20 seconds and 13 meters high. Even Thomas Edison built in 1885 on behalf of James Gordon Bennett Jr. a helicopter due to heavy weight but not lifted off. Around 1890 Wilhelm Kress built an aircraft with coaxial rotors and determined the relationship between rotor diameter, power and lift.
In 1901 the first flight of a helicopter by Hermann Ganswindt took place in Berlin-Schöneberg . Since there were still no sufficiently powerful motors, Ganswindt used a falling weight that also drove the rotor via a rope. The helicopter only flew for a few seconds, but it took off with two people on board. A film by the Skladanowsky brothers from the event is missing. Since Ganswindt had installed a safety bar, he was therefore accused of fraud in 1902 and taken into custody for eight weeks. In the same year, a helicopter designed by Ján Bahý erreichte also reached an altitude of 50 cm.
On November 13, 1907, Paul Cornu lifted his 260 kg flying bicycle off the ground for 20 seconds. He used tandem rotors powered by a 24 hp V8 engine. This was the first documented free manned vertical flight, although the flight is doubted due to the low engine power. In that year, the brothers Louis Charles and Jacques Bréguet, in collaboration with Professor Charles Richet, also built the gyroplane No. 1 with four counter-rotating rotors, a 45 HP petrol engine and a take-off weight of 580 kg, which, however, could only fly vertically upwards.
In 1909, with the support of the Russian Ministry of War , Vladimir Valerianovich von Tatarinoff built the Tatarinow Aeromobile , which had a car-like shape with a front propeller and four lifting propellers mounted above the vehicle. The less promising construction was destroyed by the designer after public criticism.
In 1913, the Dresden engineer Otto Baumgärtel designed a vertical take-off aircraft that could move forward without a special propeller by shifting the center of gravity.
In 1916, the Dane Jakob Christian Ellehammer built a helicopter with coaxial rotors and a bow propeller, a self-constructed 6-cylinder radial engine with 36 hp and the first use of collective and cyclic blade adjustment. The Italian Gaetano Arturo Crocco proposed this technique in 1906. Ellehammer is thus the inventor of today's commonly used rotor control. After the crash and the destruction of the machine, he gave up development. The Rüb brothers in Stuttgart built another coaxial rotor in 1917, which, however, was unable to take off due to a lack of drive power.
Towards the end of the First World War , the designers Stephan Petróczy von Petrócz , Theodore von Kármán and Wilhelm Zurovec carried out successful flight tests on behalf of the Austro-Hungarian Army with the PKZ-1 and PKZ-2 screw tether planes named after them. Such vertically ascending aircraft were intended to replace the tethered balloons that had been used up until then for enemy observation. The PKZ-2 with a coaxial rotor and three motors with 120 HP power output each reached an altitude of around 50 m, which was a record at the time. The device crashed during a demonstration flight on June 10, 1918 in Fischamend . The end of the war prevented further development.
Between 1919 and 1922, Henry A. Berliner designed helicopters in the USA with both coaxial and side-by-side rotors. With both of them he undertook short-term free hovering flights.
During the development of his Autogiro in 1923 , Juan de la Cierva ( Spain ) found essential solutions for stabilizing the rotor of a rotary wing aircraft, e.g. B. the flapping joints . This concept was patented in the German Imperial Patent No. 249702 from 1912 by Max Bartha and Josef Madzsar in connection with the head tilt control for a coaxial rotor. In the same year, the then largest helicopter in the world, developed by George de Bothezat , flew in the USA with four rotors on booms and two additional smaller control rotors. It had a takeoff mass of 1600 kg and was powered by a 220 hp engine.
On April 18, 1924, the Pescara No. developed by Raúl Pateras Pescara improved . 3 doubled the world record for rotor aircraft set by Œhmichen four days earlier and used cyclical blade adjustment for the first time to use the main rotor for propulsion. Œhmichens helicopter had four adjustable main rotors, five propellers for stabilization, two propellers for propulsion, one propeller for steering and a 180-hp Gnôme engine as drive. Despite the first two officially recognized "world records" for helicopters, these complicated machines were a technical dead end.
In Germany, senior engineer Engelbert Zaschka developed a combined gyro and helicopter in 1927. In the development of Zaschka, in contrast to the gyroscopes and helicopters known up to that time, the rotors of the Zaschka rotary aircraft were inevitably connected to a rotating mass with two gyroscopes . The helicopter model therefore had an equilibrium control using a rotating mass ( kinetic energy ). This arrangement enabled a safe vertical gliding flight with the engine switched off .
Starting in 1925, Holländer AG von Baumhauer tried to implement the rotor arrangement that is common today, with one main and one tail rotor each. His helicopter had a main rotor about 15 m in diameter, which was powered by a 200 HP motor. He used a separate 80 hp motor to drive the tail rotor. The first flight took place in 1930, but development was discontinued after a main rotor blade broke. In the same year, the Belgian Nicholas Florine and the Italian Corradino D'Ascanio successfully tested their helicopters. Nicholas Florine's machine had a tandem rotor arrangement with two four-blade rotors 7.2 m in diameter and weighed approximately 950 kg. It was powered by a 220 hp Hispano Suiza engine and allowed hovering flights of up to ten minutes. The helicopter designed by D'Ascanio with coaxial rotors and three adjustable auxiliary propellers flew up to 1078 m, reached an altitude of 18 m and a flight time of nine minutes. Also in 1930, Raoul Hafner and Bruno Nagler built a helicopter in Austria . Although this even had a swash plate, control problems led to the abortion of the tests.
Between 1930 and 1935, Oszkár Asbóth in Hungary and Walter Rieseler in Germany experimented with helicopters with coaxial rotors, in which the controllability with tail units in the rotor downdraft should be improved.
In 1932, under the direction of Boris Nikolajewitsch Jurjew, the ZAGI 1-EA was developed in the Soviet Union with a main rotor and two control rotors at the bow and two at the stern. This had a take-off weight of 1200 kg and two engines with 120 hp each.
The rest of the 20th century
In the early 1930s, Louis Charles Breguet and René Dorand built the first helicopter to fly stable for a long time with the Gyroplane Laboratoire . It had coaxial rotors and from June 1935 held all international records for helicopters.
The Focke-Wulf Fw 61 , which used two laterally arranged rotors, broke a number of previous world records for helicopters on its maiden flight in June 1936. It was also the first helicopter to make an autorotation landing .
In the USA, the Sikorsky VS-300 , which took off for its first flight in 1939, was the first practically usable helicopter. This prototype became the model of the Sikorsky R-4 , which was built in series from 1942 .
In 1941 the German Focke-Achgelis Fa 223 was the first helicopter built in series, also with two rotors arranged on the side. This was followed in 1943 by the Flettner Fl 282 , also with a double rotor, and in 1944 by the Sikorsky R-4 "Hoverfly" in the USA, which, like its predecessor, the Sikorsky VS-300, used a single rotor together with a tail rotor .
In 1943, the Doblhoff WNF 342 was the first experimental helicopter to use a hot blade tip drive. The PV-1, also designed by Frank Piasecki and Harold Venzie in 1943, had a design without a tail rotor, similar to today's NOTAR technology. However, work on it was soon abandoned in favor of a tail rotor design.
On March 8, 1946, a construction of Got Arthur M. Young goes back Bell 47 of the Bell Aircraft Corporation , a light two or dreisitziger helicopter, the first civilian helicopter flight approval in the United States. Its variants were to be found around the world until the 1980s and beyond.
In 1955, the French company Sud Aviation equipped its Alouette II helicopter with a 250 kW Turbomeca Artouste shaft turbine and thus built the first helicopter with gas turbine propulsion , which is now used by almost all commercial manufacturers. Only Robinson Helicopters ( Robinson R22 and Robinson R44 ), Brantly ( Brantly B-2 or Brantly 305 ) and Sikorsky ( Schweizer 300C ) still manufacture helicopters with piston engines.
The German MBB BO 105 was founded in 1967 as the first helicopter with a hingeless rotor head with GRP - rotor blades for the first time in the Ka-26 Kamov had been used, equipped. The Eurocopter EC 135 as the current successor uses a further developed form, the so-called jointless and bearingless rotor head. There, the bearings for the blade angle adjustment were replaced by a twist control element made of glass fiber reinforced plastic with a control bag.
In 1968, the Soviet Mil Mi-12, the largest helicopter ever built, took off. It has rotors arranged next to each other, a maximum take-off weight of 105 t with a maximum payload of 40 t and 196 passenger seats . After three prototypes that set a number of records, production was stopped.
In 1975, the lightweight and inexpensive Robinson R22, which was built in large-scale production from 1979, made its maiden flight.
In 1977 the first flight of the largest series-produced helicopter took place, the Mil Mi-26 , which is still produced and used today.
From 1980, the Kamow Ka-50 "Hokum" was the first helicopter to be developed that was equipped with an ejection seat . Together with its further development, the Kamow Ka-52 Alligator , it is the only helicopter that has so far been equipped with an ejection seat. The rotor blades are automatically blown off when the ejector seat is activated.
Starting in 1983, the Boeing-Sikorsky RAH-66 Comanche was a combat helicopter with stealth technology , but its production was stopped shortly before it was ready for use in 2004 due to escalating costs.
In 1984 the Sikorsky X-wing flew for the first time , the rotor of which is stopped and locked during forward flight and then serves as an additional wing . As with other VTOL concepts, better flight performance should be achieved compared to pure rotary wing aircraft. However, it stayed with a prototype .
In 1989, the Da Vinci III was the first muscle power helicopter to lift off the ground for a few seconds - up to 20 cm high, with a pedal crank and single rotor, in California.
Test model of the Zaschka rotary aircraft , July 1928
Coaxial helicopter Gyroplane Laboratoire from 1935
Focke-Achgelis Fa 223 , the first helicopter to be built in series
Bell 47 , the first civil helicopter in the USA
Bell UH1-D / Bell 204 , most built helicopter family
BO 105 CBS-5, first helicopter with a hingeless rotor head
In August 2008, the Sikorsky X2 demonstrated in its maiden flight the suitability of the coaxial rotor, optimized using the latest methods, in combination with a pusher propeller - the principle of earlier gyroplanes . Two years later it achieved the development goal with 250 knots of True Airspeed (463 km / h) and exceeded the previous speed record by 15%. Other manufacturers also tried out similar new high-speed models, such as Eurocopter the X³ and Kamow the Ka-92 .
In October 2011, the Volocopter was the world's first manned flight with a purely electrically powered helicopter.
In 2011/2012/2013 different teams in the USA improved the performance indoors with 3 prototypes (Gamera (I), Gamera II and AeroVelo Atlas) of muscle power quadrocopters for one person. Most recently, the Atlas achieved a flight time of 64 seconds, a maximum altitude of 3.3 m and a drift of less than 10 m, and thus won the Sikorsky Prize.
Mil Mi-12 , largest helicopter in the world
Mil Mi-26 , the largest series-produced helicopter
Eurocopter X 3 , high-speed helicopter, ILA 2012 (world record)
The rotating rotor blades generate dynamic lift from the incoming air . As with the rigid wings of an aircraft, this is u. a. depending on their profile , the angle of attack and the (not constant over the blade length) air flow velocity, see main rotor .
When a helicopter moves forward, the approach velocity changes because the orbital velocity and the airspeed of the forward moving blade add up. When the sheet returns, they subtract, see also the sketch below .
Due to the aerodynamics of the rotor blades, asymmetrical forces arise during flight on the blades that are moved forwards and backwards, which in older models had to be absorbed by flapping and swivel joints on the attachment, the rotor head. Newer constructions do without these joints. In these newer models, the rotor head and blades consist of a compound of materials of different elasticity ( elastomers as well as high-strength and light metals such as titanium ), which can cope with the dynamic forces that are constantly changing in size and direction without damaging the components. Such a hinge-free rotor head was first realized in the Bölkow Bo 105 with blades made of glass fiber reinforced plastic and a solid rotor head made of titanium in combination with elastomers. In the case of the Eurocopter EC 135 , this was further developed into a bearingless rotor head , which has established itself in most models.
The cyclic (also rotationally periodic ) blade adjustment - generally also called blade control - is used to control the horizontal movement of the helicopter, which requires an inclination of the main rotor plane. To initiate or end forward, backward or sideways flight, the setting angles of the blades are changed (cyclically) during the rotation of the rotor . This leads to a cyclical flapping movement of the blades, so that their blade tips revolve on a plane that slopes in the intended direction. The lift remains constant over the entire orbit. Correspondingly, the rotor thrust that carries the helicopter and propels it forward is at right angles to the plane of the blade tips. The force that lifts vertically while hovering now receives a forward propulsive thrust due to this inclination . Due to the fuselage resistance, the entire helicopter and thus also its rotor shaft also tilt in the direction of flight.
If the center of gravity of the helicopter (with a suitable load) is in the extension of the rotor shaft, the thrust goes through the center of gravity with every steady journey. The blade tip plane is then at right angles to the rotor shaft and flapping movements do not take place. They are only available when the center of gravity is different or when the flight speed is to be changed.
With the collective pitch ( pitch ) of the pilot changes the angle of incidence of all the blades uniformly, resulting in the rise or fall of the helicopter. Simple constructions, for example with various electric drives in model helicopters , replace this control by changing the speed. The disadvantage here is the longer response time due to the inertia of the main rotor.
The rotor blades are usually controlled with a swash plate . The lower, fixed part is shifted up or down by the pilot with the help of the "collective" adjustment lever. With the "cyclic" control stick, it can be tilted in any direction. The upper part of the swash plate (which rotates with the rotor) transmits the required setting angle to the rotor blades via push rods and levers at the blade roots.
Rotor variants and yaw moment compensation
A distinction is made between single rotor systems, double rotors , triple rotors and machines with four ( quadrocopter ) or more rotors. With the exception of the blade tip drive , the rotors are always driven by a motor in the fuselage. This creates a counter -torque (yaw moment) on the rotor axis , which in the case of a single rotor would cause the fuselage to rotate in the opposite direction. Various constructions are used to compensate for this:
- Single rotor system
- Generating a lateral counter- thrust by a tail rotor , also encapsulated as a ducted propeller in the Fenestron , or by thrust nozzles in the NO-TAil rotor (NOTAR) system
- Double rotor systems
- Two main rotors rotating in opposite directions, whose yaw moments are balanced out - by arrangement one above the other on the same axis ( coaxial rotor ), one behind the other ( tandem configuration ) or next to one another ( transversal ). Another variant is the interlocking rotors with closely spaced, mutually inclined axes of rotation in the Flettner double rotor . With the Sikorsky X2 , the coaxial design also enables higher speeds in combination with a pusher propeller, as was first used in 1947 on the Fairey Gyrodyne .
Transversal configuration of the Focke-Wulf Fw 61
Kaman K-1200 K-Max with counter-rotating Flettner double rotor from the front
- Triple rotor systems
- Only rarely ( Cierva W.11 ), in planning ( Mil Mi-32 ) or in model making (Tribelle, Tricopter) did triple rotors occur, in which the torque is compensated by slightly tilting the rotor vertical axes or by swiveling one of the rotors.
Cierva W.11 with three main rotors
- Quadro and multicopter
- The quadrocopter uses four rotors in one plane and allows all three axes to be controlled through the linked adjustment of pitch or speed. A square arrangement is common, the opposite direction of rotation of adjacent rotors is necessary. Based on this technology, samples with six, eight, twelve or more (e.g. Volocopter with 16 or 18) rotors are used.
The Curtiss-Wright VZ-7 designed as a quadrocopter
- Blade tip drive
- With the blade tip drive , the rotor is driven by the recoil of a propeller or a gas jet, so that no counter-torque acts on the fuselage.
A system with two rotors is technically the more efficient construction, since all rotors are used for lifting and propulsion, while the tail rotor costs around 15% of the total power in hover. In practice, however, the single-rotor system with a tail rotor has largely prevailed. In economic terms, the lower construction and maintenance costs with only one rotor head and gearbox each have an impact , since these are the two most complex and sensitive components of a helicopter.
Tail rotors are available in versions with two to five blades. In order to reduce the noise , four-bladed rotors in an X-shape are used. A particularly quiet variant is the Fenestron , a jacketed propeller in the tail boom with up to 18 blades.
The tail rotor is usually driven from the main gearbox via shafts and deflection gears , so that its speed is always proportional to that of the main rotor. The thrust for steering around the yaw axis is regulated by the pilot with the pedals via the setting angle of the tail rotor blades, analogous to the collective adjustment of the main rotor.
During cruising, the tail rotor is relieved in many designs by the fact that a vertical stabilizer largely compensates for the yaw moment. This is usually achieved by means of end plates on the horizontal damping surface, which are inclined to the longitudinal axis of the fuselage, and in the case of a single fin, usually also by an asymmetrical profile.
Emergency steering and autorotation
Should the drive fail, helicopters can land undamaged. To do this, the pilot has to go into a steep descent , with the free-running rotor being kept rotating or accelerated as far as possible by the air flowing in from below, in order to maintain or increase the angular momentum . The resulting autorotation, as with a gyroplane, provides the lift that limits the rate of descent and supports the helicopter when it is held in an upright position. Yaw moment compensation is not necessary, since only the small moment from bearing friction (in the main rotor head, gearbox and drive) would have to be compensated, but this does not lead to a critical increase in the yaw rate until landing. Such a landing is therefore also possible if the tail rotor fails, e.g. B. if the drive shaft for the tail rotor, the angular gear to the tail rotor or even the entire tail boom breaks. On the other hand, reaching a suitable place for this emergency landing is more critical.
Shortly before reaching the bottom, the collective angle of attack ( angle of attack ) is increased from slightly negative to positive in order to significantly increase the lift. This slows down the sinking with the aim of a more or less gentle touchdown that is safe for technology and crew, and the rotor rotation is reduced. The angular momentum of the rotor decreases and its energy is consumed, so there is only one attempt at this delicate maneuver. The loss of control around the vertical axis and the need to hit the right moment, however, always make this maneuver risky - the angular momentum of the rotor is only sufficient for one attempt.
For the emergency landing, a minimum height above ground is required, since if the main drive fails, sagging is inevitable and time is also required to transition to the new flight position .
Emergency landing with autorotation must be practiced regularly by pilots.
A helicopter is not an inherently stable aircraft - it always has the tendency, especially when hovering and slow flight, to leave its attitude and to push, tilt or turn in one direction or the other. This is u. a. based on the fact that the neutral point is above the trunk and thus above the center of gravity . The pilot must intercept these movements through continuous, counteracting control inputs. At a flight speed above approx. 100 km / h, a helicopter behaves similarly to a hydrofoil and is accordingly easy to control. Landing involves particular dangers , since if the engine fails at too low an altitude, there will not be enough reserves to switch to autorotation. When touching the ground, the so-called ground resonance can occur, which can very quickly lead to the destruction of the helicopter.
Unlike in a fixed-wing aircraft, the helicopter pilot usually sits on the right-hand side. He needs both hands and feet to control it:
- With the left hand it controls via a lever, the collective pitch ( English pitch ). The swash plate is pushed up or down over the rotor axis and the angle of attack of all rotor blades of the main rotor is changed to the same extent and the lift of the rotor is increased or decreased. This causes the helicopter to rise or fall. In order to prevent the rotor speed dropping due to the resulting increase in air resistance when the angle of attack of the main rotor blades is increased, this lever is also used to increase the engine or turbine output. This is done either manually with a twist grip on the lever or automatically. By changing the engine or turbine output , the generated torque is also changed, which makes countermeasures necessary via the tail rotor.
- With the right hand, the pilot controls the cyclic blade adjustment using the control stick (in the photo above the S-shaped stick in the middle in front of the pilot's seat) . This inclines the swash plate and changes the rotor plane accordingly, thus initiating the movement of the helicopter around the longitudinal (roll to the left or right) and transverse axis (pitch to the front or back). The control commands given to the rotor head with the joystick via the swashplate also enable combinations of pitch and roll movements.
- On the cockpit floor there are two pedals with which the angle of attack of the tail rotor and thus the movement of the helicopter around the yaw axis (vertical axis), i.e. the rotation to the right or left, is controlled.
In principle, helicopters do not achieve the (forward) flight performance of fixed-wing aircraft : The maximum speed is usually between 200 and 300 km / h, some combat helicopters reach over 360 km / h. The speed record is 472 km / h and was achieved on June 7, 2013 with a Eurocopter X³.
The maximum speed is limited by the aerodynamics of the rotor blades: the blade moving forward has a higher speed than the one moving backwards compared to the air flowing in from the front. If the leading blade approaches the speed of sound in the outer area , there is a decrease in lift, a sharp increase in resistance and great stress on the blade due to torsional moments . This manifests itself in strong vibrations, making it difficult for the pilot to control the helicopter.
For a typical rotor diameter of 10 m, this means that the rotor cannot perform more than approx. 11 revolutions per second (that is 660 revolutions per minute) without the speed of sound in the outer areas of the rotor blades (approx. 343 m / s at 20 ° C) is exceeded. Typical speeds of the rotor during operation are therefore well below this value.
However, the speed of a helicopter is often limited by the retracting rotor blade: Here the combination of a high angle of attack (cyclical adjustment, see above) and low flow speed leads to a stall and thus to a loss of lift. When reaching critical speed, many helicopters therefore first tip over to the side on which the rotor blades are turning backwards before the forward turning blades reach the supersonic range.
The peak height is also limited and is typically around 5,000 meters, with individual models reaching up to 9,000 meters. The FAI altitude record of 12,442 m was set in June 1972 by Jean Boulet with an Aérospatiale SA-315 . It was only outbid (12,954 m) in March 2002 by Fred North's flight in a Eurocopter AS 350 (12,954 m), which, however, has not been recognized as an official record by the FAI so far (2012).
The fuel consumption of a helicopter is usually significantly higher than that of a hydrofoil aircraft with the same payload in relation to the flight route.
One advantage of the helicopter, on the other hand, is the ability to remain in the air ( hovering flight , also called hover ), to fly backwards or sideways, and to turn around the vertical axis ( yaw axis ) in slow flight . Furthermore, it can take off and land vertically (VTOL) and therefore does not need a runway . If there is no regular helicopter landing pad available, a flat and unobstructed space of sufficient diameter is sufficient.
|Horizontal speed||472.3 km / h||Eurocopter X 3||Hervé Jammayrac||June 7, 2013||Istres (FRA)|
|Highest climbing height||12,954 m||Eurocopter AS 350||Frédéric North||March 25, 2002||Cape Town (ZAF)|
|Highest starting altitude||8,848 m||Eurocopter AS 350||Didier Delsalle||May 14, 2005||Mount Everest (NPL)|
|Longest distance flight without landing||3,561.55 km||Hughes OH-6||Robert G. Ferry||April 6, 1966||Culver City , CA - Ormond Beach , FL (USA)|
NASA is planning a 1.8 kg small helicopter to fly in the Martian atmosphere in 2021. The density of the Martian atmosphere is already equal to the low density of the Earth's atmosphere at an altitude of 30,500 m when it lifts off the Martian surface. However, the gravitational acceleration on Mars (3.71 m / s²) is only about a third of that on Earth (9.81 m / s²).
The operation of a modern helicopter is significantly more expensive compared to a fixed-wing aircraft with a comparable payload. Nevertheless, due to its ability to land, take off and hover over unprepared terrain, there are a number of additional areas of application, distinguishable into civil and military.
The most common use in Central Europe , measured in terms of flight hours, is by far the work flight. This includes the monitoring of electricity, gas and oil transport lines, flights in forestry and agriculture ( agricultural flights , such as the application of pesticides or fertilizers), external load flights, survey flights, photo flights, fighting forest fires, etc. Tensioning a lead line for pulling a cable car , Overhead lines or rope bridges can also be done with a model helicopter. A sword with eight large circular saw blades is used to trim tree growth on overhead lines. A military helicopter was used by downdraft (downwash) to blow extremely heavy snow covering the branches could bring to fracture of trees along a blocked rail line.
Another important field of application is air rescue by rescue helicopter , for which there are over 70 bases in Germany alone. Further specializations are intensive-care transport helicopters , large-capacity rescue helicopters , emergency medical helicopters and mountain rescue services . Helicopters have also become an important supporting factor for the police , for example when searching for missing persons, fighting crime or fighting fires using external fire-fighting containers .
Transport helicopters are used for civilian passenger transport , for example on oil rigs , where they represent an important element of logistics. Another application is freight transport, when goods need to be brought quickly and directly to a specific location. In the high mountains , the transport of building materials and components is often important for the construction and supply of alpine facilities due to the lack of suitable land routes. The same applies to assembly work in inaccessible places; helicopters are sometimes used there as construction cranes . Alpine shelters that cannot be reached by vehicles and that were supplied with pack animals until the 1970s or with porters in the case of more difficult access routes are now mainly supplied with food and disposed of by helicopter. In steep vineyards that cannot be mechanized , plant protection products are sometimes sprayed by helicopters. In the tourism sector, sightseeing flights and heli-skiing are offered. Another use of helicopters is aerobatics , in which the high resilience of modern helicopter concepts, especially the rotors and their controls, is demonstrated.
729 helicopters are registered in Germany (as of the end of 2017). They have registration class H, i.e. they have an aircraft registration number in the form D-Hxxx.
In addition to the predominant use as a transport helicopter for troop transport, there are other typical military applications
- the fight against ground targets,
- the artillery observation ,
- Combat Search and Rescue (CSAR, German 'search / rescue in battle'),
- the air defense ( cannon , air-to-air missile ) and
- Deployment in the Navy for submarine hunting , sea reconnaissance and sea rescue ( SAR - Search and Rescue).
On September 23, 2009, during the helicopter robbery at Västberga in Sweden, a helicopter was used to rob a money deposit. The perpetrators landed with this on the roof of the building, penetrated through a skylight and escaped with the equivalent of around 4.1 million euros.
Controlling a helicopter requires special knowledge and skills, some of which are very different from those required for aircraft.
There are four types of pilot licenses in Germany:
- Private pilot license - PPL (H)
- Commercial Pilot License - CPL (H)
- Traffic pilot license - ATP (H)
- various military pilot licenses.
Compared to hydrofoil aircraft, helicopters have a significantly higher accident rate: Between 1980 and 1998 the Federal Bureau of Aircraft Accident Investigation (BFU) recorded 54 accidents with six fatalities per million departures for helicopters, and only ten accidents with 1.6 fatalities for hydrofoil aircraft . The causes of accidents are proportionately more than 80% human error.
From a technical point of view, helicopters are no more unsafe than hydrofoil aircraft and are designed and approved under the same reliability requirements. The higher risk of accidents can be explained more by the operating conditions: Rescue services and the military cannot determine a location in advance, obstacles such as antennas or power lines are then partially unknown to the pilot. Operations in the high mountains, such as load transport and mountain rescue, can in turn bring the drive to the limit due to the lower air density and downdrafts. If it fails, the conditions for an autorotation landing are often poor.
Optional rope cutters above and below the cabin can cut ropes in certain situations to prevent accidents. The ropes of power lines, mast guy ropes and cable cars are only partially marked and shown on 50,000 detailed maps and represent a particular danger on low flights.
Further details on the construction and technology of helicopters can be found in these articles:
- Variants of the design for torque compensation
- Tail rotor configuration - helicopter with side rotors - tandem configuration - coaxial rotor - Flettner double rotor - blade tip drive
- Related aircraft designs
- Gyrocopter - air screwdriver - convertible aircraft - whiz - VTOL
- Main rotor - rotor head - swash plate - flapping joint - swivel joint
- Landing device
- Helicopter engine
- Model helicopter
- Airbus Helicopters : subsidiary of the European aerospace company Airbus Group , in which u. a. the German United Flugtechnischen Werke (VFW) and Messerschmitt-Bölkow-Blohm (MBB) as well as Aérospatiale and Sud Aviation from France have risen. Airbus Helicopters employs around 14,000 people, 615 new helicopters were ordered in 2006, and the global market share is around 30 percent. There are currently around 9800 helicopters in operation in 140 countries.
- Italy / United Kingdom: AgustaWestland (formerly Agusta in Turin, Westland Aircraft in Yeovil)
- Poland: Państwowe Zakłady Lotnicze (PZL)
- Russia: Mil , Kamow
- Brazil: Helibras (part of the Eurocopter group)
- India: Hindustan Aeronautics Limited (HAL)
- South Africa: Denel
- USA: Bell Helicopter , Robinson Helicopter , Enstrom , Schweizer Aircraft Corporation , Kaman , MD Helicopters , Boeing Vertol and Sikorsky
- Category: Helicopter Manufacturers
- List of helicopter types
- Muscle power helicopter
- List of aircraft types
- Ground effect
- Category: VTOL Airplane
In chronological order:
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- Near the Flying Time . Lulu.com, 2011, ISBN 978-1-4477-5281-3 , pp. 151 ( books.google.de ).
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- Walter J. Boyne: How the Helicopter Changed Modern Warfare. New York 2011, ISBN 978-1-58980-700-6 , p. 312.
- Engelbert Zaschka : rotary wing aircraft. Gyroscopes and helicopters. CJE Volckmann Nachf. E. Wette, Berlin-Charlottenburg 1936, p. 47.
- Rolf Besser: Technology and history of the helicopter. From Leonardo da Vinci to the present. Bernard & Graefe-Verlag, Bonn 1996, p. 65.
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- Phenomenon of ground resonance: When a helicopter suddenly "goes nuts". ( Memento from February 28, 2016 in the Internet Archive ). Video on the subject of floor resonance at: spiegel.de.
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- Helicopters blow snow away. In: ORF.at . 5th February 2014.
- number of aircraft in the Federal Republic of Germany. LBA - Federal Aviation Office.