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Helikopter Hakkında Genel Bilgiler - Hubschrauber - Helicopter
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Helikopter Hakkında Genel Bilgiler - Hubschrauber - Helicopter

Helikopter, dikey kalkış ve iniş yapabilen döner kanatlı bir hava taşıtıdır. İsmin kökü yunancada heliko pteron yani hareketli kanatlar anlamından gelir. 1907 yılında Fransız Paul Cornu ilk motorlu helikopteri uçurdu.

Çalışma Prensibi

Helikopterler dikey olarak kalkış ve iniş yapabilir ve havada sabit olarak tutunabilirler. Helikopter ve uçakların uçma prensipleri aslında aynıdır. Uçaklarda tutunma kuvveti elde edebilmek için uçak hava içinde hareket ettirilir. Ancak kanat, uçak gövdesine bağlı olduğu için sabit bir yapıdadır. Fakat helikopterlerde kanat sabit değil, hareketlidir. Yani helikopterlerde taşıma kuvveti elde edebilmek için döner kanat yani pervane kullanılır.Pervane iki ya da daha fazla palden meydana gelir.Pervane palinin profili uçak kanadının profili ile aynıdır. Helikopterin motoru palleri döndürür. Paller hava içinde hareket ettikleri için üst yüzeylerinde alçak basınç, alt yüzeylerinde ise, yüksek basınç oluşur. Bu basınç farkı taşıma kuvvetini meydana getirir. Pallerin devir sayısının ve hücum açısının (pallerin havayı karşılama açısı) artması ile bu taşıma kuvvetinin büyüklüğü de artar. Tersi bir durumda ise azalır. Taşıma kuvveti helikopterin ağırlığına eşit olduğunda helikopter havada sabit olarak tutunur. Büyük olduğunda dikey olarak yükselir. Daha az olduğunda ise, dikey olarak alçalır.

Pervanenin dönme düzlemi eğildiğinde, yani pervanenin oluşturduğu taşıma kuvvetinin yönü değiştirildiğinde, helikopter ileri - geri ve sağa - sola doğru hareket eder. Böylece helikopterin hava içinde hareket etmesi sağlanır. Pervane sürekli döndüğü için (gövde üzerinde yarattığı moment nedeniyle) helikopterin gövdesini de döndürmeye çalışır. Bunu engellemek için helikopterin kuyruğunda daha küçük olan bir pervane daha kullanılır. Kuyruktaki pervane gövde üzerindeki dönme momentini sönümler. Ayrıca sönümleme miktarı değiştirilerek gövdenin dönüşü de sağlanabilir.
Rotor adedi

Helikopterler çift ve tek rotorlu olmak üzere ikiye ayrılır. Tek rotorlu helikopter bir dikey hareketi sağlayan ana rotor ve gövdenin dönmesini engelleyen yardımcı rotor bulunur.İlk olarak bu sistem Rus asıllı göçmen Igor Sikorsky tarafından tasarlanır ve 1939 yılında başarıyla uçurulur.

Çift rotorlu helikopterler daha karmaşık olmakla birlikte yük ve yolcu taşımaya daha elverişlidir. Çift rotorlu helikopter

Uçak mühendisliği

Uçak mühendisliği, hava ile etkileşimde bulunan taşıt, hareketsiz nesne ve cihazların tasarlanması, geliştirilmesi, üretilmesi, test edilmesi, bakım/onarım işlemlerinin yapılması ve tüm bu süreçlerin yönetilmesiyle ilgilenen mühendislik dalıdır.

Bu mühendislik dalının ilgi alanına,

uçaklar : uçak, helikopter, savaş uçağı, yolcu uçağı, uzaktan kumandalı (U/K) uçaklar, U/K helikopterler vb.
deniz ve rüzgar taşıtları/araçları: gemi, denizaltı, torpido, yelkenli, paraşüt, rüzgâr gülü, rüzgâr türbini vb.
balistik cisimler: top, mermi, gülle, cirit, golf topu, fırlatmalı diğer spor dalları, göktaşı vb.
kontrollü uçan cisimler: roket, füze, uzay mekiği vb.
etrafından kuvvetli hava akımı geçen binalar: gökdelen, asma köprü vb.

gibi ürünlerin ve bu ürünlerle ilgili aerodinamik, yapı, motor, kontrol dizgelerinin tasarım, geliştirme ve inceleme (analiz) çalışmaları girer.

Havacılık ve uzay mühendisliği

Havacılık ve uzay mühendisi, hava ile etkileşen her çeşit mühendislik ürünün tasarlanması ve inşaat projelerinin hazırlanması, üretilmesi, bakım ve onarım teknolojisi ve işletmesi konularında eğitim ve araştırma yapar. Yapımı düşünülen hava taşıtının dizaynını, ön projesini hazırlar. Uçak yapımı için gerekli üretim, yöntemleri arasından hangisinin niçin daha ekonomik olacağına karar verir. Bu konuda gerekli modelleri hazırlayarak deneylerini yapar, tasarladığı hava taşıtının performans özelliklerini saptar ve istemlere göre incelemesini yapar.

Havacılık ve uzay mühendisliği programı havada seyreden her çeşit aracın tasarlanması ve inşa projelerinin hazırlanması, üretilmesi, bakım ve onarım teknolojisi ve işletmesi konularında eğitim ve araştırma yapar.

Uzay mühendisliği


Uzay mühendisliği (geniş anlamıyla "roket ve uzay aracı mühendisliği"), havada ve uzayda hareket eden araçların tasarımına yönelik bir mühendislik dalıdır. Uzay mühendisleri sivil ve askeri kuruluşlarda, dünya çevresinde yörüngeye konacak insanlı ve insansız hava-uzay araçlarını ve bunları yörüngeye koyacak roketleri tasarlayan ve inşa eden, görev ve yol planlarını hesaplayan, sürekli kontrol ederek, görevlerini yerine getirmelerini sağlayan mühendislerdir. Hava-uzay araçlarında (uçak, helikopter, roket, füze, uydu, hava-uzay robotiği vs) yapılacak bilimsel ve teknolojik amaçlı deneylerin gerçekleştirilmesinde görev alırlar.

Kuyruk rotoru

Kuyruk rotoru, tek rotorlu helikopterlerin kuyruğunun uç kısmında, dikey veya dikeye yakın bir şekilde bulunan, ana rotora göre boyut olarak daha küçük olan rotor. Kuyruk rotoru, ana rotorun neden olduğu kendi etrafında dönme hareketini engellemek için bir kuvvet uygular ve pilotun helikopteri döndürmesini sağlar.

Günümüz taşıtları içinde en çok yönlü ve şaşırtıcı olanı helikopterdir. Üç boyutta da hareket edebilmesi, hemen hemen her yere gidebilmesi nedenleri ile uçaklarla yapılamayan birçok özel görevlerde de kullanılabilirler. Ancak helikopterlerin uçma mekanizmaları uçaklara göre oldukça karışık, üretim maliyetleri de daha yüksektir. Helikopterleri uçaklardan ayıran önemli özellikler, havada asılı durabilmeleri, kendi eksenleri etrafında döne-bilmeleri ve geri geri uçabilmeleridir.

Uçaklarda gerekli gücü motor sağlar ama asıl havada kalabilmelerini sağlayan kanatlarıdır. Helikopterlerde ise havada kalmayı sağlayan motora bağlı pervanelerdir. Onları bir çeşit dönen kanat olarak düşünebiliriz. Bir helikopterde iki veya daha fazla kanat olabilir.

Kanatlara hafif bir açı verilip, ana motor çalıştırılınca, dönen kanatlar helikopteri kaldırmaya çalışır. Yerde iken sorun yoktur ama havalanınca helikopterin gövdesi, pervanenin dönüş yönünün tersine dönmeye başlar. İşte burada bu hareketi durdurabilecek ilave bir güce ihtiyaç vardır.

Bu ilave gücü sağlamanın en kolay yolu, dönüş yönüne dik ilave bir pervane koymaktır. Buna kuyruk rotoru denilir. Kuyruk rotoru aynen uçak pervanesi gibi bir itiş gücü yaratır ve helikopterin gövdesinin dönmesini dengeleyerek sabit kalmasını sağlar.

Kuyruktaki pervaneyi döndüren ayrı bir motor yoktur. Hareketini ana motordan bir şaft ile alır ve altındaki dişli kutusu vasıtası ile dönmesi gereken devirde döner. Helikopterleri tam olarak kontrol edebilmek için ana ve kuyruk pervanelerinin ayarlanabilir olmaları gerekir. Kuyruk pervanesinde kanatların eğimlerinin, yani açılarının ayarlanması ile helikopterin kendi ekseni etrafında dönebilmesi sağlanır.

Ana pervane ise çok önemlidir. Yükseklik değiştirmeyi, ileri ve geri gitmeyi, dönmeyi o sağlar. Bunun için de inanılmaz derecede dayanıklı olması gerekir. İşin asıl sırrı ise ana pervanenin dönen kanatlarının eğiklik açılarının bir tam tur süresince değişmesidir.

Helikopterlerin havada hareketsiz kalabilmeleri için pervanelerin açılan da sabit olmalıdır. Bu açılan tüm kanatlarda aynı anda değiştirmekle alçalma ve yükselme sağlanır. Kanatlar arkaya geldiklerinde açılan büyük, öne geldiklerinde daha küçük ise ileri doğru hareket, tersi durumda da geriye doğru hareket sağlanır.

Helikopter hem ileri doğru uçabilen, hem de dikine yükselip alçalabilen bir uçuş aracıdır . Tepesindeki büyük pervaneye rotor denir . Rotor havayı yatay olarak keser . Öbür uçakların pervaneleri ise havayı dikey keser . Helikopter hızla aşağı, yukarı, ileri ve geri hareket edebilir . Havada neredeyse hiç kımıldamadan da durabilir . Helikopterlerin birden çok rotoru olabilir . Rotorlar iki, üç ya da dört kanatlıdır. Bir motor kanatları hızla döndürür . Rotor kanatlarının altından geçen hava helikopteri yukarı doğru iter , üstünden geçen hava ise yukarı doğru çeker. Böylece helikopter havada yükselir . Helikopter uçak kadar hızlı yol alamadığı için, kısa mesafeli uçuşlarda kullanılır . Kalkışı ve inişi için geniş bir pist gerekmez. Bu nedenle kentlerin içinden de yolcu alabilir . Helikopterlerden karadaki ve denizdeki kurtarma işlerinde de yararlanılır . Leonardo da Vinci daha 1483'te bir helikopter tasarımı yapmıştı. Kullanıma elverişli ilk Amerikan helikopterini 1940'ta Igor Sikorsky yaptı.

ENGLISH

Helicopter

From Wikipedia, the free encyclopedia
"Helicopters" redirects here. For other uses, see Helicopter (disambiguation).
A US police Bell 206 helicopter

A helicopter is a type of rotorcraft in which lift and thrust are supplied by rotors. This allows the helicopter to take off and land vertically, to 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 VTOL (vertical takeoff and landing) aircraft cannot perform.

The English word helicopter is adapted from the French word hélicoptère, coined by Gustave Ponton d'Amécourt in 1861, which originates from the Greek helix (ἕλιξ) "helix, spiral, whirl, convolution"[1] and pteron (πτερόν) "wing".[2][3][4][5] English language nicknames for helicopter include "chopper", "copter", "helo", "heli", and "whirlybird".

Helicopters were developed and built during the first half-century of flight, with the Focke-Wulf Fw 61 being the first operational helicopter in 1936. Some helicopters reached limited production, but it was not until 1942 that a helicopter designed by Igor Sikorsky reached full-scale production,[6] with 131 aircraft built.[7] Though most earlier designs used more than one main rotor, it is the single main rotor with anti-torque tail rotor configuration that has become the most common helicopter configuration. Tandem rotor helicopters are also in widespread use due to their greater payload capacity. Coaxial helicopters, tiltrotor aircraft, and compound helicopters are all flying today. Quadcopter helicopters pioneered as early as 1907 in France, and other types of multicopter have been developed for specialized applications such as unmanned drones.

History
Early design
See also: Bamboo-copter and Science and inventions of Leonardo da Vinci
A decorated Japanese taketombo bamboo-copter

The earliest references for vertical flight came from China. Since around 400 BC,[8] Chinese children have played with bamboo flying toys (or Chinese top).[9][10][11] This bamboo-copter is spun by rolling a stick attached to a rotor. The spinning creates lift, and the toy flies when released.[8] The 4th-century AD Daoist book Baopuzi by Ge Hong (抱朴子 "Master who Embraces Simplicity") reportedly describes some of the ideas inherent to rotary wing aircraft.[12]

Designs similar to the Chinese helicopter toy appeared in Renaissance paintings and other works.[13] In the 18th and early 19th centuries Western scientists developed flying machines based on the Chinese toy.[14]
Leonardo's "aerial screw"
Experimental helicopter by Enrico Forlanini (1877), exposed at the Museo nazionale della scienza e della tecnologia Leonardo da Vinci of Milan

It was not until the early 1480s, when Leonardo da Vinci created a design for a machine that could be described as an "aerial screw", that any recorded advancement was made towards vertical flight. His notes suggested that he built small flying models, but there were no indications for any provision to stop the rotor from making the craft rotate.[15][16] As scientific knowledge increased and became more accepted, men continued to pursue the idea of vertical flight.

In July 1754, Russian Mikhail Lomonosov had developed a small coaxial modeled after the Chinese top but powered by a wound-up spring device[14] 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 flight feathers[14] 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.[15] 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.[17]
Prototype created by M. Lomonosov, 1754

In 1861, the word "helicopter" was coined by Gustave de Ponton d'Amécourt, a French inventor who demonstrated a small steam-powered model. While celebrated as an innovative use of a new metal, aluminum, the model never lifted off the ground. D'Amecourt's linguistic contribution would survive to eventually describe the vertical flight he had envisioned. Steam power was popular with other inventors as well. In 1878 the Italian Enrico Forlanini's unmanned vehicle, also powered by a steam engine, rose to a height of 12 meters (40 ft), where it hovered for some 20 seconds after a vertical take-off. Emmanuel Dieuaide's steam-powered design featured counter-rotating rotors powered through a hose from a boiler on the ground.[15] In 1887 Parisian inventor, Gustave Trouvé, built and flew a tethered electric model helicopter.[citation needed]

On July 1901, Hermann Ganswindt demonstrated maiden flight of his helicopter took place in Berlin-Schöneberg, which probably was the first motor-driven flight carrying humans. A movie covering the event was taken by Max Skladanowsky, but it remains lost.[18]
Drawing from Edison's 1910 patent[19]

In 1885, Thomas Edison was given US$1,000 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.[20] Ján Bahýľ, a Slovak inventor, adapted the internal combustion engine to power his helicopter model that reached a height of 0.5 meters (1.6 ft) in 1901. On 5 May 1905, his helicopter reached four meters (13 ft) in altitude and flew for over 1,500 meters (4,900 ft).[21] 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,[19] but it never flew.[22]
First flights

In 1906, two French brothers, Jacques and Louis Breguet, began experimenting with airfoils for helicopters. In 1907, those experiments resulted in the 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 two feet (0.6 m) for a minute.[6] The Gyroplane No. 1 proved to be extremely unsteady and required a man at each corner of the airframe to hold it steady. For this reason, the flights of the Gyroplane No. 1 are considered to be the first manned flight of a helicopter, but not a free or untethered flight.
Paul Cornu's helicopter in 1907

That same year, fellow French inventor Paul Cornu designed and built a Cornu helicopter that used two 20-foot (6 m) counter-rotating rotors driven by a 24 hp (18 kW) Antoinette engine. On 13 November 1907, it lifted its inventor to 1 foot (0.3 m) and remained aloft for 20 seconds. Even though this flight did not surpass the flight of the Gyroplane No. 1, it was reported to be the first truly free flight with a pilot.[n 1] Cornu's helicopter completed a few more flights and achieved a height of nearly 6.5 feet (2 m), but it proved to be unstable and was abandoned.[6]

In 1911, Slovenian philosopher and economist Ivan Slokar patented a helicopter configuration.[23][24][25]

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.[26]
Early development
File:Bits & Pieces - BP374 - Test flight of Pescara's helicopter - 1922 - EYE FLM7760 - OB105716.ogvPlay media
Silent film of a test flight of Pescara's helicopter, 1922. EYE Film Institute Netherlands.

In the early 1920s, Argentine Raúl Pateras-Pescara de Castelluccio, while working in Europe, demonstrated one of the first successful applications of cyclic pitch.[6] 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. 1 was tested but was found to be underpowered and could not lift its own weight. His 2F fared better and set a record.[27] The British government funded further research by Pescara which resulted in helicopter No. 3, powered by a 250 hp radial engine which could fly for up to ten minutes.[28][29]
Oehmichen N°2, 1923

On 14 April 1924 Frenchman Étienne Oehmichen set the first helicopter world record recognized by the Fédération Aéronautique Internationale (FAI), flying his quadrotor helicopter 360 meters (1,181 ft).[30] On 18 April 1924, Pescara beat Oemichen's record, flying for a distance of 736 meters[27] (nearly a half mile) in 4 minutes and 11 seconds (about 8 mph, 13 km/h), maintaining a height of six feet (1.8 meters).[31] On 4 May, Oehmichen set the first 1 km closed-circuit helicopter flight in 7 minutes 40 seconds with his No. 2 machine.[6][32]

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]

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,[33] 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 cyclic and collective.[34][35] Patents were granted to von Baumhauer for his cyclic and collective controls by the British ministry of aviation on 31 January 1927, under patent number 265,272.[citation needed]

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.[36][37]

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,[38] 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).[38][39]

In the Soviet Union, Boris N. Yuriev and Alexei M. Cheremukhin, two aeronautical engineers working at the Tsentralniy Aerogidrodinamicheskiy Institut (TsAGI, 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 1.8-meter (6-foot) 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 9 Type B-2 100 CV output rotary engine of World War I, the TsAGI 1-EA made several low altitude flights.[40] By 14 August 1932, Cheremukhin managed to get the 1-EA up to an unofficial altitude of 605 meters (1,985 ft), shattering d'Ascanio's earlier achievement. As the Soviet Union was not yet a member of the FAI, however, Cheremukhin's record remained unrecognized.[41]

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 six meters (20 ft) and an endurance of eight minutes. Florine chose a co-rotating configuration because the gyroscopic stability of the rotors would not cancel. Therefore, the rotors had to be tilted slightly in opposite directions to counter torque. Using hingeless rotors and co-rotation also minimised the stress on the hull. At the time, it was one of the most stable helicopters in existence.[42]

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 500-meter (1,600 ft) diameter.[43] The next year, on 26 September 1936, Claisse set a height record of 158 meters (520 ft).[44] And, finally, on 24 November 1936, he set a flight duration record of one hour, two minutes and 50 seconds[45] over a 44 kilometer (27 mi) closed circuit at 44.7 kilometers per hour (27.8 mph). The aircraft was destroyed in 1943 by an Allied airstrike at Villacoublay airport.[46]

Arthur M. Young, American inventor, started work on model helicopters in 1928 using converted electric hover motors to drive the rotor head. Young invented the 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 to build 2 working helicopters. In just 6 months they completed the first Bell Model 1, which spawned the Bell Model 30, later succeeded by the Bell 47.[47]
Autogyro
Main article: Autogyro
Pitcairn PCA-2 autogyro, built in the U.S. under licence to the Cierva Autogiro Company

Early rotor winged flight suffered failures primarily associated with the unbalanced rolling movement generated when attempting take-off, due to dissymmetry of lift between the advancing and retreating blades. This major difficulty was resolved by Juan de la Cierva's introduction of the flapping hinge. In 1923, de la Cierva's first successful autogyro was flown in Spain by Lt. Gomez Spencer. In 1925 he brought his C.6 to Britain and demonstrated it to the Air Ministry at Farnborough, Hampshire. This machine had a four blade rotor with flapping hinges but relied upon conventional airplane controls for pitch, roll and yaw. It was based upon an Avro 504K fuselage, initial rotation of the rotor was achieved by the rapid uncoiling of a rope passed around stops on the undersides of the blades.

A major problem with the autogyro was driving the rotor before takeoff. Several methods were attempted in addition to the coiled rope system, which could take the rotor speed to 50% of that required, at which point movement along the ground to reach flying speed was necessary, while tilting the rotor to establish autorotation. Another approach was to tilt the tail stabiliser to deflect engine slipstream up through the rotor. The most acceptable solution was finally achieved with the C.19 Mk.4, which was produced in some quantities; a direct drive from the engine to the rotor was fitted, through which the rotor could be accelerated up to speed. The system was then declutched before the take-off run.

As de la Cierva's autogyros achieved success and acceptance, others began to follow and with them came further innovation. Most important was the development of direct rotor control through cyclic pitch variation, achieved initially by tilting the rotor hub and subsequently by the Austrian engineer Raoul Hafner, by the application of a spider mechanism that acted directly on each rotor blade. The first production direct control autogyro was the C.30, produced in quantity by Avro, Liore et Olivier, and Focke-Wulf.

The production model, called the C.30A by Avro, was built under licence in Britain, France and Germany and was similar to the C.30P. It carried small movable trimming surfaces. Each licensee used nationally built engines and used slightly different names. In all, 143 production C.30s were built, making it by far the most numerous pre-war autogyro.

Between 1933 and 1936, de la Cierva used one C.30A (G-ACWF) to perfect his last contribution to autogyro development before his death in late 1936.[48] To enable the aircraft to take off without forward ground travel, he produced the "Autodynamic" rotor head, which allowed the rotor to be spun up by the engine in the usual way but to higher than take-off r.p.m at zero rotor incidence and then to reach operational positive pitch suddenly enough to jump some 20 ft (6 m) upwards.[49]
Birth of an industry
Igor Sikorsky and the world's first mass-produced helicopter, the Sikorsky R-4, 1944
First airmail service by helicopter in Los Angeles, 1947

Heinrich Focke at Focke-Wulf was licensed to produce the Cierva C.30 autogyro in 1933. Focke designed the world's first practical transverse twin-rotor helicopter, the Focke-Wulf Fw 61, which first flew on 26 June 1936. The Fw 61 broke all of the helicopter world records in 1937, demonstrating a flight envelope that had only previously been achieved by the autogyro.

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 Fl 265—was used in the Mediterranean, while the Focke Achgelis Fa 223 Drache twin-rotor helicopter was used in Europe.[citation needed] Extensive bombing by the Allied forces prevented Germany from producing any helicopters in large quantities during the war.

In the United States, Russian-born engineer Igor Sikorsky and W. Lawrence 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 XR-1.[50] Meanwhile, Sikorsky settled on a simpler, single rotor design, the VS-300, 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 tailboom.

Developed from the VS-300, Sikorsky's R-4 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, when it was used primarily for search and rescue (by the USAAF 1st Air Commando Group) in Burma;[51] 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 R-5 and the R-6. In all, Sikorsky produced over 400 helicopters before the end of World War II.[52]

While LePage and Sikorsky built their helicopters for the military, Bell Aircraft hired Arthur Young to help build a helicopter using Young's two-blade teetering rotor design, which used a weighted stabilizer bar placed at a 90° angle to the rotor blades. The subsequent Model 30 helicopter showed the design's simplicity and ease of use. The Model 30 was developed into the Bell 47, which became the first helicopter certified for civilian use in the United States. Produced in several countries, the Bell 47 was the most popular helicopter model for nearly 30 years.
Turbine age
See also: Gas turbine and turboshaft

In 1951, at the urging of his contacts at the Department of the Navy, Charles Kaman modified his K-225 synchropter — a design for a twin-rotor helicopter concept first pioneered by Anton Flettner in 1939, with the aforementioned Fl 265 piston-engined design in Germany — with a new kind of engine, the turboshaft engine. This adaptation of the 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 December 1951, the 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.[53] However, it was the Sud Aviation Alouette II that would become the first helicopter to be produced with a turbine-engine.[54]

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.
Uses

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 been chosen to conduct tasks that were previously not possible with other aircraft, or were time- or work-intensive to accomplish on the ground. Today, helicopter uses include transportation of people and cargo, military uses, construction, firefighting, search and rescue, tourism, medical transport, law enforcement, agriculture, news and media, and aerial observation, among others.[55]

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 logging industry to lift trees out of terrain where vehicles cannot travel and where environmental concerns prohibit the building of roads.[56] These operations are referred to as longline because of the long, single sling line used to carry the load.[57]

The largest single non-combat helicopter operation in history was the disaster management operation following the 1986 Chernobyl nuclear disaster. Hundreds of pilots were involved in airdrop and observation missions, making dozens of sorties a day for several months.

"Helitack" is the use of helicopters to combat wildland fires.[58] The helicopters are used for aerial firefighting (water bombing) and may be fitted with tanks or carry helibuckets. Helibuckets, such as the Bambi bucket, are usually filled by submerging the bucket into lakes, rivers, reservoirs, or portable tanks. Tanks fitted onto helicopters are filled from a hose while the helicopter is on the ground or water is siphoned from lakes or reservoirs through a hanging snorkel as the helicopter hovers over the water source. Helitack helicopters are also used to deliver firefighters, who rappel down to inaccessible areas, and to resupply firefighters. Common firefighting helicopters include variants of the Bell 205 and the Erickson S-64 Aircrane helitanker.

Helicopters are used as air ambulances for 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.[59]

Police departments and other law enforcement agencies use helicopters to pursue suspects. Since helicopters can achieve a unique aerial view, they are often used in conjunction with police on the ground to report on suspects' locations and movements. They are often mounted with lighting and heat-sensing equipment for night pursuits.

Military forces use attack helicopters to conduct aerial attacks on ground targets. Such helicopters are mounted with missile launchers and miniguns. 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 systems (UAS) helicopter systems of varying sizes are developed by companies for military reconnaissance and surveillance duties. Naval forces also use helicopters equipped with dipping sonar for anti-submarine warfare, since they can operate from small ships.

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 platforms continue to operate. Various companies specialize in this type of operation.

Other uses of helicopters include:

Aerial photography
Motion picture photography
Electronic news gathering
Reflection seismology
Search and rescue
Tourism and recreation
Transport

Design features
Rotor system
Main article: Helicopter rotor
A teetering rotor system with a weighted flybar device

The rotor system, or more simply rotor, is the rotating part of a helicopter that generates 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.

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. The rotor blades are attached to 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.
Anti-torque features
MD Helicopters 520N NOTAR

Most helicopters have a single main rotor, but torque created as the engine turns the rotor causes the body of the helicopter to turn in the opposite direction to the rotor (by conservation of angular momentum). To eliminate this effect, some sort of anti-torque control must be used.

The design that Igor Sikorsky settled on for his 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.

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 tailboom.[60]
Boeing CH-47 Chinook is the most common dual rotor helicopter deployed today

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 drive the tail rotor to be applied to the main rotors, increasing the aircraft's 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.
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.
Transverse rotors are pair of counter-rotating rotors mounted at each end of the wings or outrigger structures. They are found on tiltrotors and some earlier helicopters.
Quadcopters have four rotors often with parallel axes (sometimes rotating in the same direction with tilted axes) which are commonly used on model aircraft.

Tip jet designs let the rotor push itself through the air and avoid generating torque.[61]
Engines
A turbine engine used in the Mi-2 helicopter.
Main articles: Aircraft engine and Turboshaft

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]

Early helicopter designs utilized custom-built engines or rotary engines 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]

Turbine engines revolutionized the aviation industry, and the turboshaft engine 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]

Special jet engines developed to drive the rotor from the rotor tips are referred to as tip jets. Tip jets powered by a remote compressor are referred to as cold tip jets, while those powered by combustion exhaust are referred to as hot tip jets. An example of a cold jet helicopter is the Sud-Ouest Djinn, and an example of the hot tip jet helicopter is the YH-32 Hornet.[citation needed]

Some radio-controlled helicopters and smaller, helicopter-type unmanned aerial vehicles, use electric motors. Radio-controlled helicopters may also have piston engines that use fuels other than gasoline, such as nitromethane. Some turbine engines commonly used in helicopters can also use biodiesel instead of jet fuel.[62][63]

There are also human-powered helicopters.
Flight controls
Main article: Helicopter flight controls
Controls from a Bell 206

A helicopter has four flight control inputs. These are the cyclic, the collective, the anti-torque pedals, and the throttle. The cyclic control is usually located between the pilot's legs and is commonly called the cyclic stick or just cyclic. On most helicopters, the cyclic is similar to a joystick. However, the Robinson R22 and Robinson R44 have a unique teetering bar cyclic control system and a few helicopters have a cyclic control that descends into the cockpit from overhead.

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

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

The anti-torque pedals are located in the same position as the rudder pedals in a fixed-wing aircraft, and serve a similar purpose, namely to control the direction in which the nose of the aircraft is pointed. Application of the pedal in a given direction changes the pitch of the tail rotor blades, increasing or reducing the thrust produced by the tail rotor and causing the nose to yaw in the direction of the applied pedal. The pedals mechanically change the pitch of the tail rotor altering the amount of thrust produced.

Helicopter rotors are designed to operate in a narrow range of RPM.[64][65][66][67][68] 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. In single-engine helicopters, the throttle control is a motorcycle-style twist grip mounted on the collective control, while dual-engine helicopters have a power lever for each engine.

A swashplate 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 both blades. This causes the helicopter to push air downward or upward, depending on the angle of attack. The swashplate can also change its angle to move the blades angle forwards or backwards, or left and right, to make the helicopter move in those directions.
Flight
File:Svalbard helicotper.ogvPlay media
Helicopter hovering over boat in rescue exercise

There are three basic flight conditions for a helicopter: hover, forward flight and the transition between the two.
Hover

Hovering is the most challenging part of flying a helicopter. This is because a helicopter generates its own gusty air while in a hover, which acts against the fuselage and flight control surfaces. The end result is constant control inputs and corrections by the pilot to keep the helicopter where it is required to be.[69] Despite the complexity of the task, the control inputs in a hover are simple. The cyclic is used to eliminate drift in the horizontal plane, that is to control forward and back, right and left. The collective is used to maintain altitude. The pedals are used to control nose direction or heading. It is the interaction of these controls that makes hovering so difficult, since an adjustment in any one control requires an adjustment of the other two, creating a cycle of constant correction.
Transition from hover to forward flight

As a helicopter moves from hover to forward flight it enters a state called translational lift which provides extra lift without increasing power. This state, most typically, occurs when the airspeed reaches approximately 16–24 knots, and may be necessary for a helicopter to obtain flight.
Forward flight

In forward flight a helicopter's flight controls behave more like those of a fixed-wing aircraft. Displacing the cyclic forward will cause the nose to pitch down, with a resultant increase in airspeed and loss of altitude. Aft cyclic will cause the nose to pitch up, slowing the helicopter and causing it to climb. Increasing collective (power) while maintaining a constant airspeed will induce a climb while decreasing collective will cause a descent. Coordinating these two inputs, down collective plus aft cyclic or up collective plus forward cyclic, will result in airspeed changes while maintaining a constant altitude. The pedals serve the same function in both a helicopter and a fixed-wing aircraft, to maintain balanced flight. This is done by applying a pedal input in whichever direction is necessary to center the ball in the turn and bank indicator.
Safety
HAL Dhruv at the 2008 Royal International Air Tattoo, England
Royal Australian Navy Squirrel helicopters during a display at the 2008 Melbourne Grand Prix
A Robinson R44 Raven II arrives for the 2014 Royal International Air Tattoo, England
Maximum speed limit
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The main limitation of the helicopter is its low speed. There are several reasons a helicopter cannot fly as fast as a fixed-wing aircraft. When the helicopter is hovering, the outer tips of the rotor travel at a speed determined by the length of the blade and the 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 drag and vibration.

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.

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, velocity, never exceed.[70] 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.
Noise

During the closing years of the 20th century designers began working on helicopter noise reduction. Urban communities have often expressed great dislike of noisy aircraft, and police and passenger helicopters can be unpopular. The redesigns followed the closure of some city heliports and government action to constrain flight paths in national parks and other places of natural beauty.
Vibration

Helicopters also vibrate; an unadjusted helicopter can easily vibrate so much that it will shake itself apart. To reduce vibration, all helicopters have rotor adjustments for height and weight. Blade height is adjusted by changing the pitch of the blade. Weight is adjusted by adding or removing weights on the rotor head and/or at the blade end caps. Most also have vibration dampers for height and pitch. Some also use mechanical feedback systems to sense and counter vibration. Usually the feedback system uses a mass as a "stable reference" and a linkage from the mass operates a flap to adjust the rotor's angle of attack to counter the vibration. Adjustment is difficult in part because measurement of the vibration is hard, usually requiring sophisticated accelerometers mounted throughout the airframe and gearboxes. The most common blade vibration adjustment measurement system is to use a stroboscopic flash lamp, and observe painted markings or coloured reflectors on the underside of the rotor blades. The traditional low-tech system is to mount coloured chalk on the rotor tips, and see how they mark a linen sheet. Gearbox vibration most often requires a gearbox overhaul or replacement. Gearbox or drive train vibrations can be extremely harmful to a pilot. The most severe being pain, numbness, loss of tactile discrimination and dexterity.
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.

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.[71]

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.

These issues are due to the exposed tail rotor cutting through open air around 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.
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.[72]

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.
Transmission
Pascal Chretien hovering the world's first manned electric helicopter, August 2011

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] 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.[73]

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 September 10, 2010 to the first testing at 30% power on March 1, 2011 - less than six months. The aircraft first flew on August 12, 2011. All development was conducted in Venelles, France.[74][75]
Hazards

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, also known as a vortex ring state, is when the aircraft is unable to arrest its descent due to the rotor's downwash interfering with the aerodynamics of the rotor.[76]
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 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.[77]
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).
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 in dusty conditions or whiteout in snowy conditions.
Low rotor RPM, or "rotor droop", 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.[78]
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[

AUF DEUTSCH

Hubschrauber
Ein Hubschrauber oder Helikopter ist ein senkrecht startendes und landendes Luftfahrzeug, das Motor­kraft auf einen oder mehrere Rotoren für Auftrieb und Vortrieb überträgt. Diese arbeiten als sich drehende Tragflächen oder Flügel, weshalb Hubschrauber zu den Drehflüglern zählen.

Das Wort Helikopter, kurz auch Heli, setzt sich zusammen aus altgriechisch ἕλιξ hélix „Windung, Spirale“ und πτερόν pterón „Flügel“ (Drehflügler).

Nicht zu den Hubschraubern gezählt werden Mischformen aus Flugzeug und Drehflügler, beispielsweise Hybride aus Dreh- und Starrflüglern oder Luftfahrzeuge ohne angetriebenen Hauptrotor wie Tragschrauber.

Geschichte

Schon Leonardo da Vinci hatte um 1487–1490 in seinen sogenannten „Pariser Manuskripten“ Skizzen eines Hubschraubers angefertigt,[1] aber erst im 20. Jahrhundert gelang die technische Umsetzung dieser Idee. Pioniere der Hubschrauberentwicklung waren u. a. Jakob Degen, Étienne Œhmichen, Raúl Pateras Pescara, Oszkár Asbóth, Juan de la Cierva, Engelbert Zaschka, Louis Charles Breguet, Alberto Santos Dumont, Henrich Focke und Igor Sikorski.
Anfänge
Experimental-Hubschrauber von Enrico Forlanini (1877), ausgestellt am Museo nazionale della scienza e della tecnologia Leonardo da Vinci Milan
Datei:Bits & Pieces - BP374 - Test flight of Pescara's helicopter - 1922 - EYE FLM7760 - OB105716.ogvMediendatei abspielen
Testflug eines Hubschraubers von Raúl Pateras-Pescara auf dem Flugplatz von Issy-les-Moulineaux, Paris (1922)

Am 13. November 1907 hob Paul Cornu mit seinem 260 kg schweren fliegenden Fahrrad für 20 Sekunden senkrecht vom Boden ab; es handelte sich hierbei um den ersten dokumentierten freien bemannten Vertikalflug. Er benutzte Tandemrotoren, die von einem 24 PS starken V8-Motor angetrieben wurden.

Ab 1910 löste Boris Nikolajewitsch Jurjew einige theoretisch-konstruktive Grundprobleme der Stabilität und des Antriebs und entwickelte die Taumelscheibe.

Im Jahr 1913 konstruierte der Dresdner Ingenieur Otto Baumgärtel einen Senkrechtstarter, der durch Verlagerung des Schwerpunktes ohne besonderen Propeller Vorwärtsbewegungen vollführen konnte.[2]

Gegen Ende des Ersten Weltkrieges führten die Konstrukteure Stephan Petróczy von Petrócz, Theodore von Kármán und Wilhelm Zurovec im Auftrag der k.u.k. Armee erfolgreiche Flugversuche mit den nach ihnen benannten Schraubenfesselfliegern PKZ-1 und PKZ-2 durch. Durch solche senkrecht aufsteigenden Fluggeräte sollten die bis dahin üblichen Fesselballone zur Feindbeobachtung ersetzt werden. Der PKZ-2 erreichte eine Flughöhe von rund 50 Metern, was zu jener Zeit einen Rekord darstellte. Bei einem Demonstrationsflug am 10. Juni 1918 in Fischamend stürzte das Gerät ab. Der zu Ende gehende Krieg verhinderte eine weitere Entwicklung.[3][4]

Am 11. November 1922 brachte Étienne Œhmichen erstmals seinen Œhmichen No.2 in die Luft, den ersten dokumentierten und zuverlässig fliegenden manntragenden Senkrechtstarter, der eine Quadrocopter-Bauweise verwendete.

Bei der Entwicklung seines Autogiro gelangen Juan de la Cierva (Spanien) im Jahr 1923 wesentliche Lösungen zur Stabilisierung des Rotors eines Drehflüglers, so z. B. die Schlaggelenke.

Am 18. April 1924 schlug der von Raúl Pateras Pescara entwickelte Pescara No. 3 den vier Tage vorher von Œhmichen aufgestellten Weltrekord für Rotorflugzeuge um das Doppelte und setzte dabei erstmals zyklische Blattverstellung ein, um den Hauptrotor zum Vortrieb zu nutzen.
Das weitere 20. Jahrhundert

In den frühen 1930er Jahren bauten Louis Charles Breguet und René Dorand mit dem Gyroplane-Laboratoire den ersten längere Zeit stabil fliegenden Hubschrauber. Er hatte Koaxialrotoren und hielt ab Juni 1935 alle internationalen Rekorde für Hubschrauber.

Die Focke-Wulf Fw 61, die zwei seitlich angeordnete Rotoren benutzte, konnte beim Jungfernflug im Juni 1936 eine Reihe von bisherigen Weltrekorden bei Hubschraubern brechen. Sie war zudem der erste Hubschrauber, mit dem eine Autorotationslandung gelang.

1941 war die deutsche Focke-Achgelis Fa 223 der erste in Serie gebaute Hubschrauber, ebenfalls mit zwei seitlich angeordneten Rotoren. Es folgten 1943 die Flettner Fl 282, ebenfalls mit Doppelrotor, und 1944 die Sikorsky R-4 „Hoverfly“ in den USA, die wie ihr Vorgänger Sikorsky VS-300 einen Einzelrotor zusammen mit einem Heckrotor verwendete.

Am 8. März 1946 erhielt die Bell 47 der Bell Aircraft Corporation, ein leichter zwei- oder dreisitziger Hubschrauber, als erster ziviler Hubschrauber die Flugzulassung in den USA. Seine Varianten waren bis in die 1980er Jahre und darüber hinaus weltweit anzutreffen.

1955 rüstete die französische Firma Sud Aviation ihren Hubschrauber Alouette II mit einer 250-kW-Turbomeca-Artouste-Wellenturbine aus und baute damit den ersten Hubschrauber mit Gasturbinenantrieb, der heute von fast allen kommerziellen Herstellern verwendet wird. Lediglich Robinson Helicopter (Robinson R22 und Robinson R44), Brantly (Brantly B-2 bzw. Brantly 305) und Sikorsky (Schweizer 300C) stellen noch Hubschrauber mit Kolbenmotoren her.

Die mit bis heute 16.000 Exemplaren meistgebaute Hubschrauberfamilie, die Bell 204 – militärisch Bell UH-1 genannt – startete am 22. Oktober 1956 zu ihrem Jungfernflug.

Die deutsche Bölkow Bo 105 wurde 1967 als erster Hubschrauber mit einem gelenklosen Rotorkopf zusammen mit GFK-Rotorblättern, die erstmals bei der Kamow Ka-26 zum Einsatz gekommen waren, ausgerüstet. Der Eurocopter EC 135 als aktueller Nachfolger benutzt eine weiterentwickelte Form, den sogenannten gelenk- und lagerlosen Rotorkopf. Dort wurden auch die Lager für die Blattwinkelverstellung durch ein aus glasfaserverstärktem Kunststoff bestehendes Drillsteuerelement mit Steuertüte ersetzt.

1968 startete mit der sowjetischen Mil Mi-12 der größte jemals gebaute Hubschrauber. Er verfügt über nebeneinander angeordnete Rotoren, ein maximales Startgewicht von 105 t bei einer maximalen Nutzlast von 40 t und 196 Passagierplätzen. Nach drei Prototypen, die eine Reihe von Rekorden erzielten, wurde die Produktion eingestellt.

1977 fand der Erstflug des größten in Serie gebauten Helikopters statt, der Mil Mi-26, die bis heute produziert und eingesetzt wird.

Ab 1983 entstand mit der RAH-66 Comanche ein Kampfhubschrauber mit Tarnkappentechnik, dessen Fertigung jedoch kurz vor Erreichen der Einsatzreife 2004 aufgrund ausufernder Kosten gestoppt wurde.

1984 flog erstmals die Sikorsky X-wing, deren Rotor beim Vorwärtsflug angehalten und festgestellt wird und dann als zusätzliche Tragfläche dient. Wie bei anderen VTOL-Konzepten sollen damit gegenüber reinen Drehflüglern bessere Flugleistungen erreicht werden. Es blieb bei einem Prototyp.
21. Jahrhundert

Im August 2008 bewies der Sikorsky X2 im Erstflug die Tauglichkeit des mit neuesten Verfahren optimierten Koaxial-Rotors in Kombination mit einem Schubpropeller – dem Prinzip der früheren Tragschrauber. Zwei Jahre später erreichte er mit 250 Knoten True Airspeed (463 km/h) das Entwicklungsziel und überbot damit den bisherigen Geschwindigkeitsrekord um 15 %. Auch andere Hersteller erprobten ähnliche neue Hochgeschwindigkeits-Muster, so Eurocopter den X³ und Kamow den Ka-92.

Im Oktober 2011 fand mit dem Volocopter der weltweit erste bemannte Flug mit einem rein elektrisch angetriebenen Hubschrauber statt.

Funktion
Starrer Rotorkopf einer Bo 105

Die rotierenden Rotorblätter erzeugen durch die anströmende Luft einen dynamischen Auftrieb. Wie bei den starren Tragflächen eines Flugzeugs ist dieser u. a. abhängig von ihrem Profil, dem Anstellwinkel und der (über die Blattlänge nicht konstanten) Anströmgeschwindigkeit der Luft, siehe Hauptrotor.

Wenn ein Hubschrauber sich vorwärts bewegt, ändert sich die Anströmgeschwindigkeit, da sich Umlauf- und Fluggeschwindigkeit des nach vorne bewegten Blattes addieren. Beim zurücklaufenden Blatt subtrahieren sie sich, siehe auch die Skizze weiter unten.

Durch die Aerodynamik der Rotorblätter entstehen beim Flug asymmetrische Kräfte auf die jeweils nach vorne und nach hinten bewegten Blätter, die bei älteren Modellen durch Schlag- und Schwenkgelenke an der Befestigung, dem Rotorkopf, aufgefangen werden mussten. Neuere Konstruktionen kommen ohne diese Gelenke aus. Rotorkopf und -blätter bestehen bei diesen neueren Modellen aus einem Verbund von Materialien unterschiedlicher Elastizität (Elastomeren sowie hochfesten und leichten Metallen wie Titan), welche die in Größe und Richtung sich ständig ändernden dynamischen Kräfte bewältigen können, ohne dass die Bauteile hierdurch Schaden nehmen. Ein solcher gelenkloser Rotorkopf wurde erstmals bei der Bölkow Bo 105 durch Blätter aus glasfaserverstärktem Kunststoff und einem massiven Rotorkopf aus Titan im Verbund mit Elastomeren realisiert. Beim Eurocopter EC 135 wurde dieser zum lagerlosen Rotorkopf weiterentwickelt, der sich bei den meisten Modellen durchgesetzt hat.
Blattverstellung

Die zyklische (auch rotationsperiodische) Blattverstellung – allgemein auch Blattsteuerung genannt – dient der Steuerung der Horizontalbewegung des Hubschraubers, die eine Neigung der Haupt-Rotorebene erfordert. Zum Einleiten oder Beenden von Vorwärts-, Rückwärts- oder Seitwärtsflug werden die Einstellwinkel der Blätter während des Umlaufs des Rotors (zyklisch) verändert. Dies führt zu einer zyklischen Schlagbewegung der Blätter, sodass ihre Blattspitzen auf einer Ebene umlaufen, die sich in der beabsichtigten Richtung neigt. Der Auftrieb bleibt auf dem gesamten Umlauf konstant. Dementsprechend steht der Rotorschub, der den Hubschrauber trägt und vorwärtsbringt, im rechten Winkel zur Blattspitzenebene. Die im Schwebeflug rein senkrecht hebende Kraft erhält durch diese Neigung nun einen nach vorne treibenden Schub. Aufgrund des Rumpfwiderstandes neigt sich der gesamte Hubschrauber und damit auch seine Rotorwelle ebenfalls in Flugrichtung.

Wenn der Schwerpunkt des Hubschraubers (bei geeigneter Beladung) in Verlängerung der Rotorwelle liegt, geht der Schub bei jeder gleichbleibenden Fahrt durch den Schwerpunkt. Die Blattspitzenebene befindet sich dann im rechten Winkel zur Rotorwelle, und Schlagbewegungen finden nicht statt. Sie gibt es nur bei anderen Schwerpunktlagen oder wenn die Fluggeschwindigkeit geändert werden soll.

Mit der kollektiven Blattverstellung (Pitch) verändert der Pilot den Anstellwinkel aller Rotorblätter gleichmäßig, was zum Steigen oder Sinken des Hubschraubers führt. Einfache Konstruktionen, etwa bei verschiedenen Elektroantrieben in Modellhubschraubern, ersetzen diese Steuerung durch eine Drehzahländerung. Nachteilig ist dabei die längere Reaktionszeit durch die Massen-Trägheit des Hauptrotors.

Die Rotorblätter werden meist mit einer Taumelscheibe angesteuert. Deren unterer, feststehender Teil wird vom Piloten mit Hilfe des „kollektiven“ Verstellhebels nach oben oder unten verschoben. Mit dem „zyklischen“ Steuerknüppel kann dieser wiederum in jede Richtung geneigt werden. Der obere (sich mit dem Rotor drehende) Teil der Taumelscheibe überträgt über Stoßstangen und Hebel an den Blattwurzeln den gewünschten Einstellwinkel auf die Rotorblätter.
Rotorvarianten und Giermomentausgleich

Man unterscheidet Einrotorsysteme, Doppelrotoren und vier Rotoren (Quadrocopter). Mit Ausnahme des Blattspitzenantriebs werden die Rotoren dabei stets durch einen Motor im Rumpf angetrieben. Dadurch entsteht an der Rotorachse ein Gegen-Drehmoment (Giermoment), das bei einem einzelnen Rotor eine gegenläufige Drehung des Rumpfes erzeugen würde. Um dieses zu kompensieren, werden verschiedene Konstruktionen benutzt:

Einrotorsystem
Erzeugung eines seitlichen Gegenschubs durch einen Heckrotor, auch gekapselt als Mantelpropeller beim Fenestron, oder durch Schubdüsen beim NO-TAil-Rotor-(NOTAR)-System.

Heckrotor eines Super Pumas

Fenestron an einem EC 120

Doppelrotorsysteme
Zwei gegenläufige Hauptrotoren, deren Giermomente sich ausgleichen – durch Anordnung übereinander auf derselben Achse (Koaxialrotor), hintereinander (Tandem-Konfiguration) oder nebeneinander (transversal). Eine weitere Variante sind die ineinandergreifenden Rotoren mit nahe zusammenliegenden, zueinander schräggestellten Drehachsen beim Flettner-Doppelrotor. Beim Sikorsky X2 ermöglicht die Koaxial-Bauweise auch höhere Geschwindigkeiten in Kombination mit einem Schubpropeller, wie er erstmals 1947 beim Fairey Gyrodyne verwendet wurde.

Koaxialhubschrauber KA-27 der russischen Marine

Transversal-Konfiguration des Focke-Wulf Fw 61

Kaman K-1200 K-Max mit gegenläufigem Flettner-Doppelrotor von vorn

Chinook der Royal Air Force mit Doppelrotor in Tandem-Konfiguration

Dreifachrotorsysteme
Nur selten (Cierva W.11), in der Planung (Mil Mi-32) oder im Modellbau (Tribelle, Tricopter) traten Dreifach-Rotoren auf, bei denen das Drehmoment durch leichtes Kippen der Rotorhochachsen oder auch durch Schwenkbarkeit eines der Rotoren ausgeglichen wird.

Cierva W.11 mit drei Hauptrotoren

Quadrocopter
Der Quadrocopter verwendet vier Rotoren in einer Ebene und erlaubt allein durch verknüpfte Verstellung von Pitch oder Drehzahl eine Steuerung um alle drei Achsen. Üblich ist quadratische Anordnung, nötig ist gegenläufiger Drehsinn benachbarter Rotoren. Auf Basis dieser Technologie werden auch Muster mit sechs, acht und zwölf Rotoren eingesetzt.

Die als Quadrocopter ausgelegte Curtiss-Wright VZ-7

Der AirRobot AR 100-B

Blattspitzenantrieb
Beim Blattspitzenantrieb wird der Rotor durch Rückstoß eines Propellers oder Gasstrahls angetrieben, sodass kein Gegendrehmoment auf den Rumpf wirkt.

Ein System mit zwei Rotoren ist zwar technisch die effizientere Konstruktion, da alle Rotoren zum Auf- und Vortrieb genutzt werden, während der Heckrotor im Schwebeflug etwa 15 % der Gesamtleistung kostet. In der Praxis hat sich jedoch weitgehend das Einrotorsystem mit einem Heckrotor durchgesetzt. Ökonomisch schlagen hier die niedrigeren Bau- und Wartungskosten bei nur je einem Rotorkopf und Getriebe ins Gewicht, da diese die beiden aufwendigsten und empfindlichsten Baugruppen eines Hubschraubers sind.

Heckrotoren gibt es in Ausführungen mit zwei bis fünf Blättern. Um den Lärm zu verringern, werden teils vierblättrige Rotoren in X-Form eingesetzt. Eine besonders leise Variante ist der Fenestron, ein ummantelter Propeller im Heckausleger mit bis zu 18 Blättern.

Meist wird der Heckrotor aus dem Hauptgetriebe über Wellen und Umlenkgetriebe angetrieben, sodass seine Drehzahl stets proportional zu der des Hauptrotors ist. Der Schub zur Steuerung um die Gierachse wird hierbei vom Piloten mit den Pedalen über den Einstellwinkel der Heckrotorblätter analog der kollektiven Verstellung des Hauptrotors geregelt.

Während des Reiseflugs wird bei vielen Konstruktionen der Heckrotor dadurch entlastet, dass ein Seitenleitwerk das Giermoment weitgehend kompensiert. Dies wird meist durch Endscheiben an der horizontalen Dämpfungsfläche realisiert, die zur Rumpflängsachse schräg gestellt sind, bei einer einzelnen Seitenflosse in der Regel zusätzlich durch ein asymmetrisches Profil.
Notsteuerung und Autorotation

Sollte der Antrieb ausfallen, können Hubschrauber trotzdem noch landen.[5] Dazu muss der Pilot in einen steilen Sinkflug übergehen, wobei der freilaufende Rotor durch die nun von unten nach oben anströmende Luft in Drehung gehalten bzw. möglichst beschleunigt wird, um den Drehimpuls zu erhalten oder zu erhöhen. Diese daraus resultierende Autorotation wie beim Tragschrauber liefert den die Sinkgeschwindigkeit limitierenden Auftrieb und unterstützt den Helikopter beim Halten in aufrechter Position. Ein Giermomentausgleich ist dabei nicht notwendig, da nur das geringe Moment aus der Lagerreibung (im Hauptrotorkopf, Getriebe und Antrieb) auszugleichen wäre, das aber bis zur Landung nicht zu einem kritischen Anstieg der Gierrate führt. Eine solche Landung ist daher auch beim Ausfall des Heckrotors möglich, z. B. bei Bruch der Antriebswelle für den Heckrotor, des Winkelgetriebes zum Heckrotor oder gar des ganzen Heckauslegers.

Kritisch ist schon das Erreichen eines geeigneten Platzes für diese Notlandung. Kurz vor dem Erreichen des Bodens wird nun der kollektive Einstellwinkel (Anstellwinkel) von leicht negativ auf positiv vergrößert, um den Auftrieb deutlich zu erhöhen. Damit wird das Sinken mit dem Ziel eines halbwegs sanften und für Technik und Besatzung sicheren Aufsetzens abgebremst, doch auch die Rotordrehung. Der Drehimpuls des Rotors nimmt dabei ab, seine Energie wird aufgezehrt, es gibt daher nur einen Versuch für dieses heikle Manöver. Der Verlust der Steuerung um die Hochachse und die Notwendigkeit, den richtigen Moment genau zu treffen, da der Drehimpuls des Rotors nur für einen Versuch ausreicht, macht dieses Manöver jedoch stets riskant. Weiterhin bedarf es einer Mindesthöhe über Grund, da beim Ausfall des Hauptantriebes ein Durchsacken unvermeidlich ist und auch Zeit benötigt wird, um in die neue Fluglage überzuleiten.
Steuerung
Cockpit eines AS 332 L1 „Super Puma“ der deutschen Bundespolizei

Ein Hubschrauber ist ein nicht eigenstabiles Luftfahrzeug – er hat vor allem im Schwebeflug und langsamen Flug stets die Tendenz, seine Fluglage zu verlassen und in die eine oder andere Richtung zu schieben, sich zu neigen oder zu drehen. Dies ist u. a. darin begründet, dass der Neutralpunkt über dem Rumpf und damit über dem Schwerpunkt liegt. Der Pilot muss diese Bewegungen durch kontinuierliche, entgegenwirkende Steuereingaben abfangen. Bei einer Fluggeschwindigkeit oberhalb von ca. 100 km/h verhält sich ein Hubschrauber ähnlich wie ein Tragflächenflugzeug und ist entsprechend einfach zu steuern. Besondere Gefahren beinhaltet die Landung, da bei einem Motorausfall in zu geringer Höhe nicht genug Reserven vorhanden sind, in Autorotation überzugehen. Bei der Bodenberührung kann die sogenannte Bodenresonanz auftreten, die sehr schnell zur Zerstörung des Hubschraubers führen kann.[6]

Anders als im Starrflügel-Flugzeug sitzt der Pilot eines Hubschraubers in der Regel auf der rechten Seite. Zur Steuerung benötigt er beide Hände und Füße:

Mit der linken Hand kontrolliert er über einen Hebel die kollektive Blattverstellung (englisch Pitch). Dabei wird die Taumelscheibe gerade über die Rotorachse nach oben bzw. unten geschoben und so der Anstellwinkel aller Rotorblätter des Hauptrotors in gleichem Maße geändert und damit der Auftrieb des Rotors erhöht oder vermindert. Dadurch steigt bzw. sinkt der Hubschrauber. Um bei Vergrößerung des Anstellwinkels der Hauptrotorblätter den Abfall der Rotordrehzahl durch die daraus resultierende Erhöhung des Luftwiderstandes zu verhindern, wird über diesen Hebel auch die Motor- bzw. Turbinenleistung erhöht. Das erfolgt entweder manuell mit einem Drehgriff am Hebel oder automatisch. Durch die Änderung der Motor- bzw. Turbinenleistung wird auch das erzeugte Drehmoment geändert, was ein Gegensteuern über den Heckrotor erforderlich macht.
Mit der rechten Hand kontrolliert der Pilot über den Steuerknüppel (im obigen Foto der S-förmig gebogene Knüppel mittig vor dem Pilotensitz) die zyklische Blattverstellung. Dadurch wird die Taumelscheibe geneigt und die Rotorebene entsprechend geändert und so die Bewegung des Hubschraubers um die Längs- (Rollen nach links oder rechts) und Querachse (Nicken nach vorne oder hinten) eingeleitet. Die mit dem Steuerknüppel über die Taumelscheibe an den Rotorkopf gegebenen Steuerbefehle ermöglichen auch Kombinationen von Nick- und Rollbewegungen.
Am Cockpitboden befinden sich zwei Pedale, mit denen der Anstellwinkel des Heckrotors und damit die Bewegung des Hubschraubers um die Gierachse (Hochachse), also die Drehung nach rechts bzw. links, gesteuert wird.

Flugleistungen
Geschwindigkeitsüberlagerung am vor- und rücklaufenden Blatt
Datei:EC 145.oggMediendatei abspielen
Flugvorführung mit einem Airbus Helicopters H145

Hubschrauber erreichen prinzipiell nicht die Flugleistungen von Starrflügelflugzeugen: Die Höchstgeschwindigkeit liegt meist zwischen 200 und 300 km/h, einige Kampfhubschrauber erreichen über 360 km/h. Der Geschwindigkeitsrekord liegt bei 472 km/h und wurde am 7. Juni 2013 mit einem Eurocopter X³ erzielt.

Die Höchstgeschwindigkeit wird dabei durch die Aerodynamik der Rotorblätter begrenzt: Das jeweils nach vorne laufende Blatt hat gegenüber der von vorn anströmenden Luft eine höhere Geschwindigkeit als das nach hinten laufende. Nähert sich nun das vorlaufende Blatt im Außenbereich der Schallgeschwindigkeit, kommt es dort zu einem Abfall des Auftriebs, starker Erhöhung des Widerstands und großer Blattbeanspruchung durch Torsionsmomente. Dies äußert sich etwa in starken Schwingungen und erschwert so dem Piloten die Kontrolle über den Hubschrauber.

Für einen typischen Rotordurchmesser von 10 m bedeutet dies, dass der Rotor nicht mehr als ca. 11 Umdrehungen pro Sekunde (das sind 660 Umdrehungen pro Minute) ausführen kann, ohne dass in den Außenbereichen der Rotorblätter die Schallgeschwindigkeit (ca. 343 m/s bei 20 °C) überschritten wird. Typische Drehzahlen des Rotors im Betrieb liegen daher deutlich unter diesem Wert.

Häufig wird die Geschwindigkeit eines Hubschraubers jedoch durch das rücklaufende Rotorblatt begrenzt: Hier führt die Kombination aus hohem Anstellwinkel (zyklische Verstellung, s. o.) und geringer Strömungsgeschwindigkeit zum Strömungsabriss und damit zum Auftriebsverlust. Viele Hubschrauber kippen daher beim Erreichen der kritischen Geschwindigkeit zuerst auf die Seite, auf der sich die Rotorblätter nach hinten drehen, bevor die nach vorne drehenden Blätter in den Überschallbereich gelangen.

Auch die Gipfelhöhe ist begrenzt und liegt typisch etwa bei 5.000 Metern, wobei einzelne Modelle bis zu 9.000 Meter erreichen. Der FAI-Höhenrekord von 12.442 m wurde im Juni 1972 von Jean Boulet mit einer Aérospatiale SA-315 aufgestellt.[7] Erst im März 2002 wurde er durch einen Flug von Fred North mit einem Eurocopter AS 350 überboten (12.954 m),[8] der allerdings bisher (2012) von der FAI nicht als offizieller Rekord anerkannt wurde.

Der Kraftstoffverbrauch eines Hubschraubers liegt bei gleicher Zuladung auf die Flugstrecke bezogen meist deutlich über dem eines Tragflächenflugzeugs.

Ein Vorteil des Hubschraubers liegt hingegen in der Fähigkeit, in der Luft stehen zu bleiben (Schwebeflug, auch Hover genannt), rückwärts oder seitwärts zu fliegen, sowie sich im langsamen Flug um die Hochachse (Gierachse) zu drehen. Weiterhin kann er senkrecht starten und landen (VTOL) und benötigt daher keine Start- und Landebahn. Steht kein regulärer Hubschrauberlandeplatz zur Verfügung, reicht dazu bereits ein ebener und hindernisfreier Platz von ausreichendem Durchmesser.
Rekorde (Auswahl)
Typ Rekord Hubschraubertyp Pilot Datum Ort
Horizontal-
Geschwindigkeit 472,3 km/h Eurocopter X3 Hervé Jammayrac[9] 7. Juni 2013 Istres (FRA)
Höchste
Steighöhe 12.954 m Eurocopter AS 350 Frédéric North 25. März 2002 Kapstadt (ZAF)
Höchste
Starthöhe 8.848 m Eurocopter AS 350 Didier Delsalle 14. Mai 2005 Mount Everest (NPL)
Längster Distanzflug
ohne Landung 3.561,55 km Hughes OH-6 Robert G. Ferry 6. April 1966 Culver City, CA –
Ormond Beach, FL (USA)
Verwendung

Der Betrieb eines modernen Hubschraubers ist im Vergleich zu einem Flächenflugzeug mit vergleichbarer Zuladung deutlich teurer. Dennoch ergeben sich aufgrund seiner Fähigkeit, auf unvorbereitetem Gelände starten und landen zu können, eine Reihe von zusätzlichen Einsatzgebieten, unterscheidbar in zivile und militärische.
Zivile Verwendung
Rettungshubschrauber Eurocopter EC 135 der ADAC Luftrettung
Französische Aérospatiale SA-315 Lama als Kamerahubschrauber

Die häufigste Verwendung in Mitteleuropa ist, gemessen am Flugstundenaufkommen, mit Abstand der Arbeitsflug. Dazu zählen die Überwachung von Strom-, Gas- und Öltransportleitungen, Flüge in der Land- und Forstwirtschaft, Außenlastflüge, Vermessungsflüge, Bildflüge, Waldbrandbekämpfung etc. Das Spannen einer Vorausleine für das Seilziehen einer Seilbahn, Freileitung oder Seilbrücke kann auch mit einem Modellhubschrauber erfolgen. Zum Trimmen von Baumbewuchs an Freileitungstrassen wird ein verdrehfest vom Helikopter hängendes Schwert mit acht großen Kreissägeblättern verwendet.[10] Ein Militärhubschrauber wurde eingesetzt, um per Downwash außerordentlich starken Schneebelag, der Äste zum Brechen bringen könnte, von Bäumen entlang einer gesperrten Bahntrasse zu blasen.[11]

Ein weiteres wichtiges Einsatzfeld ist die Luftrettung mit dem Rettungshubschrauber, wofür es allein in Deutschland über 50 Stützpunkte gibt. Weitere Spezialisierungen stellen Intensivtransporthubschrauber, Großraum-Rettungshubschrauber, Notarzteinsatzhubschrauber und Bergrettungsdienst dar. Auch bei der Polizei und bei der Feuerwehr sind Hubschrauber zu einem wichtigen unterstützenden Faktor geworden.

Für den zivilen Passagiertransport werden Transporthubschrauber eingesetzt, etwa bei Bohrinseln, wo sie ein wichtiges Element der Logistik darstellen. Eine weitere Anwendung ist der Frachttransport, wenn Güter schnell direkt an einen bestimmten Ort zu bringen sind. Im Hochgebirge ist der Transport von Baumaterial und Bauteilen mangels geeigneter Landwege oft wichtig für die Errichtung und Versorgung von alpinen Einrichtungen. Gleiches gilt für Montagearbeiten an unzugänglichen Stellen; mitunter werden Hubschrauber dort auch als Baukran eingesetzt. Alpine Schutzhütten, die nicht mit Fahrzeugen erreichbar sind und bis in die siebziger Jahre mit Tragtieren oder bei schwierigeren Zugangswegen mit Trägern versorgt wurden, erhalten heute den Lebensmittelnachschub und die Entsorgung überwiegend mit dem Hubschrauber. In nichtmechanisierbaren steilen Weinbergen werden Pflanzenschutzmittel zum Teil von Hubschraubern versprüht. Im Touristikbereich werden Rundflüge und Heliskiing angeboten. Eine weitere Verwendung von Hubschraubern ist der Kunstflug, bei dem die hohe Belastbarkeit moderner Hubschrauberkonzepte, vor allem der Rotoren und deren Steuerung, demonstriert wird.

In Deutschland sind 745 Hubschrauber zugelassen (Stand 2014).[12] Sie haben die Kennzeichenklasse H, tragen also ein Luftfahrzeugkennzeichen der Form D-Hxxx.
Militärische Verwendung
Kampfhubschrauber AH-64D Apache Longbow mit Radareinheit über dem Rotor

Neben dem überwiegenden Einsatz als Transporthubschrauber zum Truppentransport findet man als weitere typische militärische Anwendungen

den Kampf gegen Bodenziele
die Panzerabwehr durch spezialisierte Kampfhubschrauber wie den Eurocopter Tiger, den Hughes AH-64 oder den Mil Mi-24,
die Artilleriebeobachtung,
Combat Search and Rescue (CSAR, deutsch ‚Suchen/Retten im Gefecht‘),
die Luftabwehr (Bordkanone, Luft-Luft-Rakete) und
Einsätze bei der Marine zur U-Jagd, Seeaufklärung und Seenotrettung (SAR – Search and Rescue).

Siehe auch: Bordhubschrauber, Militärhubschrauber und Hubschrauber der Bundeswehr
Unfälle
In den Bergen Albaniens während einer Übung abgestürzter Kampfhubschrauber des Typs Hughes AH-64 Apache

Verglichen mit Tragflächenflugzeugen weisen Hubschrauber eine deutlich höhere Unfallhäufigkeit auf: Zwischen 1980 und 1998 verzeichnete die Bundesstelle für Flugunfalluntersuchung (BFU) bei Hubschraubern statistisch pro einer Million Abflüge 54 Unfälle mit sechs Toten, bei Tragflächenflugzeugen lediglich zehn Unfälle mit 1,6 Toten. Die Unfallursachen liegen dabei anteilig mit über 80 % im menschlichen Versagen.

Aus Sicht der Technik sind Hubschrauber nicht unsicherer als Tragflächenflugzeuge und werden unter den gleichen Zuverlässigkeitsforderungen ausgelegt und zugelassen. Die höhere Unfallgefahr kann mehr durch die Einsatzbedingungen erklärt werden: Rettungsdienste und Militär können einen Einsatzort nicht vorher bestimmen, Hindernisse wie Antennen oder Stromleitungen sind dem Piloten dann teilweise unbekannt. Einsätze im Hochgebirge, wie Lastentransport und Bergrettung, können wiederum durch die geringere Luftdichte und Abwinde den Antrieb an die Leistungsgrenze bringen. Bei dessen Ausfall sind zudem die Bedingungen für eine Autorotations-Landung häufig schlecht.

Optionale Seilschneider oberhalb und unterhalb der Kabine können in bestimmten Situation Seile durchschneiden, um Unfälle zu verhindern. Seile von Stromleitungen, Mastabspannungen und Seilbahnen sind nur teilweise markiert und auf 50.000er-Detailkarten verzeichnet und stellen eine besondere Gefahr bei niedrigen Flügen dar.
Technik-Artikel

Weitere Details zu Bauweise und Technik von Hubschraubern finden sich in diesen Artikeln:

Varianten der Bauweise zum Drehmomentausgleich
Heckrotor-Konfiguration – Hubschrauber mit seitlichen Rotoren – Tandem-Konfiguration – Koaxialrotor – Flettner-Doppelrotor – Blattspitzenantrieb
Verwandte Flugzeug-Bauweisen
Tragschrauber – Flugschrauber – Wandelflugzeug – Senkrechtstarter – VTOL
Rotor
Hauptrotor – Rotorkopf – Taumelscheibe – Schlaggelenk – Schwenkgelenk
Schwebeflug
Landevorrichtung
Hubschraubertriebwerk
Modellhubschrauber

Wichtige Hersteller

Europa:

Airbus Helicopters: Tochter des europäischen Luft- und Raumfahrtkonzerns Airbus Group, in der u. a. die deutschen Vereinigten Flugtechnischen Werke (VFW) und Messerschmitt-Bölkow-Blohm (MBB) sowie Aérospatiale und Sud Aviation aus Frankreich aufgegangen sind. Airbus Helicopters beschäftigt rund 14.000 Mitarbeiter, im Jahr 2006 wurden 615 Hubschrauber neu bestellt, der Marktanteil weltweit beträgt etwa 30 Prozent. Aktuell sind etwa 9800 Hubschrauber in 140 Ländern in Betrieb.
Italien/Vereinigtes Königreich: AgustaWestland (früher Agusta in Turin, Westland Aircraft in Yeovil)
Polen: Państwowe Zakłady Lotnicze (PZL)
Russland: Mil, Kamow

Südamerika:

Brasilien: Helibras (Teil der Eurocopter-Gruppe)

Asien:

Indien: Hindustan Aeronautics Limited (HAL)

Afrika:

Südafrika: Denel

Nordamerika:

USA: Bell Helicopter, Robinson Helicopter, Enstrom, Schweizer Aircraft Corporation, Kaman, zu Boeing Helicopters gehören u. a.: MD Helicopters und Vertol, Sikorsky

Siehe auch

Kategorie:Hubschrauberhersteller
Liste der Hubschraubertypen
Muskelkraft-Hubschrauber
Heliskiing
Liste von Flugzeugtypen
Hubschrauberlandeplatz
Bodeneffekt
Heli-Expo
Kategorie:VTOL-Flugzeug

Literatur

In chronologischer Sortierung:

Engelbert Zaschka: Drehflügelflugzeuge. Trag- und Hubschrauber. C. J. E. Volckmann Nachf. E. Wette, Berlin-Charlottenburg 1936, OCLC 20483709, DNB 578463172.
Rolf Besser: Technik und Geschichte der Hubschrauber. Von Leonardo da Vinci bis zur Gegenwart. Bernard & Graefe, Bonn 1996, ISBN 3-7637-5965-4.
Kyrill von Gersdorff, Kurt Knobling: Hubschrauber und Tragschrauber. Bernard & Graefe, Bonn 1999, ISBN 3-7637-6115-2.
Heinrich Dubel: Helikopter Hysterie Zwo. Fantôme, Berlin 2011, ISBN 978-3-940999-18-4.
Steve Coates, Jean-Christophe Carbonel: Helicopters of the Third Reich. Ian Allen 2003, ISBN 1-903223-24-5 (englisch).
Ernst Götsch: Luftfahrzeugtechnik. Motorbuchverlag, Stuttgart 2003, ISBN 3-613-02006-8.
Walter J. Wagtendonk: Principles of helicopter flight. Aviation Supplies & Acad., Newcastle 2003, ISBN 1-56027-217-1 (englisch).
Yves Le Bec: Die wahre Geschichte des Helikopters. Von 1486 bis 2005. (Originaltitel: La véritable histoire de l'hélicoptère.) Vorwort von Jean Boulet. Ducret, Chavannes-près-Renens 2005, ISBN 2-8399-0100-5.
Walter Bittner: Flugmechanik der Hubschrauber. Technologie, das flugdynamische System Hubschrauber, Flugstabilitäten, Steuerbarkeit. Springer, Berlin 2005, ISBN 3-540-23654-6.
Marcus Aulfinger: Hubschrauber-Typenbuch. Motorbuchverlag, Stuttgart 2007, ISBN 978-3-613-02777-0.
J. Gordon Leishman: Principles of helicopter aerodynamics. Cambridge University Press, Cambridge 2008, ISBN 978-0-521-85860-1 (englisch).
Helmut Mauch: Das große Buch der Hubschrauber. Geschichte, Modelle, Einsatz. GeraMond, München 2009, ISBN 978-3-7654-7001-1.
Hans-Joachim Polte: Hubschrauber. Geschichte, Technik, Einsatz. 5., völlig neu überarbeitete und erweiterte Auflage, Mittler, Hamburg/Berlin/Bonn 2011, ISBN 978-3-8132-0924-2.

Helikopter Resimleri

[Image: helikopter_1oolnz.jpg]

[Image: helikopter_27dzqr.jpg]

[Image: helikopter_3gbyac.jpg]

[Image: helikopter_4joy4z.jpg]




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