Helicopter awal

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a. Penemuan Helikopter

Sebenarnya, perjalanan helikopter menjadi bentuk yang dikenal pada saat ini

memakan kurun waktu yang cukup panjang. Dalam perjalanannya, juga melibatkan

perkembangan teknologi dan juga para penemu serta pengembang helikoter.

Helikopter pertama yang menerbangkan manusia adalah Helikopter Breguet-Richet,

tahun 1907. Heli ini terbang di Douai, Perancis pada 29 September 1907. Helikopter

ini masih memperoleh bantuan dari empat orang yang memegangi keempat kakinya.

Upaya ini tidak memperoleh catatan baik sebagai helikopter pertama yang terbang

bebas. Walaupun demikian, helikopter ini membuktikan keberhasilan teori terbang

vertikal yang saat itu masih dianggap sebagai teori. Ini merupakan mesin pertama

yang bisa terbang dengan sendirinya membawa seorang pilot secara vertikal sebagai

akibat daya angkat sayap putarnya. Heli ini menggunakan mesin Antoinette

berkekuatan 50 hp.

Terbang heli sesungguhnya dilakukan oleh Paul Cornu menggunakan heli bermesin

ganda Antoinette 24 hp di Lisieux, Perancis pada 13 November 1907. Penerbangan

berlangsung 20 detik hingga ketinggian 0,3 Meter. Sedangkan Helikopter berjenis

Gyroplane pertama diraih oleh C4 Autogiro buatan Juan de la Cierva. Autogiro

terbang pertama pada 9 Januari 1923. Rahasia sukses pada pengadopsian sistem

flapping hinges joint the blades to the rotor head. Sementara helikopter yang sukses

terbang pertama dilakukan oleh jenis Fock Wulf FW-61 berotor ganda yang didesain

oleh Professor Heinrich Focke pada tahun 1933-1934. Helikopter ini melakukan

terbang perdananya pada 26 Juni 1936 dan ditenagai oleh mesin Siemens-Halske Sh

14A bertenaga 160 hp. Heli ini diterbangkan oleh Ewald Rohlfs. Heli ini mencatat

rekor terbang sejauh 122,35 km dan lama terbang satu jam 20 menit 49 detik. Pada

waktu lain ia terbang hingga ketinggian 3427 meter dan rekor kecepatan 122 km/jam.

a. Pionir pengembang teknologi Helikopter

Leonardo da Vinci (1452-1519)

Leonardo da Vinci sebenarnya mengembangkan konsep terbang vertikal yang

sebelumnya merupakan mainan anak-anak dari dataran Cina, tidak jelas sebenarnya

sejak kapan mainan anak-anak ini dikembangkan disana dan siapa inisiatornya atau

penemunya. Pada tahun 1483 Leonardo da Vinci mengembangkan konsep sekrup

terbang.

Sir Goerge Cayley (1773-1857)

Sir George Cayley dikenal sebagai insinyur dan inovator dalam navigasi udara dan

aerodinamika. Salah satu yang dikenalkannya adalah istilah angle of attack dalam

dunia penerbangan. Dalam sejarah, dia merupakan sosok yang mengembangkan

pesawat sayap tetap dan pesawat layang atau glider namun demikian dia

mengembangkan sayap putar atau helikopter. Helikopter yang diperkenalkannya

merupakan kompilasi dari bahan kayu, bulu, gabus dan kawat.

Pada 1842, Cayley mendesain helikopter lebih baik , khususnya ketika mengetahui

bahwa putaran baling-baling dapat menimbulkan petaka sehingga memerlukan

penangkalnya. Teori penangkal ini juga dikemukakan olehnya. Agar bisa terbang,

helikpter ini menempatkan dua rotor yang bergerak berlawanan arah. Meski

helikopter rancangannya belum berwujud dengan helikopter yang mengudara, konsep

helikopternya dipakai oleh Kamov dari Rusia dan Focke dari Jerman.

Nikolai Egorovich Zhikovsky (1847-1921)

Zhukovsky mengawali karier di dunia penerbangan dengan menekuni matematika,

hidrodinamika dan aerodinamika. Zhukovsky kemudian menemukan terowongan

angin pertama di dunia untuk menguji teknologi aerodinamika. Terjun dalam

pengembangan helikopter pada tahun 1910 dan pada Perang Dunia I mengembangkan

banyak pesawat terbang dan helikopter

Juan de la Cierva (1895-1936)

Cierva mengembangkan helikopter setelah pesawat pembom bersayap ganda

buatannya jatuh pada tahun 1919, alasannya adalah kestabilan helikopter dianggapnya

lebih tinggi. Dalam membangun rancangan helikopternya, Cierva mengabaikan

berbagai teori yang berkembang sebelumnya, dengan menggunakan rancangan-

rancangan baru buatannya yang didasarkan pada teori yang dikembangkannya lewat

berbagai eksperimen. Hasinya adalah Autogiro yang merupakan konsep pesawat

gado-gado antara pesawat terbang umumnya sehingga bisa melakukan terbang landas

secara vertikal, yang setengah pesawat terbang dan setengah helikopter. Autogiro

Cierva terbang pada 1923. Lima tahun kemudian Cierva melakukan penerbangan

keliling Eropa dengan Autogiro sejauh lebih dari 5000 km seraya berpromosi.

Upayanya tidak sia-sia karena Autogiro rancangannya banyak diminati sejumlah

industri di Eropa. Cierva meninggal dalam kecelakaan Autogiro di Croydon pada

tahun 1936.

Igor Ivanovich Sikorsky (1889-1972)

Sikorsky menaruh minat pada penerbangan dengan merancang berbagai pesawat

model di antaranya berupa helikopter sejak usia dini. Pada awalnya dia masuk Naval

Academy di St. Petersburg yang kemudian mengundurkan diri dan pergi ke Paris

untuk mendalami ilmu teknik dan penerbangan. Setelah dari Paris, dia kembali ke

Kiev, Ukraina dan mengembangkan helikopter namun gagal. Revolusi Bolshevik

memaksa Sikorsky hijrah ke Paris dan selanjutnya menetap di Amerika Serikat.

Pada tahun 1939 dia menerbangkan helikopter pertamanya VS-300 dan selama

pengembangannya, helikopternya mencatat berbagai rekor penerbangan. Sampai

memasuki abad ke-21 ada sekitar 40.000 helikopter buatan Sikorsky terbang

diberbagai belahan dunia ini.

Mikhail Mil (1909-1970)

Seperti halnya Sikorsky, Mil menaruh minat pada penerbangan diusia dini. Dia

memenangkan kompetisi pesawat model pada usia 12 tahun. Ia kemudian masuk ke

Insitut Aviasi di Novocherkassk, Uni Soviet dan mengembangkan autogiro

pertamanya dengan pengawasan dan bimbingan Kamov dan Skrzhinsky. Setelah lulus

pada 1931, dia masuk ke pusat aerodinamika Rusia TsAGI, dan disinilah melakukan

penelitian pada aerodinamika helikopter dengan penekanan pada stabilitas dan desain

rotor.

Pada tahun 1947, Mil diangkat menjadi kepala desain helikopter yang baru dan

memunculkan helikopter GM-1 yang dikenal menjadi Mi-1 Hare. Sukses Hare

menuntun pengembangan helikopter selanjutnya yang sangat terkenal seperti Mi-4,

Mil Mi-6 Hook, hingga Mi-8 dan Mi-17 yang terkenal, serta heli serang-angkut Mi-24

Yum Soemarsono (1916-1999)

Yum Soemarsono dikenal sebagai bapak helikopter Indonesia. Berbeda dengan

penemu dan pengembang helikopter lainnya, dia mengembangkan helikopter sendiri

berdasarkan pengalaman dan intuisi serta keterampilannya yang tidak diperoleh dari

pendidikan tinggi. Rancangannya berupa Rotor Stabilizer dibuatnya hanya

berdasarkan intuisi.

Helikopter pertama rancangannya adalah RI-H yang selesai pada tahun 1948 namun

tidak sempat diterbangkannya karena lokasi pembuatannya di Gunung Lawu dibom

Belanda pada saat Revolusi Kemerdekaan Indonesia. Heli kedua adalah YSH yang

dirancang bersama Soeharto dan Hatmidji, selesai pada tahun 1950 dan melayang

setinggi 10 cm di lapangan Sekip Yogyakarta. Sementara Helikopter ketiga adalah

Seomarcopter yang berhasil terbang ketinggian 3 meter sejauh 50 meter dengan mesin

berdaya 60 hp pada 1954. Helikopter kepik yang ironisnya mengalami kecelakaan dan

menyebabkan kehilangan tangan kirinya dan sekaligus menewaskan asistennya, Dali.

Nama kepik sendiri adalah nama pemberian presiden Republik Indonesia pertama

Soekarno.

Kehilangan tangan kirinya membuatnya menemukan suatu alat yang dinamakan

throttle collective device untuk mengganti tangan kirinya yang putus, sehingga

penerbang cacat masih mampu menerbangkan helikopter. Alat ini digunakan untuk

mengangkat dan memutar collective, salah satu kemudi yang terletak pada sisi kiri

penerbang. Semula hanya didesain untuk helikopter jenis Hiller, namun kemudian

dikembangkannya untuk dipakai pada helikopter Bell 47G dan Bell 47J2A, hadiah

dari Solichin GP. Meski alat ini kemudian diminati oleh pabrik helikopter Bell di

Amerika Serikat, tidak ada kejelasan selanjutnya mengenai pengembangan alat ini

dan sekaligus juga hak patennya. Beliau meninggal pada 5 Maret 1999.

Sumber lain

There are several authoritative sources that document the development of helicopters and other rotating-wing aircraft such as autogiros. These authors include Gregory (1944), Lambermont (1958), Gablehouse (1967), Gunston (1983), Apostolo (1984), Boulet (1984), Lopez & Boyne (1984), Taylor (1984), Everett-Heath (1986), Fay (1987) and Spenser (1999), amongst others. Boulet (1984) has a unique perspective, giving a first-hand account of the early helicopter developments though interviews with the pioneers, constructors, and pilots of the machines. A detailed history of very early, and perhaps even obscure, helicopter developments is given by Liberatore (1950, 1988, 1998). For original publications documenting the earliest technical developments of the autogiro and helicopter, see Warner (1920), von Kármán (1921), Balaban (1923), Moreno-Caracciolo (1923), Klemin (1925), Wimperis (1926) and Seiferth (1927).

As described by Liberatore (1998), the early work on the development of the helicopter can be placed into two categories: inventive and scientific. The former is one where intuition is used in lieu of formal technical training, whereas the latter is one where a trained, systematic approach is used. At the beginning of the twentieth century nearly all prior attempts at vertical flight can be considered as inventive, the inherent aerodynamic and mechanical complexities of building a vertical flight aircraft resisting many ambitious efforts. A contributing factor was the relatively few scientific investigations of flight or studies into the science of aerodynamics -- see Anderson (1997). The history of flight documents literally hundreds of failed helicopter inventions, which either had inadequate installed power or limited control capability, or more often than not, the machine just vibrated itself to pieces. Some of the better designed early machines made brief hops into the air, but control of the aircraft was limited. Yet, the quest for true mastery of the air continued to inspire many inventors and, in time, their work led to sustained technical efforts by trained engineers and, ultimately, to the successful development of the modern helicopter. The technical contributions of Juan de la Cierva, Louis Breguet, Heinrich Focke, Raoul Hafner, Igor Sikorsky and Arthur Young stand out, and their work was instrumental in the design of truly safe and practical helicopters.

Six fundamental technical problems can be identified that limited early experiments with helicopters. These problems have been described by Igor Sikorsky (1938) and other sources. In summary, these problems were:

1. Understanding the basic aerodynamics of vertical flight: The theoretical power required to produce a fixed amount of lift was an unknown quantity to the earliest experimenters, who were guided more by intuition than by science. While basic theories describing the operation of thrusting rotors had been established by the end of the nineteenth century by William Rankine (1855), W. Froude (1878) and R. E. Froude (1889), the first significant application of aerodynamic theory to helicopter rotors came about in the early 1920s.

2. The lack of a suitable powerplant (engine): This was a problem that was not to be overcome until the beginning of the twentieth century by the development of internal combustion (gasoline) powered engines. Yet, it was not until the mid-1920s that engines with sufficient power and with the high power to weight ratios suitable for vertical flight became more widely available.

3. Minimizing structural weight and engine weight: Early power plants were made of cast iron and were relatively heavy. Aluminum, a common material used on modern aircraft, was not available commercially until about 1890, but even then was inordinately expensive. Aluminum was not widely used in aeronautical applications until 1920.

4. Counteracting rotor torque reaction: The idea of a tail rotor to counter torque reaction and provide directional control was not used on most early designs. Most early machines were built with either coaxial or laterally side-by-side rotor configurations. Yet, building and controlling two rotors was even more difficult that for

one rotor. Igor Sikorsky was the first to successfully use the tail rotor in the single rotor helicopter configuration we know today.

5. Providing stability and properly controlling the machine: A primary concern was to devise a means of defeating the unequal lift produced on the blades advancing into and retreating from the relative wind when in forward flight. These were problems that were only to be fully overcome with the use of blade articulation in the form of flapping and lead/lag hinges, ideas that were pioneered by Cierva, Breguet, and others, and with the development of blade cyclic pitch control.

6. Conquering the problem of high vibrations: Vibration was a source of many mechanical failures of the rotor and airframe, and reflected an insufficient understanding of the dynamic and aerodynamic behavior of rotating-wings.

While all of the factors listed above contributed in some way to the lack of initial progress in achieving successful vertical flight, the development of a practical helicopter had to wait until engine technology could be refined to the point that lightweight engines with considerable power could be built. By 1920, gasoline powered piston engines with higher power-to-weight ratios were more widely available, and the control problems of achieving successful vertical flight were at the forefront. This era is marked by the development of a vast number of prototype helicopters throughout the world. Most of these machines made short hops into the air or flying slowly in ground effect. Many of the early designs were built in Great Britain, France, Germany, Italy, and the United States, who led the field in several technical areas. However, with all the various incremental improvements that had been made to the basic helicopter concept during the pre-World War 2 years, it was not until the late interwar period that significant technical advances were made, and more practical helicopter designs that could lift both a pilot and a substantial payload began to appear.

The ideas of vertical flight aircraft can be traced back to early Chinese tops, a toy first used about 400 BC. Everett-Heath (1986) and Liberatore (1998) give a detailed history of such devices. The earliest versions of the Chinese top consisted of feathers at the end of a stick, which was rapidly spun between the hands to generate lift and then released into free flight. These toys were probably inspired by observations of the seeds of trees such as the sycamore, whose whirling, autorotating seeds can be seen to carry on the breeze. More than 2,000 years later, about 1754, Mikhail Lomonosov of Russia had developed a small coaxial rotor modeled after the Chinese top but powered by a wound-up spring device. The device flew freely and climbed to a good altitude.

In 1783, the French naturalist Launoy, with the assistance of Bienvenu, his mechanic, used a coaxial version of the Chinese top in a model consisting of a counterrotating set of turkey feathers. This relatively large device was powered by a string wound around the rotor shaft and tensioned by a crossbow. When the tension was released, the blades whirled and the device climbed high into the air. Launoy & Bienvenu's invention created quite a stir in scientific circles. Inspired by the early success with these and other such whirling tops, the French mathematician A. J. P. Paucton published in 1786 one of the first scientific papers on the problem of rotating wings entitled "Theorie de la vis D'Archimede."

Amongst his many elaborate drawings, the Renaissance visionary Leonardo da Vinci shows what is a basic human-carrying helicopterlike machine. His sketch of the "aerial-screw" or "air gyroscope" device is dated to 1483 but it was first published nearly three centuries later. (Da Vinci's original drawing is MS 2173 of Manuscript (codex) B, folio 83 verso, in the collection of the

Biblotheque L'Institute de France, Paris.) Da Vinci's idea was an obvious elaboration of an Archimedes water-screw, but with keen insight to the problem of flight. His proposed device comprised a helical surface formed out of iron wire, with linen surfaces made "airtight with starch." Da Vinci describes that the machine should be "rotated with speed that said screw bores through the air and climbs high." He obviously realized that the density of air was much less than that of water, so da Vinci describes how the device needed to be relatively large to accomplish this feat -- the number "8" in his backward mirror image script and to the left of the sketch indicates that the size of the rotor is eight braccia. (A braccia is an old Florentine unit of measure approximately equal to one arm's length, which translates into a rotor of roughly 20-feet in diameter.) Da Vinci clearly did not build his machine, except perhaps for some small models, but his idea was clearly far ahead of its time. See Hart (1961) or Giacomelli (1930) for further reading on da Vinci's aeronautical inventions. Although da Vinci worked on various concepts of engines, turbines, and gears, his sketches did not seem to unite the ideas of his aerial-screw machine to an engine. Nor did da Vinci seem to appreciate the concept of torque-reaction -- a well-known problem to all rotary-wing engineers where a torque applied to the rotor shaft will result in a reaction torque tending to rotate the platform from which the torque is applied.

Sir George Cayley is famous for his work on the basic principles of flight, which dates from the 1790s -- see Pritchard (1961). As a young boy, Cayley had been fascinated by the Chinese top, and by the end of the eighteenth century had constructed several successful vertical-flight models with rotors made of sheets of tin and driven by wound-up clock springs. As a young man, his fascination with flight led him to design and construct a whirling-arm device in 1804, which was probably one of the first scientific attempts to study the aerodynamic forces produced by lifting wings. Cayley (1809-10) published a

three-part paper that was to lay down the foundations of modern aerodynamics -- see Anderson (1997). In a later paper, published in 1843, Cayley gives details of a relatively large vertical flight aircraft design that he called an "Aerial Carriage." The machine had two pairs of lateral side-by-side rotors to provide lift, and were pushed forward by propellers. His idea seemed to be that the disks flattened down in forward flight, becoming circular wings. However, Cayley's device only remained an idea because the only powerplants available at the time were steam engines, and these were much too heavy to allow for successful powered flight.

The lack of a suitable powerplant continued to stifle aeronautical progress, both for fixed and rotating wing applications, but the use of miniature lightweight steam engines met with some success. In the 1840s, another Englishman, Horatio Phillips, constructed a steam-driven

vertical flight machine where steam generated by a miniature boiler was ejected out of the blade tips. Although impractical to build at full-scale, Phillips's machine was significant in that it marked the first time that a model helicopter had flown under the power of an engine rather than stored energy devices such as wound-up springs.

In the early 1860s, Ponton d'Amecourt of France flew a number of small steam-powered helicopter models. He called his machines helicopteres, which is a word derived from the Greek adjective "elikoeioas" meaning spiral or winding, and the noun "pteron" meaning feather or wing -- see Wolf (1974) and Liberatore (1998). However, the

novelist Jules Verne was still impressed with d'Amecourt's attempts, and in 1886 he wrote "The Clipper of the Clouds" where the hero of the novel cruised around the skies in a giant helicopterlike machine that was lifted by thirty-seven small coaxial rotors and pulled through the air by two propellers.

Other notable vertical flight models that were constructed at about this time include the coaxial design of Bright in 1861 and the twin-rotor steam-driven model of Dieuaide in 1877. Wilheim von Achenbach of Germany built a single rotor model in 1874, and he was probably the first to use the idea of a sideward thrusting tail

rotor to counteract the torque reaction from the main rotor. Later, Achenbach conducted experiments with propellers, the results of which were published by NACA -- see Achenbach (1923). About 1869 a Russian helicopter concept was developed by Lodygin, using a rotor for lift and a propeller for propulsion and control. Around 1878, Enrico Forlanini of Italy also built another type of flying steam-driven helicopter model. This model had dual counterrotating rotors, and it is recorded that it flew freely at heights of over forty feet for as much as twenty seconds.

In the 1880s, the well-known scientist and inventor Thomas Alva Edison experimented with small helicopter models in the United States. He tested several rotor configurations driven by a gun cotton engine, which was an early form of internal combustion engine. A series of explosions deterred further efforts with these engines. Later, Edison used an electric motor for power, and he was one of the first to realize from his experiments the need for a large diameter rotor with low blade area to give good hovering efficiency. Unlike other inventors and experimenters of the times, Edison's more scientific approach to the vertical flight problem proved that both high aerodynamic efficiency of the rotor and high power from an engine were required if successful flight was to be achieved. In 1910, Edison patented a rather cumbersome looking full-scale helicopter concept with boxkite-like blades, but there is no record that it was ever constructed. Edison, however, was to remain a staunch supporter of helicopter concepts for the rest of his life