Helicopters: The Long Journey
Helicopters: The Long Journey
The invention of the helicopter was a long and difficult process. Although the first practical helicopter was developed years after the first successful flight of an airplane, the concept of rotary flight predates that of the fixed-wing plane and goes back to the fourth century a.d. However, the helicopter as we now know it is an invention of the twentieth century and required the perseverance of many inventors to make this machine a reality.
The helicopter is described as a VTOL or vertical take-off and lift machine, which means it ascends vertically without benefit of a runway. The whirling action of the rotor, to which the blades are attached, gives the helicopter its lift. The blade is more curved on the top than the bottom, and the air is forced to flow faster over the top of the blade. A difference in air speed creates a difference in air pressure with less being on the upper surface of the blade, and in this way lift is created. Rotor tilt controls the direction of flight and in whatever direction the rotor is tilted the helicopter moves. It can move forward, backward, side to side, and up and down at very low speeds, and can hover in the air.
Written in the "Pau Phu Tau," the first mention of rotary flight dates back to the fourth century a.d. In this document, the alchemist Ko Hung proposed a type of flying top that could be made "with wood from the inner part of the jujube tree, using ox leather (straps), fastened to returning blades so as to set the machine in motion." Something like this later emerged in Europe as a "Chinese toy" or "Chinese top," and was a child's toy. Leonardo da Vinci (1452-1519) described a rotary machine late in the fifteeneth century, a screw made of "starched linen" to be turned "swiftly" by a single passenger. The term helicopter comes from his use of Greek to describe this craft, helix, meaning "spiral" and pteron, meaning "wing." He never attempted to build the machine, however.
As theories of rotary flight were being developed, inventors began to create helicopter models to test these ideas. In 1754, the Russian Mikhail Vasilyevich Lomonosov (1711-1765) proposed to the Russian Academy of Science, a co-axial, contra-rotating model to be operated by clockwork for the lifting of meteorological instruments. Contra-rotating means there are two sets of blades, one set below the other, on the same rotor. This counteracts the effect of torque, which causes the fuselage to spin in the opposite direction of the rotor. It is thought his model may have flown, but Frenchmen Launoy and Bienvenu are generally credited with the first flying helicopter models. They demonstrated their model to the Académie des Sciences on April 28, 1784. The model consisted of co-axial rotors powered by the spring loading action of a whalebone bow. In Britain in 1796, Sir George Cayley (1773-1857), also known as the "father of aerial navigation" due to his contributions to fixed-wing flight, constructed and flew a model helicopter. Although his model was not unlike that of Launoy and Bienvenu, Cayley probably did not know of the French models.
Recognizing the need for a substantial power source to lift a man-operated helicopter, inventors experimented with steam-powered helicopter designs during the 1800s, but they were heavy and awkward. In 1876 the German Nikolaus August Otto (1832-1891) developed the four-stroke internal combustion engine, leading the way to smaller, lighter and more powerful engines. The American Thomas Edison (1847-1931) had experimented with model helicopters driven by electricity and even gunpowder during this time. Although unsuccessful, he felt a practical helicopter would one day be built.
Other great inventors like Wilbur (1867-1912) and Orville (1871-1948) Wright did not agree. They flew the first airplane in 1903, the Flyer II, at Kitty Hawk, North Carolina. The success of the airplane in many ways made continuing exploration into rotary machines appear foolish and backwards, and the Wright brothers condemned helicopter development by saying, "Like all novices, we began with the helicopter (in childhood) but soon saw it had no future and dropped it." Work on rotary designs did continue, as the piston engines of the early 1900s became lighter and more efficient.
Full-sized helicopters did not achieve any success until 1907, when Frenchmen Louis Breguet and Charles Richet designed the first. It was a massive machine weighing 1,272 pounds (577 kg) with the pilot, powered by a 50-hp Antoinette eight-cylinder inline engine that drove four rotors. On September 29, 1907, at Douai, France, it lifted for two minutes but was stabilized by four men with poles. Next, on November 13, 1907, fellow Frenchman Paul Cornu (1881-1914) piloted his design, which remained aloft for a few seconds at six feet (1.8 m). It did not need to be steadied and although tethered, it never reached the end of the lines and is now recognized as the first free flight of a piloted rotary-winged vehicle. Their successes inspired further development.
One of the most important figures in the history of rotary flight was the Spaniard Juan de la Cierva (1895-1936). He was responsible for the development of the autogiro, differing from the helicopter in that the rotors are not powered by an engine, but rather depend on auto-rotation for sustained flight. The success of autogiros aided the development of the helicopter. After the First World War in 1919, he began to work on rotary machines. In 1922, he designed and built an autogiro that had flapping hinges where the blades attach to the rotor, and is credited with solving the problem of dissymmetry of lift, which causes the machines to flip over and crash. The machine was flown on January 9, 1923, about 200 yards (183 m) off the ground and executed some maneuvers. In 1926 he launched the Cierva Autogiro Co., Ltd. and built the C. 6C, the first rotary vehicle for the British Royal Air Force, as an experimental machine. Cierva flew the English Channel in 1928, in his autogiro and toured 3,000 miles (4,827 km) in short flights across Europe. Harold Pictarin, in the United States, secured the rights to manufacture autogiros in 1928, and in the late thirties he and Cierva licensed the Kellett Autogiro Co., developing the Kellet YG-1, which became the U.S. Army's first rotary-winged craft.
As rotary flight was shown to have practical applications, interest in helicopters ignited. Heinrich Focke (1890-1979), gaining experience with rotary flight when Germany built C.19s and C.30s under license, built the Focke-Wulf 61. This machine is considered the first practical helicopter ever built, and it flew to 11,000 feet (3,353 m) for 80 minutes in 1937. That year Hannah Reitsch flew the FW 61 for a crowd at the Berlin Sports Hall, which proved a great success and showed off the machine's maneuverability. Hannah Reitsch was to later become Hitler's personal pilot.
After experimenting with rotary flight for years Igor Sikorsky (1890-1972), a Russian-American, built the VS 300 in 1939. The VS 300 had a single main rotor with a tail and tail prop similar to many of the designs today, and marked the first flight of a helicopter in the U.S., flying untethered in 1940. Sikorsky improved upon this design, and the production of the VS 300 as the R.4 is heralded as the beginning of helicopter production in the United States. The R.4, based on the VS 300, flew in 1942 and the U.S. military bought hundreds of models during WWII. This design became a direct link between early designs and the helicopter of today.
During the mid-1900s military use of helicopters increased, leading to improvements in design. Able to hover in one place, move in every direction slowly, and land in an area little more than the size of the craft itself, the maneuverability of the helicopter made it valuable to the American military during the wars in Korea and Vietnam. Initially, it was not used for combat, but was used to carry troops, supplies, guns, and ammunition into remote and difficult areas. Helicopters were used to rescue downed pilots behind enemy lines, and airlifted more than 23,000 causalities to field hospitals. The Bell H-13 was responsible for 18,000 of those rescued and received the nickname "Korean Angel," for that reason. It was during the Vietnam War that helicopters became true gunships. Beginning in 1964, they were used in combat and the Huey UH-13 was fitted with anti-tank missiles and turret mounted grenade launchers. While the helicopter still carried on its important role of transporting and rescuing troops, it was also being used to suppress enemy fire. During the war, helicopters were modified to function better under attack and were made narrower and faster. These wars prompted much advancement in the development of the helicopter, and now there are more helicopters in the world's airforce than airplanes.
While helicopters do not enjoy a glamorous reputation, they are indispensable pieces of equipment. They have developed into more economical and practical machines powered by lighter, more powerful engines. Today, helicopters are used to perform important services for cities, industry, and government. Rescue missions and operations depend on the versatility of the helicopter for disaster relief efforts at sea and on land. The Coast Guard uses them regularly, and the ability of the helicopter to hover allows for harnesses to be extended to victims on the ground or at sea, who can then be transported to safety. Helicopters are also useful when rescuing lost or injured hikers or skiers in mountainous terrain. Hospitals now have helipads so accident victims can be transported faster for emergency treatment. Police use them for aerial observation, tracking fleeing criminals, searching for escaped prisoners, or patrolling borders for illegal activity. Police and news agencies even use the helicopter to watch for traffic problems in major cities.
Wildlife and forestry employees rely on the helicopter to conduct aerial surveys of animal populations and to track animal movements. Forestry personnel use the helicopter to observe the condition of tree stands and to fight fires. Helicopters transport personnel and equipment to base camps, and spray fires. The agricultural industry engages helicopters to spray fields and to check on and round up cattle.
Helicopters are of particular interest to industry, performing a variety of jobs that require strength and maneuverability, such as hoisting heavy building materials to the upper levels of a skyrise and hauling awkward and large objects under their fuselage. They have also been used to erect hydro towers and other tall structures. Petroleum industries rely on the helicopter to observe pipelines for damage and to transport personnel to offshore drilling operations.
Able to perform a number of passenger services, helicopters are frequently employed by businesses to transport clients and employees. Although expensive, it is a convenient way to beat the traffic for those with time constraints, and downtown businesses in large cities will often have heliports on top of their buildings. Helicopters transport passengers from the airports and are enjoyed recreationally by site seers and helicopter enthusiasts.
While helicopters have improved greatly since the first piloted rotary machines of 1907, they are much slower than airplanes and cannot reach the same altitudes. Expensive and difficult to fly, helicopters are not always economical, but they are highly versatile and maneuverable, and can move in ways that are impossible for fixed-wing craft. This maneuverability makes the helicopter an essential tool for industrial, military, and civil service.
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