A helicopter is a type of rotorcraft in which the lift and thrust are provided by the rotor. This allows the helicopter to take off and land vertically, float, and fly forward, backward, and laterally. These attributes allow helicopters to be used in densely packed or isolated areas where fixed wing aircraft and many VTOL aircraft (takeoff and vertical landings) can not function.
The English word
The helicopter was developed and built during the first half-century of flight, with Focke-Wulf Fw 61 becoming the first operational helicopter in 1936. Several helicopters reached limited production, but it was not until 1942 that the helicopter designed by Igor Sikorsky reached full-scale production, with 131 aircraft built. Although most previous designs use more than one main rotor, a single main rotor with an anti-torque tail rotor configuration has become the most common helicopter configuration. The Tandem rotor helicopter is also widely used because of the larger carrying capacity. Coaxial helicopters, combined tiltrotor, and helicopters are all flying today. Quadcopter helicopters spearheaded as early as 1907 in France, and other multicopter types have been developed for specialized applications such as unmanned aircraft.
Video Helicopter
History
Initial design
The earliest reference for vertical flights comes from China. Since about 400 BC, Chinese children have been playing with flying bamboo toys (or Chinese tops). This bamboo balloon rotates by rotating the stick attached to the rotor. Spinning creates lift, and flying toys when released. The 4th century AD Taoist Book Baopuzi by Ge Hong ( ??? "Master Embracing Simplicity") reportedly describes some of the ideas attached to the rotary wing aircraft./span>
Designs similar to Chinese chopper toys appear in some Renaissance paintings and other works. In the 18th century and early 19th century, Western scientists developed glyphs based on Chinese toys.
It was not until the early 1480s, when Leonardo da Vinci made a design for a machine that could be described as an "air screw," that any recorded progress was made toward a vertical flight. His records suggest that he make a small flying model, but there is no indication for any provision to stop the rotor from making a spinning craft. As scientific knowledge increases and becomes more accepted, people continue to pursue the idea of ​​vertical flight.
In July 1754, Russian Mikhail Lomonosov had developed a small coaxial model after China's top but was supported by a wounded spring device and showed it to the Russian Academy of Sciences. It is supported by springs, and is recommended as a method for lifting 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 as a rotor blade, and in 1784, showing it to the French Academy of Sciences. Sir George Cayley, influenced by his childhood appeal by flying China, developed a feather model, similar to Launoy and Bienvenu, but supported by rubber bands. By the end of this century, he had advanced using tin sheets for rotor blades and springs for power. His writings on his experiments and models will be influential on future aviation pioneers. Alphonse PÃÆ'Ã… © naud then developed a coaxial rotor helicopter model toy in 1870, also supported by a rubber band. One of these toys, given as a gift by their father, will inspire the Wright brothers to pursue the dream of flying.
In 1861, the word "helicopter" was created by the palace of Gustave de Ponton d'Amà © à ©, the French inventor who demonstrated the small steam-powered model. While celebrated as an innovative use of new metal, aluminum, its model never gets off the ground. D'Amecourt's linguistic contribution will persist to finally describe the vertical flight he imagined. The power of steam is popular with other inventors as well. In 1878 the Italian-owned Enrico Forlanini unmanned vehicle, also powered by a steam engine, climbed to a height of 12 meters (40 feet), where it floated for about 20 seconds after a vertical takeoff. The steam-powered design of Emmanuel Dieuaide features rotating rotor through a hose from a boiler on the ground. In 1887, the inventor of Paris, Gustave Trouvà ©  ©, built and flew helicopters of moored electric models.
In July 1901, the premier helicopter flight Hermann Ganswindt took place in Berlin-Schöneberg; this is probably a flight driven by the first motor that carries humanity. A film covering the event was taken by Max Skladanowsky, but remained lost.
In 1885, Thomas Edison was awarded US $ 1,000 by James Gordon Bennett, Jr., to conduct experiments on aviation development. Edison built a helicopter and used the paper to create a stock ticker to create a guncotton, with which he attempted to power an internal combustion engine. The helicopter was damaged by an explosion and one of the workers was badly burned. Edison reported that it would take a motor with a ratio of three to four pounds per horsepower generated to be successful, based on his experiments. JÃÆ'¡n BahÃÆ'½?, A Slovak inventor, adapted an internal combustion engine to propel his helicopter model to a height of 0.5 meters (1.6 feet) in 1901. On May 5, 1905, his helicopter reached four meters (13 feet) in altitude and flying for over 1,500 meters (4,900 feet). In 1908, Edison patented his own design for a helicopter powered by a gasoline engine with a kite box attached to a pole with a cable for the rotor, but never flew.
First flight
In 1906, two French brothers, Jacques and Louis Breguet, began experimenting with airfoils for helicopters. In 1907, the experiment yielded Gyroplane No.1 , possibly the earliest example of a quadcopter. Although there was some uncertainty about the date, between August 14th and September 29th 1907, Gyroplane no. 1 lifts its pilot into the air about two feet (0.6 m) for one minute. Gyroplane No. 1 proved very unstable and needed a man in every corner of the fuselage to hold it steady. For this reason, the Gyroplane flight no. 1 is considered to be the first manned helicopter flight, but not a free or unmanned flight.
That same year, French inventor Paul Cornu designed and built a Cornu helicopter that uses two 20-foot (6 m) counter-rotary rotors powered by an 18-hp (18-kW) Antoinette engine. On November 13, 1907, he raised his inventor to 1 foot (0.3 m) and remained taller for 20 seconds. Although this flight does not extend beyond Gyroplane flights. 1, it was reported as the first absolutely free flight with a pilot. The Cornu helicopter completed several more flights and reached a height of nearly 6.5 feet (2 m), but proved unstable and abandoned.
In 1911, Slovenian philosopher and economist Ivan Slokar patented a helicopter configuration.
Danish inventor Jacob Ellehammer built the Ellehammer helicopter in 1912. It consisted of a frame equipped with two opposite discs, each equipped with six propellers around its perimeter. After the indoor test, the plane was exhibited outside and made several free takeoffs. The experiment with the helicopter continued until September 1916, when it was reversed during the take-off, destroying its rotor.
During World War I, Austria-Hungary developed PKZ, a prototype experimental helicopter, with two built-in aircraft.
Initial development
In the early 1920s, Argentina RaÃÆ'ºl Pateras-Pescara de Castelluccio, while working in Europe, demonstrated one of the first successful applications of cyclic pitch. Coaxial, counter-rotating, biplane propellers can be twisted to cyclically increase and decrease the lift power they generate. The rotor hub can also be tilted forward several degrees, allowing the aircraft to move forward without a separate propeller to push or pull it. Pateras-Pescara is also able to demonstrate the principle of autorotation. In January 1924, No. Pescara helicopter. 1 tested but found to be less powerful and unable to lift its own weight. Its 2F fared better and broke the record. The UK government funded further research by Pescara, which produced the No. 1 helicopter. 3, powered by a 250 hp radial engine that can fly up to ten minutes.
On April 14, 1924, the French ÃÆ'â € ° tienne Oehmichen set the world's first helicopter record recognized by FÃÆ' © dà © Ã… © ronautique Internationale (FAI), flying its quadrotor helicopter 360 meters (1,181 feet). On April 18, 1924, Pescara defeated Oemichen's record, flying 736 meters (nearly half a mile) in 4 minutes and 11 seconds (about 8 mph, 13 km/h), maintaining a height of six feet (1.8 meters). On May 4, Oehmichen assigned the first 1km closed circuit helicopter flight in 7 minutes 40 seconds with the No. 1 machine. 2 of his.
In the US, George de Bothezat built a helicopter quadrotor de Bothezat helicopter for the United States Air Force but the Air Force canceled the program in 1924, and the plane was canceled.
Albert Gillis von Baumhauer, a Dutch aeronautical engineer, began studying rotorcraft designs in 1923. His first prototype "flew" ("leaping" and hovering in reality) on September 24, 1925, with the Dutch Air Force captain, Captain Floris Albert van Heijst in control. The control van Heijst used was the invention of von Baumhauer, cycle and collective. The patent was granted to von Baumhauer for cyclic and collective control by the UK aviation ministry on January 31, 1927, with patent number 265,272.
In 1927, Engelbert Zaschka of Germany built a helicopter, fitted with two rotor, in which gyroscopes were used to improve stability and serve as an energy accumulator for the flight glide for landing. The Zaschka aircraft, the first helicopter, ever worked so successfully in miniatures, not just up and down vertically, but able to stay still at any height.
In 1928, the Hungarian aviation engineer OszkÃÆ'¡r AsbÃÆ'³th built a helicopter prototype that took off and landed at least 182 times, with a maximum single flight duration of 53 minutes.
In 1930, Italian engineer, Corradino D'Ascanio built his D'AT3, a coaxial helicopter. The relatively large engine has two, two propellers, a rotating propeller. The control is achieved by using an additional wing or servo-tab at the end of the trailing blade, a concept that was later adopted by other helicopter designers, including Bleeker and Kaman. Three small propellers fitted to the airframe are used for additional pitch, roll, and yaw controls. D'AT3 has a record of FAI speed and altitude for simple time, including altitude (18 m or 59 ft), duration (8 min 45 sec) and flying distance (1,078 m or 3,540 ft).
In the Soviet Union, Boris N. Yuriev and Alexei M. Cheremukhin, two aeronautical engineers working at the Tsentralniy Aerogidrodinamicheskiy Institute (TsAGI, Central Aerohydrodynamic Institute), built and flew a single elevator TsAGI 1-EA - Helicopter motor, which uses an open tube frame, a four-blade main lifter rotor, and twin sets with a diameter of 1.8 meters (6 feet), a two-blade anti-torque rotor: a set of two in the nose and a set of two on the tail. Supported by two M-2 powerplants, up-rated Gnome Monosoupape 9 Type B-2 100 CV rotary engine output CV World War I, TsAGI 1-EA made several low altitude flights. On August 14, 1932, Cheremukhin managed to get 1-EA to an unofficial height of 605 meters (1,985 feet), destroying the previous performance of d'Ascanio. Since the Soviet Union was not yet a member of the FAI, however, Cheremukhin's record remains unrecognized.
Nicolas Florine, a Russian engineer, built the first twin tandem rotor engine for a free flight. It flew in Sint-Genesius-Rode, at the Laboratoire AÃ © Ã © rotechnique de Belgique (now von Karman Institute) in April 1933, and reached a height of six meters (20 feet) and endurance of eight minutes. Florine chose the co-rotating configuration because the gyroscopic stability of the rotor will not be canceled. Therefore, the rotor must be slightly tilted in the opposite direction to resist torque. Using irregular rotors and joint rotation also minimizes the pressure on the stomach. At that time, it was one of the most stable helicopters available.
BrÃÆ' Â © guet-Dorand Gyroplane Laboratoire was built in 1933. It was a coaxial helicopter, spinning around. After many ground and crash trials, it first flew on June 26, 1935. In a short time, the plane was recording with pilot Maurice Claisse in control. On December 14, 1935, he set a record for a closed-circuit flight with a diameter of 500 meters (1,600 feet). The following year, on September 26, 1936, Claisse set a record high 158 meters (520Ã, ft). And, finally, on November 24, 1936, he set a record of one hour, two minute, and 50 seconds flight duration for 44 kilometers (27 mi) closed circuit at 44.7 kilometers per hour (27.8 mph). The aircraft was destroyed in 1943 by Allied air strikes at Villacoublay airport.
Arthur M. Young, the American inventor, began working on a helicopter model in 1928 using an electric hover motor that was altered to drive the rotor head. Young finds the stabilizer bar and patents it soon afterwards. A mutual friend introduced Young to Lawrence Dale, who had seen his work asking him to join the Bell Aircraft company. When Young arrived at Bell in 1941, he signed his patent and started working on a helicopter. The budget is 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, then succeeded by Bell 47.
Autogyro
Early rear wingless flights have failed primarily due to the unbalanced rolling motion generated while attempting to take off, due to the asymmetry of lifting between the forward and backward blades. This great difficulty was solved by the introduction of Juan de la Cierva about the flapping hinges. In 1923, the first successful autologro de la Cierva was flown in Spain by Lt. Gomez Spencer. In 1925 he brought C.6 to England and demonstrated it to the Air Ministry in Farnborough, Hampshire. This machine has four rotor blades with hinged hinges but relies on conventional aircraft control for pitch, roll and yaw. It is based on the Avro 504K plane, the initial rotation of the rotor is achieved by rapid disassembling the rope passing around the stop at the bottom of the blade.
The main problem with autogyro is to drive the rotor before takeoff. Some methods are tried in addition to a circular rope system, which can take the rotor speed up to 50% of the required, where point motion along the ground to reach the required flying speed, while tilting the rotor to set the autorotation. Another approach is to tilt the tail stabilizer to bend the engine slipstream through the rotor. The most acceptable solution was finally achieved with C.19 Mk.4, produced in a certain quantity; the drive directly from the engine to the rotor is installed, where the rotor can be accelerated to speed. The rotor coupling is then released before taking off.
As autologro de la Cierva achieved success and acceptance, others began to follow and with them came further innovation. Most important was the development of direct rotor control through a cyclic pitch variation, achieved initially by tilting the rotor hub and then by Austrian engineer Raoul Hafner, by the application of a spider mechanism acting directly on each rotor blade. Autogyro's first automated production control is C.30, produced in quantity by Avro, Liore et Olivier, and Focke-Wulf.
The production model, called C.30A by Avro, was built under license in England, France and Germany and was similar to C.30P. It carries a small moving pruning surface. Each licensee uses a machine made nationally and uses a slightly different name. Overall, 143 C30 production was built, making it the pre-war autologro most.
Between 1933 and 1936, de la Cierva used one C.30A ( G-ACWF ) to perfect his last contribution to the development of the autogyro before his death in late 1936. To allow the plane to take off without traveling, "Autodynamic" rotor head, which allows the rotor to be rotated by the engine in the normal way but to a higher take-off rpm at the zero rotor incident and then reaches a positive operational pitch suddenly enough to jump some 20Ã, ft (6 m) into on.
Birth industry
Heinrich Focke at Focke-Wulf was licensed to produce the autogiro Cierva C.30 in 1933. Focke designed the first practical twin-rotor helicopter in the world, the Focke-Wulf Fw 61, which first flew on 26 June 1936. Fw 61 broke all world records helicopter in 1937, showing a flight envelope previously only achieved by autogyro.
During World War II, Nazi Germany used small helicopters for observation, transportation, and medical evacuation. Flettner Fl 282 hummingbird synchropter - using the same basic configuration as Anton Flettner's own own flu Fl 265 - used in the Mediterranean, while Focke Achgelis Fa 223 Drache twin-helicopter rotors are used in Europe. Extensive bombing by Allied forces prevented Germany from producing large numbers of helicopters during the war.
In the United States, Russian-born engineers Igor Sikorsky and W. Lawrence LePage competed to produce the first US military helicopters. LePage received a patent to develop a patterned helicopter after Fw 61, and built the XR-1. Meanwhile, Sikorsky chose a simpler single-rotor design, the VS-300, which turned out to be the first single rotor single chopper design helicopter. After experimenting with the configuration to counter the torque generated by a single main rotor, Sikorsky settled on a smaller single rotor mounted on the tail boom.
Developed from VS-300, Sikorsky's R-4 is the first large-scale mass-produced helicopter, with production orders for 100 aircraft. The R-4 was the only Allied helicopter stationed in World War II, when used primarily for search and rescue (by the USAAF First Air Command Group) in Burma; in Alaska; and in other areas with harsh terrain. Total production reached 131 helicopters before R-4 was replaced by other Sikorsky helicopters such as R-5 and R-6. Overall, Sikorsky produced over 400 helicopters before the end of World War II.
While LePage and Sikorsky built their helicopters for the military, Bell Aircraft hired Arthur Young to help build a helicopter using a Young-blade two-knife rotor design, which uses a weighted stabilizer rod placed at a 90 ° angle to the rotor blades. The next Model 30 helicopter demonstrates simplicity of design and ease of use. The Model 30 was developed into Bell 47, which became the first certified helicopter for civilian use in the United States. Manufactured in several countries, the Bell 47 is the most popular helicopter model for nearly 30 years.
Turbine age
In 1951, at the urging of his contact at the Department of the Navy, Charles Kaman modified the K-225 synchropter - a design for the twin-rotor helicopter concept first pioneered by Anton Flettner in 1939, with the mentioned piston 265 Fl in Germany - with new engine type, turboshaft engine. The adaptation of this turbine engine provides a large amount of power to the Kaman helicopter with a lower weight penalty than a piston engine, with heavy engine blocks and additional components. On December 11, 1951, Kaman K-225 became the world's first turbine powered helicopter. Two years later, on March 26, 1954, the modified HTK-1 Navy, another Kaman helicopter, became the first twin-turbine helicopter to fly. However, it is the Sud Aviation Alouette II which will be the first helicopter produced with a turbine engine.
Reliable flying helicopters were developed several decades after the fixed wing aircraft. This is largely due to the need for higher engine power density than fixed wing aircraft. Fuel and engine improvements during the first half of the 20th century were an important factor in the development of helicopters. The availability of lightweight turboshaft engines in the second half of the 20th century led to the development of larger, faster, and higher-performing helicopters. While smaller and cheaper helicopters still use piston engines, turboshaft engines are the preferred engines for helicopters today.
Maps Helicopter
Usage
Due to the helical operating characteristics of the helicopter - its ability to take off and land vertically, and to hover for a long time, as well as the nature of handling aircraft under low airspeed conditions - it has been selected to perform tasks previously impossible with planes other, or time or work-intensive to reach on the ground. Currently, the use of helicopters includes the transportation of people and cargo, military use, construction, fire, Search and rescue, Tourism, medical transport, law enforcement, agriculture, news and media, and air observations, among others. They can be used for seismology or recreational Reflection.
The helicopter used to carry loads connected to long wires or sling is referred to as an air crane. Air cranes are used to place heavy equipment, such as radio transmission towers and large air-conditioning units, on top of tall buildings, or when goods must be raised in remote areas, such as radio towers raised on hills or mountains. Helicopters are used as air cranes in the logging industry to lift trees outside the terrain where vehicles can not travel and where environmental problems prohibit road construction. This operation is called a long line because of the long, single sling line used to carry the load.
The largest single non-combat helicopter operation in history was a disaster management operation after the 1986 Chernobyl nuclear disaster. Hundreds of pilots were involved in airborne missions and observation missions, making dozens of daily sorties for several months.
"Helitack" is the use of helicopters to combat forest fires. Helicopters are used for air firefighting (water bombing) and may be equipped with tanks or carrying helibuckets. Helibuckets, like Bambi buckets, are usually filled with soaking buckets into lakes, rivers, reservoirs, or portable tanks. Tanks mounted on a helicopter are filled from the hose while the helicopter is on the ground or the water is sucked from the lake or reservoir through a snorkel suspended when the helicopter hovers over the water source. Helitack helicopters are also used to send firefighters, who descend to hard-to-reach areas, and supply firefighters. Common fire helicopters include the Bell 205 and Erickson S-64 Aircrane helitanker variants.
Helicopters are used as air ambulances for emergency medical assistance in situations where ambulances can not easily or quickly reach the scene, or are unable to transport patients to medical facilities on time. Helicopters are also used when patients need to be transported between medical facilities and air transport is the most practical method. Air ambulance helicopters are equipped to stabilize and provide limited medical care to patients while on a flight. The use of helicopters as air ambulances is often referred to as "MEDEVAC", and patients are referred to as "flown", or "medevaced". This use was pioneered in the Korean war, when the time to reach medical facilities was reduced to three hours of the eight hours needed in World War II, and subsequently reduced to two hours by the Vietnam war.
Police departments and other law enforcement agencies use helicopters to pursue suspects. Because helicopters can achieve unique aerial views, helicopters are often used along with police in the field to report on the location and movement of suspects. They are often installed with lighting equipment and heat sensing for night activities.
Military forces use attack helicopters to carry out air strikes on ground targets. Such helicopters are fitted with missile launchers and miniguns. Helicopter carrier is used to transport troops and supplies where the lack of an airstrip will make transportation via fixed wing aircraft impossible. The use of transport helicopters to send troops as attack power on purpose is referred to as "air strikes". Unmanned aerial helicopter (UAS) systems of various sizes developed by the company for military reconnaissance and supervisory duties. Naval forces also use helicopters equipped with sonar dipped for anti-submarine warfare, because they can operate from small vessels.
Oil companies hire helicopters to move workers and spare parts quickly to remote rigged sites located at sea or in remote locations. The superiority of speed on board makes the high operating cost of the helicopter cost-effective to ensure that the oil platform continues to operate. Various companies specialize in this type of operation.
NASA is developing the Mars Scout Helicopter, a 1.8 kg (4.0 pound) helicopter to be launched for the Mars survey (together with the plow) in 2020. Given that the atmosphere of Mars is 100 times thinner than the Earth's atmosphere, its two blades will spin approaching 3,000 revolutions per minute, approximately 10 times faster than a terrestrial helicopter.
Market
By 2017, 926 civilian helicopters were shipped for $ 3.68 Billion, led by Airbus Helicopters with $ 1.87 Billion for 369 rotorcraft, Leonardo Helicopters with $ 806 Million for 102 (first three quarters only), Bell Helicopter with $ 696 Million for 132, then Helicopter Robinson with $ 161 Million for 305.
Design features
rotor system
The rotor system, or simpler rotor , is the rotating part of the helicopter that produces lift. The rotor system can be mounted horizontally, such as the main rotor, providing vertical appointment, or can be mounted vertically, such as the tail rotor, to provide a horizontal drive to eliminate torque from the main rotor. The rotor consists of a mast pole, hub and rotor.
The pole is a cylindrical metal shaft extending upward from the transmission. At the top of the pole is an attachment point for a rotor blade called a hub. The rotor blades are attached to the hub. The main rotor system is classified according to how the rotor blades are attached and moved relative to the hub. There are three basic types: non-stop, fully articulated, and hobbled; although some modern rotor systems use this combination.
Anti-torque
Most helicopters have a single main rotor, but the torque created by its aerodynamic drag must be countered by the opposing torque. The design that Igor Sikorsky sets for his VS-300 is a smaller tail rotor. The tail rotor pushes or pulls the tail to counteract the torque effect, and this has been the most common configuration for helicopter design, usually at the end of the tail boom.
Some helicopters use other anti-torque controls instead of the tail rotor, such as fan funnel (called Fenestron or FANTAIL ) and NOTAR. NOTAR provides an anti-torque similar to the way the wings develop lift power through the use of Coand? effect on the tail boom.
The use of two or more horizontal rotors in opposite directions is another configuration used to counteract the effects of torque on an aircraft without relying on an anti-torque tail rotor. This allows the power normally required to drive the tail rotor to apply to the main rotor, increasing the lift capacity of the aircraft. There are some common configurations that use counter-rotating effects to benefit rotorcraft:
- Tandem rotor are two rotating propellers with one mounted behind the other.
- The coaxial rotor are two rotating rotors which are mounted one on top of the other with the same axis.
- Rotor intermeshing is two rotating opposite vanes mounted adjacent to each other at an angle sufficient to allow the intermesh rotor above the top of the plane without colliding.
- The transverse rotor is a pair of counter-rotating rotor mounted on each wing tip or outrigger structure. They were found in tiltrotors and some previous helicopters used first and now.
- Quadcopters have four frequent rotors with parallel axes (sometimes rotating in the same direction as the bevel axis) normally used on model aircraft.
The jet tip design let the rotor propel itself through the air and avoid generating torque.
Machine
The number, size and type of machine (s) used on the helicopter determine the size, function and capability of the helicopter's design. The earliest helicopter machine was a simple mechanical device, such as a rubber band or spindle, which reduced the size of the helicopter into toys and small models. For half a century before the first plane flight, steam engines were used to continue the development of aerodynamic understanding of helicopters, but limited power did not allow manned flights. The introduction of internal combustion engines in the late 19th century became a watershed for the development of helicopters when machines were developed and manufactured that were strong enough to enable helicopters capable of lifting humans.
The initial helicopter design used a specially made engine or rotary engine designed for aircraft, but this was soon replaced by a more powerful car engine and radial engine. The single most limiting factor of helicopter development during the first half of the 20th century was that the amount of power generated by the engine was unable to cope with the engine weight in the vertical flight. This was successfully overcome by successful early helicopters using the smallest available machines. When a flat, compact engine was developed, the helicopter industry found light-heavy powerplants easily adjusted by small helicopters, although radial machines continued to be used for larger helicopters.
The turbine engine revolutionized the aviation industry, and the turboshaft engine finally gave the engine helicopter with a large amount of power and low weight penalties. Turboshafts are also more reliable than piston engines, especially when producing the sustainable high power levels required by helicopters. The turboshaft engine can be adjusted to the size of the designed helicopter, so all of the lightest helicopter models are currently powered by turbine engines.
A special jet engine developed to drive the rotor from the end of the rotor is referred to as a jet tip. The tip jet driven by the remote compressor is referred to as a cold jet tip, whereas the jet driven by the combustion exhaust is referred to as a hot tip jet. An example of a cold jet helicopter is Sud-Ouest Djinn, and an example of a hot-jet tip helicopter is the YH-32 Hornet.
Some helicopters are radio controlled and unmanned aerial vehicle helicopter type smaller, using electric motors. Radio controlled helicopters may also have piston engines that use fuel other than gasoline, such as nitromethane. Some turbine engines commonly used in helicopters can also use biodiesel as a substitute for jet fuel.
There are also human-powered helicopters.
Flight control
The helicopter has four flight control inputs. It is a cyclic pedal, collective, anti-torque, and throttle. Cyclic controls are usually located between the pilot's feet and are usually called cyclic bars or just cyclic . In most helicopters, the cyclic is similar to a joystick. However, Robinson R22 and Robinson R44 have unique cyclic control systems and some helicopters have cyclic controls that descend into the cockpit from above.
The control is called cyclic because it converts the cyclic rotor pitch cyclically. The result is to tilt the disk rotor in a certain direction, so the helicopter moves in that direction. If the pilot pushes the cyclic forward, the disk rotor is tilted forward, and the rotor produces a forward impulse. If the pilot pushes the cyclic aside, the disc rotor tilts to that side and generates a thrust in that direction, causing the helicopter to drift sideways.
Collective pitch control or collective is located on the left side of the pilot seat with adjustable friction control to prevent unintentional movements. Collective change of the pitch angle of all the main rotor blades collectively (ie at the same time) and regardless of their position. Therefore, if the collective input is made, all the vanes are changed equally, and the result is the helicopter rising or decreasing in altitude.
The anti-torsion pedals are located in the same position as the steering pedals in fixed wing aircraft, and serve the same purpose, ie to control the direction in which the nose of the aircraft is directed. The pedal application in a certain direction changes the pitch of the tail blades, increasing or decreasing the impulses generated by the tail rotor and causing the nose to evaporate toward the applied pedal. The pedals mechanically alter the tail rotor pitch that changes the amount of thrust produced.
The helicopter rotor is designed to operate within a narrow RPM range. Throttle controls the power generated by the engine, which is connected to the rotor with fixed ratio transmission. The purpose of the throttle is to maintain sufficient engine power to keep the rotor of the rotor within the allowable limit so that the rotor produces sufficient lift to fly. On a single-engine helicopter, throttle control is a motorcycle touch grip mounted on collective control, while a twin-engine helicopter has power levers for each machine.
Swashplate controls the collective and cyclic pitch of the main blade. Swashplate moves up and down, along the main axis, to change the pitch of the two blades. This causes the helicopter to push air down or up, depending on the angle of the attack. Swashplate can also change the angle to move the angle of the blade forward or back, or left and right, to make the helicopter move in that direction.
Flights
There are three basic conditions for helicopter flight: hover, forward flight and transition between the two.
Hover your cursor
Hovering is the most challenging part of flying helicopters. This is because the helicopter produces its own strong air while on a hover, which acts on the plane's surface and flight controls. The end result is a constant control input and correction by the pilot to keep the helicopter where needed. Despite the complexity of the task, the control inputs in hover are simple. Cyclic is used to remove drift in the horizontal plane, ie to control forward and backward, right and left. Collective is used to maintain altitude. Pedals are used to control the direction or head of the nose. This is the interaction of the controls that make float very difficult, because adjustment in one control requires adjustment of the other two, creating a constant correction cycle.
Transition from hover to forward flight
When a helicopter moves from hover to forward flight, it enters a state called a translational elevator that provides an additional lift without increasing power. This situation, most often, occurs when the air velocity reaches about 16-24 knots, and may be required for a helicopter to get a flight.
Flight forward
In forward flight, helicopter flight controls behave more like fixed wing aircraft. Replacing the cyclic forward will cause the nose to lift down, with increasing air velocity generated and loss of altitude. The wrong cycle will cause the nose to lift, slow the helicopter and cause it to climb. Increasing the collective (power) while maintaining a constant air velocity will drive the climb while reducing the collective will lead to a decline. Coordinating both inputs, collective downs plus aft cyclic or up collective plus forward cyclic, will result in changes in air velocity while maintaining a constant height. The pedal serves the same function both in helicopters and fixed wing aircraft, to maintain a balanced flight. This is done by applying the pedal input in what direction it takes to center the ball at the turn and the bank indicator.
Security
Maximum speed limit
The main limitation of a helicopter is its low speed. There are several reasons why a helicopter can not fly as fast as a fixed-wing aircraft. When the helicopter hovers, the outer end of the rotor journey at the speed is determined by the blade length and the rotation speed. But in a moving helicopter, the speed of the propeller against the air depends on the speed of the helicopter and its rotational speed. The air speed of the advanced rotor blade is much higher than the helicopter itself. Perhaps this blade exceeds the speed of sound, and thus produces much greater drag and vibration.
At the same time, the forward blade creates more thrust forward, the backward blade yielding less lift. If the aircraft accelerates to air velocity so that the tip of the blade turns, the blade that retreats through the air moves at the same speed at the blade and does not produce an elevator at all, resulting in very high torque pressure on the central shaft that can tip down the rear side of the vehicle, and causing loss of control. Double counter-rotating blades prevent this situation because it has two forward blades and two back propellers with balanced strength.
Because the advanced blade has a higher airspeed than a backward blade and results in asymmetry of lift force, the rotor blades are designed to "flap" - lifting and rotating in such a way that the forward blade flaps upward and develops a smaller angle of attack. Instead, the knife backward flaps downward, develops a higher attack angle, and generates more lift. At high speeds, force the rotor in such a way that they "pack" excessively, and the backward knife can reach too high corners and holes. For this reason, the maximum safe speed of a helicopter is rated design called V NE , speed, never exceeds . In addition, it is possible for helicopters to fly at airspeed where excessive amounts of knife stalls are retreating, which produces high vibrations, rises, and rolls into the backward knife.
Noise
During the closing years the designers of the 20th century began to work on helicopter noise reduction. Urban communities often express great displeasure with noisy flights or noisy aircraft, and passenger police and helicopters can become unpopular and therefore annoying by sound. The redesign follows the closing of several city helmets and government action to restrict flight paths in national parks and other natural beauty spots.
Vibration
The helicopter also vibrates; an unadjusted helicopter can easily vibrate so much that it will shake by itself. To reduce vibration, all helicopters have adjustable rotors for height and weight. The height of the blade is adjusted by changing the blade pitch. The weight is adjusted by adding or removing the load on the rotor head and/or on the blade cap. Most also have vibration dampers for high and high tones. Some also use mechanical feedback systems to sense and resist vibration. Usually the feedback system uses mass as a "stable reference" and the relation of the masses operates the flap to adjust the angle of the rotor attack to counteract the vibrations. Adjustment is difficult because the measurement of vibration is hard, usually requires a sophisticated accelerometer installed throughout the fuselage and gearbox. The most common blast vibration adjustment measurement system is to use stroboscopic flash lights, and observe painted marks or colored reflectors at the bottom of the rotor blades. The traditional low-tech system is to install colored chalk on the rotor ends, and see how they mark the linen sheet. Gearbox vibrations most often require repair or replacement of the gearbox. The vibration of the gearbox or drive train can be very dangerous for the pilot. The most severe is pain, numbness, loss of tactile discrimination and agility.
Loss of rotor-tail effectiveness
For a standard helicopter with a single main rotor, the main rotor blade tip produces a vortex ring in the air, which is a rotating air flow and a circular spin. As the plane moves forward, this vorticity runs behind the plane.
When drifting with a forward diagonal crossover, or moving in the forward diagonal direction, the rotating vortices left behind from the main rotor blade will be parallel to the rotation of the tail rotor and cause instability in flight control.
When the trailing vortex collides with a tail rotor spinning in the same direction, this causes the loss of thrust from the tail rotor. When trailing the vortex spins in the opposite direction of the tail rotor, the thrust rises. The use of foot pedal is needed to adjust the angle of the rotor tail attack, to compensate for this instability.
These problems are due to the cut tail rotor cut through the open air behind the vehicle. This problem is lost when the tail is channeled, using a closed internal impeller in the tail and high pressure air to the side out of the tail, since the main rotor vortex can not affect the internal impeller operation.
Azimut crucial wind
For a standard helicopter with a single main rotor, maintaining a fixed flight with crosswind presents additional flight control issues, where strong crosswinds from a certain angle will increase or decrease the ride from the main rotor. This effect is also triggered in a windless condition when moving the plane diagonally in various directions, depending on the direction of the main rotation of the rotor.
This can lead to loss of control and crash or landing when operating in the lowlands, due to sudden unexpected losses, and the time and distance available are not sufficient to recover.
Transmission
The conventional wing aircraft uses a set of elaborate mechanical gearboxes to convert the high-speed rotation of the gas turbine into the low speed required to drive the main rotor and tail. Unlike powerplants, mechanical gearboxes can not be duplicated (for redundancy) and have always been a major weak point in helicopter reliability. Failure of catastrophic teeth in the plane often results in congestion of gearboxes and subsequent casualties, while loss of lubrication can lead to fires on ships. Another disadvantage of mechanical gearboxes is their limited transient power, due to the limit of structural fatigue. The latest EASA study shows engine and transmission as the main cause of crashes only after pilot error.
In contrast, the electromagnetic transmission does not use any part of contact; then lubrication can be drastically simplified, or eliminated. Their inherent redundancy offers good resistance to a single point of failure. The absence of gears allows high power transients without impacting service life. The concept of electric propulsion applied to helicopters and electromagnetic actors was brought to the real world by Pascal Chretien who designed, built and flew the first flying electric helicopters that brought humans. This concept was taken from a computer aided design model on September 10, 2010 for the first test with a 30% strength on March 1, 2011 - less than six months. The first aircraft flew on August 12, 2011. All the development is done in Venelles, France.
Dangers
As with any moving vehicle, unsafe operations can result in loss of control, structural damage, or loss of life. Here is a list of some potential dangers for helicopters:
- Settling with power is when the plane has insufficient power to hold its landing. This danger can develop into a Vortex ring status if not fixed early.
- The status of the Vortex ring is a hazard caused by a combination of low air speed, high power settings, and high drop rate. Vorticity of the rotor-tip circulates from high-pressure air under the disk rotor to low-pressure air above the disk, so that the helicopter settles into its own descending airflow. Adding more power will increase the rate of air circulation and worsen the situation. Sometimes confused with power settings, but both are different aerodynamically.
- Retractable blaster kiosks are experienced during high-speed flights and are the most common limiting factor of helicopter speed.
- Soil resonance is a self-amplifying vibration that occurs when the lead/lag blade distance from the articulated rotor system becomes irregular.
- The Low-G condition is a sudden change from a positive G-force status to a negative G-force state resulting in a loss of lift (disc not loaded) and subsequent scrolling. If aft cyclic is applied when the disc is lowered, the main rotor can strike the tail causing catastrophic failure.
- The dynamic scrolling where the helicopter rotates around one of the sliding parts and "pulls" itself to its side (almost like a fixed-wing aircraft plane).
- Powertrain failures, especially those that occur in shaded areas on high speed diagrams.
- Failure of tail rotor that occurs either from mechanical damage to the tail rotor control system or loss of the thrust authority of the tail rotor, called the "loss of effectiveness of tail rotor" (LTE).
- Brownout in dusty or white conditions in snowy conditions.
- Low rotor rot, or "rotor droop", is when the machine can not push the blades with enough RPM to maintain the flight.
- The overspeed rotor, which can over-stress the rotor hub pitch bearing (brinelling) and, if quite severe, causes the blade separation of the plane.
- Wire and tree strikes due to low-altitude operations and takeoffs and landings in remote locations.
- A controlled flight into a field where the aircraft was flown into the ground accidentally due to a lack of situational awareness.
- The pole crashed into several helicopters
The most lethal damage
World record
See also
References
Note
Bibliography
External links
- "www.helicopterpage.com - How Helicopters Work" The full website explains the various aspects of helicopters and how they work.
- "A Straight Plane." 1935 articles on early development and research on helicopters.
- "Flights - from Imagination." 1918 article on helicopter design concept.
- "Twin Windmill Blades Fly Wingless Ship" Popular Mechanics , April 1936
- Russian-language video of the Cheremukhin/Yuriev pioneer helicopter TsAGI 1-EA
- Graham Warwick (Jun 17, 2016). "How Helicopters Have Been Growing". Week Flight & amp; Space Technology . Moving from idea to reality takes longer for helicopters than for fixed wing aircraft. < span>
Source of the article : Wikipedia
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