دفئ الكون
15-12-2008, 02:02 PM
((The helicopter))
A helicopter is an aircraft which is lifted and propelled by one or more horizontal rotors, each rotor consisting of two or more rotor blades. Helicopters are classified as rotorcraft or rotary-wing aircraft to distinguish them from fixed-wing aircraft because the helicopter derives its source of lift from the rotor blades rotating around a mast. The word 'helicopter' is adapted from the French hélicoptère, coined by Gustavo de Pontoon d'Amecourt in 1861. It is linked to the Greek words helix/helik- (ἕλικ-) = "spiral" or "turning" and pteron (πτερόν) = "wing”.
As an aircraft, the primary advantages of the helicopter are due to the rotor blades that revolve through the air, providing lift without requiring the aircraft to move forward the way an airplane does. This creates the ability for the helicopter to take off and land vertically without the need for runways. For this reason, helicopters are often used to operate in congested or isolated areas where airplanes are generally not able to take off or land. The lift from the rotor also allows the helicopter to hover in one area for extended periods of time, and to do so more efficiently than other forms of vertical takeoff and landing (VTOL) aircraft, allowing it to accomplish tasks that airplanes are unable to perform.
Although helicopters were developed and built during the first half-century of flight, some even reaching limited production, it wasn't until 1942 that a helicopter designed by Igor Sikorsky became the first helicopter to enter full-scale production with 131 aircraft built, Even though most previous designs utilized more than one main rotor, it was the single main rotor with antitorque tail rotor configuration of this design that would come to be recognized worldwide as the helicopter.
History:
Since 400 BC, Chinese children have played with bamboo flying tops. Eventually, this flying top made its way to Europe and is depicted in a 1463 European painting Pao Phu Tau (抱朴子) was a 4th-century book in China reported to describe some of the ideas inherent to rotary wing aircraft
Someone asked the master about the principles of mounting to dangerous heights and traveling into the vast inane. The Master said, "Some have made flying cars 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, Leonardo da Vinci conceived a machine that could be described as an "aerial screw".
He wrote that he made small flying models but could not stop the rotor from making the whole craft rotate. Later machines would more closely resemble the ancient bamboo flying top, with spinning wings rather than screws.
In July 1754, Mikhail Lomonosov showed the Russian Academy of Sciences a small coaxial rotor powered by a wound-up spring, intended to lift meteorological instruments In 1783, Christian de Launoy, and his mechanic, Bienvenu, made a model pair of counter-rotating rotors (not coaxial) using turkey's flight feathers as rotor blades, and in 1784 demonstrated it to the French Academy of Sciences, In 1861, the word "helicopter" was coined by Gustave de Ponton d'Amécourt , a French inventor who demonstrated a small steam-powered model.
From 1860 to 1880, many small helicopter models were designed and made these included Alphonse Pénaud's model coaxial rotors, powered by twisted rubber bands (1870). Enrico Forlanini's unmanned helicopter was powered by a steam engine. It was the first of its type that rose to a height of 13 meters, where it remained for some 20 seconds, after a vertical take-off from a park in Milan (1877). Emmanuel Dieuaide's design featured counter-rotating rotors and was steam-powered through a hose from aboiler on the ground (1877). Melikoff designed a "man carrier," but it was almost certainly not built (1877).
Dandrieux's design had counter-rotating rotors and a 7.7-pound (3.5-kilogram) steam engine. It rose more than 40 feet (12 meters) and flew for 20 seconds (circa 1878).
In the 1880s, Thomas Edison experimented with small helicopter models in the USA. First with a guncotton-powered engine, which caused damage by explosions, and tests were ended. Next he used an electric motor. His tests showed that a large rotor with low blade area was needed.
Ján Bahýľ, a Slovak inventor, developed a model helicopter powered by an internal combustion engine, which in 1901 reached a height of 0.5 meters. On 5 May 1905, his helicopter reached four meters in altitude and flew for over 1,500 meters.
Uses:
Due to the unique operating characteristics of the helicopter—its ability to takeoff 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 grown increasingly popular for conducting tasks that were previously not possible, or were time- or work-intensive. Today, helicopters are used for transportation, for construction, for firefighting, search and rescue, and a variety of other jobs that require the special capabilities of the helicopter.
As aerial cranes, helicopters carry loads connected to long cables or slings in order to place heavy equipment such as 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, far from the nearest road. The most popular use of helicopters as aerial cranes is in the logging industry to lift large trees out of rugged terrain where vehicles aren't able to reach, or where environmental concerns prohibit the building of roads.
These operations are referred to as longline because of the long, single sling line used to carry the load. Aerial firefighting (or water bombing) is a method to combat wildfires that often uses helicopters. Helicopters may be fitted with tanks or carry buckets or deliver firefighters who rappel to the ground below. Buckets, such as the Bambi bucket, are usually filled by submerging in lakes, rivers, reservoirs, or portable tanks. Tanks may be filled on the ground or water may be siphoned from lakes or reservoirs through a hanging snorkel.
Helicopters are also used to resupply firefighters on the ground with tools, food, water and other supplies. Popular firefighting helicopters include variants of the Bell 205 and the Erickson S-64 Air crane helitanker.
Helicopters are used as an air ambulance for emergency medical assistance in situations where either a traditional ambulance cannot easily or quickly reach the scene or when a patient needs to be transported at a distance where air transportation is most $$$$$$$$$. Air ambulance helicopters are equipped to provide medical treatment to a critically injured or ill patient while in flight. The use of helicopters as an air ambulance is often referred to as MEDEVAC and patients are referred to as being "airlifted", or "medevaced".
Police departments and other law enforcement agencies use helicopters to search for and pursue suspects. Since helicopters can achieve a unique aerial view and don't need to negotiate ground obstacles, 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. Transport helicopters used to deliver troops as an attack force on an objective is referred to as Air Assault.
Other uses:
[list]
Aerial photography
Motion picture photography
Electronic news gathering
Search and Rescue
Touring or personal pleasure
Transport
منقول
A helicopter is an aircraft which is lifted and propelled by one or more horizontal rotors, each rotor consisting of two or more rotor blades. Helicopters are classified as rotorcraft or rotary-wing aircraft to distinguish them from fixed-wing aircraft because the helicopter derives its source of lift from the rotor blades rotating around a mast. The word 'helicopter' is adapted from the French hélicoptère, coined by Gustavo de Pontoon d'Amecourt in 1861. It is linked to the Greek words helix/helik- (ἕλικ-) = "spiral" or "turning" and pteron (πτερόν) = "wing”.
As an aircraft, the primary advantages of the helicopter are due to the rotor blades that revolve through the air, providing lift without requiring the aircraft to move forward the way an airplane does. This creates the ability for the helicopter to take off and land vertically without the need for runways. For this reason, helicopters are often used to operate in congested or isolated areas where airplanes are generally not able to take off or land. The lift from the rotor also allows the helicopter to hover in one area for extended periods of time, and to do so more efficiently than other forms of vertical takeoff and landing (VTOL) aircraft, allowing it to accomplish tasks that airplanes are unable to perform.
Although helicopters were developed and built during the first half-century of flight, some even reaching limited production, it wasn't until 1942 that a helicopter designed by Igor Sikorsky became the first helicopter to enter full-scale production with 131 aircraft built, Even though most previous designs utilized more than one main rotor, it was the single main rotor with antitorque tail rotor configuration of this design that would come to be recognized worldwide as the helicopter.
History:
Since 400 BC, Chinese children have played with bamboo flying tops. Eventually, this flying top made its way to Europe and is depicted in a 1463 European painting Pao Phu Tau (抱朴子) was a 4th-century book in China reported to describe some of the ideas inherent to rotary wing aircraft
Someone asked the master about the principles of mounting to dangerous heights and traveling into the vast inane. The Master said, "Some have made flying cars 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, Leonardo da Vinci conceived a machine that could be described as an "aerial screw".
He wrote that he made small flying models but could not stop the rotor from making the whole craft rotate. Later machines would more closely resemble the ancient bamboo flying top, with spinning wings rather than screws.
In July 1754, Mikhail Lomonosov showed the Russian Academy of Sciences a small coaxial rotor powered by a wound-up spring, intended to lift meteorological instruments In 1783, Christian de Launoy, and his mechanic, Bienvenu, made a model pair of counter-rotating rotors (not coaxial) using turkey's flight feathers as rotor blades, and in 1784 demonstrated it to the French Academy of Sciences, In 1861, the word "helicopter" was coined by Gustave de Ponton d'Amécourt , a French inventor who demonstrated a small steam-powered model.
From 1860 to 1880, many small helicopter models were designed and made these included Alphonse Pénaud's model coaxial rotors, powered by twisted rubber bands (1870). Enrico Forlanini's unmanned helicopter was powered by a steam engine. It was the first of its type that rose to a height of 13 meters, where it remained for some 20 seconds, after a vertical take-off from a park in Milan (1877). Emmanuel Dieuaide's design featured counter-rotating rotors and was steam-powered through a hose from aboiler on the ground (1877). Melikoff designed a "man carrier," but it was almost certainly not built (1877).
Dandrieux's design had counter-rotating rotors and a 7.7-pound (3.5-kilogram) steam engine. It rose more than 40 feet (12 meters) and flew for 20 seconds (circa 1878).
In the 1880s, Thomas Edison experimented with small helicopter models in the USA. First with a guncotton-powered engine, which caused damage by explosions, and tests were ended. Next he used an electric motor. His tests showed that a large rotor with low blade area was needed.
Ján Bahýľ, a Slovak inventor, developed a model helicopter powered by an internal combustion engine, which in 1901 reached a height of 0.5 meters. On 5 May 1905, his helicopter reached four meters in altitude and flew for over 1,500 meters.
Uses:
Due to the unique operating characteristics of the helicopter—its ability to takeoff 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 grown increasingly popular for conducting tasks that were previously not possible, or were time- or work-intensive. Today, helicopters are used for transportation, for construction, for firefighting, search and rescue, and a variety of other jobs that require the special capabilities of the helicopter.
As aerial cranes, helicopters carry loads connected to long cables or slings in order to place heavy equipment such as 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, far from the nearest road. The most popular use of helicopters as aerial cranes is in the logging industry to lift large trees out of rugged terrain where vehicles aren't able to reach, or where environmental concerns prohibit the building of roads.
These operations are referred to as longline because of the long, single sling line used to carry the load. Aerial firefighting (or water bombing) is a method to combat wildfires that often uses helicopters. Helicopters may be fitted with tanks or carry buckets or deliver firefighters who rappel to the ground below. Buckets, such as the Bambi bucket, are usually filled by submerging in lakes, rivers, reservoirs, or portable tanks. Tanks may be filled on the ground or water may be siphoned from lakes or reservoirs through a hanging snorkel.
Helicopters are also used to resupply firefighters on the ground with tools, food, water and other supplies. Popular firefighting helicopters include variants of the Bell 205 and the Erickson S-64 Air crane helitanker.
Helicopters are used as an air ambulance for emergency medical assistance in situations where either a traditional ambulance cannot easily or quickly reach the scene or when a patient needs to be transported at a distance where air transportation is most $$$$$$$$$. Air ambulance helicopters are equipped to provide medical treatment to a critically injured or ill patient while in flight. The use of helicopters as an air ambulance is often referred to as MEDEVAC and patients are referred to as being "airlifted", or "medevaced".
Police departments and other law enforcement agencies use helicopters to search for and pursue suspects. Since helicopters can achieve a unique aerial view and don't need to negotiate ground obstacles, 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. Transport helicopters used to deliver troops as an attack force on an objective is referred to as Air Assault.
Other uses:
[list]
Aerial photography
Motion picture photography
Electronic news gathering
Search and Rescue
Touring or personal pleasure
Transport
منقول