Helicopter

Helicopter — A helicopter (informally known as a “chopper”) is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed wing aircraft would usually not be able to take off or land. The capability to efficiently hover for extended periods of time allows a helicopter to accomplish tasks that fixed wing aircraft and other forms of vertical takeoff and landing (VTOL) aircraft cannot perform.

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’ itself, adapted from the French helicoptere, originates from the Greek words elikoeides (helical or spiral) and pteron (wing or feather); a spiraling wing.

Helicopters were developed and built during the first half-century of flight, with the Focke-Wulf Fw 61 being the first operational helicopter in 1936. Some helicopters reached limited production, but it was not until 1942 that a helicopter designed by Igor Sikorsky reached full-scale production, with 131 aircraft built. Though most earlier designs used more than one main rotor, it was the single main rotor with ant torque tail rotor configuration of this design that would come to be recognized worldwide as the helicopter.

History

Ancient China: non-powered toy

Since 400 BC, the Chinese had a bamboo flying top that was used as a children’s toy. Eventually, this flying top toy made it to Europe and is depicted in a 1463 European painting. Pao Phu Tau was a 4th-century book in China describing some of the ideas inherent to rotary wing aircraft.

1493: Leonardo da Vinci: model and theoretical

In 1493, Leonardo da Vinci first sketched a semi-practical machine, named in his “Codice Atlántico”, 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.

1754: Lomonosov

In July 1754 Mikhail Lomonosov showed to the Russian Academy of Sciences a small coaxial rotor powered by a wound-up spring, intended to lift meteorological instruments.

1783: Launoy and Bievenu: two separated rotors

In 1783 Christian de Launoy and his mechanic Bienvenu, made a model pair of counter-rotating rotors using turkey’s flight feathers as rotor blades, and in 1784 demonstrated it to the French Academy of Sciences.

1861: d’Amecourt: steam-powered model, and the word “helicopter”

In 1861 the word “helicopter” (hélicoptère) was coined by Gustave de Ponton d’Amécourt, a French inventor who demonstrated a small steam-powered model.

1860 to 1880

In this period many small helicopter models were designed and made. Examples were:

1870: Alphonse Penaud: coaxial rotors, powered by twisted rubber bands.

1877: Emmanuel Dieuaide: counter-rotating rotors, steam-powered through a hose from a boiler on the ground.

1877: Melikoff: design for a man-carrier, almost certainly not built.

1878 or 1879: Dandrieux: counter-rotating rotors, 7.7-pound (3.5-kilogram) steam engine. It rose more than 40 feet (12 meters) and flew for 20 seconds.

1880’s: Edison

In the 1880s, Edison experimented with small helicopter models in USA:

• With a guncotton-powered engine: caused damage by explosions, tests ended.
• With an electric motor: showed that a large rotor with low blade area was needed.

1901: Ján Bahýľ: first with an internal combustion engine

Ján Bahýľ, a Slovak inventor, developed a helicopter model powered by an internal combustion engine, that in 1901 reached a height of 0.5 meters. On May 5, 1905 his helicopter reached 4 meters in altitude and flew for over 1500 meters.

1906: Breguet: first man-carrier

In 1906, two French brothers, Jacques and Louis Breguet, began experimenting with airfoils for helicopters and in 1907, those experiments resulted in the Gyroplane No.1. Although there is some discrepancy about the dates, sometime between 14 August and 29 September 1907, the Gyroplane No. 1 lifted its pilot up into the air about two feet (0.6 meters) for a minute. However, the Gyroplane No. 1 proved to be extremely unsteady and required a man at each corner of the airframe to hold it steady. For this reason, the flights of the Gyroplane No. 1 are considered to be the first manned flight of a helicopter, but not a free or untethered flight.

Paul Cornu’s helicopter, built in 1907, was the first flying machine to have risen from the ground using rotor blades instead of wings.

1906: Paul Cornu

In 1906, fellow French inventor Paul Cornu designed and built a helicopter that used two 20-foot (6-meter) counter-rotating rotors driven by a 24-hp (18-kW) Antoinette engine. On November 13, 1907, it lifted its inventor to 1 foot (0.3 meters) and remained aloft for 20 seconds. Although this flight was smaller in its achievement than that of the Breguet brothers, it was greater in accomplishment being that it was the first true free flight with a pilot. The Cornu helicopter would achieve a height of nearly 2 meters but also proved to be unstable and was abandoned after only a few flights.

Early 1920’s: competition between Pescara and Oemichen

In the early 1920s, Raul Pateras Pescara, an Argentinian working in Europe, demonstrated one of the first successful applications of cyclic pitch. His coaxial, contra-rotating, biplane rotors were able to be warped to cyclically increase and decrease the lift they produced; and the rotor hub could also tilt, both allowing the aircraft to move laterally without a separate propeller to push or pull it. Pescara is also credited with demonstrating the principle of autorotation, the method by which helicopters land safely after engine failure. By January 1924, Pescara’s helicopter No. 3 was capable of flights up to 10 minutes.

On 14 April 1924 one of Pescara’s contemporaries, Frenchman Etienne Oemichen, set the first helicopter world record recognized by the Fédération Aéronautique Internationale, flying his helicopter 360 meters (1,181 feet).

On 18 April 1924, Pescara beat Oemichen’s record, flying for a distance of 736m (nearly a half mile) in 4 minutes and 11 seconds (about 8 mph, 13 km/h) maintaining a height of six feet.

On 4 May 1924, Oemichen reclaimed the world record when he flew his No. 2 machine again for a 14-minute flight covering 5,550 feet (1.05 mi, 1.692 km) while climbing to a height of 50 feet (15 meters). Oemichen also set the 1-km closed-circuit record at 7 minutes 40 seconds.

1923: Juan de la Cierva: first autogyro

During this time, Juan de la Cierva was developing and introducing the first practical autogyro. In 1923, the rotorcraft that became the basis for the modern helicopter began to take shape, in the form of an autogyro. Cierva discovered aerodynamic and structural deficiencies in his early designs that could cause his autogyros to flip over after takeoff. The flapping hinges Cierva designed allowed the rotor to develop lift equally on the left and right halves of the rotor disk. A crash in 1927 led to the development of the drag hinge. These two developments allowed for a stable rotor system, not only in a hover, but in forward flight.

1925: von Baumhauer

In 1922, Albert Gillis von Baumhauer, a Dutch aeronautical engineer, started studying VTOL rotor craft. His first prototype ‘flew’ (‘hopped’ and hovered really) on September 24, 1925, with Dutch Army-Air arm Captain Floris Albert van Heijst at the controls. The controls that Captain van Heijst used were Von Baumhauer’s inventions, the cyclic and collective. Patents were granted to Von Baumhauer by the British Ministry of Aviation on January 31, 1927, under number 265,272.

1930: Corradino d’Ascanio

In 1930 the Italian engineer Corradino d’Ascanio built a coaxial helicopter. His relatively large machine had two, two-bladed, counter-rotating rotors. Control was achieved by using auxiliary wings or servo-tabs on the trailing edges of the blades, a concept that was later adopted by other helicopter designers, including Bleeker and Kaman. Three small propellers mounted to the airframe were used for additional pitch, roll, and yaw control. This machine held modest FAI speed and altitude records for the time, including altitude (18 m), duration (8 minutes 45 seconds) and distance flown (1,078 m).

1931: Russian

In 1931 Soviet aeronautical engineers Boris Yuriev and Alexei Cheremukhin began experiments with the TsAGI 1-EA helicopter. A single rotor helicopter, with dual forward and aft anti-torque propellers, it reached an altitude of 605 meters (1,984 ft) on August 14, 1932 with Cheremukhin at the controls.

1935: Breguet

In 1935 Louis Breguet flew the Gyroplane Laboratoire, a twin coaxial rotor helicopter (like a Kamov). It had a tail plane. Its blades had cyclic pitch and collective pitch blade control. During tests on 26 September 1936, it reached 120km/h and an altitude of 158m. A flight on 24 November 1936 lasted more than one hour at 44.7km/h. The last prototype was destroyed in 1943 by an Allied air strike at Villacoublay airport.

1936 to 1945: Germany: first useful helicopter

In 1936 the German Focke-Wulf Fw 61 was the first viable helicopter first flying. The Fw 61 broke all of the helicopter world records in 1937. It was like a fixed wing aircraft including a a tailplane and front propeller but with the wings replaced by long sideways struts with counter-rotating rotors on their ends. Nazi Germany used helicopters in small numbers during World War II.

The Flettner Fl 282 Kolibri synchropter’s hull was more like a modern helicopter’s in shape, with no tail rotor, and counter-rotating intermeshing rotors set close together on the cabin top, each tilted outwards so that its blades would not hit the other rotor’s shaft top. Models such as it were used in the Mediterranean Sea.

The Focke Achgelis Fa 223 Drache was used in Europe. It was like a fixed wing aircraft with long sideways rotor struts instead of wings, and tail plane, and no front propeller.

1942: Sikorsky

In May 1942 mass production of the military version of the Sikorsky XR-4 began for the United States Army; this was used over Burma for rescue duties. It was also used by the Royal Air Force, the first British military unit to be equipped with helicopters being the Helicopter Training School, formed in January 1945 at RAF Andover with nine Sikorsky R-4B Hoverfly I helicopters.

1946: Bell 47

In March 1946 the Bell 47 designed by Arthur Young became the first helicopter to be licensed for certified civilian use in the United States. Two decades later the Bell 206 became the most successful commercial helicopter ever built with more hours and more industry records than any other aircraft in the world.

1951: first with a gas turbine engine

Reliable helicopters capable of stable hover flight were developed decades after fixed wing aircraft. This is largely due to higher engine power density requirements than fixed wing aircraft. Improvements in fuels and engines during the first half of the 20th century were a critical factor in helicopter development. The availability of lightweight turbo shaft engines in the second half of the 20th century, pioneered by the Kaman K-225 synchropter,, which first flew with gas turbine power late in 1951, led to the development of larger, faster, and higher-performance helicopters. Turbo shaft engines are the preferred power plant for all but the smallest and least expensive helicopters today.

Uses of helicopters

This short section requires expansion.

Aerial Cranes

One of the most unusual commercial uses of helicopters is the aerial crane or sky crane. 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.

Helicopters were first used as aerial cranes in the 1950s, but it was not until the 1960s that the popularity of the use of sky cranes in the construction and other industries began to catch on. 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

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 fire-fighters who rappel to the ground below. Buckets are usually filled by submerging in lakes, rivers, reservoirs, or portable tanks. The most popular of the buckets is the flexible Bambi bucket. 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 re supply fire fighters on the ground with tools, food, water and other supplies. Popular fire fighting helicopters include variants of the Bell 204 and the Erickson S-64 Air crane helitanker. The Erickson helitanker also has a sea snorkel for filling while in flight.

Air Ambulance

Helicopters are often 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 practical. Air ambulance crews are supplied with equipment that enables them to provide medical treatment to a critically injured or ill patient. The use of helicopters as an air ambulance is sometimes referred to as MEDEVAC, or patients are referred to as being “airlifted”, or “medevaced”.

Law Enforcement

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 Helicopters

Military forces use helicopters to conduct aerial attacks on ground targets. Such helicopters are mounted with missile launchers and miniguns. Militaries also use transport helicopters to ferry troops in and out of constrained combat zones where the lack of an airstrip would make transport via fixed wing aircraft impossible.

Motion Picture Photography

In the United States, use of helicopters in making films and television can fall under the safety rules set by collective bargaining. For instance, bargaining agents have guidelines that all aerial coordinators and/or pilots in command possess a current FAA approved Motion Picture and Television Operations Manual.

News gathering

Helicopters are often used by news services to observe scenes where newsworthy incidents have occurred. The helicopter can carry a camera to capture an aerial view of a scene, to be recorded for later broadcast or transmitted to a newsroom for live broadcast. News helicopters are most often used to report on traffic conditions of local roads, highways, and bridges.

Other Uses

• Search and Rescue
• Aerial still photography
• Logging
• Transport