Supplementary Reading Antitorque configurations

Most helicopters have a single main rotor, but torque created as the engine turns the rotor against its air drag causes the body of the helicopter to turn in the opposite direction to the rotor. To eliminate this effect, some sort of antitorque control must be used. The design that Igor Sikorsky settled on for his VS-300 was a smaller rotor mounted vertically on the tail. The tail rotor pushes or pulls against the tail to counter the torque effect, and has become the recognized convention for helicopter design. The use of two or more horizontal rotors turning in opposite directions is another configuration used to counteract the effects of torque on the aircraft without relying on an antitorque tail rotor. This allows the power normally required to drive the tail rotor to be applied to the main rotors, increasing the aircraft's lifting capacity. Primarily, there are three common configurations that use the counterrotating effect to benefit the rotorcraft. Tandem rotors are two rotors with one mounted behind the other. Coaxial rotors are two rotors that are mounted one above the other with the same axis. Intermeshing rotors are two rotors that are mounted close to each other at a sufficient angle to allow the rotors to intermesh over the top of the aircraft. Transverse rotors is another configuration found on tiltrotors and some earlier helicopters, where the pair of rotors are mounted at each end of the wings or outrigger structures. Tip jet designs permit the rotor to push itself through the air, and avoid generating torque.

Civilian Uses of Helicopters

The first production helicopters were built for the military, which has been their largest user. In addition to their military function, these aircraft also have offered great promise for civil government and commercial customers even though they are complicated and expensive machines. Thousands of helicopters have performed many commercial and civil functions throughout the United States and worldwide.

The first helicopter to enter commercial use was the Sikorsky S-51. But the most popular early commercial helicopters were the light utility craft such as the Bell 47. These aircraft were used for many different jobs that required remote operations in areas that fixed-wing aircraft could not access.

Helicopters were also used by civilian government agencies, such as police departments. Police used helicopters to monitor traffic and even to catch speeders. Fire departments occasionally used them to monitor brushfires, rescue people from tall buildings, and drop chemicals on forest fires.

Also in the 1950s, ranchers began using helicopters to reach distant parts of their property and even to herd cattle. Farmers also equipped some helicopters for crop-dusting.

British European Airways launched the first commercial passenger service in June 1950, travelling between Liverpool, England, and Cardiff, Wales, using a Westland-Sikorsky S-51. New York City's first helicopter station began operating from a pier on the East River on May 18, 1949. On July 9, 1953, New York Airways became the first scheduled passenger helicopter air carrier to operate in the United States.

But early helicopters were slow and noisy and could not carry many passengers. By the 1960s, when larger military helicopters like the Boeing-Vertol CH-46 had entered service, some airlines anticipated creating commercial "heliports" in the centre of New York and other cities that would allow passengers to fly from downtown to major airports such as LaGuardia and JFK airports. Boeing-Vertol even began to market civilian versions of its large helicopters. The airlines and helicopter manufacturers anticipated that the primary customers would be businessmen who were on tight schedules and had the money to pay for expensive helicopter services. This market never developed, however, and most commercial heliport proposals died by the 1970s. However, helicopters did enter extensive use as corporate transports.

Commercial passenger helicopters did establish niche markets in other areas, such as the offshore oil business. Early offshore oil platforms had crews that stayed aboard for long periods of time. This was unattractive to potential workers. But the advent of the helicopter allowed crews to be rotated fairly easily—replacement crews could now reach a drilling platform in an hour by air rather than in ten hours by boat. In fact, in the United States, by the 1960s and 1970s, oil crews became highly mobile, often travelling cross-country by commercial air to take a two-week tour on an oil platform before returning home. The helicopter made this possible. They were also used for oil surveying missions to remote areas.

Early commercial helicopters were often ex-military aircraft, such as the Sikorsky H-34 and its variants. They were usually converted to carry more seats. The Bell Huey and its commercial variants such as the Model 212 and 214 have been popular for servicing offshore oil rigs.

Helicopters are also used in a number of unusual and unexpected commercial tasks. They are used to drop seeds over inaccessible territory, such as hills and mountains stripped clean after forest fires or logging operations. They are also used in the firefighting role, usually under contract to state and local governments. They can drop foam or water with precision over wildfires and, unlike airplanes, can refill their tanks without landing.

As it had in other fields, the military helicopter mission soon crossed over to the civilian world, such as medical evacuation ("medevac"). In 1965, 34 hospitals in the United States had heliports.

Finally, helicopters are used extensively by local television stations to monitor breaking news events, as well as traffic. They have also added a third dimension to movie photography, allowing the camera to film things that were impossible in the early days of motion pictures.