Helicopters

A. Rotary wing aircraft (helicopters) are made to fly by fast-turning blades, or rotors. These aircraft can land in a small space, take off without running along the ground, and hover in the air.

B. The helicopter is a rotary wing aircraft. It depends in flight on the lift generated by one or more rotors. Rotating blades send the airflow downward thus creating lift. It enables the helicopter to take off and land vertically.

C. Besides its main, or lift rotor, the helicopter usually has an auxiliary, or tail rotor. This is a small rotor mounted at the tail to counteract the torque of the main rotor. The tail rotor diverts some part of engine power and lowers the powerplant efficiency.

D. 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. The lift from the rotor also allows the helicopter to hover in one area for extended periods of time. It is also able to load and unload without actually landing due to hovering capability and special loading equipment. This is one of the greatest advantages as compared to fixed-wing aircraft.

E. Heavy fuel consumption, restricted range and speed make the helicopter impractical for long range transportation. Even the best helicopter makes have an endurance not exceeding 3-4 hours. Among the disadvantages – vibration and noise generated by the rotors.

F. At present helicopters are extensively used for military and peaceful purposes and a result of that there is a great variety of helicopter types and designs.

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

H. 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. Buckets are usually filled by submerging in lakes, rivers, reservoirs, or portable tanks. Helicopters are also used to resupply firefighters on the ground with tools, food, water and other supplies.

I. 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.

J. 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.

K. Military forces use helicopters to conduct aerial attacks on ground targets. Such helicopters are fitted 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.

Comprehension Check

Дата добавления: 2015-07-11