Saturday, May 23, 2009

Helicopter

Hi guys,  
Helicopters are lifted, propelled, and steered by powerful rotating blades (rotors). Able to take off vertically, hover, and fly in any direction, these versatile machines are held stable in flight by the balancing action of their tail rotor. First developed in the 1920s, modern helicopters date from the advent of turbojet engines in 1955. They are now used for such diverse purposes as military gunships, air ambulances, and air taxis; for spraying crops; and for aerial survey and observation, particularly of road traffic conditions. Thank you.

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