Metal Birds, Part 2

Metal Birds, Part 2

Metal Birds, Part 2
Reading Level

	edHelper's suggested reading level:	grades 5 to 7
	Flesch-Kincaid grade level:	10.24

Vocabulary

	challenging words:		air-sea, airfoil, power-driven, propellers, resupply, rotor, tourism, propeller, aircraft, military, sixteenth, extremely, adjustment, rotate, helicopter, opposite
	content words:		Metal Birds, Leonardo DaVinci, Igor Sikorsky, Russian-born American, Louis Breguet, Persian Gulf, Iraq Wars, Korean War

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Metal Birds, Part 2
By Trista L. Pollard

¹     In Metal Birds, Part 1 you learned about the parts of airplanes. In this article we will explore the world of helicopters. Helicopters are aircraft that use one or more power-driven horizontal propellers to obtain lift. These propellers are called rotors. Helicopters can do what airplanes cannot: they can take off or land vertically and fly forward, backward, and sideways. Some historians say that Leonardo DaVinci described a machine similar to a helicopter in the sixteenth century. However, the first practical helicopter came onto the scene in 1942. It was built by Igor Sikorsky, a Russian-born American engineer. Other developers of the helicopter were Louis Breguet of France and Juan de la Cierva of Spain.

²     The blades of a helicopter's rotor are long and shaped like an airfoil. A helicopter's blades or propellers spin in a circle, which allows them to move through the air even when the helicopter is standing still. Since the air is flowing faster over the top of the propeller than the bottom of the propeller, lift is produced for the helicopter. If the helicopter had only this one set of propellers spinning in one direction, the helicopter would rotate out of control in the opposite direction. This is why the tail rotor is extremely important. The propellers of the tail rotor are smaller than the propellers of the main rotor. The tail rotor turns in the opposite direction of the main rotors and as a result, prevents the helicopter from rotating out of control. The second rotor is most often located on the tail on smaller helicopters and on the rear end of larger helicopters.

³     Helicopter pilots are able to control the movement of the aircraft by adjusting the angle of each propeller blade as they turn. This adjustment allows the helicopter to tilt. When it is tilted, it can use the force from its lift to move horizontally forward, .....
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