Helicopter - Intro

Helicopter
Helicopter is an aircraft that is lifted into the air and kept aloft by one or two powerful whirling rotors. A helicopter rotor resembles a huge propeller that is parallel to the ground. However, the rotor is actually a rotating wing. The name helicopter refers to the rotor. It comes from Greek words meaning spiral and wing. Nicknames for the helicopter include "chopper," "eggbeater," and "whirlybird."
A helicopter can fly straight up or straight down, forward, backward, or sideways. It can even hover (stay in one spot in the air). Unlike most airplanes, helicopters can take off and land in a small space. In addition, they can fly safely at much slower speeds and lower altitudes than airplanes. However, they cannot fly as fast as most planes. Most helicopters cannot exceed 200 miles (320 kilometers) per hour. At faster flight speeds, the velocity of the rotor blade tips approaches the speed of sound, and it becomes difficult to rotate the rotor. At high speeds, strong vibrations also develop that could damage the blades. Helicopters also use more fuel than airplanes to travel the same distance. In general, helicopters can fly only two to three hours