I'd like to take this time to explain a little bit of how helicopters work, because they're really cool. Helicopters basically fly by sucking air from above the big rotor blade on top of the machine and forcing it downward with a thrust greater than the force of gravity acting on the helicopter. This allows the helicopter to get lift off the ground and fly into the air. Not only does the thrust created by the rotor blades have to be stronger than the force of gravity, or the weight, of the helicopter, it also has to be able to overcome the drag force created by the rotors. A thing about the rotor blades is that they continue spinning at the same speed the whole time. They do not slow down or speed up in order to change the height that the helicopter is flying at. The rotor blades do, however, control the amount of "lift" that a helicopter has, or the height at which it is flying, in a different way. Helicopters change their height by altering the angle at which the rotor blades make contact with the air. The pilot of a helicopter can increase or decrease the angle of the blades in order to go up or down. Another thing about helicopters is that they do not fly in straight lines, they are able to move side to side. This is also made possible because of the angles of the rotor blades. By altering the angle of each individual blade, a pilot is able to control the way in which the air contacts the blades in order to fly either to the left or to the right. Nifty stuff.