helicopter (2)

Last time I talked about the mechanism of how helicopters can change their movement, the swashplate, now let's take a look about the anti-torque system. Why does a helicopter need an anti-torque system? What exactly the anti-torque system is? Or why airplanes don't need the anti-torque system?

Since most helicopters have one single rotor, when the rotor starts to spin, it will create a torque that try to turn the boy of helicopter to the opposite direction to the rotor. Therefore we need some mechanism to eliminate or balance this torque. The anti-torque system commonly seen on helicopters are like this one:

The rear rotor we usually see on a helicopter is the anti-torque system. It works just like a fan in every common family, it blows out wind. By giving an opposite force to the body of the helicopter, we can eliminate the torque created by the main engine, thus prevent the helicopter from going off. Some people may ask that there also have one engine airplane, a small one like this:

Why don't they need the anti-torque system? Well, actually they do have a system. Don't you see the big wings on the above picture? Those wings here can function as a anti-torque system, due to the contrast of the body to the wings are so big. Turning the airplane's body requires much force than turning the helicopter's body, so airplanes won't need a rear rotor. However, the engine does take effect on airplanes' movement. If you loose your hand on the lever, the plane will gently moves to the right by suggesting the propeller moves clock-wise. If the propeller's spin direction is counter clock-wise, the plane will gently move to the left.

We have seen helicopters lost control and crash. The malfunction of rear rotor causes the helicopter to spin and the pilot no longer hold the control of the helicopter. The video is here:

Helicopter crash: http://www.youtube.com/watch?v=aArnj1nuPJg

So here is the question: How to control the wind speed or the output power of rear rotor in order to stabilize the helicopter? An important invention comes in, the gyro-meter. This topic will leave to the next post~~

Today is Christmas Eve. I want to introduce my favorite Christmas song: Same old lang syne. You can find the lyrics and the song at here:

http://www.tacocity.com.tw/abs1984/s20.htm

Wish everyone happy Christmas!!