How Helicopter Works | Video about Helicopter's working

[postlink]https://videomiracles.blogspot.com/2011/12/how-helicopter-works-video-about.html[/postlink]

http://www.youtube.com/watch?v=I9ScVZ437xAendofvid
[starttext] This is a useful video for anyone who want to know about helicopter.  Really great. [endtext]