How can this helicopter fly?

[PHY]

Watch and try to answer the question.

[youtube]http://www.youtube.com/watch?v=DjPfzKbYDXw[/youtube]


The blades are moving, you can hear them. They just happen to be synchronized with the camera's frames per second. Multiple of 24 or something... so they only appear on camera to be stationary.

[PHY]

Here's another video of the chopper. Note at the end as it flys by the crowd and comes into perspective. This isn't a toy or model on a string.

[youtube]http://www.youtube.com/watch?v=HZJJK-XAnso[/youtube]