Helicopter that seems to fly without moving the propeller

The small propeller attached to the rear seems to be turning properly, but it seems that the main propeller is stopped. However, the helicopter is flying normally.

What on earth is it?

The movie is from the following.
New Anti-Gravity Helicopter Video


This helicopter is made in RussiaMi-24So, as a result of the main propeller rotation and the frame rate of the video camera being synchronized perfectly, it seems that the propeller has stopped appearing. Certainly, I hear the loud sound that the propeller is turning. There is such a terrible coincidence.