Tiger, this is what I was showing Leo prior to going down, when a helicopter descends down with no forward airspeed greater than 300 feet per minute, the blade tip vortex rings (which are always present) travel down the blades towards the center of the hub. When they reach the stall area of the blade (the center does not have enough surface speed to make lift), you keep going down with no hope of recovery unless you gain forward flight and get out of your own down wash you are creating. A bare 450 has enough power to get out of it, but heavy birds will crash, my gopro box is close to causing it, thus the sound I was making. The more you pull lift in a panic, the worse you make it and the faster you fall. http://www.aneclecticmind.com/2011/05/06/on-air-vortexes RC Jet almost piles it up with no forward air speed drop, he was full up collective all the way to the ground..... http://www.youtube.com/watch?v=MkOEq4gS8ro&t=9m22s Blade MCPX demo, you can hear the sound somewhat... http://www.youtube.com/watch?v=0Kz_gOWaR7Y
BTW, new flybar, JB Weld on the frame, some zip ties and it seems ready to fly, passed the hold in hand spool up with no weird vibrations test...
Interesting videos. The sound was familiar. Wikipedia has a good explanation and also some good images. http://en.wikipedia.org/wiki/Vortex_ring BTW: It looks like the first link you posted is not working. I see "The content you are trying to view is available to visitors of the source web site only. To see this content visit aneclecticmind".
I guess I should have read the article better, it was a VRS that crashed the Seal Heli during Bin Laden. Link changed.....
