ORIGINAL: sfinckster
I have the same falling problem. I usually fly in my shop at work, but I flew at home a couple times last weekend and it did not have the problem. I am wondering if there is some kind of RF interference at work. I think that what's happening is, the pitch changes on the blades to negative but only for a fraction of a second and then comes back. I can see the blades flash differently when it happens. I cannot see the servo arms when it happens because the heli drops so suddenly it makes it hard to see. I have tried to reproduce the problem while holding the heli in my hand, and spinning up the blades for a while so I can see what's going on, but it will not fail while I am holding it for some reason. Maybe it is vibration causing the glitch, and holding it reduces the vibration. I don't know...
I posted my theory a while ago. I've been flying the heli all winter with NO glitches (knock-on-wood), then I decided one day to install the shim upgrade. Shortly after that, the heli would drop about 3 inches just for a split second. I believe that some sort of interference is causing this. In my cause it is being caused from the 2 shims on each side spinning and rubbing together causing a harmonic vibration, probably so faint that it's just enough to make this happen.
I will be removing the shims and going back to stock until my B&H arrives. If I don't notice anymore bobbing after I take the shims out, I'm confident I solved the problem.
James