Thanks all for the advice. I tried different CG placements, cyclic gains, and recentered my servos, levee swash, got perfect blade tracking, etc etc.

Unfortunately the model keeps tilting out of piros as in the movie I posted above. And Oxy helis have an oval boom so it’s impossible for the tail shaft to be misaligned.

I even tried moving the servo horns in for more precision and all that. Nope.

I did notice that there is a 0.5 degree difference between my boom and the top of my motor can. So something is out of alignment maybe? But there’s no wiggle room anywhere so I don’t know. I wonder if that has something to do with it.

Not sure what to do. I might try putting the FBL in a different location just to see what happens. Hours of work. Bah.

But from what you all say it’s not a Spirit issue at all, so I’ll reach out on HeliFreak and see if others have a similar issue with this model.

Thanks for the suggestions.

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Find me on HeliFreak, username Xoexoe

i had an oxy2 with a micro spirit, it piro'd like garbage, all over the place and wobbly.
I think that's an oxy thing.

My xl520 on spirit piros like a spinning top, everything is perfectly flat and stationary.

I think what you're getting is a normal and correct behavior of the helicopter...
I mean, if you would constantly pirouette, then yes - it can be stationary and FBL makes some compensations here. But if you just rotate a heli 90 or 180 degrees, you will get a drift and it is correct. You need to compensate for that. At least unless there's something I don't know about FBLs..

You will get exact same behavior in simulators which do simulate tail rotor thrust, like RealFlight or AccuRC (neXt doesn't).