If I'm in a tail-in hover and then I pirouette 90 degrees CCW so that the nose is left and the tail is right, my heli will start drifting to the right, toward its tail.

I understand the idea of translation tendency and how the heli needs to be leaning to the right in a tail-in hover to be stationary. My question is, is there something I can do either on the heli mechanically or in the FBL setup to improve the piro compensation so that if I pirouette from stationary, the heli will remain stationary? I had assumed that the unit would compensate itself.

I also notice the issue in forward flight. If I'm going away from me tail-in and then I do a 180 degree CCW piro so the heli is going backward but away from me, the heli will drift to my right side.

The swashplate is as level as I could get it with 1/2 increments on my links. The heli (Oxy 4 Max, Spirit II) is a little bit nose-heavy with the 1800 mAh battery. But I get exactly the same situation on my other heli (Oxy 2, µSpirit) that is very tail heavy.

Anything I should change either mechanically or in the FBL setup?

Heli 1:
Oxy 4 Max, Spirit 2, 3.1.0
KST 215 cyclics (333 Hz, 1520 µs)
MKS DS95i tail (560 Hz, 760 µs)
Slightly nose heavy.

Heli 2:
Oxy 2 stretch, µSpirit, 3.1.0
Lynx DS-895 cyclics (333 Hz, 1500 µs)
Blue Arrow tail (333 Hz, 760 µs)
Very tail heavy.

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Find me on HeliFreak, username Xoexoe

You should move the batteries to get the best cg balance you can first of all. Cg matters a lot. This is probably the most important thing you can do.

Second make sure you’re not giving false inputs, tighten your transmitter springs or increase expo, check st what values the spirit is reading your inputs based on the selected deadband (i the diagnostic screen you’ll see the numbers turn bold).

Play with raising head gain as well.

Do you notice this issue only in one direction? I am seeing the same thing with a uSpirit and a Blade Fusion 180.

I took off my canopy and adjusted my battery to get excellent CG. (The heli won't rotate in any direction if I hold it sideways by the center hub/main grips.) I fly in Mode 2 so I cannot give accidental cyclic input. But I did double check the Spirit channel settings and all is good. I have plenty of deadband anyways.

I tried it both CW and CCW. In all cases the heli will drift toward its initial right side, so if it's tail in the heli will mainly go to my right. This is consistent with the Spirit not compensating for tail translation during piros, or at least not compensating enough.

I made a short video showing it. Any ideas?

My head gain was around 80 during the video. QUite high, but I'm flying 2000 RPM on 386 mm blades.






https://www.youtube.com/watch?v=OsyrcPCiT_U

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Find me on HeliFreak, username Xoexoe

I think that's just the nature of flying helicopters honestly, especially small ones.

I don't think I notice this on the big stuff though, but I always expect to do some small corrections.

Mechanical setup? Swash leveling and servo setup...I know the FBL will compensate for a lot of error here but think it may manifest in the way the video shows.

Can anyone else try on a 380 or larger heli and see how it fares?

I’ll double check servo horns and swash again next time I have it out.

Thanks for the responses so far.

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Find me on HeliFreak, username Xoexoe

I don't have this problem on any of my helis; one 550 and three 700's.

It should not matter how helicopter is big. The pirouette should be stationary more or less.
You can check one of our development videos from the first version of our units. There it holds pretty well even with 450 class (323mm blades).

Problem is usually in the mechanical servo centering. So that when you enable Servos/Subtrim (tuning) menu all servo arms must be in the middle as close as physically possible.
At the same time your swashplate should be perfectly horizontally. And at the same time there should be 0° between main blades.

If this is the case then pirouettes should be perfect.

In some cases, with some models tail rotor is not aligned perfectly - as it can rotate at the tail boom. It is causing up or down thrust which is moving with the model then. Some models have no lock to prevent from this issue.

To improve the precision you could increase Geometry 6° value (for example by 20 points). It is not correct solution, but it should help. Unfortuntely it has impact on the flight behavior too.

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Spirit System developer

same here: my Spirit 2 is on a Logo 400SE... 480 blades. piro consistency is excellent... only little movement with very slow piros cw (due to tail rotor thrust).

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cheers
Michael