I have finally rebuilt the XK120 using an 1103 outrunner on the tail. I am using a uSpirit with the tail motor option. The 6 deg Geometry setting is correct.

The heli is flying, but still has a slow wag on the tail. It wags about 20-30 degrees every second or so. I have followed your recommendations in the 'Tune rudder, uSpirit with 230s' thread, my settings are now:
Rudder delay = 0
Gyro gain = 10
Rudder Revomix = 4
With these settings the wag is a bit slower, but still as big as before.
If I engage rescue the heli goes straight up with the tail holding well.

What to try next?

Hello,

what is your Piroutte Consistency? This value has the biggest impact (after Gyro Gain).
Gyro Gain is very low, so I guess you will need to decrease Pirouette Consistency value.

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Spirit System developer

At the moment still 130, I will try adjusting that.

It is much better now, with these settings:
Rudder delay = 0
Gyro gain = 5
Rudder Revomix = 2 or 4
Rudder Dynamic = 7
Pirouette Consistency = 80.

The tail is now mostly stable, with small wags of about 10 deg. every few seconds. However the tail kicks out about 30 deg to the right (tail in) in pitch pumps. A little better when Revomix is 4.
I am unable to adjust Pirouette Consistency in flight, because the minimum value at Input = -100 is 130. However I can edit the value to 80. I believe it will accept down to 50.

What is the best sequence of adjustment from here? Is it possible to describe the expected result when increasing and decreasing each value? The descriptions in the manual are difficult to relate to what I am seeing.

Can I please have a firmware version that allows Pirouette Consistency to be tuned inflight between 50 and 150?

Yes, we will be releasing new firmware this week.

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Spirit System developer

Wonderful, thank you very much!

Stay safe!

I am now on 3.1.1 and have the following settings on the XK120 with brushless tail motor:
Rudder Delay = 0
Gyro Gain = 0
Rudder Revomix = 4
Piro Consistency = 50
Rudder Dynamic = 6
Rudder Rotation Speed = 5

There less wag than when I started with the defaults, but not stable yet. What change do you recommend?

Here is a video clip https://www.youtube.com/watch?v=6NsLOkqqKlw&feature=youtu.be

Hello,

firmware 3.1.1 is not released yet. Maybe this is mistake.

Are you sure Gyro Gain is 0?

You can try to increase Rudder Delay to 25.

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Spirit System developer

Sorry, firmware is 3.1.0.

Gain is 0 via adjustable pot. I will try the Rudder Delay change as soon as the weather allows.