It's been suggested to adjust elevator D gain, but not sure what that would be called on Spirit or if such adjustment exists.

To me, it seems like a slight tail kick, but it translates to head instability during a hard collective stop.

What parameters should I start tweaking first?


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Can you describe the behavior little bit more, please?
What is bouncing? Rudder or elevator?

Usually on hard collective stops it is only tail (yaw axis).
But if for example there is bad CG or some servo adjustments, it might result in elevator bounce.

Both issues have a different solution, so we have to know what is really happening first.

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Spirit System developer

It happens so fast it's hard to get a good idea as to what's happening.

If I were to guess, I think the tail is yawing and that ends up "feeling" like cyclic instability for a brief moment before changing directions and punching out.

Is there a way to test this to see what the cause is? I've asked other pilots to watch and assess but they aren't able to give me a definite answer.

There's a pause at the stop where the disc seems to slightly shift, but it does seem like the tail kicks slightly.

Tail Gyro gain may still be a bit high as I do feel some shuddering through very high speed banked turns.


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You can try to decrease Gyro gain.
Then the issues should be more visible.

In any way, if it is the tail, then it is probably caused by low Pirouette Consistency (so that the tail is not holding well even with too high gyro gain).
By increasing it will be better.

On the other hand, to fix Elevator bounces, you can increase Elevator Filter. If it is bigger helicopter (600+), then you will need values 3-4.

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Spirit System developer

The tail holds quite well in inverted backwards flight at full collective when travelling horizontal to the ground. If I change to in upline in this orientation at full collective, I get some high gain based shuddering (rapid wagging).

It's been really windy lately so I figured the gain setting would likely be optimal when the wind was calmer so haven't changed it.

Does this make sense for what you are thinking with Piro Consistency?

I'll try increasing the Piro Consistency though.

How much do I increase at a time? How high is too high?

I'll also play with the Elevator Filter too if the tail tweaking doesn't workout.


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Fast oscillations can be due to high Rudder Delay. Please check our Servo list - http://manual.spirit-system.com/index.p ... Servo_list
There you can find optimal values for your rudder servo.

I recommend to increase by 5 (change should be noticeable, but not too much).

Can you attach your settings, please? I can check it.

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Spirit System developer

Hi Tomas,

I have a KST 565X on the tail and the rudder delay is in the 2-5 range. I think it's currently at 4 if memory serves me.

Finally got back to the field today to do more tweaking.

I increased the cyclic gain a bit and the collective stops feel better, stability wise, but the tail is definitely an issue.

On pitch pumps from a hover, the tail definitely kicks about 5-10 degrees to the right.

I have the gyro gain set to the highest I can go before I get fast shuddering oscillations through FFF banked turns. It's at 48% with a three blade tail assembly at 2300rpm on this tri-head 380mm X3. I have 3-4º (slider closer to boom) on neutral tail servo. Still kicks at 2500rpm.

I've adjusted the piro consistency from 165 all the way to 200 and everywhere between. No significant change.

I am set at 4 on Rudder Delay but dropped to 2 to try as well. I've upped the gyro gain to try and see if it the pitch related kick went away, but it's still there and it's not ideal for FFF above 48%.

I am at a loss. Settings returned to the posted ones in the last post. I am using Spirit Gov. Should I adjust the 2 response or hold next?

Debating changing my head back to stock 2 main blade/2 Tail blade setup to try if I can't figure it out. I really like the 3 bladed setup, but maybe it's not helping. I dunno.

Hello,

to make the rudder performance good, how head speed is holding is extremely important.

So sometime, it is enough if RPM is dropping, then you will be unable to tune the rudder. Unfortunately it is hard to tell, how your RPM is holding.
It is something you should hear during pitch pumps. So that there are drops not bigger than 50 RPM.
If it is Governor, increasing Governor Response will solve the problem. But I recommend value of 7 maximally for you.

Pirouette Consistency should be not too high for this helicopter. So value you have in the provided settings is OK.

What you can also try is to use even shorter servo arm, then update both Rudder End-Points. After this, you will be able to increase Gyro Gain little bit and hopefully the performance will be better. This KST servo has quite good resolution, so even that values are high, mechanical gain can be way too high which will not allow too high Gains in the unit.

If nothing will help, I can recommend to add just Revomix to 2-3 (but not more).

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Spirit System developer

Ok, will try to address the Governor settings first.

I can hear some bogging during pitch pumps and 2300rpm is well below the rpm it's geared for.

Even with my current servo arm length, the control rod bends near servo slightly, no I'll effect though), so I wouldn't want to go shorter as there would be even more bending.

Thanks. I'll report back.


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