I've been setting up a Spirit on the Synergy N7. First flight was OK, no wobbles or anything (all settings pretty low) and I've begun tuning the tail.
I can't get rid of a bounce back.

Flight Style: 4
Rudder end-points: 134/143
Cyclic gain: 55%
Piro consistency: 160
Rudder Common Gain: 1.0
Rudder dynamic: 3
Rudder delay: 10

The tail servo is a Gaui GS504 running on a 2S lipo.
I was able to reduce it by lowering Rudder dynamic to 3.
Lowering overall gain (from the tx) down to 37 or having it up to 50, didn't make much difference.

It holds pretty well in pitch pumps, but in right and/or left piro stops, there's pretty significant bounce (prob 10-15 deg or so).

The tail control rod is connected near the end of the servo horn (one hole away from max, 16.25mm from servo centre). Before I start moving that inward (to slow down the tail servo response), I wanted to ask if there were other settings I should try first.

Questions:
* Is 10 OK for rudder dynamic?
* Whenever I have to modify a parameter right to the end of it's range, it makes me think something ain't quite right. That's how I feel about Rudder Dynamic (3). Is moving the tail control rod connection further in on the horn the right thing to do?

Hello,

I recommend to set Rudder Dynamic to values 6 - 8 if you like great stopping behavior. Value of 10 could be also fine, but it is mostly too agressive and require faster servos.

First of all, rudder should hold as good as possible. So if your tail is holding well during pitch pumps, it probably is OK.
Mostly tail bounce-back can be observed to just one side.

The cause why it is happening is mostly in tail mechanical center - what angle do you have on your rudder blades (approximately)?
It should be measured while Servo/Subtrim (tuning) is enabled - your servo horn should be at 90° while enabled.

For Synergy N7 your piro consistency could be too low, so you can try to increase value to 175 - 185.

Do you use Revomix? It should work without this.

Tail Gain should be always configured to max. possible value without oscillations/wag during FFF or pitch pump.

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Spirit System developer

Thanks for the info.

I had previously setup the N7 in rate mode using a BD. This was because I was trying to get consistent piro stop behaviour.
As a result, the N7 is setup to hover with as little input as possible in rate. i.e: I believe it's setup mechanically very well.

I actually DO get bounce back on both left & right piro stops. And it's pretty consistent both sides.
My issue is that even though I've begun with a setup that I believe should require "tightening", it's still overly aggressive. To the point where I cannot get tame it down enough to reduce the bounce at all.

With the N7, it's designed so that when the rudder arm is 90 deg, there's about 4-5deg of right-stick bias built in.

* At full deflection I see from 29-34 deg on the tail blades.
* There is no revomix yet as I'm right at the beginning of tuning.
* Would remove affect bounce back? It is 160 at the moment, reasonably low I thought.

My original plan was to build up from hopefully a sluggish tail to a tight and responsive tail. The problem is that it is bouncing back (the bounce is reasonably aggressive, it is NOT a soft slow bounce) even before I turn up any parameters.

Is moving the tail control rod towards the centre of the servo horn the right direction to go in?

No problem.

I do not recommend changing rudder angle more then 4-5°.
I recommend to set piro consistency to at least 170 and also to decrease rudder end-points little bit (you can try -10 for both sides)

Decreased end-points will help you, but it shouldn't be decreased too much else rudder can blowout in demanding manouver.

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Spirit System developer

OK. I'll try that. I was under the impression increasing the piro consistency would make the bounce worse (harder). Is that not the case?

If your piro consistancy is too low it can cause problems as well.

I would not be surprised if your issue is gone by raising the piro consistancy and adjusting the gains.

For my Logo 480 when I raised the piro consistancy, I actually had to increase my gains. It stopped any tail kicks on collective moves and it is very locked in now.

Interesting. Thanks, OK - I'll give it a shot.
I had presumed it'd make it worse since when piro consistency has been low in the past, I've had a sluggish tail. I figured that if I increased that param, it'd just be more violent (but I didn't actually try that).

Got to wait for some decent weather!

Solved.

It turns out I made a large mistake.

I thought I had setup the servos to 333Hz. I probably had, but I must have not saved the setup when setting up the head, etc.

I found at the field they were set at 50Hz.
I can tell you right now: A GS504 tail servo running at 50Hz isn't going to work ... well.

I changed it to 333Hz all round (running BK 7001Hv's on cyclic) and what do you know, suddenly the entire heli was tuneable.
Got it almost perfect now!

Perfect, thank you very much for the update.

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Spirit System developer