Hi, I've been fighting an issue on my helis.

When pirouetting left and right, the stop behavior is different. The rates seem even as far as I can tell. When pirouetting nose left, when you let off, the tail has a nice hard stop and stays still, it's perfect in this direction. When pirouetting nose right, the tail will keep going for a fraction of a second and then swing back to the right an a few inches. At first I thought this was only happening on my Trex 550, but then I noticed it on my 700's as well.

I'm using Align BL855H brushless tail servos on all of my helis. I upped the rudder dynamic/stop behavior to 8,9, and 10 because I liked how quickly it stopped at those settings. Rudder delay is set to 0 on the helis, as the tail was super sloppy at default settings and this seemed to fix that. I don't recall trying setting rudder delay to anything in the 1-5 range, if that might be the issue. Pirouette consistency is set to 160 on all the helis.

Any suggestions would be appreciated. The tails are set up exactly how they're supposed to be per Align manuals. If you power up the heli and give no stick inputs, the tail servo arms are 90 degrees to the boom, and the tail slider hinges are straight/90 degrees to the tail shaft.

Also, on the Trex 550 dfc pro (600 boom), my tail travel adjustments are extreme and it's telling me one direction is too much. Those are the values I have to set to get full travel using the exact setup in the align manual (tail servo horn ball is in the third hole out 13mm). I've tried moving the ball to the fourth hole and it helped somewhat, but I still had to add a ton to the travel adjustments. Around 125 on the left side of the setup screen and 250 on the right! The mechanics on the 550 are odd.

Hi,

thank you for the details.
Can you attach your settings profile here, please?

First, we have to set correct values so it can suit your setup.
For your tail servo, Pirouette Consistency should be approx. between 170 - 180 and Rudder Delay can be set to 0.
I also recommend to set Rudder Dynamic to 6 for the beginning, because it is making initial settings much harder (demands for servo and mechanics is much greater).
Next thing, what rotation speed you have configured? If it is way too high, it will cause more troubles too. Same apply for the cyclic. This is because mechanics will be very close its mechanical limits (or will reach it). You will get also messages about reaching limits in the log. Usually value of 13 is used for extreme 3D, so if you need higher, something is probably wrong.

What is very important, what values you can get in the Rudder Limits. They should be approx. same for both sides and not exceed approx. 140 in both directions.
If there is a bigger differences, then it will cause this behavior, because mechanics has much more room for stopping on the one side, but on the opposite there is nothing.

We have tested Trex 550 many times and there is no problem with the mechanics. Travel as yours is really wrong. If values is higher than 140, then you should increase servo arm length. Both sides should end ideally in 90 - 120 range.
When you enable Subtrim (tuning) your servo arm must be at 90° (as precise as possible). Then, by changing length of the push rod, you can get tail center (so that the slider is little bit closer to the boom) - when tail blades are folded, they are not at 0 degrees - ends are not touching.
Trex 550 is performing well even with align 620 servo for 3D so with your servo it should be just perfect.
For Trex 550, pirouette consistency can be 160 which I recommend for the beginning.

When all is OK, you can manually lower the rudder limit (as stated in the manual) to get equal tail stopping. But always remember to not decrease it too much. You can lower side with the higher value. This will help always - but it is not needed usually.

Next thing, some mechanics offer way to high travel for the rudder (not case of Trex helicotpers), so that you should not use full travel (else you can reach extremely high angles) and even damage the helicopter.

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Spirit System developer

Thanks for the quick reply. I have different banks with different rates but nothing extreme. 11 for cyclic and 12 for rudder fees very good to me, I've gone up to 14 on rudder and 12 on cyclic and that's as high as I'd ever need at my skill level. Attached is my basic bank, the settings are the same in all my banks except for rotational speeds.

Great,
in any case I recommend to move ball linkage further to the last hole.

From which helicopter is the profile?

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Spirit System developer

From the photo travel range of the tail seems to be nearly equal. So it is very strange that you can see so big difference in the end points.

It looks like on one side servo arm is in so high degree (more than 45°) so changing it even more is making very small difference.

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Spirit System developer

This profile is from the trex 550 dfc pro, same as the photos. I'm attaching my default bank for my 700N here. I have a spirit pro on my 700L as well, but I have not flown it with the spirit yet so I don't know how that one will be acting.

Other than this I absolutely love the units.

Looks like the travel on the 700N is equal in both directions

I did try using the 4th ball hole (16mm?) on the horn on the 550 and it allowed me to screw my links on the tail rod back to a safer length, but it did not make any difference to this problem.

I recommend to change it in any case along with other recommendations.
Don't forget to update the tail limits.

What values you can get in this configuration?

With trex 550 there should be max of 1/3 difference between limits, not more.

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Spirit System developer

It brought me down from 250 to about 225 on the right side limit.

I might just flash the unit and start setup over from scratch to see if that helps.

I guess I could try lowering the rudder dynamic as well. It's basically overshooting when pirouetting nose right on stops and then creeping back to where it should be, but not doing that at all for nose left pirouettes.

I'll bump pirouette consistency to 175 on both helis as well. It's definitely more noticeable on the 550 than on the 700.

Ah .. It is really strange that the value is so high. Definitively there is something very inequal. This difference can be caused only by:
1. servo travel (faulty servo)
2. rudder center position (it is hard to see it precisely, but can be little bit off). Changing by CH4 subtrim should help.

At the moment it looks like your servo need 2x more travel in one direction to reach approx. same angle as in the opposite side. This is really not OK even if we account differences in the mechanic.

This is what should be solved as the first thing.

Doing setup again will very likely not help. Only rudder settings are important here so when you verify everything now, the result will be same as with the new setup.
Unit has no hidden settings inside so factory defaults will just take you some more time.

Yes, using less "sharp"/agressive values is good to start with. Then making it more agressive when it will be tuned is a good way.

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Spirit System developer