1) I am interested in learning what "Rudder Delay" is. I've never seen this parameter in other FBL units. It almost sounds like a bad thing. Why would we want a delay in the rudder?


2) According to the Servo Chart, all of my servos have a Rudder Delay range of 0-3 or 0-4. I have all the servos set to "0". What would happen if I use the other extreme of the range, say "3" or "4"? What would I notice different? Why choose "0" vs. "3" or "4"? Is it best to use a value right in the middle like "1" or "2"?

Without fully understanding what "Rudder Delay" does, it is hard to make an educated decision on which value to pick.

1) This parameter is nearly in any Gyro or FBL system, it has just different name but the function is similar.
The closest thing to this parameter could be D-term of the regulation system. But in Spirit it is not this exactly, thus the name is different.
When you will hover with mouse cursor over any parameter, you will find a description of it.
It is parameter which correspond to response speed/rate of the servo. Lower value = lower delay of the servo, when it is moving from point A to B.
So fast servos do not need high values. But to help slower servos, it is necessary to change the regulation so it will try to make the movement faster by applying higher initial torque.
Because servo speed is usually not changing, it is good to set it.

2) Each model has a different mechanics which could slow down the reaction with comparison to other. With some very fast servos you can't feel any difference, because it is that fast it will work always well even with not optimal configuration.
With some, especially Futaba BLS it is important to set 0.
Usually you will not feel a difference between 1-2 points. So if you dont know, set average value (something in the middle).

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Spirit System developer

This description is still not as helpful as it could be. Maybe I can summarize what I think you said, and you can confirm or update my understanding...

It sounds like it's a value that tries to give the Spirit some understanding as to how much delay to expect in the rudder system, so that it knows how tune the feedback loop to not expect instant heading changes.

If that is correct, then I would expect small values on slow servos might make the system oscillate on stops because the spirit is applying more change before it should expect to see some, and on fast servos the spirit gets the changes it's commanding right away and thus additional anticipated delay doesn't matter a lot.

Please confirm....

Also, is this on the tuning guide? What would we expect to see if this was way off?

You are nearly correct with understanding.
The parameter does not cause any delay, actually it is applying kind of acceleration. For fast servos there is no need for it. For slow the response needs to be faster to mimic fast servo.

Yes, when servo is slow, it will cause oscillations especially during demanding maneuvers without any Rudder delay.

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Spirit System developer

According to the servo chart, all of my tail servos fall in the 0-3 "Rudder Delay" range. I have all of these servos set to "0". Lets say I already maximized the "rudder gain" and the "Pirouette Consistency" parameters, but I am still experiencing a slight right (CCW) tail kick when banging on the collective stick. Should I try increasing the Rudder Delay to "3" before I start increasing the "Rudder - Revomix"?

Rather no. For tail kick reduction you should increase Pirouette Consistency value.
The problem with tail kick is that it could be caused by more things such as:

• Head speed is dropping too much.
• Head speed is holding too agressively.
• Too high pitch on the main rotor.
• Improper servo arm length - can be distinguished from too low or too high end point values.
• Some issue in the mechanics (the most common - tight ball linkages).

If there is fast servo and tail is still not holding and it is not easy to get rid off it, usually there are more problems at the same time.

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Spirit System developer

Am I right in thinking that a tail motor (rather than tail servo) would benefit from a relatively high rudder delay value?

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Yes, correct Rudder Delay value can help a lot. Unfortunately there could be a big difference between ESCs, some can react very fast, some slowly.

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Spirit System developer