Cyclic Gain in Relation to Head Speed

[Grees01]

  Hello everybody. Welcome to all the new members if I happened to miss anyone. I have a question concerning cyclic gain? I would like to understand a little better the relationship between cyclic gain and head speed. On my E5, with an Ikon I have 2200, 2300, and 2400 for the head speeds. My gain is set the same for all head speeds. At 2200 it smooth, 2300 smooth, but at 2400 I get a little bit of a shake in the skids looking at it from tail in. I'm wondering about the relationship between gain and head speed, in general does it usually stay the same, increase, or decrease with higher head speeds. I am aware of the possible many causes of a little shake, but it says in the setup information in the Ikon software that if the helicopter exhibits a little shake try lowering the gain settings by a few points until the shaking goes away. Ok, but why? and how does the one affect the other? Thank you in advance for any feedback given.

Glen

[Danny Dugger]

It's the same principle as when you tune the tail. A PID control loop is most effective at an ideal gain setting, if the gain is too high the gyro corrections will overshoot and cause oscillations. Too low and it will feel loose and sloppy. Just as the tail wags when gain is too high, the skids will shake if aileron gain is too high. Higher head speeds generally will require lower gain settings.

[J Anthony]

Hmm... thank you Danny for explaining that. I'm still wondering myself why the higher head speed requires lower gains? Is it because the higher speeds create less vibration so not as much gain is needed or is it a case of nothing more than every heli just has a certain group of settings that it works better with?
     I must admit I'm kinda' lazy with this myself. If I'm running my 635 at 2250 for example, I just tune the heli for that headspeed but I never go back to the lower speeds and tune the gains for them. I'm probably missing some performance on my lower headspeeds if they'd fly better with higher gains. On the other hand, I really never fly on the lower headspeeds.

[Danny Dugger]

Generally if you tune for your highest head speed the others will fly pretty well... unless you're doing extreme hs differences like 1400 IU1 to 2200 IU2. The main rotor has more of a physical gyroscopic effect at higher head speeds which can also make cyclic rates feel a little slower and the system as a whole may generate slightly higher vibrations than at lower head speeds. There are many factors that may contribute to different gain settings as well as rate settings. Add in build technique and your personal "feel" preferences, governor performance, blade weight & balance, etc etc etc and you have a big part of why everyone's helicopter will have a unique tune.

[J Anthony]

Great. Thank you very much. Makes sense.

[Arsenox]

Thank you for the helpful stories that have shaken us to read.