Trovato questo articolo fantastico di
Justin P
Estratto dove si racconta un pò del P-gain e del I-gain:
2. V-Bar Tail Tuning:
If you believe that you've exonerated all of your potential mechanical causes, then move on to the V-Bar. Are you running stock settings? In other words, check that your P-Gain = 80, I-Gain = 60, Common Gain = ~90 (Common Gain will vary with heli size and type, but for Logos, I usually start at 90 to 100). Note that P and I gains are found in the advanced menu while Common Gain is the slider on the front panel.
How does the tail behave with stock settings? Does it overgain (hard wag with buzzing...i.e. the tail sounds pissed) in hard maneuvers like backwards inverted tail slides, funnels, or hurricanes? If so, start off by dropping your common gain a few points at a time while repeating the maneuvers. If you're not able to do any of the above moves yet, then try flying in fast forward or fast backward flight. If it doesn't get aggravated with that, then throw some hard turns into your routine. My rule of thumb is to find the gain value where you can JUST BARELY hear the tail get angry in a hard funnel and then back it off by 2 or 3 points. Find the right common gain value and once you're confident that the tail will hold and not overgain, then move on to the next step...
Fast Wags~
scodinzola veloce
Too high of a P-Gain can cause what most would consider to be a "fast" (>2-3Hz), but small amplitude (a few degrees) tail wag. I like to decrease it by 5 points from 80 until I get down to around 60. If it doesn't change the behavior at all, then I would automatically assume that I've missed something mechanically...Go back to #1 and try again. If a lower P-Gain does fix it, then re-run the common gain optimization as described in the above paragraph and you should be set.
Valore alto di P-gain fà scodinzolare veloce e con piccole ampiezze la coda
Slow/Medium Wags~
scodinzola piano/medio
Too high of an I-Gain can cause what most would consider to be a "slow" (1Hz or less), but small-to-moderate amplitude tail wag because, as you may recall, I-gain represents the heading-hold portion of the tail control loop and when it is too high, it results in an overshoot-reaction to sudden changes. As in the case of P-Gain, decrease the value from 60 by 5 points each time until you get to 40.
Valore alto del I-gain fà scodinzolare lentamente e con piccole ampiezze la coda...c'è una "sovraelongazione" XD della reazione ai cambiamenti improvvisi.....e qui c'è il fattaccio! I-gain lavora a braccetto con la precomp se abbassi la prima devi alzare la seconda e viceversa!In ogni caso dopo aver eliminato l'effetto della coda che scodinzola c'è il consiglio di rifare l'optimize
If you do change your I-gain, be aware that you may need to adjust your precomps as well. I-gain and precomps are inversely proportional in effect. In other words, if you lower your I-gain (reduce the amount of overshoot you allow), then you need more precomp to get the same effect. Conversely, if you increase you I-gain, you may need to lower your precomp. If you've gotten rid of the wag and checked the precomp, then simply re-run the common gain optimization and fly! If it still exists, then check your mechanical setup again, but this time if the tail linkage mechanics pass the test from #1 above, then move to on to the next step.
Ragazzi correggetemi se ho scritto castronerie!L'inglese mi odia 
p.s. Insomma ...meno si toccano i P-gain e I-gain e meglio mi sento!
