[Woodchuck12]

I've been learning to fly my 250 with a CC3d board, however, one thin I've noticed is that the tail blows out whenever I raise the throttle too much. I have the PID set so that the proportional is just below where it begins to oscillate. Integral is a bit over double and derivative is where it is. The tail also wanders pretty bad. (Have to hold slight counterclockwise to keep straight)

The cyclics also feel sort of mushy and wander all over.

The system seems overall pretty stable, just wanders a bunch. I am trying to raise my derivative a bit to see if that helps, but also, how much of this is just normal 250 behavior? What else could I try to have it track a bit more true?

[daveapplemotors]

What do you mean by tail blow out? Does the heli spin?

When the PIDs are happy with a low throttle setting I raise up the throttle to get closer to my 3D flying headspeed. It took a few tries. I recommend starting with a low headspeed to get a handle on things and then raising headspeed gradually as you change (lower) PIDs to accomodate higher speeds

Raise the P values to get more precise handling on any axis. My P values are roughly double my I values. I don't mess with D much unless I can't get any joy with P and I.

I don't know why there is a 2:1 ratio between P and I. I don't know why I have it upside down with P approximately double I.

[Woodchuck12]

The tail was trying to spin continuously. I mostly fixed that by addressing the neutral position of the tail servo. Now, if I raise the throttle too quickly, the heli will start doing 360's until throttle is lowered. I spent all day yesterday playing with PID and other than that, it hovers fairly well with some minor oscillations.

Mine is opposite right now, the P values are ~.400 and I is closer to .00900. I will try setting up a flight mode with lower I and see where that gets me.

[daveapplemotors]

Hey Charley,

TBO ==Tail blow out, what we called it on stock Blade mcpx. I have not seen it on my 250s. Do you have enough throw on the tail rotor? Are the maximum and minimums sufficient to get yaw control? Once you get the yaw neutral set pretty close you can: move the servo, adjust the push rod or I believe--use some trim. I just use yaw neutral without changing the other adjustments. Know that moving the servo or changing the pushrod also moves the endpoints. 

I have learned that higher throttle settings require smaller PI numbers. Try tuning with a flat throttle curve  to eliminate one of the two variables you're dealing with: pitch AND throttle. I start maybe at 40% , get it stable and then raise the throttle, readjust the PIDs and raise the throttle again. I am at 70% with both of mine now and am trying to learn a ratio between headspeed and PIDs.

What mode are you using? I fly mostly in Rate, Rate, AxisLock.

Are you in calm air? Do you try different TX flight modes to compare PIDs?

good luck,
Dave

[Filippo94]

I had the same problem on a 450, having to keep right yaw to manually compensate the rotor torque, both rate and axisLock, managed to fix moving the neutral position of the tail servo in the output panel.

If I move the neutral position of the servo, should I correct again the pushrod to get to the middle of the tail pitch slider range? Right now the endpoints are correct, but of course I got less travel on the right, and plenty on the left. At middle of the range the tail blades pitch is at 0 degrees.

[daveapplemotors]

I like my servo arm at 90 degrees when the heli is hovering with no rudder input. The tail rotor blades are at about 15- 20 degrees as a guess. I will measure the distance between tips (or find the angle) at hover on my 37mm tail rotors. I have one that is just right so that measurement will be a good starting point on my other ones.

Yes. Your question is really good. To get the rudder right you would set the servo at 90 degree. Test hover. Move servo or change pushrod length. Test hover and adjust physically again until good. Then set endpoints.

I will try this method if my servo arms aren't already near 90 degrees. I haven't given it much thought.
Thanks.