Tricopter Tuning - lets me pitch down, but not up

[ummagawd]

PID tuning my tricopter, everything seems to fly OK so far. Now that i'm trying to fine tune my PID... i noticed that in ACRO... I can push the nose down and it lets me, if i try to pull it up, it's nice and firm (this is all with my hands of course).

Isn't it weird that it lets me do that going only one way? I would understand if it let me change the pitch axis forward AND back... but only forward?

Roll and yaw seem to be dialed in just fine (won't let me change the axis by hand at all).

So... what do I need to tune here? Settings as follows

Roll (P, I, D) = 6 - 0.039 - 23
Pitch = 5.9 - .065 - 21
Yaw = 5.4 - 0.014 - 22

Note - anything lower than 0.065 on Pitch lets me pitch backwards too easily. If I go around 0.075, i start to get that low frequency oscillation.

Any ideas?

[Hamburger]

behaviour sounds kinda normal.
To induce and counteract pitch, on a TRI you only have the rear motor+prop.
That prop works well when it is pulling the tail up but it cannot efficiently pull the tail down - instead it simply decreases speed and tail lift which is not very fast and not a strong control force.

[ummagawd]

that makes total sense. I had not even thought about the fact that i'm tuning a tricopter.

I'm sort of a perfectionist in this regard... and is why i'm always out to squeeze every little thing I've got. But it seems like i'm all set as far as PID tuning goes....

Now onto the GPS tuning

thanks hamburger