AutoTune could not measure D on this axis and left it at the minimum

What ArduPilot says:

• AutoTune: Min Rate D limit reached

While tuning the D gain of this axis, AutoTune brought it down to AUTOTUNE_MIN_D (0.0005 by default) and could go no lower. It keeps that value, ends the step and goes on to the next; the tune can still end in “Success”. It is a hint that the D term could not be measured well: the bounce back AutoTune looks for, set by AUTOTUNE_AGGR (0.075 by default), did not shrink as D came down.

What to do, most likely first

1. Vibration or noise looks like bounce back to AutoTune.

   CheckThe log's vibration levels and the gyro noise in a hover.

   FixReduce the vibration and set up the notch filter before tuning again.

2. A large aircraft with slow, heavy props really wants less D than the limit allows.

   FixLower AUTOTUNE_MIN_D (down to 0.0001) and tune that axis again.

3. AUTOTUNE_AGGR is at the low end, so the bounce back it accepts is very small.

   FixRaise AUTOTUNE_AGGR towards 0.1, its upper limit, and tune again.

Parameters to look at

Where to do it:Setup & Tuning GuideSetup & Tuning GuideSetup & Tuning Guide