After 14 successful flights with a new IRIS+, it also hit me. Arming in LOITER, taking off and just half a meter above the ground, the IRIS started drifting to the right. No control inputs helped, neither did any mode change. It went around, bounced off a tree and finally got stuck in a hill with crash detection not detecting the crash. Luckily I was able to disarm it through the GCS.
First I thought, it was an IMU problem but I overlooked a scale difference in the visualization…
So, bottom line, I have no clue what went wrong…
Log is here: home.gofferje.net/DFLOGS/15-06-12_19-37-32.bin
And the solution is:
All THR_ PIDs were 0. I didn’t have stabilize on my TX and with zero THR_ PIDs, the alt hold controller couldn’t follow my command to descend and I couldn’t move the copter. So she drifted around and bounced off stuff.
Before the flight, I quickly changed configuration of CH7_OPT with APM Planner 2 and did not notice that it didn’t update the PIDs in the extended tuning screen properly, so I wrote the zero THR PIDs when writing the CH7_OPT change.
[ul][li]ALWAYS have stabilize mode available on your TX[/li]
[li]ALWAYS double check the display - not only values you changed but ALL values - before writing back parameters to your vehicle[/li][/ul]