Iris kept climing in Loiter with throttle closed

Hi Guys - I’m new to the Iris and have been trying different flight modes. Tonight I switched from stabilize to Loiter and started the aircraft in a vertical climb. It was a couple hundred feet up (estimated) and I reduced throttle to keep it from going any higher. The Iris kept climbing, so I lowered the throttle further, and the climb continued. I pressed the right stick forward from center, and that finally stopped the climb, and it began to descend. The descent rate seemed pretty high, I added throttle and it started climbing again. Again, forward right stick got it out of the climb, so I didn’t add any throttle until it got to a comfortable altitude. I’ve attached a screenshot of the seemingly pertinent CTUN values form Mission Planner, along with the log file.

From what I can tell, the aircraft was properly receiving my throttle input, but the autopilot was ignoring the stimulus - this based on the ThrOut graph. However, the ThrOut graph did get very noisy, and it looks like the AngBst parameter may have had a factor in this. The mission planner dataflash logs page gives this definition for AngBst:

AngBst: throttle increase (from 0 ~ 1000) as a result of the copter leaning over (automatically added to all pilot and autopilot throttle to reduce altitude loss while leaning)

Some conditions: I had a GoPro mounted on the front, and had to hold aft elevator in stabilize mode. It was apparent the COG was too far forward and I made no effort to trim it out with the SkyRC controller. I did have the datalink receiver hooked up to a Nexus 7, which seemed to be working OK, but I was too busy worrying to check it during the event.

This wasn’t what I expected, and either I don’t understand Loiter mode, or the root cause could have been the fore COG. What should I have done to prevent this? I wouldn’t think trimming from the transmitter would help this situation. That would be just like holding the stick aft. Should an autopilot parameter be changed to prevent this from occurring again? I do have a tarot gimbal that would solve the COG issue, but I’m not ready to destroy that just yet :smiley:

I’m hoping somebody with more experience than I can explain this - I’m reluctant to use loiter again at this point.

Thanks in advance,

So does anybody know if there is a parameter that can compensate for “tilt” from the GoPro on front to prevent loss of control in loiter?

Sorry I can’t help but wanted to bump this topic as it was just posted on Twitter by DIY Drones…

Thanks. I’ve flown several times now and the iris always climbs uncontrollably with the gopro on the front when in loiter. I suspect that this is an undesired artifact of angbst and / or vibration. I wish there was a parameter to cut back the angbst gain.

From my understanding and from what I’ve experienced, loiter should hold the current position with or without the Gopro attached to the front. I’m not very good at troubleshooting logs yet so I’ll leave that to the pros.

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