Losing altitude / Can't give enough throttle

Iris+ brand new out of the box. Firmware is 3.2.1 (downgraded during troubleshooting).

Ive got about 50 hours on a previous one and have some pretty good experience with the Iris+. My last one had a 4in1 power problem failure and it was cheaper / easier to just buy another than to replace it - plus now I have spare parts.

Seems that after 4-6 minutes of flying perfectly the copter loses altitude and eventually crash lands. This last test I flew in Loiter mode for a few minutes and then when noticing it losing altitude I switched over into Stablize and still couldn’t give it enough throttle to keep it up.

Trying to figure out if I have a motor that is bad and therefore its compensating to stay level … I can’t really figure it out after review this log for hours. Hoping an expert can review.

I believe around the 178,000 mark in the logs is where the problem begins. You can see the switch to Stablize after the problem began (noticing it couldnt stay afloat any longer).


I am hoping someone can review logs and point me in the right direction. After about 15 flights I keep running into this problem a few minutes in and don’t feel safe flying it anymore until I can determine the problem. I am guessing its either a bad motor or cold solder joint but haven’t found any physical signs of it.

Log download: https://drive.google.com/file/d/0B1TNiat_6ssYakh3QmN4eXY2Y2M/view?usp=sharing

After it gracefully landed in some bushes it never detected a crash - because it landed so softly this time. The motors were still trying to spin so logging / sensors / etc show unrelated info after that.

it’s grossly underpowered.
hovering at >82% throttle.
Assuming your ESC’s are calibrated to max throttle, and you are not carrying too much payload, check propeller direction and if they are right type.
the descend /fall you see is at 100% throttle, caused by VRS , a forward speed would help, but it’s not really a flyable configuration.
something is very wrong here, get help from an experienced multirotor builder, should be easy to spot it…

The problem was my iris+ controller was not calibrated properly. It was producing 80% throttle instead of 100%. Then when calibrating the ESC it never saw full speed therefore struggled to stay up. Awesome now!