Iris *almost* crash and logs...

I flew Iris yesterday for the first time in a few weeks. I had just updated it to 3.2-rc9 and run through all the needed re-calibrations. When it lifted off in Stabilize it didn't quite feel right but it wasn't anything obvious. When I switched to Loiter it got really twitchy and wouldn't stay at a stable altitude. I didn't even try any of the other modes since it was plain something wasn't right. I flew it twice yesterday, the first was bad but the second was way worse and I almost didn't get it down without crashing. The last time it flew it was on 3.2-rc6 I believe and everything was fine. No problems at all. I did post this over in the 3.2 beta forum but I figure it probably really belongs here.

I've included the logs but an't find anything myself that would explain what was happening. I don't even want to try and fly it again until I have some idea of what's wrong.


2014-09-14 09-56-23.bin

2014-09-14 10-36-11.bin

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  • I will install the Pixhawk relocation fix when I upgrade the rest of Iris. I have the kit on order and I figure since I have to tear everything apart anyway it's a good time to install it. As for the firmware, there are some features in the newer 3.2 firmware that I really wanted to try out. I can always go back to 3.1.5 but I don't think now that the beta version has anything to do with the problems I was having.

  • Update: After discovering the vibration issue, I decided to try swapping props. Problem gone! Flies perfectly! I'm not sure what happened to the props I had on Iris but they must have got damaged somehow but I can't see anything. No nicks, missing pieces, warped blades, etc. They used to fly good. Oh well, it's fixed now and I'm happy.

    • I wouldn't call that fixed. It's probably just luck. 

      Before I discovered that the Pixhawk would touch the GPS module I could have a series of a dozen or more flights without issues and all of a sudden a flight where IRIS dropped out of the sky. 

      Without you applying the fix of relocating the Pixhawk, you'll always have trouble waiting for you. 

    • Ditto on what Christian said. If your Iris is version 1 and you haven't moved the Pixhawk or the GPS/compass module, the problems will be intermittent. It could go bad for 3 flights and then good for 12 flights.

      I put a mast on mine and it's all good. Doing the Pixhawk relocation should help a lot. You want more distance between the Pixhawk and the GPS module.

    • BTW - I'm still running 3.1.4. I don't upgrade the OS on a stable machine unless it has something I need really bad. Don't know if that makes a difference.

  • If you are running the Beta code, I think you will get better/faster answers in the Beta forum.

    • I tried that and was generally ignored. I finally deleted my post there out of frustration. I think I have the answer though. It's taking me a bit to learn to read these logs but it seems there is a vibration problem. I have to thank Christian for finding that but once he pointed me in the right direction I started to see it in the logs for myself. It will take time but I'll get there eventually!

  • Gary, the altitude reported by your Barometer and GPS differ quite a bit. That shouldn't be the case. I can see that the vibrations along the z-axis are very high, which is most likely the cause for the barometer malfunctioning. 

    It appears that your Pixhawk flight controller is receiving vibrations from the motors. This is a known issue with early manufactured IRISes. Did you ever receive and apply the Pixhawk relocation kit (

    It was sent out by 3DR a while ago and would address your issue. If you didn't receive it, contact 3DR support. 
    If you did, use it. If you used it, check if something else is touching your Pixhawk.

    • Hi Christian. Thanks for the reply. I was starting to wonder if anyone noticed any of my posts here or on Facebook. I did get the relocation kit but at the time, I wasn't having any problems (or so I thought) so I never installed it. I now have the "Iris+ upgrade kit" on order so I'll install it then since it will all be apart anyway. I just couldn't figure it out since it seemed to fly fine when I was on 3.2-rc5 (maybe rc6?) and then I updated to rc9 and that was when the problems seem to start. Maybe that was just coincidence since everyone else is having no real problems with rc9.

      I really need to learn how to read those logs!

      Again, Thanks!

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