'Long range' Auto mission crash

Hi all,

I'm new here and new to droning in general - I'm struggling to understand why my UAV just suddenly landed during a long-ish auto mission. I have disabled the geo-fences, all the fail safes (except GPS) are set to return to land - GPS failsafe is set to altitude hold.

I've tried to analyze this data log from the drone and I just can't see anything. GPS looks good, battery looks good. What am I missing?

I have video from the Drone and basically it was merrily going on the mission, and then just suddenly decided to land - not crash/fall out of the sky - but actually land itself - in a bush unfortunately but all is OK.

I'd appreciate if someone with some experience can check out this log and tell me the mistake I'm making :(



PS: After the auto mission (and after I found the drone) I just did a quick loiter test to see if the Drone was still functioning, you can ignore this data (I guess).


You need to be a member of diydrones to add comments!

Join diydrones

Email me when people reply –


  • I just wanted to update the thread, I've replaced the props with the HQ Slow Flyer Props (10x4.7) and I haven't since had such a problem. The hover throttle still sits around 65% at sea level but better than 75% it used to be.

    If anyone has any other propellers they have tried on the IRIS+ that could improve this, please let me know.

    Thanks for the help

  • Hi, I reviewed the logs.  It appears your quad has a power problem.  It is hovering at about 80% throttle, and was hitting 100% while travelling.  For most of the trip, the autopilot was correctly limiting forward speed to maintain the set altitude.  As the battery drained, power was reduced, and eventually the autopilot basically gave up forward flight to try to maintain altitude, couldn't, and so it basically landed.

    It was not an intentional landing.  Rather, it was still trying to reach the waypoint, but just just reduced speed to zero to try and prioritize altitude over forward speed.  Eventually, it didn't have enough power to even maintain altitude, and landed.  You're actually lucky it landed so well.

    I suspect maybe your battery is damaged, it starts off at only 12.3V, drops to 11.8V almost immediately as power is applied, and then after 4 minutes is down to 11V which is when it landed.

    • Hi Rob,

      Sorry to hassle again, please see attached from exmaps of the flight data - can you point out what you are seeing? I'm probably misinterpreting this but it looks like the voltage + current are 'OK' even at the time it crashed.

      Again I'm very new at this so please excuse ignorance if I'm missing something.



      Screenshot 2015-03-13 21.06.01.png

      • HI Donald,

            you may want to load up a copy of  windows/mission planner/dataflash log/review a log to examine

        that log it will show a LOT more granularity about what was going on with your flight.... and help you to have some understanding...



        • Hi Donald,

              repropping IRIS+ to 10x47 apc with phantom 6mm nuts and stock equipment brings the xcoptercalc model down to 54% at sea level from 68-76%(and higher in your case with heat and altitude).

          See christians blog.. its what you are running into... besides the bum Lipo...(dispose of very carefully) flammable/firebally if you piss that lipo off by mishandling be very careful ie recycle if possible if not



          How-To: Safe lipo preparation for disposal - TJinTech
          Home of TJinGuy's heli info
          • Hi Hzl,

            Thanks for taking all the time - I have one of those battery testers and a balance charger but it seems to be telling me things are OK on all my batteries ;(

            I think it might just be a combination of everything (heat, altitude, weight, etc). See the attached screenshot from Mission Planner - successful mission vs failed - I can see what Rob was talking about now - right before the 'landing' the throttle output was stuck on 100%, it obviously just couldn't keep itself in the air anymore.

            I actually live at the coast and I've never experienced this before - so I'm learning here.

            Thanks again for the help

            Screenshot 2015-03-13 23.19.30.png

            • Hi Donald,

                 the stock balance charger is not very bright about lipos .. the HK one I use shows me all kinds of neat data like the internal resistance of the cells(indicates just how bad that lipo is getting).

              You will need something similar and need to number those lipos to screen out the bad one...

              they ALL look alike :(

                      but yes the poor little IRIS+ just ran out of steam .. need to get your hover throttle down to 50-60% before initiating automissions at that temp/altitude to have enough safety margin of power.. ie density altitude is what pilots term it as ..here is some suggestions for manned craft for dealing with it from the AOPA http://www.aopa.org/Pilot-Resources/Safety-and-Technique/Weather/De...

              and here is a web calculator to calculate your actual density altitude based on air temp elevation and humidity level.. http://wahiduddin.net/calc/calc_da.htm

              ie missions flown in the morning before the airtemp goes up will experience more sucess and require less throttle due to denser air..


              ps I think rob is RIGHT on that LIPO being damaged and it needs to be filtered out from your flight packs before it causes issues...

              and we ALL learn by helping others... how this whole passion we call drones works..

              • More to report :)

                So today was a really hot day here (+- 37 degrees C) so I decided it would be the perfect day to test the batteries (without having access to a proper battery tester).

                I ran all four of my batteries (now labelled) for +- 10 minutes (or to 10.6V) and all of them survived the entire time and this is with a fully loaded IRIS+ (Gimbal+GoPro+video transmitter)

                I tested it by rising to 20 meter altitude (relative) and hovering while just keeping the drone 'busy' with the right stick. I've also downloaded all the telemetry logs and all the patterns of the draw down of the battery/throttle look similar. It does hit 100% throttle a few times on all the batteries but for a few moments.

                If we're still pointing fingers at the battery - is it possible that one of them just had a 'bad' charge? IE wasn't fully charged even though it was reporting so?

                Or is the more simple explanation that the drone ran into some difficult conditions along its route (wind/heat/etc) and couldn't keep the heavy payload in the air at that moment?

                Thanks for your help.


                • as rob said 100% power and settled out of the air ie

                  I am going for density altitude and too much load for IRIS+ in conditions...


    • Thanks Rob.

      I actually 'like' this explanation as its better than unsolvable magic :) I have 4 batteries - so perhaps one of them is faulty. Now to identify which one...

      Is there any rudimentary way of testing batteries? Or should I just hover the drone at a safe height and see which one collapses?

      Thanks for your time

This reply was deleted.