I am dumb struck!!

I have a Bixler 1 and have been flying it for three to four months with no problems at all.

Have a bigger motor in and FPV gear on it. Last Thursday went to fly and something very strange happened. The Bixler nose-dived on its own, in stabilize mode. I did manage to save the bird, but 1 min later it did it again. But this time I could not save it as it was too low. I also did not have any telemetry connected.


Rebuilt it and went to the field Saturday morning. This time I had telemetry connected. I took her up and flew in manual mode for 3min, then switched to stab. It was not even 1min and it happened again. Saved her but the second time I could not. Crashed again !! I was busy turning (with the ail and elev) the nose just went down uncontrollably. I looked at the tlogs with Graham Dyer, what we could see is that the vcc was not very consistent at the time of the crash. Tlog attached named Saturday.

Rebuilt the Bixler AGAIN !!  I swapped the ESC too and reloaded the APM firmware (v2.68). Calibrated everything and tested it on the table. Sunday morning went out to the field. Once again took her up in manual and flew around for a while. Switched to stab and it went well for a couple of min’s. Then it happened again. Nose down 100% and whatever I did, did not help. CRASH NUMBER THREE !!!

We looked at the tlog and the power this time was 100%. But at the point of the crash there was nearly no input from ch2 but 100% output on ch2. Tlog is attached below, named Sunday

Rebuilt Bixler AGAIN !!!! Took out the APM 2 and swapped it for another one I had in my quadcopter. I went this morning and flew the Bixler again. It was much better but found something interesting, when I bank full ail the Bixler will tip over and dive, but this time it recovered after a second or two. Still very stressful to see. I tested this a couple of times, it loses control but gets it back again. Still not 100%.


Thursday I flew with 2.66 the rest was done with 2.68. I also loaded the default bixler.para from this site every time.


Please can someone look at the tlogs and give me some advice.



Monday 1.tlog

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  • Hi.  I know this is an old thread. 

    I have had a similar situation.  Was flying quite happily in stabilize mode (ardupilot 2.5), practicing launches and landings.  Last flight of the day, launched plane as normal, it went straight up for about 30m, did a turn at the top and nose dived straight into the ground.  I had no control.  I noticed afterwards that the voltage on my transmitter was very low, I suspect it was sending bad data to the receiver.

  • It happens to me too.

    One day everething goes more than awesome and the next day everething goes wrong... I lost 3 airplanes with reliability issues.

    I was working for hours triying to find what goes wrong...

    I was thinking in a Manual mode board that act as a bypass to have a real manual mode. because in my case the APM reinitializing is a recurrent cause of problems. and almost everytime ends in a crash.

  • Im having this exact same problem on my Skywalker 1900. Flew awsome for the past week and havent made any changes. Now all of a sudden, today I am getting the exact same symptoms as you descrobe above. I crashed once this morning, rebuilt and tested again this evening and crashed again. The plane has had it, but I would like to know why this happened.


  • I figured it out just by looking at the pics. It's because it's green. Problem solved everyone go about your business, nothing to see here! Kidding. Sorry for your loss hope you figure it out.

  • I've had similar incidents with a bixler.  They develop nasty stall behaviour with some weight on them, especially if the weight isn't centered laterally.  You have to level the wings using rudder and aileron before applying up elevator otherwise it will just keep going down (been there done that!).  They fly much more nicely fresh out of the box with no extra weight!

  • Developer

    This thread is a great read. I just want to add that it is important to remember that even the best autopilot is not some magic box that will prevent any kind of airplane crash. Basic principles like weight restrictions, proper center of gravity and trust vectors still has to be correct. Or simply put, if you have a hard time flying the plane in manual, sooner or later it will probably crash in auto also.

  • Moderator

    If anyone wants to see the trouser changing stall/spin/crash, attached is a Google Earth "Tour" of it. You'll need the latest version of Google Earth to view it (v7+) - (I didn't know GE could do this, thanks to Vince for mentioning it)

    (@Khairul, yours looks like a stall and spin too right at the end of the flight.)

    Bixler stall, spin and crash.kmz

  • Hi Louis,

    My team and i have been experiencing the same issue.

    I posted previously in the Arduplane User Group:

    Today we just had another crash and its already about 7 crashes due to the same issue and 3 planes are somewhere in the forest which we are yet to locate. 2 Skywalker Condor and 1 Bixler. All with APM 2.5

    The issue remains even after updating to 2.68 fresh clean firmware without any modifications.

    We are using Ublox GPS and 3dr Radios, Futaba radio systems. And its always the same characteristics, Throttle will power up more than what it should in Auto and a gradual nose down..sometimes im able to recover in stabilize or manual but most times no. It happens randoom, sometimes at the start of auto mission, sometimes middle or at the end. Past few days we stressed test tour plane and covered total flying time equivalent of 200km and all was fine and we thought problem was solve. But today this crash happened again.

    I read people here talking about tip stall but our crashes all happen on a straight path.

    Lousi, do share which GPS and electronics were on your Bixler?

    My TLOGS and KML from today are attached.



    2012-12-12 12-46-32.tlog

    2012-12-12 12-46-32.tlog.kmz

  • @ Vince, LOL !!

    At least someone had a thrill, I still want to cry. LOL !!!


    Here are the tlogs from yesterday’s flying with Graham. If someone want to look at the controlled tip/stall and spin.


    Graham made the Bixler stall to see what it does, and there it happened, stall and death spin. But guys I have to say seeing a Master like Graham handling that plane in the air is amazing!! He made it stall and spin and never lost control, I would have made it a grass dart!! Vince you are not the only one that have to change the trousers.


    Thanks again Master Graham!!


    @ Andrew, thank you very much for all your insight, as Graham said it was spot on.


    We did two flights, one with the rudder as Graham said and one without rudder, belowe are the two tlogs. Look at the time, first with rudder, second without.


    2012-12-11 16-57-31.tlog

    2012-12-11 18-31-06.tlog

  • Louis, I just converted your Saturday file into a KML and did a ‘first person view’ on google earth. From being ‘inside’ the plane it just looks identical to a classic tip stall/spin. Will have to change my trousers now.


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