Twinstar APM takes to the sky!



Today I flew my Twinstar with APM in the hotseat. It's the second flight I've had with it wired in, but yesterday I was only using the stabilise mode. It's been a couple of great days from a weather and wind point of view, so ideal for testing.  The Stabilise mode is lovely.  The Twinstar (mine has a stock power system) when it is trimmed up is a super stable platform anyway, so I'm not too surprised that stabilise didn't have a massive impact, but it was certainly noticeable and very pleasant to fly!  The plane does have about a 5 degree nose down pitch when hands off (in stabilise) and I don't know how to fix this, can it just be trimmed out with the radio?  I thought the AP would compensate for any trimming I did to the control surface, and the fact that it has a nose down attitude is probably an autopilot config issue.


Return to launch was interesting.  I took off in stabilise mode and flew fairly straight away into the wind gaining a bit of altitude.  I then changed mode to RTL and took my hands of the control for the next few minutes.  The plane held attitude well, and executed well controlled turns.  However, you couldn't in all honesty describe what it was doing as a circle overhead the launch site.  Figures of eight perhaps, it seemed to be hunting for something.  It certainly seemed to be controlled and comfortable in the sky, I wasn't too worried.  I still don't understand it's behaviour though.


I would like to share the log file with you, but I can't.  For some reason this flight wasn't logged.  The previous two were and I have the KML and log files for those (not huge files, probably about 3-4mins flying each). Log three only shows one 'page' of data.


I will fully admit that this may all be my own fault.  I'm still learning, but in my excitement and the heady sense of progress, I havn't run the tests and tuning using FBW_A that the manual suggests that I should do.  I've not got my head around PID settings, and I suspect that this is the root cause of the issues i was seeing with RTL.  I'm guessing the AP couldn't hit it's mark to begin the orbit.


If the weather holds I'll be out again tomorrow to diligently follow the FBW_A tuning guide!



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  • Hi Jim,

    I have build a APM Twinstar too and have flown it a few days ago in RTH mode too.
    How was the behavior of the motor during the automatic flight ? Mine was oscillating between 75% and throttle off.
    You can see some flight test videos at
    Can you tell me more about your setup ?

  • I used Sony vegas to overlay the video, but syncing was done by eyeballing it, and listening. Both videos had us talking at the begining, which made it fairly easy to sync.
  • Jim

    little OT, but wondering how you overlayed the video from the onboard camera to the video taken from ground camera. And did you managed to synchronize them somehow ?


  • Ahh yes, that would explain the logs, I did turn on 'all' logs which i've found is a bit excessive! Chris, I was holding off from moving to v2 just yet as I was only just getting comfortable with 1.5. On your advice I'll upgrade tomorrow.
  • 3D Robotics
    I'd suggest you upgrade to APM 2.012. Remember to do a reset and EEPROM clear from the CLI after upgrading. Also, as Darren suggest, erase all the logs.
  • I believe 4098 is the end of the log space. so basicly your log is full... if you are able; try to erase your logs after each mission.
  • Hi Thomas
    I'll pay attention to the planes resting position while booting, but i'm pretty sure it was level. The PID settings are entirely stock for APM 1.5 i've not changed them yet. Do you have any suggestions what to look out for with the pid tuning on a twinstar? I'd also be keen to hear what you've upgraded your power train to, as i'm going to be doing this soon, and the options are extensive!
  • Admin

    Hi Jim,

    Glad to read that you had a successful flight. The pitch down attitude might be due to aircraft attitude during calibration or the APM/IMU Mega is not parallel to the fuse.

    I presently have two Twinstar IIs that have upgraded power systems. One TS II has a Copilot II installed while the other is waiting for an APM/IMU Mega to be installed. I have flowing the Copilot II equipped TS II and like how it handles. Can you provide the PID values that you used with your TS II?



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