Singlecopter Frame

Hello Guys,

I’m trying to setup a Singlecopter config with 1 motor and 4 servos. As Flight Controller I’m using a Omnibus F4 v5.

As it’s my first time with ArduPilot, it’s quite hard to figure out the right parameters. Anyway, I managed to get the Servos as well as the BLDC running. (based on

At one point, I’m not quite sure whether it’s an issue of ArduPilot or whether I’m doing something wrong: So far my Singlecopter doesn’t fly stable. I think this is related to the wrong Frame setup: When I’m checking the servos (ROLL / PITCH), they do what they should (in disarmed mode). YAW controls on the other hand seem not to have any effect on the servos, so I assume YAW is compensated by the 2nd motor which does not exist on a Singlecopter.

I have choosen 8 as FRAME_CLASS according to the instructions. Nevertheless, my Copter always appears as CoaxCopter when I’m connecting the flight control and also SERVO6_FUNCTION is always resettet to 38, although it should be disabled for a Singlecopter. Am I doing something wrong or is this a known bug?

Thanks a lot in advance for your support,


Ask this question in this thread there are some developers involved

Hi Louis, I can answer some of your questions:

  • the single copter will appear as a coax copter in mission planner because there isn’t a specific single copter vehicle display type
  • I’ve looked at the code and if the system is disarmed/shut down yaw stick movement has no effect on the servo movement. However, if the system is armed and/or spun up yaw commands should be sent to the servos according to the code. Perhaps try arming and spinning up without the prop connected and see if the actuators behave like they should.
  • It looks like the single copter code always initializes a second motor even if not required. So you can disregard Servo6

So it looks like the behaviour you’re seeing is expected behaviour according to the code, perhaps you need some further tuning?

Hi Jason,

thanks a lot for your feedback, now I’ve got a little more confidence to start tuning the PIDs!

Unfortunately I did not manage to get the configuration working with Betaflight, INAV oder dRonin together with my Omnibus F4 SD, so I have to find a working config with ArduCopter.

Currently I the copter is still not stable around the YAW axis and starts spinning as soon as I increase throttle. I will try to solve the issue and keep you posted.

Best, Louis

I don’t have the code in front of me this morning but perhaps the only other thing I can think of is that the yaw output to the servos is in the wrong direction. So if there’s an option to reverse yaw you could try, or alternatively try it with a prop spinning the other direction.

So finally I managed the Copter to hover (although still attached to a string to avoid severe damage).

Now I need to tune the PIDs - currently the copter still starts spinning as soon I apply too much Pitch or Roll via the RC. I will keep you updated, would be great to get this thing flying after several attempts with different FCs and Firmwares. :slightly_smiling_face:

Good luck with it! Seems odd that the pitch and roll would feed into yaw, perhaps you need to double check the servo endpoints so the servo throw for each flap is identical?

I’m so happy that I found this thread. I am working on the same project. The ball MKII drone. I would love it if anyone here knows a link to an write up or an article or a pdf file that discusses in detail the mechanism of the MKII ball drone and how all the components interact with each other. By interacting with each other I mean things like how the fins counteract the motors torque while at the same time stabilizing the copter and controlling directional movement?, what would be the most effective distance between the propeller and the fins?, how much the fins need to rotate/deflect for effective control? what should be the ratio of the propeller diameter compared to the diameter of the vanes? and other related critical details that I can’t think of right now.
Even just a video explaining how the copter works, how the vanes move, and how to tune the PID to make the copter fly better will be very much appreciated.
My single copter (single rotor) ball drone just goes crazy and smashes into things as soon as the thrust is enough to raise the copter. Also I’ve gone through this, SingleCopter and CoaxCopter — Copter documentation, and I was a bit confused. When it says something like * transmitter roll right makes forward and back fins move right, is it the top of the fins or the bottom of the fins that should move right?
Thanks in advance.

Well, it helps to think about it in terms of thrust vectoring. If you wish the airframe to roll to the right, you need to push the bottom of the airframe to the left, which would be accomplished by rotating the bottoms of the front and rear vanes to the right.

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Thank you very much. I’ve made some impressive progress on my single copter. Tweaking the PID values really make a lot of change.