Would be fun to have bicopter support (Avatar type).


Two rotors and two servos outputs.


Servos outputs would need diffential mixing.



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I was thinking about this the other day. maybe there's an easy way. If you have two side by side  heli type rotors, then using 2 servo's per side, you can change the pitch ( differential ) or the collective ( together ). So with the 4 servo's you can pitch, roll, yaw and apply collective for altitude. Then the 4 ESC outputs off a standard quad configuration can control the 4 servo's without the need for mixers. This scheme in theory should give better stability because you don't have worry about propellor speed delay.

the easy way is the one JMD describes, yours is a lot more complicated


jmd: no you don't need diffential mixing.. (you need a bit more..)

it should be quite easy to implement bicopters to the code


I think that servos outputs need differential mixing because :


- yaw is controlled by opposite rotor inclination

- pitch is controlled by synched rotor inclination


But you are right, differential between yaw and pitch is certainly only the basic part of the mixing work.


Do you think that it would need more than new motors_bi.pde mixing code and PID adjustments ?





yes, we know that one, but it has a fraction of APM capabilities

you could also post a link to aeroquad when somebody asks for quads...

like the tri-config you would need a hack to move the servos at 50Hz (in arducoptermega.pde line753)

Hi Sebastian, not sure what you mean about having a fraction of the APM capabilities.  Deifinitely am interested to learn.  My new bicopter prototype - the Nymbus 650 - uses a mod of the original APM airplane code.  Uses two fixed-pitch airplane props. Here are some clips of it hovering with an Align heli and doing circuits:










A condensed version.  - Gary

Both differential thrusts and prop tilting (in opposite directions) are now used to control roll in Gress Aero Bicopters. 

The tilt rate generates a gyroscopic rolling moment, and happens sooner than the control obtained with diff. thrust.  Which means potentially better roll response, gust tolerance and stability than a quad - or any other mutlicopter with fixed motors.  I do see an improvement, so far, indoors.

As an added benefit, yaw is no longer coupled with roll.  Before, diff. thrusts created a yawing moment, but is now offset by the diff. tilts.

This was all done by reprogramming the APM.



Hi there, im new here, im trying to build a bicopter myself and have been fascinated by your machines for a long time Mr.Gress. All has been well through my build but i hit a stumbling block..the controls. I based my wiring and connections on this diagram..but it seems to not work. Im not sure whats wrong, might it be the components im using? I was hoping you may be able to help me with this if its not too much trouble..

I will just list down the components im using;

hobbyking 20A esc x2

hxt900 9g servo x2

turnigy sk2822 1200 motor x2

futaba r606fs Rx

copterx gy240 gyro

blue arrow nano vtail mixer x2 (BV01-J)





Can you describe the problems you are having?  Also, a photo of your aircraft will help.


One thing I noticed:  you need a proportional gyro for pitch, like the CSM SL560.



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