I wanted to bring attention to the work that Tridge and the rest of the CUAV team have done to demonstrate the possibility of flying a Helicopter with a standard FBL controller handling the rate control duties.  They have been testing gas powered helicopter for next round of the Outback Challenge which will require a long-range VTOL aircraft.  Helicopters are a natural target for this mission of course.

Several of the CUAV team are experienced RC helicopter pilots, but not as familiar with installing a Pixhawk on a helicopter which can be difficult, especially in the case of gas engine helis.  As such, they were more comfortable having a normal Flybarless Controller handling rate control. In this case, the Skookum Robotics 540.   Tridge has made changes to the code which allow for a pure control pass-through from the RC Rx, through the Pixhawk, and straight to the FBL controller. This pass-through occurs in Acro mode, whereby the Pixhawk running ArduCopter has no effect on the flight control, so even if the Pixhawk should have a major AHRS/EKF failure, the helicopter is still controllable. 


Of course, the Pixhawk is capable of controlling a Helicopter without any FBL system, and this is the most common arrangement.  But the possibility of running an FBL controller in series with the Pixhawk helps lower the barrier to entry for many existing RC Helicopter pilots.  And also offers helicopters similar failsafe-function to airplanes, where they can survive the loss of the autopilot.

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  • @AndrewTridgell  would it be possible to get a copy of this pixhawk code?

  • What way, be able to use a single connection Pixhawk sbus of sbus out to FBL system (Vbar, SK540 / 720) of sbus in it? Which parameters need to modify it?

  • Thanks both for the reply.

    Sorry I did in fact mean for quads, aka FPV racing, and potentially quadplanes for R&D purposes. I've read on several occasions people asking for a way to integrate another AP with PXH, and the idea came to me over the weekend that this would likely make that possible.

    So currently both heli and plane support this, but not multicopter? I suppose it will work for quadplanes then, but not multis yet. Is there a wiki/manual page for setup? Thx.


  • And Naze32 doesn't have a helicopter program.

    I assume JB was asking about multirotors.  In that case, this could be made to work, but the multirotor code does not support it now.

    Personally, I don't think the other controllers have anything on us in Acro mode anyway.  And the extra mass/size/complexity of the system wouldn't work out for FPV racers either.

  • Developer

    @JB, yes, I think this would work fine. The 2nd board would have to be in a pure rate controlled mode, with stick movement proportional to rate about that axis.

    I should note that this is only possible so far for heli and fixed wing. For multi-rotors we don't have a pure feed-foward term in the rate controllers that is needed to setup for a pure rate controlled downstream board

  • Tridge or Rob

    With the way FBL is now implemented, is it also possible to use a secondary autopilot instead of the gyros, like a Naze 32 etc, to control the aircraft instead of the PXH, but then possibly use the PXH for navigation control? I know some FPV racing guys prefer other AP's for flight control but would like to have the PXH connected as well. I suppose it could be potentially used as a way to switch to a failsafe AP as well.

  • nice work

  • Speaking about vibes how well does the FC handle this in gas helis?

    It requires skilled design and engineering of the vibration isolating mount.  I have several hours of flight time on my gas heli with no issues.  Actually, on it's second flight the GPS failed due to vibrations, that is isolated now too.

  • The point I was trying to make was that greater awareness and precautions are required to safely operate large traditional helis compared to commonly sized multi copters, though this definitely should also apply to large multi copters.  The CUAV team's modification of APM to allow for FBL controller passthrough is an example of an additional safety measure that responsible operators should consider adopting.

    I completely agree with your first point.  Serious jobs require serious tools, which require serious operators.

    But on the second point, I disagree.  I'm a responsible operator, and will not be installing an FBL onto any of my helicopters.  I don't require it, and it adds nothing to operational safety for my systems.  

  • "From my understanding a gasser or electric heli typically both experience more vibrations than a multi. Every application has it's own merits, helis can lift lots for longer."

    Speaking about vibes how well does the FC handle this in gas helis?

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