This is my first post so please bear with me. I have searched and browsed this forum but I cannot find what I need.

I have a HK450 (T-rex 450 clone) that I have converted to a flybarless setup. Also I have installed APM 2.5 with Arducopter 3.1. I have followed the manual and guides on the internet. Now I am ready for the PID tuning of the Arducopter.

When I spool up the helicopter main motor all is well. At the moment of lift off i notice that the swash plate tilt to the left and the helicopter wants to flip over. I then reduce engine thrust because else the helicopter would destroy it self. The swash is level at mid stick. It seems the swash plate becomes unlevel when engine thrust is near maximum. So it seems the swash plate is level at mid stick but at > 80% stick is not level anymore. I have no idea what is causing this and it prohibits me to tune the PID. I am so close to being able to fly this bird (finally).

Please hand me any advice you can. By the way the throttle curve and pitch curves in the TX are set like you would with a helicopter without APM.

Hope to hear. Regards.

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  • Testuser:  What flight mode are you taking off in?  How are your vibration logs?  Could be a trim problem.  For anyone to give some sort of help more information is needed.


    David R. Boulanger

    • Hi David.

      I am trying to take off in stabilize mode. At the moment I don't have a vibration log. Good suggestion, I will make a log.

      Do you mean swash servo trim? I can almost take off when I put full aileron to the right. However at mid stick (collective) the swashplate is level but at full collective the swash is not level anymore.

      Could it also have to do with throttle or pitch curves in the TX?

      Kind regards.

      • One more thing.  Maybe your servos are not all centered together.  could one be at its maximum travel causing the swash to tilt at higher collective inputs?


        David R. Boulanger

        • It seems the APM tilts the swash to the wrong direction when I tilt the heli. So I have changed the servo settings in MP and reversed the channel in the radio. Now it does not flip over when trying to take off.

          However, I cannot take of fully because it seems the heli will oscillate (violently) when it does take off. I think I have to tweak the PID settings some.

          One day this bird will fly but with one step (month) at a time.

      • Testuser; vibrations could give you a leaning problem.  I mean trimming it in flight.  Hows the blade tracking?  I got rid of the throttle/ pitch curve and switched to airplane mode. I use channel 8 as a fixed pwm to the esc and run in governor mode with a set head speed.  I don't however think that is the problem.  Do you have telemetry coming into a ground station?  I have always used a lazy susan turntable to do initial test on my heli.  I strap it down kinda loose to the turn table with a bit of weight on it. Its like a heavy set of training gear. Maybe servo geometry is bad.  really need to see a vibration log for x,y,z axis and your parameter file. Just my opinion.  If you post your problem on the Arducopter support forum for traditional helicopter Rob L. will respond at some point.  He will need more information.


        David R. Boulanger 

        • Hi David. I will get a vibrations log soon. That could be it. Also, I will set the radio to airplane mode and check the blade tracking. I have telemetry from the USB cable because I have difficulty getting the bluetooth module to a higher rate then 9600. My bird has a training gear on it so that it does not flip over completely. The trim could be off at high collective pitch.

          I will get the vibration log and parameter file in the next couple of days.

          Kind regards.

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