Bormatec Maja weak flight performance

Hello, mates!

I have recently received the Bormatec Maja airframe and despairingly trying to make it flight well.

  • Electronics is set#1 from HERE, 10A battery, Pixhawk, Analog Airspeed.
  • FBWA or STABILIZATION mode
  • Arduplane 3.1

So I tried 2 different parameters file\sets: one from here, another I found in internet. But with them it flew extremely bad: the plane just either crushed instantly, or stalled, or I couldn’t pitch it down at all. Then I asked Bormatec for their parameters and they share it with me. I am not considering myself as a good pilot, but I have flown with some others plane in FWBA without any issues.

So today I achieved the best fly performances so far, but they are still far-far away from desired ones. In made a takeoff with FBWA mode, but after some time I changed to STAB mode,'cause the plane was much more controllable in that mode. It was quite windy about 8-10 m\s. I have noticed that, although the LIM_PITCH max-min were confined in +15,-28 deg range the plane was oscillating in about ±30 deg, sometimes it even went to ±40 deg.

So I would like to ask you:

  • could you please advice me what might be a main problem?
  • there are 3 different orientation parameter’s extensions in log files ATT,CTUN and EKF1, are the first two actual ones and EKF1 desired?

Thank you in advance.

Link to logs and parameters - ex.ua/552710338824

There is no simple answer or one set of parameters that will give you perfect performance as there are so many variables that have a profound effect on the way a plane is flying. I suggest to read through this: plane.ardupilot.com/wiki/roll-pi … er-tuning/ and then try Autotune as it works really well.

To expect the autopilot to compensate for a badly setup plane is a sure way to be disappointed, it’s vital that any new plane be flown a few times in manual first by someone with a fair bit of experience to determine the following:

  1. Set the roll, pitch and yaw trims for straight and level flight, throttle on and off.
  2. Check that the servo throws are adequate, not too much or too little (the pushrod clevis position on the servo horn can have a major effect here and cause one plane to be completely different to another seemingly identical plane)

Also check for CG in flight (not too sensitive in pitch), lateral balance (very few people check this), thrustlines, etc.

Foam planes also change over time, temperature and with use so the trims should be checked manually for nearly every flight.

Good luck.

@Graham Dyer
Thank you for you reply, I will try your tips and autotune on my smaller plane first, as soon as the weather will get better!
And maybe you can point me out about my another question?
- there are 3 different orientation parameter’s extensions in log files ATT,CTUN and EKF1, are the first two actual ones and EKF1 desired?

It appears that I had 1cm further from leading edge shifted center of gravity.
And thank’s to moglos, who adviced me to move it 1-2 cm to the leading edge (reference from manual 8 cm). So eventually I had about 2-3 cm uncertainty with my first CG shift.

Now it flies much much better!