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nav_pitch offset error in FBWA

Posted by Nigel Brown on February 5, 2016 at 10:22pm

Hi All,

Running DX8 with spektrum satellite on pixhawk, latest firmware.

Radio has been calibrated 3 times all perfect 1500 centre sticks. 

I am however getting a -2.0 offset on nav_pitch in FBWA mode. Any ideas how to fix this without adjusting the trim values on the radio as it needs the correct trims for manual flight. 

I have tried increasing the deadband zone on RC2_DZ from 30 to 60. This didnt help. I also changed the RC2_TRIM from 1500 to 1455 this does change the value close to 0 but i dont see why i should do this. As the RC calibration screen is showing 1500 as neutral very accurately and repetitively. 

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Help would be greatly appreciated. Thanks

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Tags: fbwa, calibration, error, nav_pitch, offset
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Replies

  • Devin Unice August 26, 2016 at 6:46am

    This nav offset looks like it is from the STAB_PITCH_DOWN parameter.  According to the wiki this is a pitch down applied to the plane in FBWA when the throttle is below TRIM_THROTTLE.  This is meant to help maintain airspeed when hands are off. 

    Hope this helps

  • juan pablo gayoso August 25, 2016 at 7:17am

    great!.....It knowledge cost me many "&%!* in my pants" moments, and crashes. It was a pleasure to help you.

    ....happy fly from Peru.

    (edited by moderator)

  • George Georgiev August 25, 2016 at 7:07am

    Hello again guys!

    Firstly, I would like to thank Juan Pablo Gayoso for the great tip he gave me in getting my wings in the air. Pablo, today I managed to get it right following your advice.

    In result the plane flies great! 

    Thank you, 

    George (Gastaroll)

  • juan pablo gayoso August 23, 2016 at 11:57am

    Apparently , auto-Trim function has to work, like you mention. but I read many comment about the manual trim gives better result than auto-trim. I never used that function, so  I can not give my personal opinion. I only have experience made all manually.

  • George Georgiev August 23, 2016 at 11:46am

    Thank you Juan, 

    Thank you very very much for your reply.

    Just to clarify... I will use trim_auto and after the new trims are saved I should keep the physical trims position of the elevons while keeping the trims on the RC to neutral. Is this correct?

    After I finish the trim_auto procedure should I center the RC trims?

    I believe the following video explains it but I was not quite following. https://www.youtube.com/watch?v=ucy6VnlMHy8 ;

    Thank you again, 

    George.

     

  • juan pablo gayoso August 23, 2016 at 11:42am

    The likely reason is that you didn't trim your plane before.You have to trim the control suface manually, the RC have to be in neutral position.....

  • George Georgiev August 23, 2016 at 11:34am

    Hello, 

    This is driving me crazy! Please help me too as I can not get around it. When I switch to FBWA the plane pitches up a lot, so much it goes vertical. 

    Any help is greatly appreciated.

    Thank you.

  • juan pablo gayoso June 16, 2016 at 10:57am

    Hi Nigel

    Could you resolve the issue? I have the same doubt.

    Kind Regards

This reply was deleted.

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