Pitch tuning for change in CG

Hi Guys,

I need some help

I have a plane that is tuned nicely and flying very well. Last weekend I did a endurance test and changed the battery for a much larger one. This shifted the CG forward a bit. On Auto takeoff I noticed that the plane wanted to pitch down a little but then flew off and did the next 48 minutes without a hitch until Auto Land.

Looking at the Logs later, I noticed that Nav Pitch and Pitch are now off by -+10 degrees. (See picture attached)
How can I change this without retuning the plane?
Could I trim the plane up a few clicks and then redo a radio calibration?
Would changing the AHRS_Trim parameter do anything?
I often change the payload of my plane, and experiment with different batteries and would therefore not like to re tune and trim my plane every time.
Thank you
Regards
Andreas

Screenshot 2015-05-30 07.43.16.png

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Replies

  • Hi,

    A larger wing loading requires a larger angle of attack to produce the appropriate lift, if the aircraft is flying at the same speed.

    Are you sure this pitch difference does not result from controller trying to keep a constant altitude for the same speed, and as such a larger angle of attack? If the PIDs are well tuned and pitch dynamics are not too different, I would assume the integral term would compensate for the change in the CG, resulting also in the elevator deflecting more upward.

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