Should One Re-Calibrate After First Flight?

Posted by Jacques Eloff on May 21, 2016 at 7:15am

I have a question regarding calibration, hoping someone can give some steer:

After initial flights have been conducted in manual mode to baseline a plane, should it not be necessary to recalibrate the controls such that the PWM trim value is right for "straight" flight? I have never actually done this, and my aircraft all fly well, but is there not some conflict between the PWM trim value stored in the flight controller and the "override" value from the transmitter's trim position?

Jacques

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Replies

  • iskess May 21, 2016 at 10:50am
    There is an auto trim parameter. Use this to automatically set your trims for the Pixhawk. Or manually copy your transmitter trim PWM into the corresponding RCX_TRIM parameters.
    • Jacques Eloff > iskess May 21, 2016 at 11:12am

      Thanks Iskess, that answers my question. 

      I always try get my planes flying as close to centre trim on the TX as possible (ie. by adjusting pushrod length) which means the value is not far off from the TRIM value established during calibration. But I'm surprised this issue is not covered in the wiki.

      Thanks,

      Jacques

  • Christopher Rice May 21, 2016 at 7:46am
    Jacques,

    I highly recommend trying out two flight modes: FBWA and Cruise. Before you do this, you must ensure your travel on all surfaces are correct and not reversed. You may need to reverse the horizontal stab. As far as trim values are concerned, each mode will have whatever values you hard set on your TX. Once you have mastered cruise mode youre ready for auto flight mode, setting up a flight plan etc.

    In addition if you do not have an airspeed indicator (pitot), cruise mode gets a little squirrelly especially if there is a breeze.

    I know I didn't fully answer your question but it took me awhile to get confident trying out these flight modes. I had a crash of my first bird because I did not reverse the stab. Good luck.
    • Jacques Eloff > Christopher Rice May 21, 2016 at 11:04am

      Hi Chris - just to point out, I'm happily flying in various modes - assisted and auto, not sure what the elevator issue you mention is about. Perhaps you misunderstood my question?

    • Christopher Rice > Jacques Eloff May 21, 2016 at 12:22pm

      Yep, sure did. Sorry I couldn't help but looks like you figured it out. I learned something too!

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