3691047956?profile=originalHi all. Trying to tune in my APM 2.0 with V3 firmware for Alt Hold for a customer on my custom, folding, 400-size quadcopter. She oscillates (vertically), then gently starts dropping until it lands.

I've tried some of the tuning tips, and reduced the oscillations, but she still drops. Any hints folks?

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  • Good idea to check, Scott. And if you have some log files, then that is an easy one to check. But I was having a similar response, and found that I had to set THR_MID. the default is for the 3dr quad.

    @Owen: what is your batt/motor/prop setup? if it is different from the 3dr by some amount, then you need to adjust the THR_MID parameter. 

    randy outlines this procedure here, but in essence:

    You can do this by flying in stabilize, and just focus on getting a good stable hover in for a few minutes. Then land, open up the .log from this flight, and graph the "THR IN" parameter that can be found in the "CTUN" message/row. you should see some nice flat plateaus from your hovering. read that value (or the average, it will obvious vary a small amount).

    In the full parameter list, there is a parameter titled "THR_MID" (list is alphabetic) change its value to the value you read from your hover, write parameters and go try it.

    Unrelated: I tried the different colored props, too to try to provide some orientation clues while flying. I found the havings the different colors left/right actually allowed me to get orientation even when the copter was flying L/R across my view. the problem with F/B that I found was that if the copter is pointed to your left or right, and it rolls, it can be hard to see which orientation is front. TL;DR, I found L/R colors to be more helpful.

  • Log a flight and compare GPS relative Alt to BaroAlt.

    It's also possible that the prop-wash is affecting your barometer since it's so small and the props are so close to and above your APM.

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