On occasion when hovering I find my quad descends all the way to ground without being commanded to do so. Nothing spectacular, it just sinks until it touches the ground then sometimes comes back up a bit. Increasing the throttle doesn't necessarily stop it. This also occurs in Alt-Hold and Loiter modes.

I've had this issue with my APM 1 and now APM 2 so I figure the issue may lie with my motors/props. I'm using 1050kv motors with 10x6 props to lift around 1.5kg. These are driven by 18A plush ESCs. Does this sound like it should be adequate?

Cheers,

Chris

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  • Apologies for bringing up this old thread but I thought I should update it with my latest findings.

    I took the plunge and replaced the motors with the 850kv ones from the DIYdrones store. This didn't make much of a difference.

    However, I then replaced the 10x6 props with 10x4.5 and suddenly the quad is like a completely different beast. No more unrecoverable sinking!

    I'm an electrical guy, so I don't really understand the significance of what I changed. Perhaps someone with more knowledge in this field could fill me in.

  • Does this sinking happen after the batteries are getting depleted? I have found that moter thust at a given throttle setting is directly proportional to battery voltage. Your batery voltage could be sagging quicker than the altitude controler can compensate.

  • I was having this problem. I was using 25C 2700mah batteries and they just weren't strong enough (and my copter was only ~1200g).

    I went up to 30C 3400Mah battery and 30a ESC's. Now I'm flying with my throttle end point at 60%, and it flies like a dream. No more sinking to the ground. 

  • You don't mention what software your using.

    I am finding this happens with v2.7.1, amongst other things.

    There is definitely a bug with the Alt hold.

    Do you have the wobbles as well?

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