Hope one of you guys can help me identify a root cause to this accident here:

I have just finished a large hexacopter build (Tarot X6, 18" props, 325Kv motors), and on it's second flight, shortly after takeoff, it slowly started yawing left, feeling fairly "wafty", and then as I tried to set it down, it caught a skid and flipped over.

I had, just prior to this second flight, swapped props from some CF ones to APC props. After the crash, investigating the machine, I realized I can turn the right rear prop, admittedly with a fair amount of force, but I'm wondering if prop slip caused this issue? Or perhaps a ESC/sync problem?

Thank you for any insight into this you might have.

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Anyone possibly have any thoughts on this? I'm going to be rebuilding it in the next few days and would love to have a little help in pinning down the problem!



Andy McAllister said:

Anyone possibly have any thoughts on this? I'm going to be rebuilding it in the next few days and would love to have a little help in pinning down the problem!

I haven't looked at your logs (I'm not that far advanced in this hobby yet), but I believe a loose 18" prop (even if it is hard to turn manually after the flight) with such powerful motors could certainly account for the uncommanded yaw.. You didn't say which direction the rotation of that prop was ( CW or CCW) but if it was slipping on the shaft that would throw the yaw moment off kilter (in the opposite direction of that prop rotation, I think(!))

The loose prop was CCW, as was the yaw direction. I *think* this makes sense, as the CCW prop would be producing a CW rotation on the airframe under normal circumstances, so when the prop slips, it would the reduce the CW force, allowing it to rotate CCW (the same direction as that slipping prop).

I would love someone well-versed in logs to have a look at see if this correlates though!

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