Unexplained crash due to uncontrollable yaw

Hi,
I’m running a Cinetank multicopter with a HK Pilot 32 and Neo7M compass unit (Firmware 3.2). The compass unit is raised approximately 6 inches above the quad on a stand.

Yesterday I was flying along at a high altitude in acro mode when I lost all control of the yaw and the copter started spinning uncontrollably. I switched it into PosHold mode hoping that it could right itself but it was of no avail.

When I recovered the quad from it’s watery grave (just my luck that it happened over a river), there was a loose prop – whether caused by the accident or was the cause of the accident I’m unsure. I tend to believe it was caused by it since I’ve had an uncontrollable yaw issue with this flight controller previously. I replaced the compass unit and it went away (or so I thought).

I attach the flight log in hopes of further insight from anyone that can help.

Thanks!

was it the front right that was loose? the channel for that is pegged at full throttle for some period before the yaw started happening…amazed it took as long as it did for it to yaw/struggle.

It was the front right looking at the quad. I picked up on that as well, after I originally posted. I went through the log from the flight just prior to this one, both CW motors start out working harder than the CCW motors and then progressively diverge as the flight goes on.

This same pattern is seen in the flight with the crash.

Video from the crash can be seen here.
[youtube]https://www.youtube.com/watch?v=5uHmPC2Tpj8[/youtube]

I’m now 90% certain it was the loose prop that caused it. Time to change out the prop adaptors on the CW motors for the CCW threaded ones.

ooof! hope you get it sorted…as for the ccw thing …I much prefer nyloc nuts with conventional thread.

My new little racer quad has ccw spinners and I already lost one! Nylocs on my big octa quad with out issue, and easy to replace.

[quote=“RabbitStu”]ooof! hope you get it sorted…as for the ccw thing …I much prefer nyloc nuts with conventional thread.

My new little racer quad has ccw spinners and I already lost one! Nylocs on my big octa quad with out issue, and easy to replace.[/quote]
Thanks, no damage to frame, and pretty much all the electronics look like they’ve survived… should be back up in the air before to long.

The killer is that I had nyloc nuts on the CW motors, but they still loosened. Even if they’re extremely tight, the props still seem to slip a bit with a little force, and once they do that enough, it’s just a matter of time before there’s no bite at all. I’m not a fan of the CCW threads either, but can’t seem to find a t-style prop adaptor (my preferred mounting method) for the Lumenier FM-4006 motors. I could change motors, but I’ve already invested so much in these (initial purchase price+upgraded bearings)… So I think the CCW adaptors are the cheapest way forward.