Strange AQ behavior resulting in crash.

[epyonxero]

I recently reconfigured my AQ from a Y6 to a flat hexacopter. It flew very well yesterday bare bones (no camera or gimbal) for about 16.5 minutes with no issues. Today I flew it with a gimbal and camera mounted and it flew well for about 6 minutes before I took it up to a higher altitude in DVH mode and it suddenly rolled hard to the right and towards the ground. I switched to RTH and the copter recovered from the dive and returned to home normally. At about 6 ft altitude I switched back to DVH mode for a landing and the copter immediately rolled again to the right and hit the ground pretty hard.

Im not sure what went wrong; the fact that it flew normally in RTH leads me to believe it wasnt a mechanical issue. I thought maybe there was an erroneous RC signal that caused it to roll but the angle of bank was well beyond the normal limits and I dont see anything in the logs that show a roll signal at the time of the crash.

Heres a link to the log file: https://dl.dropboxusercontent.com/u/2317679/013-AQL.LOG

EDIT: Heres the video, the problem starts just after the 6 minute mark:
http://youtu.be/EJNnRLXwznQ

[Max]

Ouch, sorry to see that!

What do you mean by "DVH" mode? Position hold? DVH is more of a feature than a mode, allowing you to still move the machine around while it is in PH mode. In the video it seems like it's coming down normally for a while... is that still it returning to home? Also what is unclear is that "RTH" is just a one-time command, again not really a mode per se. So you told it to go home, but after it completed the command it would still be in whatever flight mode your ch6 switch is on (manual/ph/mission).

Those aren't coax motors I'm seeing a brief flash of?

-Max

[epyonxero]

[bn999]

It looks like prop slip. You can see in the logs and hear the saturation while trying to compensate for it. Switching between modes may have given a quick jolt that the prop needed to stick or unstick to the rotor. If you consider your motor layout, you might be able to determine the prop that was slipping from the log.

[Mike Barton]

there's a high frequency sound starting @ 5:58 just before 'things' start happening - bit too much of a coincidence i think ?

[epyonxero]

[Max]

Yea I read that also... Just keep in mind that in pusher config the props will want to loosen themselves. I recommend double nuts or reverse threads (t-motor makes reverse threaded prop adapters).

Have you seen my ?

I just replayed your log in GE and it looks kinda similar. At any rate your machine pitched violently to the right both times and tried to recover (successfully the first time). If not a prop slip then something else intermittent.

-Max

[epyonxero]

I hadnt seen that before but the roll/plummet action does look similar. Ill make sure my props stay secure.