Crash analysis, please help

Hi guys,

After not being able to make any sense of my previous build (re another thread I posted about me being at my tuning-wits end) I found myself a used QAV500 and mounted my stuff on it. The first few flights were a joy, but I got a serious problem on my last flight when testing different flight modes.

It turns out that my magnetometer was not behaving very well (at least loiter and other similar modes failed to keep the quad were it should be). Then suddenly, after switching back to stabilise mode all engines stopped and everything fell to the ground.

I have not been able to figure out what the reason for the sudden stop was. Perhaps you could help me out by taking a look at the log?

From what I can gather from the log the throttle output was suddenly cut to 0 around line 12,300, and it appears that this was caused by throttle in also suddenly dropping to 0. There is also a drop in throttle input around line 9100. It is difficult to see if any of the other channels blanked out during this period since I was in RTL mode. Now that I think about it, there was one time when this was very slow to switch modes, and this was from RTL to another mode. This could very well be the same time that my first throttle glitch occurs.

I have reviewed all cable connections, and nothing seems to be disconnected or connected poorly.

I feel I should also mention that the same occurred for around 0.25 seconds on my first flight, but it recovered in time to keep flying. At the time I assumed that this was caused by me using a new receiver which I had never used before. I changed back to my original receiver that has never failed on me before this flight. Based on this I think it is fair to conclude that the receiver is not the problem. Could it be that it is caused by my transmitter?

I am using a relatively old Futaba 9C with a spectrum module. Could it be that my radio and receiver simply lost connection?

Any ideas on how I should proceed with determining the cause of the problem? My gut feeling is that it seems to be triggered when changing modes, but I’m not absolutely sure. I have tried to provoke this while connected to the mission planner sitting on the ground, but no luck so far.

Looks like you may have the same problem I had. My quad droped suddenly twice and i was able to recover. The third time I didn’t, and it got away from. I looked at my logs and we both have two GPS errors. GPS-2 and GPS-0. Mine was at the begining of the flight as yours appears to be a few minutes in.