Why did it crash

My F550 hexa, running last nights master was flying well. It dropped a fishing payload perfectly but half way back to the beach just sort of roll over and died. It went down in about 3 to 4 feet of salt water. There is a log file but I can’t tell what went wrong. Please help. I use APM2 to view logs and always have CTUN errors, 8 values instead of 9. Why? I hope I had enough things logged. Also, where are the TLOGS now? I managed to recover everything but the battery. Everything was washed with fresh water as soon as possible, and alcohol before testing anything. My pixhawk seems fine. I haven’t tested anything else yet.

The log

It seems all if the electronics survived salt water. I think because the battery came out and could have been the cause. I cant tell from the log.

There really isn’t any useful data in the logs. No battery voltage, no current draw, to total current used, no RCOUT data.

The battery data is there. If I’m reading this right CTUN ThO is throttle out, and went to zero. I’m trying to find some kind of motor data or climb rate to check that.

It’s there under BAT parameter.

there is visible high current spike just before the crash.

most likely mechanical failure (motor/ESC) , but it’s difficult to till which motor without RCOUT.

It rolls right and back so I think it’s most likely a failure of the back right motor or ESC. As @Mark57 says there’s no RCOU message so we can’t see the bad motor go high but we can see the voltage suddenly spike upwards which is a sign that one of the motors stopped drawing power.

Any reason why the vehicle is loaded with master instead of Copter-3.6? We normally recommend sticking with an official release if it’s got all the features you require, beta if you’d like to help out with beta testing.

Anyway, txs for the report!

I saw it falling and gave it full throttle which may have caused the spike. I got lucky I think when the battery detached. I had to remove the heatshrink from the ESCs to clean and dry them, and the heat sinks came off because the adhesive dissolved. I’m not sure what to use to reattach the heat sinks. I’m also concerned about the motor bearings. I oiled them but they were in salt water. All the other electronics have been tested and work fine. It was only in the water for a few minutes, and the whole thing was built for about $250 to $300 just in case this happened. I mounted the drop servo at the bottom of the landing gear and I think it needs to be as high as possible to reduce the leverage imparted to the hexa by the fishing line and bait. Its at the center already but flight was pretty jerky getting started. I think I may need longer arms and bigger motors and props for more lift and stability. I would also like 30 mins of flight time on one battery. I’m researching F550 upgrades now.

What should be enabled in LOG_BITMASK for good diagnosis and still allow FrSky passthru to work?

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I added some debug messages to autotune. The current messages are not very useful unless you read the source code. If I have time I’ll clean them up and add some details to the explanation at the top of the file. I could not get autotune to finish just roll due to the local windy conditions before my battery died. I ended up relaxing the wait for level constraints by about 15%. I just built the latest master but I can see where it would be better to checkout a released version. I’d like to be able to contribute to the project at some point, to say thanks.