P4 disconnected in flight, found with battery missing

You're right. You're .DAT stimulated 2 bugs, one in DatCon , the other in CsvView. Independently they each don't cause a problem. But, together they are a problem. Anyway, I'll be fixing those bugs. I've attached a .zip containing a .csv that can be fed to CsvView and a FLY048.txt.log. These include the second flight you referred to.

At time 980 APP_AUTO_GOHOME was initiated at the direction of the pilot. Following at time 1007 connection with RC was lost and the go home action changed to OUTOF_CONTROL_GOHOME.

It's worth noting, according to the eventLog stream, that the AC was aware of the airport restriction at time 927. See the attached FLY048.txt.log. I haven't looked closely, but it doesn't seem that the AC's flight path was ever affected by this.

Not much changed as a result of the RC disconnect. The AC had already entered a GoHome and had turned towards home. It then flew sideways (to the left) and started descending.This continued after the disconnect but the descent stopped at 20 meters.
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Just for grins I took a closer look at the the very end of the recording. To do this I ran DatCon with a sample rate of 200 hZ instead of the default 30 hZ. Then looked at the volts being applied to the motors by the ESC. This is much higher speed data than the battery data.
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I'll speculate that the voltage fluctuation at the very end was the result of the battery coming loose.

Wow, that's interesting analysis... I just wonder if the flight controls were some way confused being at the boundary of the authorized zone. The log entries that I saw seemed to bounce back and forth like it was arguing with itself about what to do. That's an over-simplification, but my concern all along has been that the software didn't perform as we understood it should.

When my son commanded a RTH, since the direction it turned was away from the authorized flight zone, I could see no reason for it to hesitate. It appeared to begin gaining altitude, then went back on its downward path and disconnected. The fact that it hovered at 20 meters for some time then began descending again is odd. Could the last little bit of time where the voltages went nuts been it coming into contact with a tree? In Google Earth 3D, the last elevation was close enough to the height of trees in the vicinity that it wouldn't surprise me. I know the 3D render is just an approximation based on the aerial photos it has available, so trees could've been taller, and altitude wouldn't be precise enough to exclude that possibility.

Thanks for your efforts on this... we are not yet ready to test fly the P4 after this. I am pretty sure the firmware is in need of updating, so if anyone has words of advice or warning about which version to avoid, would appreciate that as well as feedback on DJI Go vs. DJI Go 4.
 
.... Could the last little bit of time where the voltages went nuts been it coming into contact with a tree? In Google Earth 3D, the last elevation was close enough to the height of trees in the vicinity that it wouldn't surprise me. I know the 3D render is just an approximation based on the aerial photos it has available, so trees could've been taller, and altitude wouldn't be precise enough to exclude that possibility.
...
Good question .Looking at the accelerometer and gyro data it does appear to have hit something.
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And looking at the motor data it appears the props (particularly the the right back) got caught in something.
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And looking at the motor data it appears the props (particularly the the right back) got caught in something.
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The forensic capabilities of the .dat files is really something else. I have little doubt that the bird got caught in a tree top... my concern now is strictly with HOW it ended up getting there after being told to RTH. I'm reluctant to go flying again (or let my son go flying again) until I understand that better.
 
Just to close out this thread...my son has successfully flown the P4 since we received it back. The only issue we had was the battery which was ruined when it fell into the ditch. There were no performance issues with the drone at all.

As to the cause of the incident, I am going to presume it had to do with the control system not being up-to-date. When I connected to DJI Assistant, it needed to be updated on firmware, as did the remote control. At the time of the incident (Dec. 2016), the bird had V01.02.0503 (where latest was V01.02.0602 - Nov. 2016 release) and the RC had 1.6.0 (where latest was 1.8.0 - Oct. 2016 release). I don't know if either or both of these factored into the unexpected behavior, but we have learned from the experience.

1. Always verify the firmware is up-to-date (or at least not incredibly outdated - maybe hold off on updates by a month)
2. Always maintain VLOS
3. Always stay away from flight region boundaries where drift or GPS issues could trick the system into thinking it was somewhere it wasn't supposed to be
 
My son was flying his P4 on Christmas Day (not a Christmas gift, he's had it about 6 months) and it disconnected mid-flight. It was about 1700 ft away and 150 ft. in the air, and not within line-of-sight, so he waited while trying to reconnect and/or RTH automatically. When it didn't show up, we went looking for it at the last known location.

We weren't ever able to reconnect with it or find it that day, but today I went back to look in the vicinity of LKL and found it. The battery was missing, so I thought it might have come out in-flight since we were very close to it on the day he lost it. The other possibility is it had a hard landing and that jarred the battery out. Although I didn't see it laying close by, it was near a ditch with high weeds and I wasn't going to dig around and find a snake instead!

Just wondered if anyone here has knowledge of a battery coming out mid-flight... seems unlikely, and I've not found any other posts that mention it... but figured I'd ask.
Yes I was flying my p4 all of sudden it lost power and dropped right into the lake, I swam in and retrieved it and battery was missing found about 2 feet away from the craft so yes I had a issue with the battery popping out on it's own.
 

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