Hi everyone, i'm new in this forum and i also don't speak english as my first language so excuse me for all errors.

This morning (10 hours ago) i went for a flight straight from my house to a little town over a mountain, when i arrived at 3000m (10000ft) of distance i pressed rth button because the signal was not very strong, just to be safe. so the drone turned around (it was already at 300mt, 1000ft, so it didn't ascend, it just went straight home) and started going home in a straight line, after about 700m since it had turned around i totally lost signal and i couldn't reconnect it (i tried restarting the rc), so i just waited for it to come back home since it was already doing the rth procedure i was pretty confident it would. but after about 5 minutes i realised it wasn't coming back and i couldn't even hear it so it wasn't even near (the place is in the countryside so it is very silent). To go and find it i traced a line on google maps from the coordinates of where i lost signal to my house and went on walking through this line for hours (it is mixed hills, fields and trees) and i couldn't find it.
For my hypothesis i first need to share the battery percentage and speed at every moment: it took off at 58%, it then turned with rth at 34% ( i know, i should've done it before) when it was at 3000m of distance and stared going back at 9,4m/s, i lost signal when it was at 2293m of distance and at 27% of battery, still going at 9,4 m/s towards home. My hypothesis is that it was going back home when it hit 10% battery and started an emergency landing right where it was, based on the data i had it went from 33% to 32% of battery in 100m so in the time that it went from 27% to 10% it must have done around 1700m (17*100) along the said trajectory. i went there and the drone is not there (i looked around 50m on the right and on the left from the trajectory, it's an empty field so i would've saw it). what do you guys think happened? am i missing something?

here is the flight log link:       https://app.airdata.com/share/LLtLQA      (if you need anything else ask me right away)

Thanks a LOT in advance for anyone who can help me.

Hello and good day lucacolombarini1224. I am sorry to read and to know what happened to your DJI Phantom 3 Advanced. Since this unfortunate incident happened. I would highly recommend to contact our DJI support team at https://www.dji.com/support?site=brandsite&from=nav for us to be able to assist you further with regards to this issue.  We have the team who would do their best to find out the reason of the said incident and then the corresponding resolution would be provided. Please note that DJI will not perform data analysis for cases occurring after the expiry of the warranty period; otherwise, valid charges will apply. Again I am sorry for the trouble and thank for your support.

Upload your log here                 https://www.phantomhelp.com/LogViewer/Upload/

ALABAMA Posted at 1-4 12:44
Upload your log here                 https://www.phantomhelp.com/LogViewer/Upload/

here you go, thanks for the help.
https://www.phantomhelp.com/LogViewer/G51VDYAHBGVLCOU8XDIZ

Looks like your battery probably just ran to 0.  Never good to begin a flight not fully charged. The 58% was probably false.

ALABAMA Posted at 1-4 12:57
Looks like your battery probably just ran to 0.  Never good to begin a flight not fully charged. The 58% was probably false.

So it probably crashed near the last position given,  probably a bit further because of the momentum it had right?
just out of curiosity, did you assume that it ran to 0 based on something abnormal on the log or just based on the starting battery %?
if it fell from that height it will probably be in pieces but it's worth trying to find it, i will look for it again tomorrow morning and i'll let you know.

The one thing that bothers me is the fact you didn't get a low or critical battery warning.  The log just abruptly ends. It possibly could have been a malfunction.  Would be good to find and look for burns on the battery connection.

Sorry for your loss.

Here is a better site for looking at your data:  https://www.phantomhelp.com/LogViewer/TNYXPG6IOYSMO6R99VF1/#

The beginning of the log is odd.  It shows a time of 7m 42 secs before you launched.  A normal log would show 0m 1 sec before launch.  It appears you flew a flight for around 7 mins, landed, turned motors off, and then started motors for a second time and took off again without turning off the AC/battery.  Hence, the old log closed and a new log opened.  

You launched with only 58% battery which is normally a pilot error.  One must always launch with a fully charged battery because history has shown a great risk of sudden drop in the sky otherwise.   But if you had been on a previous flight and never turned off the battery, that risk is removed, from what I've read from many posts.  

Two mins into the flight, the smart battery requested to Go Home.  You took your hands off the sticks at that point, apparently to cancel the Go Home request via the app screen.  You then put your hands back on the sticks, made an adjustment in yaw to aim east, and the pushed both sticks extreme full forward as you continued to fly further away at top speed while gaining altitude at top speed..

...

I don't see an explanation for your losing signal at the end of the log.

The puzzling thing is, the log shows you racing home in RTH with the right stick full forward, but then returning the stick to mid point only a few seconds before the end of the log.   Apparently your FPV locked up and so you instinctively let go of the right stick.  Then you lost the downlink completely with 27% battery and almost a mile and a half away.

So in theory, if all was well with the AC, it would then putter home at about 21 mph, but it will start auto land at 10% battery.  You seem to have a nice balanced battery.  

It would take you about 4.5 mins to reach home point, but then it would have to descend too.  You were 1100 feet up, so it would be a long time-consuming descent.  The smart battery may have forced the AC to land sooner (further away).  It may have calculated you didn't have enough battery to land, even if you had enough to make it overhead.

But none of this explains the disconnect.  

It may have landed safely somewhere in those fields, or it may be in pieces somewhere in those fields or even the woods.  MHO

Good luck

ALABAMA Posted at 1-4 13:26
The one thing that bothers me is the fact you didn't get a low or critical battery warning.  The log just abruptly ends. It possibly could have been a malfunction.  Would be good to find and look for burns on the battery connection.

That's weird indeed, i was just watching the live feed with top signal and the connection just stopped all of a sudden, when i went on to search it i had the controller on and it never connected back so it wasn't a range problem. i have to add that it was pretty cold today (about 10°C) so the battery malfunction is even more likely

Mark The Droner Posted at 1-4 13:34
Sorry for your loss.

Here is a better site for looking at your data:  https://www.phantomhelp.com/LogViewer/TNYXPG6IOYSMO6R99VF1/#

Thanks for the help, with all the stuff happening after the crash i forgot i actually did fly the drone before the log i sent (here is the link for the first flight
https://www.phantomhelp.com/LogViewer/A83Y71BK5JWO6QVBRGK2 ), because i hadn't flown in a while it was just a test flight (a reckless test to be sure considering the altitude, that's my bad), i went all the way up to 1600 ft to see how was the transmission vertically and then back down, the VERY bad idea was to then fly again at that distance without re-charging the battery. As you said i did cancel the rth prompt on the screen because i usually could make it further without problems.
about the stick position at the end of the log, if i remember correctly i wasn't sure if  it was better to leave the stock speed of rth or to speed it up with the stick when it comes to battery drainage (i was at this point very worried about the drone), so it was just me deciding to let the drone come back with it's own speed when the stick went back to middle. Also because i didn't have the chance to react to the fpv locking up, the rc just lost signal togheder with the live feed.

After another 10 hours or so spent searching it I still couldn't find it.
I saw online the footage of some drones that disconnected all of sudden just like in my case and then just started going up or down and moving around by themselves before crashing in the ground. Does anyone know what is it likely to do in a case like this? Like move forward, sideways, upwards or something else.

I think you're referring to RTH scenarios with P4s and obstacle avoidance.  The sun will sometimes cause a P4 to think there is an obstacle so it will rise up to get over it.  This has nothing to do with P3s, and there is no evidence your AC did anything but continue its RTH path to the end of the log.  

Mark The Droner Posted at 1-6 04:09
I think you're referring to RTH scenarios with P4s and obstacle avoidance.  The sun will sometimes cause a P4 to think there is an obstacle so it will rise up to get over it.  This has nothing to do with P3s, and there is no evidence your AC did anything but continue its RTH path to the end of the log.

The Phantom 3 advanced at what battery percentage starts to land by itself? Because I was pretty sure it was 10% but I saw some videos that show it happening at 12%. This could help me restrict the crash area quite a bit.

Critical low battery forced autoland is 10%.  But that doesn't mean it won't land before then - for lots of varied reasons.  

Edit:  Look at the verbose log.  There is tons of info there.  

Look at the smart battery columns.  

Under the column SMART_BATTERY.seriousLowWarning, the number is 10 all the way down.  This, I think, is the forced auto-land percentage number.  

Under the column SMART_BATTERY.landBattery, the number starts off at 10 (I assume it is percent), but then, interestingly, the number goes up.  And the timing of it is in line with your decision to gain altitude (and distance) after having been warned by the smart battery to return to home.  The number increases to 16 and then levels off as your altitude levels off at 130 meters.  But then you increased altitude again and the "landBattery" number began increasing again.  It then leveled off.  Once you broke through the 200 meter height ceiling and continued climbing towards 300 meters, the "landBattery" number began increasing again.  It climbed all the way to 25, which to me means it's going to want to land when the battery hits 25%.  However, it then levels out and comes down to 19.  But then it reverses direction again and goes up to 23 where the log ends.  

So my guess is the AC would begin to land when the battery reaches 23% power in a last-ditch attempt to save itself.  This makes some amount of sense when you consider it takes significantly longer to land from 1100' than it does from 400'.  

It was at 27% power and you were 7500 feet (almost a mile and a half) from home when the log ended.  

Mark The Droner Posted at 1-9 08:29
Critical low battery forced autoland is 10%.  But that doesn't mean it won't land before then - for lots of varied reasons.  

Edit:  Look at the verbose log.  There is tons of info there.  

Thanks for that information, i didn't know you could see that from the log. I do realise that i did a very, very dumb move not coming back home before but i was way too confident in the drone and surely didn't expect it to disconnect suddently and never reconnect. Even if i couldn't bring it back home i surely could have landed it in a safe place for me to pick it up since i know the place well. it's interesting (and totally makes sense) that the drone battery percentage to force land would go up as the altitude goes up and the fact that at the end of the log it's at 23% makes the probable crash spot a lot before than i calculated thinking about 10% force land battery. This if the drone battery didn't die right there where i lost signal, as another user suggested could have happened. I will try to find it knowing this and let you know. Thanks for the Feedback.

fansb0d4ea94 Posted at 1-9 11:40
Thanks for that information, i didn't know you could see that from the log. I do realise that i did a very, very dumb move not coming back home before but i was way too confident in the drone and surely didn't expect it to disconnect suddently and never reconnect. Even if i couldn't bring it back home i surely could have landed it in a safe place for me to pick it up since i know the place well. it's interesting (and totally makes sense) that the drone battery percentage to force land would go up as the altitude goes up and the fact that at the end of the log it's at 23% makes the probable crash spot a lot before than i calculated thinking about 10% force land battery. This if the drone battery didn't die right there where i lost signal, as another user suggested could have happened. I will try to find it knowing this and let you know. Thanks for the Feedback.

Good luck.

Mark The Droner Posted at 1-9 11:42
Good luck.

Good News!  I actually found my Phantom! it was laying on the grass along the path back to home perfectly fine, I really need to thank you all for the help and especially Mark the Droner for telling me about the verbose log and the SMART_BATTERY.landbattery column, thanks to that i calculated where it could have landed if it did so at 23% and the drone was right there waiting for me without a scratch.
So the drone just disconnected for some reason and continued coming back home till it hit 23% battery and auto landed right where it was (and luckily it didn't rain from the 4th to today).
i will now check if it still works properly and see what happened in the log file inside it, if i find out how to do so.
Thanks again everyone.

Boy... that is the way to do a search.  The Phantom did exactly was it was suppose to do.  Fantastic!

fansb0d4ea94 Posted at 1-10 07:21
Good News!  I actually found my Phantom! it was laying on the grass along the path back to home perfectly fine, I really need to thank you all for the help and especially Mark the Droner for telling me about the verbose log and the SMART_BATTERY.landbattery column, thanks to that i calculated where it could have landed if it did so at 23% and the drone was right there waiting for me without a scratch.
So the drone just disconnected for some reason and continued coming back home till it hit 23% battery and auto landed right where it was (and luckily it didn't rain from the 4th to today).
i will now check if it still works properly and see what happened in the log file inside it, if i find out how to do so.

Wonderful news!  Congrats!