Communication error.

[Themanwithnoname.]

I have a Mavic 2 Pro and on Saturday about a minute and a half into a flight a message appeared onscreen saying Communication error, from then on I had no control and watched as my drone descended without command. I was able to confirm from the map that it had gone into water. It was a new battery, only done about three flights, and the map was still showing the drone at sixteen metres even though it was in the water by then. For some reason the camera recorded five seconds of video showing its decent to the bottom of the river even though I had it set to take photographs. The drone was 357 metres away at the time. This was in an area where I have flown many times without issue.
Anyone have any idea what happened.

 

[AeroJ]

Eurgh - sorry for the loss of your machine In the absence of any more information than that it's a total guess, but that sounds to me like something that might happen if there was GPS jammer in the area or something similar that can disrupt control signals. Does that seem possible / likely ?

Are you able to retrieve the flight log from the Remote ?

 

[slup]

...Anyone have any idea what happened.

Maybe... you mention just "Communication error" but suspect that it actually was Battery communication error.

The flight controller in DJI drones needs to be able to communicate with the BMS in the battery to get for instance amp draw, cell voltage levels & other data in order to calculate & handle certain automated actions. If this communication fails (due to a battery failure or a bad connector connection between battery & drone) the flight controller will command a forced auto landing.

Was the new battery a 3:rd party one or a DJI original battery?

To be able to say this for sure we need the flight log from this flight... it's stored in the screen device you used (either a phone a Tab or a screened RC). Retrieve the .txt log & go here ---> DJI Flight Log Viewer | Phantom Help & upload it... the log viewer will then provide you with a link to the log, copy that & come back to this thread & share it (the page I link to also describe where to find the .txt log in your screen device if you scroll down a bit).

...it's a total guess, but that sounds to me like something that might happen if there was GPS jammer in the area or something similar that can disrupt control signals.

Not likely... those will not separately cause a forced auto landing. If the GPS positioning gets disrupted you will get ATTI mode but still be able to control the drone. If something disrupts the RC control signal, the drone will execute the failsafe action which in most cases is RTH.

It's only when you both have ATTI mode & loose RC control signal a auto landing will occur... this seems to be a bit far fetched at this stage.

 

[Themanwithnoname.]

I've been offline for a couple of days as my computer was being upgraded.
I managed to recover the flight log, it's here :- DJI Flight Log Viewer - PhantomHelp.com

 

[slup]

I've been offline for a couple of days as my computer was being upgraded.
I managed to recover the flight log, it's here :- DJI Flight Log Viewer - PhantomHelp.com

The log shows 79sec & ends with the drone still airborne... just in the end the drone hovers & nothing indicate anything odd. This usually means a major power failure, affecting the motors and the transmission between the RC & drone... (& by that, the log recording).

The descent you saw was likely the drone freefalling.