Short flight in mountains drone drops, wondering why?

[Meta4]

and the battery elsewhere but in good-looking condition

It looks like you were lucky to have missed splashing down in that lake.
How far away was the battery from the drone?
Maybe the ballistics expert (@sar104) could comment on what he would expect for the falling path of the battery separate from the drone?
If separated in flight at the speed it was moving (V = 7.6 m/s height = ~40 metres), would they fall close together or further apart?

 

[Craig Smith]

I THINK the battery was found a couple of yards down the hill from the drone (further away from me than the drone). I did not see the actual locations of drone and batt, just from a distance saw the people that went to pick up the items - those young ones were fast!

 

[sar104]

It looks like you were lucky to have missed splashing down in that lake.
How far away was the battery from the drone?
Maybe the ballistics expert (@sar104) could comment on what he would expect for the falling path of the battery separate from the drone?
If separated in flight at the speed it was moving (V = 7.6 m/s height = ~40 metres), would they fall close together or further apart?

There was little wind, and from that height even a purely ballistic, zero drag trajectory for the battery puts it within 5 meters of the aircraft on the ground.

 

[BudWalker]

FLY183.DAT

DAT File

1drv.ms

this is the next DAT file. According to dates/times visible during export it was created while AC was on as I was downloading the DAT files (the first time I downloaded). I noticed during the export that there were two logs (one of which was a vision log) exported for each earlier flight, but no vision export for the crash. I was also using goggles on that flight. Is it because I wasn't using the goggles for controlling the AC that there was no Vision log generated?

The size of FLY182.DAT is an exact 4096 multiple. The file block size is likely 4096 meaning the DAT precisely filled the last block. That's very suspicious. There was probably another partially filled block that got lost. I suspect that was because of an abrupt power loss.

Also, we can and should check that ExtractDJI didn't lose that partially filled block. This would likely show up as a discrepancy between the size of FLY182.DAT (38,408, 192) and what's reported in the ExtractDJI message panel.

If you aren't confident checking this you could provide the EXPORT_FILExxxxx.DAT that contained FLY182.DAT

 

[7thstring]

battery elsewhere but in good-looking condition. Pretty amazing for falling a bit more than 100 feet I think. Also wondering about thoughts on whether I should trust this battery? I haven't recharged it since the accident, its still at a bit more than 50 percent.

Can you ascertain if the battery bottom presents some sort of swelling?
This reminds me of my case. And even in mine logs don't show voltage drops.

 

[sar104]

Can you ascertain if the battery bottom presents some sort of swelling?
This reminds me of my case. And even in mine logs don't show voltage drops.

The aircraft DAT file is not readable from the Mavic 2, and so you would not be able to see the resulting voltage sag even if you looked.

 

[Craig Smith]

DJI_ASSISTANT_EXPORT_FILE_2019-08-31_17-52-10.DAT

DAT File

1drv.ms

This is a 1 Gb file with 5 flights and the Dat for the actual download *183.DAT. I do not understand why CSVviewer's Geoplayer doesn't seem to show the full flight path for for some of the previous flights, or why some of the motors seem to be running at the end of the DAT file? I flew each flight back to originating point or near it, except for 182, the crash, and 183, the data export.

 

[Craig Smith]

The battery appears good, no swelling, etc. I kept it separate from the other batteries for several days . . . it seemed ok, so I eventually stuck it back in with my gear. That accident was 1/2 a month ago. Haven't used it but for downloading dat files. It was just about new . . .

 

[BudWalker]

DJI_ASSISTANT_EXPORT_FILE_2019-08-31_17-52-10.DAT

DAT File

1drv.ms

This is a 1 Gb file with 5 flights and the Dat for the actual download *183.DAT. I do not understand why CSVviewer's Geoplayer doesn't seem to show the full flight path for for some of the previous flights, or why some of the motors seem to be running at the end of the DAT file? I flew each flight back to originating point or near it, except for 182, the crash, and 183, the data export.

ExtractDJI is working correctly - FLY182.DAT has a size which is an exact multiple of 4096. As per above I suspect that FLY182.DAT is lacking the final records due to an abrupt power loss.

You didn't provide any examples where the motors are running at the end of the .DAT, or the GeoPlayer path is incomplete. But, I suspect you're referring to FLY178. When the .DAT reaches 300 MB it is closed and a new one begins - in this case FLY179. You can concatenate the two to obtain the whole flight. Unix style looks like this
cat FLY178.DAT FLY179.DAT > FLY7879.DAT

 

[Craig Smith]

Yes, also 180.Dat/181.Dat. Good to know, thanks.

 

[Craig Smith]

Just to let everyone know as a followup . . .

I had a DJI refresh plus covering the drone. I sent it back to DJI for assessment/analysis, asking them to honor the warranty if there was no way that the logs proved it wasn't hardware failure. They did honor the warranty in this case so I still have the dji refresh coverage for an accident just in case. It is good to be flying again. Phew! Though they did not give me their analysis results I figured I should not push it.

The customer service was great through the process. A big shout out to the company for making their customer happy, and keeping me coming back for more.