Lost power and crashed

[Melvoid]

Just a thought, that was an iron or steel bridge, with rock out cropping on each side. Several red flags for me.
1) Steel bridge, bad juju, compass errors common.
2) Bridge and rock both bad for GPS signals.
3) Venturi effect, water flowing through the gap, pushed air with it, as it passes the gap, the wind speeds up, then as it leave the gap, pressure drops and turbulence is likely.
I know you were aware of the dangers, I could see it in your flight path. So not chastising, but rather pointing out indicators for analyzing this flight before hand.
Hope it works well, I would let it dry a bit extra, just to be sure. Fresh water is not so bad, if you got it out in time, maybe no real damage.

I agree about the steel bridge. I was trying to get out of the bright sun so I could see my iPad better, leaned into the open trunk of my car... lost all contact. Luckily I hadn't taken off yet, but figured it was the fact that the controller was surrounded by steel.

 

[kingfisher555]

I would say the bridge had something to do with it.

 

[igor.L]

Hi all, I have tried to get LOG file, but something doesn't work. Can't connect drone to the mac. Watched few videos, but can't connect.
Anyway, I had managed to watch video with the report on my phone and it said: low power, emergency landing. Not sure why, I believe that the battery was at least 50% charged and I didn't plane to fly much so this should be enough for the flight

 

[sar104]

Hi all, I have tried to get LOG file, but something doesn't work. Can't connect drone to the mac. Watched few videos, but can't connect.
Anyway, I had managed to watch video with the report on my phone and it said: low power, emergency landing. Not sure why, I believe that the battery was at least 50% charged and I didn't plane to fly much so this should be enough for the flight

Starting a flight with a battery that low can lead to poor estimates of remaining power, and your video is certainly consistent with an emergency landing situation; you had some lateral control but the aircraft was going down.

 

[igor.L]

Starting a flight with a battery that low can lead to poor estimates of remaining power, and your video is certainly consistent with an emergency landing situation; you had some lateral control but the aircraft was going down.

So 50% at the beginning of the short flight is a no-no situation? I'm surprised as normally I'm flying until 30% battery charge and never had an emergency situation

 

[sar104]

So 50% at the beginning of the short flight is a no-no situation? I'm surprised as normally I'm flying until 30% battery charge and never had an emergency situation

You might imagine that starting at 50% would be OK for a short flight, for the reason that you stated, and sometimes it seems to work fine. However, there have been numerous reports of flights in that situation where the battery level dropped unexpectedly fast. It really would be helpful if you posted either the mobile device log or the DAT file - then we wouldn't need to guess.

DJI Flight Log Viewer

CsvView/DatCon

 

[igor.L]

It really would be helpful if you posted either the mobile device log or the DAT file - then we wouldn't need to guess.

DJI Flight Log Viewer

CsvView/DatCon

I will try

 

[RodPad]

Since the flight log file is on his Android, could he skip the USB PC part and email from the Android to get to any PC?

Rod

 

[Meta4]

So 50% at the beginning of the short flight is a no-no situation? I'm surprised as normally I'm flying until 30% battery charge and never had an emergency situation

Launching with a battery that has been sitting for several days and is at 50% is not the same as reaching 50% during a flight that started at with a fully charged battery.
The big problem is that when launching with a partially discharged battery the % indicator is not reliable at all.
The Phantom needs a minimum of 3.3 volts per cell to be able to fly.

To see a genuine case of launching with a partially discharged battery and why you shouldn't do it, read this thread: Water Loss
DJI Flight Log Viewer - PhantomHelp.com

Look at the voltage the battery was able to deliver.
Some cells were already below 3.3 V under load at 49%, after only 30 seconds in the air.
That is what triggered the Critically Low Power autolanding.
Never launch with a battery that has been sitting around and has partially discharged.

It would be very helpful to see the flight data from your crash.

 

[igor.L]

Launching with a battery that has been sitting for several days and is at 50% is not the same as reaching 50% during a flight that started at with a fully charged battery.
The big problem is that when launching with a partially discharged battery the % indicator is not reliable at all.
The Phantom needs a minimum of 3.3 volts per cell to be able to fly.

To see a genuine case of launching with a partially discharged battery and why you shouldn't do it, read this thread: Water Loss
DJI Flight Log Viewer - PhantomHelp.com

Look at the voltage the battery was able to deliver.
Some cells were already below 3.3 V under load at 49%, after only 30 seconds in the air.
That is what triggered the Critically Low Power autolanding.
Never launch with a battery that has been sitting around and has partially discharged.

It would be very helpful to see the flight data from your crash.

Amazing explanation. Thank you

 

[igor.L]

I've got DAT files, but not TXT.
Sorry feel myself silly that I can't get the correct files

 

[sar104]

I've got DAT files, but not TXT.
Sorry feel myself silly that I can't get the correct files

Post the DAT file - it contains much more information than the device txt log. You may need to use Dropbox or similar since those files are large.

 

[igor.L]

Dropbox - FLY145.DAT

Dropbox - FLY146.DAT . – I think this one is the One

 

[sar104]

Dropbox - FLY145.DAT

Dropbox - FLY146.DAT . – I think this one is the One

That flight was FLY145.DAT.

This event was an autoland due to critically low battery voltage, but has at least one unusual feature:

The reported battery level starts at 52% and only drops to 50%. The battery voltage starts at 15.3 V and then drops to a fairly steady 13.3 V or so, but at 51 seconds the FC announces a low-voltage condition and goes directly to auto land, during which time you only had limited lateral control. Impact occurs at 63.75 seconds, as indicated by the wild excursions in the pitch angle.

This looks like an example of the problem that @Meta4 discussed where the % indication is very unreliable if launching with a battery that is not fully charged. The cells are hovering around the 3.3 V level for most of the flight.

 

[BudWalker]

The smart battery subsystem seems confused. It shows a very steep drop in percentageVolts from about 64% to 0% at about time 22 secs. But, it isn't until about 52 secs when the smart battery system says VoltageLowNeedLand.

 

[sar104]

The smart battery subsystem seems confused. It shows a very steep drop in percentageVolts from about 64% to 0% at about time 22 secs. But, it isn't until about 52 secs when the smart battery system says VoltageLowNeedLand.
View attachment 88341

Good spot on the percentage voltage - I didn't look at that. Further evidence that the battery is confused, since the voltage, voltage percentage, and battery percentage bear no obvious relationship to each other in this case.

 

[igor.L]

Crazy staff. But there are no real reason for the drop? So iron bridge or walls didn't really cause any issue?
Anyway, one more big thank you for all your help guys

 

[sar104]

Crazy staff. But there are no real reason for the drop? So iron bridge or walls didn't really cause any issue?
Anyway, one more big thank you for all your help guys

No - there was a perfectly clear reason for the drop – auto landing, caused by low battery voltage. The question is why the smart battery reporting was so inconsistent and incorrect.

The bridge and walls did not cause any problems.

 

[igor.L]

Sorry, I mean the iron bridge and walls wasn't the reason. As a lot of people were arguing that they may cause a problem.

 

[sar104]

Sorry, I mean the iron bridge and walls wasn't the reason. As a lot of people were arguing that they may cause a problem.

Correct. There is usually plenty of data-free speculation when anyone posts about an incident. It's sometimes useful as a brainstorming exercise, but shouldn't be considered definitive in any way.