Phantom 3 Pro crash in fog

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My first Phantom 3 Pro crash from 120 m. I have some previous great footage going into or out of fog and decided to get some more. I knew moisture could be bad, but... I'll be more cautious in the future.

Anyway, the day started bad because a recent iOS 11.2.5 update prevented DJI GO 3.1.26 from connecting to the AC. But Litchi connected and seemed to work OK.

The short Litchi mission went OK but just when the RTH should have kicked in, the AC started spinning around and there were alerts "Battery Error. Battery Current Overload" and "Disconnected" on the tablet (I don't know in which order those alerts appeared. I guess the AC was disconnected at least when it reached the ground a few hundred meters away behind some buildings and trees).

I found the AC nearby on its side in soft snow with at least two props still spinning and the two other props jammed in the snow. I had to take the battery out to stop the motors spinning because the battery button didn't do it. One prop was broken from both ends -- I don't know whether it was already like that but I guess I broke it when taking out the battery while avoiding the spinning props, I guess one prop hit some concrete then. Surprisingly no other apparent damage. Camera recorded to the SD card to the very end. After taking off the props I powered the motors and surprisingly they all seemed to work OK. I have spare props but haven't yet tried to fly because the DJI GO still doesn't work with iOS 11.2.5 with my iPad Pro 9.7". I used an old iPad mini 1 with old software and the IMU and gimbal calibrated OK.

.DAT file is below. I might also edit and send the footage from the crash moment. It was foggy so not much to see up there at the crash site until at somewhat lower altitude. According to the video clip from the SD card it took 18 seconds for the AC to drop from 120 m to the ground.

Dropbox - FLY336.DAT

Do the log files indicate the reason for the crash? Was it just too much icy moisture for the motors? There was a flock of birds nearby but no feathers on the AC. Or was it the 2-year-old previously well-behaving battery (it was only -2°C outside and the battery was 22°C when starting the mission)?
 
Ok, I want to know about this one I was doing some fog flying myself.

The first that come to mind for looking at the .dat file from the Phantom.

@Oso, @sar104 ;)

Rod

Added: Upload your litchi .csv file to this link, then share the result url here.
DJI Flight Log Viewer
 
Unless I am mistaken, and someone else can also have a look. It appears you may have lost the Left front motor.


MOTOR (RPM).png
 
Not the prop, but the motor went open (no continuity)?

Rod
 
My graphing error. I had 4 sets open at once. But the Data plot lines are correct.
 
I had the motor load message on a phantom when flying in fog. Quickly landed and found the leading edge of the props had ice on them.
 
I stand corrected. 2 Motors??? ( Corrected Graph)


MOTOR RPM2.png
 
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The .csv file from iTunes will show more data then airdata, if uploaded it to the link I provided.

Rod
 
@Fly Dawg
Can you view current draw, other words, are these the two motors that where stuck in the snow?

Rod
 
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Good catch @RodPad I completely negated the time frame in the snow, and yes can get current draw.
 
I don't remember which props were jammed in the snow, AFAIR they were not spinning while on the ground but I'm not sure. I'm not sure if they started spinning when I picked it up. But SOME props surely were spinning because I had trouble taking the battery out without hurting myself and apparently then broke one prop when it hit concrete I was resting my other hand on.

But soon after the crash without the props ALL motors do spin and seem to react to the RC as far as I can tell.

Maybe the props gathered ice and stalled??

Based on the footage and .srt text the AC seemed to drop 120m in 18s which is just 24km/h i.e. quite slow?!
 
That motor loss, may have been pre-mature. Will need to synchronize "prior" to the impact point to be sure. I did not consider the long length of time that the aircraft were stuck in the snow, still running.
 
Hum, Thanks for uploading, I sure didn't see what I thought I would see. ;)

Anyways I wonder what the temperature was in the fog at 200'

Ice on the tips, would bring the current draw up, and more drain on the battery on a cold day.

Just wondering if you have been using the litchi screen recorder, I have and starting to remember every time now, sure helps you realize what you missed
when all the panic is over.

Rod
 
Sure was pushing it on that battery. You got down really close to the cutoff point which would have resulted in the same effect. Still looking at the timing prior to impact.
 
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A week prior to the crash the same battery was OK at -13°C on a longer mission, but the weather wasn't so humid at the time, only slightly foggy in some places.

In the summer I have got some nice effects when the water drops start to slowly gather to the lens...

I almost cancelled this mission at its midpoint because the preview on the tablet was getting too blurred, but then decided continue to the finish because I didn't want the footage end prematurely. Well, I did get the whole clip and then some for Final Cut...

I had planned to get another battery when HealthyDrones/Airdata starts to complain about it but maybe it is time to do that now. And maybe get another P3P, too. And avoid flying in humid conditions.
 
Ok, no definitive answer on my part. I separated the loss of signal time vs the time until impact, where the Phantom was still transmitting while in the snow. There were numerous battery warnings, and speed errors all were occurring within a 30 second or less window as the Phantom had already prepared to RTH, but obviously never made it. These charts don't say much, honestly but for what it's worth, I suspect the combination of the errors caused the incident.

IMPACT TIME.png
 
Holy crap man, So did the data show it had started RTH?

Looking at the log at 3m 47s is when the Phantom home distance start decreasing, would this not show up as returning home, because of a litchi command?

@matti
Is you mission on the hub, and could you share it?

Rod
 
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