Cause of this crash? Gust of wind?

[dave_i]

Hello, I am looking for some assistance in determining the cause of this Mavic Air crash.

Flight was normal, with some cross wind causing tracking to the "left". turned 180 to return, and felt wobble then rapid descent 11m/s down from about 100 feet, unresponsive controllers during descent.
There was some wind, but I did not get any high wind warnings, and the video shows a wind turbine moving at fairly low speed.

This was my 90th flight, and 1st crash

Problem?
Planned to fly out and back. Felt some wind push to left on outbound. Turned 180 to return, noticed some tilt, then started losing altitude rapidly, and crashed.
Recovered. front left arm snapped.

What Go app version are you using? DJI go 4

Do you have a video or pictures of the problem? (if so post link)
Flight record: go to ~5 minute mark.

DJI Flight Log Viewer | Phantom Help

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www.phantomhelp.com

Crash video:

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drive.google.com

Thanks

 

[Astom22]

That's crazy, anxious to see what our talented flight record readers have to say.

Something went wrong when it quickly tilted after the turn, then it all went wrong. Maybe a bird hit it and messed up a prop.

Beautiful flying area.

 

[Commander]

Ouch!
Actually that wind turbine looks like it is moving very quickly, also saw a fair amount of tree movement with the wind. Perhaps it was windier than you thought? Maybe you were in a more sheltered area?
Hopefully someone can assist you with a better answer.

 

[Astom22]

I will suggest, if you haven't already, download UAV Forecast App. It has wind speeds shown from ground to 5000 feet. I have been shocked with how fast wind speeds increase just a little ways up from ground level.

 

[sar104]

The wind was 10 - 15 mph out of the SW - that wasn't the problem. The issue started at 323.7 seconds with 2.5 seconds of down throttle. The aircraft responded appropriately, descending at around 2 m/s. When the throttle was returned to center the aircraft stopped descending but, 2 seconds after that, at 329.5 seconds, went into an unsteady and accelerating descent, reaching around 12 m/s before hitting the ground.



The uncommanded descent coincided with a collapse of the cell voltages, which may have been the cause. That's not totally clear. We need to see the mobile device DAT file (FLY004.DAT) to determine if that, itself, was the cause or a symptom of a different problem.

Mobile device DAT file: How to retrieve a V3.DAT from the tablet

 

[skyrex]

Seems odd that you're horizon line was slanted almost the whole time also, first thought the wind may have attributed but it only got worse after the U-turn to go back. Perhaps IMU fault/failure?

 

[dave_i]

Here is the DAT file, attached.

The horizon tilt and the map tracking pre turn was showing me drift, from where I would have expected - which I what I was attributing to wind.

Earlier this week, I was flying, and had a fast flashing warning about a propeller issue. I landed , inspected, and nothing apparent. So I continued flying as normal.

Flight from 2 days earlier. 3min48 warning on motor. DJI Flight Log Viewer - PhantomHelp.com

Any further ideas?

 

[Mavic Mac]

The wind was 10 - 15 mph out of the SW - that wasn't the problem. The issue started at 323.7 seconds with 2.5 seconds of down throttle. The aircraft responded appropriately, descending at around 2 m/s. When the throttle was returned to center the aircraft stopped descending but, 2 seconds after that, at 329.5 seconds, went into an unsteady and accelerating descent, reaching around 12 m/s before hitting the ground.

View attachment 78080

The uncommanded descent coincided with a collapse of the cell voltages, which may have been the cause. That's not totally clear. We need to see the mobile device DAT file (FLY004.DAT) to determine if that, itself, was the cause or a symptom of a different problem.

Mobile device DAT file: How to retrieve a V3.DAT from the tablet

View attachment 78081

A "Newbie" here - Positively not questioning your stated information but trying to learn - how did you determine the wind speed from the graphs ? ?

 

[spamgnome]

I will suggest, if you haven't already, download UAV Forecast App. It has wind speeds shown from ground to 5000 feet. I have been shocked with how fast wind speeds increase just a little ways up from ground level.

UAV Forecast is WILDLY inaccurate with winds other than at the surface.

 

[Keule]

how did you determine the wind speed from the graphs ?

Airdata.com has a wind speed algorithm which is pretty accurate.
Here the output from the OP's flight:

 

[sar104]

A "Newbie" here - Positively not questioning your stated information but trying to learn - how did you determine the wind speed from the graphs ? ?

You can estimate wind speed and direction by comparing aircraft ground speed and direction with aircraft pitch and roll or, as @Keule pointed out, the AirData website runs a pretty good aerodynamic model to provide the same data. That's a premium feature on that website.

 

[silverdragon]

Ouch!
Actually that wind turbine looks like it is moving very quickly, also saw a fair amount of tree movement with the wind. Perhaps it was windier than you thought? Maybe you were in a more sheltered area?
Hopefully someone can assist you with a better answer.

I fly my MA in much windier conditions and "to me" it's hard to believe the wind that I see going by the trees, windmill the drones movement would knock it out of the sky like that... if the wind did do that then i must have a wind runner of a Mavic Air...

 

[Smecky]

Wounded for you pal. I don’t think it was wind or a bird. I’ve just sent one of my batteries back to dji as it was faulty. Seemed they had a bad batch. Take it up with dji pal.

 

[Mavic Mac]

You can estimate wind speed and direction by comparing aircraft ground speed and direction with aircraft pitch and roll or, as @Keule pointed out, the AirData website runs a pretty good aerodynamic model to provide the same data. That's a premium feature on that website.

Thanks

 

[Smecky]

I’ve just had an email back of dji saying there gonna replace it for free. Happy days.
Get a report put in.

 

[White Swan]

A very interesting discussion. thank you all!

 

[silverdragon]

A very interesting discussion. thank you all!

That's what makes the MavicPilots the best of the best...

 

[Astom22]

UAV Forecast is WILDLY inaccurate with winds other than at the surface.

What would you suggest instead? Is there an alternative? Besides the premium site mentioned above.

I'm not using it for precision, just to get a basic idea of what the wind higher up may be like.

 

[Smecky]

No can’t see the wind doing that unless it was about 90 mph.

 

[sar104]

What would you suggest instead? Is there an alternative? Besides the premium site mentioned above.

I'm not using it for precision, just to get a basic idea of what the wind higher up may be like.

Just to clarify - the AirData website computes what the wind speeds actually were on a flight when you upload the flight log, while the UAV Forecast includes predicted winds aloft from weather service data.