Mavic Air Crashed. Curious as to what occurred.

[Siananat]

Greetings! My drone crashed and I recovered it (No longer flyable). I was flying in a park and then I saw the drone pitch forward a lot. It continued this way until ending up in a tree. Though I recovered it, I'm curious to see what exactly happened to cause the crash, whether it be pilot error (more likely than not) or system error. By any chance would anyone mind taking a look at my flight log? Thanks!

 

[John MacAulay]

I'm sure one of the experts here will be along shortly to analyze your flight data and give you some clues as to what happened with your Air. Sorry for your mishap.

 

[John MacAulay]

@sar104

 

[sar104]

@sar104

I'm on it.

 

[John MacAulay]

You're the best!

 

[Siananat]

Thank you so much! I greatly appreciate it.

 

[sar104]

This one is a puzzle. The problem is clear, but the cause is not. Clearly the inertial and GPS positioning start to disagree badly at around 100 seconds:



In position space:




The problem is that the aircraft is moving in the wrong direction - the orientation arrows on the graph above show that it moved forwards, to the west. However, looking at pitch shows that it pitched backwards (positive pitch angles mean backwards), and so cannot have been moving forwards.



That suggests, perhaps, a 180° yaw error, so we'll need to look at the DAT file (FLY044.DAT) to confirm that.

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

 

[Siananat]

Thanks for your analysis. I wonder what exactly caused this... I attached the DAT file below. View attachment 19-09-18-06-22-59_FLY044.zip

 

[sar104]

Thanks for your analysis. I wonder what exactly caused this... I attached the DAT file below. View attachment 82051

There was a disagreement between the compass and the IMUs, but it arose suddenly at 98 seconds - it wasn't an initialization issue.



The compass recorded a CW rotation, but both IMU z-axis rate gyros saw nothing. That almost certainly accounted for the uncontrolled flight as the FC tried to correct. There is not much that can go wrong with a compass in the air, so normally I would trust the compass, but here it disagrees with two independent IMUs. But since the FC bases its control inputs on the IMU yaw, not the magnetic yaw, and since the aircraft entered uncontrolled flight, that suggests that the IMUs were wrong.

Another case that needs a second opinion - @BudWalker?

 

[Siananat]

There was a disagreement between the compass and the IMUs, but it arose suddenly at 98 seconds - it wasn't an initialization issue.

View attachment 82056

The compass recorded a CW rotation, but both IMU z-axis rate gyros saw nothing. That almost certainly accounted for the uncontrolled flight as the FC tried to correct. There is not much that can go wrong with a compass in the air, so normally I would trust the compass, but here it disagrees with two independent IMUs. But since the FC bases its control inputs on the IMU yaw, not the magnetic yaw, and since the aircraft entered uncontrolled flight, that suggests that the IMUs were wrong.

Another case that needs a second opinion - @BudWalker?

If the IMUs were in fact wrong, what could possibly cause something like that to happen to them in flight?

 

[Joe Boudreault]

Greetings! My drone crashed and I recovered it (No longer flyable). I was flying in a park and then I saw the drone pitch forward a lot. It continued this way until ending up in a tree. Though I recovered it, I'm curious to see what exactly happened to cause the crash, whether it be pilot error (more likely than not) or system error. By any chance would anyone mind taking a look at my flight log? Thanks!

Were there high winds?

 

[Siananat]

Were there high winds?

The winds were decent for flying. Calm with the occasional gust. The drone was flying very well but had then pitched forward and took off straight into a tree from the park after hovering there for just a few seconds. I uploaded it to airdata just now.

 

[Joe Boudreault]

The winds were decent for flying. Calm with the occasional gust. The drone was flying very well but had then pitched forward and took off straight into a tree from the park after hovering there for just a few seconds. I uploaded it to airdata just now.

You might have touched the control stick by accident. I get nervous sometimes and do that. I also notice that your system is Android - not good for these drones. Should be Apple only, as manufacturer suggests...

 

[Deleted member 94047]

I also notice that your system is Android - not good for these drones. Should be Apple only, as manufacturer suggests...

Where exactly does the manufacturer suggest that?

 

[Siananat]

You might have touched the control stick by accident. I get nervous sometimes and do that. I also notice that your system is Android - not good for these drones. Should be Apple only, as manufacturer suggests...

I hit the sticks for a little bit, just after the drone went out of control. I mostly kept my hands off to avoid messing with it. Also, where does DJI suggest using Apple products for their drones? sar104's analysis showed that the problem had to do with the IMUs disagreeing with the compass around 98 seconds into the flight, leading to the uncontrolled flight.

 

[sar104]

You might have touched the control stick by accident. I get nervous sometimes and do that. I also notice that your system is Android - not good for these drones. Should be Apple only, as manufacturer suggests...

This had nothing to do with the mobile device operating system. I've found iOS to be a bit more reliable, but Android is a fully approved operating system – DJI would not release Android versions of the Go app if that were not the case.

 

[Joe Boudreault]

Where exactly does the manufacturer suggest that?

On the outside of the packing box of all of their products. Few people read that.

 

[Siananat]

On the outside of the packing box of all of their products. Few people read that.

Just read it. That just tells people that the product is MFI certified. Has nothing to do on whether or not a product is better suited for the job or not.

 

[Deleted member 94047]

On the outside of the packing box of all of their products. Few people read that.

You mean the "Made for iphone" branding on the packaging box?

 

[Siananat]

You mean the "Made for iphone" branding on the packaging box?

Yep! That's the MFI certification. It lets consumers know that it will work with iOS devices.