Runaway Mavic 3 Cine

[sar104]

As someone who flies in urban areas regularly with a variety of drones (from DJI and others) this comment is interesting. I understand how rebar or other ferrous metal could influence and corrupt the compass but are you saying it can also cause other kinds of harm?

If you want a full explanation:

A short explanation of compass function, calibration and errors.

BACKGROUND The aircraft compass is often misunderstood, both in terms of function and purpose, but it is important to understand what the compass measures, why, and what happens to that information. At the most basic level the purpose of the compass is to measure the earth’s magnetic field in...

mavicpilots.com

 

[Meta4]

As someone who flies in urban areas regularly with a variety of drones (from DJI and others) this comment is interesting. I understand how rebar or other ferrous metal could influence and corrupt the compass but are you saying it can also cause other kinds of harm?

It's a common cause of a yaw error incident, where the compass is deflected by magnetic interference, the IMU gyro sensor takes its initial directional values from the deflected compass at startup and problems occur when the drone leaves the magneticaly distorted area and there is now a data conflict between the compass and the IMU gyro sensor.

 

[Deleted member 162835]

GPS was not fine at the start of your flight.
Your GPS reliability was low (2/5) until 17 seconds into the flight.
But this did not cause the problem.


Here's a summary and visual representation of the flight:

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

The first indications of a problem show up in the compas data 4.4 seconds into the flight.
Following this, the drone doesn't appear to properly respond to rudder input and stays on a heading of 87° despite joystick input that should have rotated the drone anti-clockwise first, and then clockwise.

At 8.8 seconds the drone starts to acellerate without any right stick input.
It is erratic and slows and speeds up on its own.

At 20 seconds there is an umcommanded descent from 47 ft to 22 ft.
The cause of this is quite puzzling.
There is another small descent at 37.4 sec when the joystick input should have caused the drone to climb.

Can you remember which way the drone was pointing while it was on the ground waiting for launch?
The data shows it to be just east of north (27°) but I suspect it was something else.
It looks like you launched from a reinforced concrete surface (never a good idea) and this might explain part of the flight problems.

@sar104 might be able to help with further analysis

I'm hear to learn. You state the GPS reliability score was low indicating GPS lock was poor. How would I know this other than trusting the DJI Fly app on my RC Pro? The RC Pro indicated satellite lock was sufficient and it was clear to take off. What else should I be using?

The exact direction in degrees would be hard to determine but using Google Maps and Streetview it looks like I was facing due East. I appreciate you taking the time to review this and provide comment back. I have flown from this location in the past and never had any any issues. Saturday was really an exception. It was not complying and I tried to bring it back which failed. The elevations the drone was reporting were not accurate. It was higher than 40'. When it nosed dived into the water it was much lower than it was reporting.

 

[Deleted member 162835]

If you want a full explanation:

A short explanation of compass function, calibration and errors.

BACKGROUND The aircraft compass is often misunderstood, both in terms of function and purpose, but it is important to understand what the compass measures, why, and what happens to that information. At the most basic level the purpose of the compass is to measure the earth’s magnetic field in...

mavicpilots.com

Thank you for posting this. I was wondering how reinforced concrete could complicate things. It helps understanding the technical details of how the drone does it's thing. I was indeed on reinforced concrete but I have flown from this location in the past and never had this issue.

 

[Meta4]

You state the GPS reliability score was low indicating GPS lock was poor. How would I know this other than trusting the DJI Fly app on my RC Pro? The RC Pro indicated satellite lock was sufficient and it was clear to take off. What else should I be using?

The data shows GPS health at 4/5 and a homepoint was recorded on the first line of data but dropped to 2/5 immediately after.
The GPS icon in the upper part of the screen turns white when the drone gets good GPS, it should turn back to yellow when GPS health drops back.

it looks like I was facing due East.

That makes sense.
At 4.8 sec when the drone climbed out of the magnetic field that had deflected the compass, the compass snapped from 27° to 87° without any corresponding joystick input.

I have flown from this location in the past and never had any any issues.

When you are talking about putting a drone on reinforced concrete, the difference between safe/not safe might just be an inch or two.
You can't see how thick the concrete is over the reinforcing rods, you can't see where the thicker rods are or where rods cross.

 

[sar104]

The data shows GPS health at 4/5 and a homepoint was recorded on the first line of data but dropped to 2/5 immediately after.
The GPS icon in the upper part of the screen turns white when the drone gets good GPS, it should turn back to yellow when GPS health drops back.

The GPS level value is initially based on the GNSS lock accuracy estimate, but after that it is also dependent on the mismatch between the inertial and GNSS position solutions. Here the satellite count is good but the GPS level (which should probably be renamed navigational health) is unstable:

That makes sense.
At 4.8 sec when the drone climbed out of the magnetic field that had deflected the compass, the compass snapped from 27° to 87° without any corresponding joystick input.

Here's the view of that process happening on the initial climb out:

When you are talking about putting a drone on reinforced concrete, the difference between safe/not safe might just be an inch or two.
You can't see how thick the concrete is over the reinforcing rods, you can't see where the thicker rods are or where rods cross.

Exactly.

 

[Deleted member 162835]

The data shows GPS health at 4/5 and a homepoint was recorded on the first line of data but dropped to 2/5 immediately after.
The GPS icon in the upper part of the screen turns white when the drone gets good GPS, it should turn back to yellow when GPS health drops back.

That makes sense.
At 4.8 sec when the drone climbed out of the magnetic field that had deflected the compass, the compass snapped from 27° to 87° without any corresponding joystick input.


When you are talking about putting a drone on reinforced concrete, the difference between safe/not safe might just be an inch or two.
You can't see how thick the concrete is over the reinforcing rods, you can't see where the thicker rods are or where rods cross.

The color of the GPS icon on the screen was white before I took off. During flight it flashed to orange for a second and then back to white. If this is the only indication a pilot has to the health/reliability of GPS lock, there needs to exist another tool because this go around it said all ok for launch but the data behind the scenes indicated otherwise.

 

[sar104]

The color of the GPS icon on the screen was white before I took off. During flight it flashed to orange for a second and then back to white. If this is the only indication a pilot has to the health/reliability of GPS lock, there needs to exist another tool because this go around it said all ok for launch but the data behind the scenes indicated otherwise.

As I explained above - the satellite lock isn't the problem.

 

[Skwirl]

I think some info has entered a brain cell or 2 now, lol.
I do have a question though.
The compass error causing a yaw error I get, it doesnt know for sure which way its pointing. The low GPS signal I get to, position hold.
Why would a yaw error cause the drone to fly up when the pilot input was down and vice versa? That's what he said actually occured.
And the only hint at a possible issue would have been the blue arrow direction on the map at take off, correct?

 

[Meta4]

I think some info has entered a brain cell or 2 now, lol.
I do have a question though.
The compass error causing a yaw error I get, it doesnt know for sure which way its pointing. The low GPS signal I get to, position hold.
Why would a yaw error cause the drone to fly up when the pilot input was down and vice versa? That's what he said actually occured.
And the only hint at a possible issue would have been the blue arrow direction on the map at take off, correct?

As sar104 pointed out, this one wasn't a straightforward yaw error incident.
There's a bit more going on that looks like a hardware problem.
It's probably a warranty issue and you should start a case with DJI.

 

[Deleted member 162835]

As sar104 pointed out, this one wasn't a straightforward yaw error incident.
There's a bit more going on that looks like a hardware problem.
It's probably a warranty issue and you should start a case with DJI.

I do have a case open with DJI. Apparently their analysis is complete but the people on the hotline could not provide specifics until I receive the official analysis report via email. He did indicate that I would be charged some fee which I’m ready to challenge. Hopefully I hear back today.

 

[sar104]

I do have a case open with DJI. Apparently their analysis is complete but the people on the hotline could not provide specifics until I receive the official analysis report via email. He did indicate that I would be charged some fee which I’m ready to challenge. Hopefully I hear back today.

I would be very surprised if they don't simply replace this under warranty. There is clear evidence of hardware failure.

 

[Deleted member 162835]

I would be very surprised if they don't simply replace this under warranty. There is clear evidence of hardware failure.

The analysis team got back to me and the drone is being replaced under warranty.

 

[Yorkshire_Pud]

The analysis team got back to me and the drone is being replaced under warranty.

Good result.
With battery and perhaps the mSD card?

Just a point, with regard to @sar104 's post no19, and, as I understand the post, 'switching of the response to the joysticks', is there any concern that the controller itself may be wonky?

 

[Meta4]

Just a point, with regard to @sar104 's post no19, and, as I understand the post, 'switching of the response to the joysticks', is there any concern that the controller itself may be wonky?

No

 

[Yorkshire_Pud]

No

ok

 

[Deleted member 162835]

Good result.
With battery and perhaps the mSD card?

Just a point, with regard to @sar104 's post no19, and, as I understand the post, 'switching of the response to the joysticks', is there any concern that the controller itself may be wonky?

I did send them a note regarding the battery that was lost as well. I’m sure they will replace it. No SD card was installed.

 

[Deleted member 162835]

To put a bow on this, I received my replacement Mavic 3 Cine on Wednesday. It was supposed to be Monday but a loader at UPS had a brain fart and put the drone on the wrong truck and UPS lost it for some time. DJI was awesome throughout this whole ordeal. Communication was spot on. It's obvious they value customer service. They even contacted UPS multiple times, unknowing to me, to track the shipment and verify delivery. An interesting fact, the replacement drone has the oval telephoto lens where my original had the round lens so I'll get to see if I notice any difference between photo quality.

I do appreciate this forum for providing serious input into the flight log. I've been on forums where it seems the community's goal is to roast people when an unfortunate event happens. For the most part, everyone provided constructive feedback and I learned a lot.

 

[DoomMeister]

@dantegl36
Thank you for commenting on our resident flight analysis experts. They are very good at what they do, and words such as yours are the only reward for their service. Great job! @Meta4 and @sar104

 

[Southfork1]

It looks like you launched from a reinforced concrete surface (never a good idea) and this might explain part of the flight problems.

Why is that a problem?