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Scary Flight Tonight - Yaw Errors - Need Help Understanding Logs

LeafPeeper

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Guys -
I could use some of your expertise. Been flying for about a year now, and been through a few crashes, a Care Refresh and learned a lot. Tonight I was having a relatively uneventful flight over the lake. Compass interference and IMU readings were all great just before take off, and after landing. However during flight the MP suddenly switched to ATTI mode for a bit. I didn't panic and luckily was able to maintain control, but upon looking at my Airdata logs, I've got TONS of Yaw Errors. Here's the link:


I've enabled KML and CSV download. If it was just momentary interference from a boat or some other source, I'm good with that - but I really want to know if it's an indicator of a problem with my Mavic. This is a refurb, and so far it has been as nearly perfect (other than lousy 1080p60 footage). I cal'd everything several flights ago, and like I said, all the compass interference readings were in the green (<<100) and the IMU readings were in the .003-.004 range.

Any ideas on whether this is a hardware problem or just interference?
Thanks,
LP
 

gnirtS

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Upload the logs to Phantomhelp.com or to dropbox.
Then people can see them an diagnose.
 

LeafPeeper

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Thanks - I uploaded the log to Phantom Help. I'll post a request in that forum as well.

DJI Flight Log Viewer - PhantomHelp.com

I thought the same info was available if I enabled CSV download capability from Airdata though. Is that not the case?

Thanks for any insight! Right now I just want to know if it looks like it might be a hardware issue - or random interference.
LP
 

gnirtS

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Its a little odd, i wouldnt normally expect magnetic interference at 80ft appearing mid flight then going away again.
Were there any masts or even just radio antenna anywhere around that location? Boats with radar, mobile phone, wifi beams or anything?
 

LeafPeeper

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Actually there was - my neighbor has a fairly good sized sailboat that is moored out there where I fly. There were a few others in the area as well, but further away. I usually fly around it though...so not sure why that flight would have been any different. I'm going to take a look at where the boat was in relation to the first yaw error.

LP
 

sar104

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Thanks - I uploaded the log to Phantom Help. I'll post a request in that forum as well.

DJI Flight Log Viewer - PhantomHelp.com

I thought the same info was available if I enabled CSV download capability from Airdata though. Is that not the case?

Thanks for any insight! Right now I just want to know if it looks like it might be a hardware issue - or random interference.
LP
The basic AirData functionality doesn't allow download of the original, more detailed, txt log file. The csv conversion contains only a fraction of the txt log data. The PhantomHelp site does include the txt file, and also now offers a more detailed csv file containing the entire txt log contents.
 

sar104

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Thanks - I uploaded the log to Phantom Help. I'll post a request in that forum as well.

DJI Flight Log Viewer - PhantomHelp.com

I thought the same info was available if I enabled CSV download capability from Airdata though. Is that not the case?

Thanks for any insight! Right now I just want to know if it looks like it might be a hardware issue - or random interference.
LP
This really requires either the aircraft or mobile device DAT files - they contain the magnetometer data which is key to these kinds of events. The aircraft DAT may or may not be accessible. The mobile device DAT definitely will be.

How to retrieve a V3 .DAT File from the AC

How to retrieve a V3.DAT from the tablet
 

LeafPeeper

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I already have the DAT file from the Mavic - just not sure what to do with it. Interestingly enough, given gnirtS question above, I did a little sleuthing. I found a satellite image that has my neighbor's boat in it, resized it and overlaid it on the Airdata notification map. Interestingly enough, H is the first Yaw Error, and it went into ATTI mode shortly after that. If a mast can cause this, it sure seems to line up. I'm just not sure if/why a mast would do it. Aren't they generally aluminum?

Interference.jpg

LP
 

sar104

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I already have the DAT file from the Mavic - just not sure what to do with it. Interestingly enough, given gnirtS question above, I did a little sleuthing. I found a satellite image that has my neighbor's boat in it, resized it and overlaid it on the Airdata notification map. Interestingly enough, H is the first Yaw Error, and it went into ATTI mode shortly after that. If a mast can cause this, it sure seems to line up. I'm just not sure if/why a mast would do it. Aren't they generally aluminum?

View attachment 43235

LP
I really doubt that this was due to a mast. In all the cases I've looked at I cannot think of any, other than in confined spaces, where magnetic interference was due to magnetic fields encountered in flight. It's almost always due to magnetic fields at the takeoff point.

If you want anyone to look at the DAT file then upload it to Dropbox or similar and then post a sharing link.
 

LeafPeeper

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I really doubt that this was due to a mast. In all the cases I've looked at I cannot think of any, other than in confined spaces, where magnetic interference was due to magnetic fields encountered in flight. It's almost always due to magnetic fields at the takeoff point.

If you want anyone to look at the DAT file then upload it to Dropbox or similar and then post a sharing link.
Understood...and what's odd is that everything looked good at takeoff. I even checked. I have a bad feeling about this. Starting to fear it might be a compass hardware issue. :(

LP
 

sar104

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Understood...and what's odd is that everything looked good at takeoff. I even checked. I have a bad feeling about this. Starting to fear it might be a compass hardware issue. :(

LP
Well maybe I was wrong. The magnetometer data look good for most of the flight, with the offset between magnetic yaw and IMU fusion yaw approximately equal to the local declination (14.25°). However, at around 230 s the magnetic yaw decreased while the IMU yaw did not. That led to the error:

230.601 : 15114 [L-FDI]ns req:fdi,0to0,reason:fusion.gps_yaw_err,result:fail for same index
2018-08-04_21-14-54.FLY073_01.png

That does look suspiciously like local magnetic interference. How tall is that mast?
 

gnirtS

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I'm just not sure if/why a mast would do it. Aren't they generally aluminium?
Although they generally are aluminIum they can also have wiring inside them along with connections for navigation lights and so on. Its also common to install radio antennas, radar, GPS antennas etc on them because the're the highest point.
Although the metal in them itself isnt huge and i doubt would cause much effect, if some of the power is live or worse, an emitter for a beacon, radar, vhf etc is running it could make it worse.
All the data i can see points to flying over an areas of localised magnetic interference.
Are you sure there are NO masts, particularly microwave ones on shore you may have flown through the beam path of?
 

LeafPeeper

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Well maybe I was wrong. The magnetometer data look good for most of the flight, with the offset between magnetic yaw and IMU fusion yaw approximately equal to the local declination (14.25°). However, at around 230 s the magnetic yaw decreased while the IMU yaw did not. That led to the error:

230.601 : 15114 [L-FDI]ns req:fdi,0to0,reason:fusion.gps_yaw_err,result:fail for same index
View attachment 43243

That does look suspiciously like local magnetic interference. How tall is that mast?
Wow - I never would have been able to interpret that data. Thanks for that! I'm not a blowboat guy, so I don't really know how tall the mast is. I do know that when I was approaching it at 50-60 ft, from my vantage point on the beach I was worried about getting too close to the top of it, so I increased my altitude to 80ft. I'd post a pic of the boat, but I think it might be an invasion of privacy. Based on some relative object sizes, I'm estimating it was 40-50ft.

gnirtS, the community is mostly vacationers, with no real industrial anything. There are no towers that I am aware of - although there are some cell towers, water towers and wireless internet transmitters within a mile or two.

FWIW, I completed 3 flights today in my backyard (all on one battery) without incident, while completely powering down between flights. It performed flawlessly - so if it's a hardware problem, it's not pervasive yet.

Thanks again guys. I guess I'm going to have to just write it off as interference and rebuild my confidence until it happens again!

LP
 

melmartin

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Sailboats can have radar and pretty strong transmitters. If he was 'on the air' as you flew nearby that might explain it. He's unlikely to be running radar while anchored.
 

LeafPeeper

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Sailboats can have radar and pretty strong transmitters. If he was 'on the air' as you flew nearby that might explain it. He's unlikely to be running radar while anchored.
Yeah...it was anchored at the time....but who knows, he may have been onboard.

LP
 
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