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Flyaway. Sudden total loss of satellites ???

Joined
Jan 2, 2018
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#1
I would really like to know if anyone can figure this one out. I was at a cabin in a federal forest in upper Wisconsin. Absolutely nothing around for ten miles or more, all trees and a river. No electricity here, just a radio tower for use in emergencies on the cabin. It was not being used or turned on. I went straight up to just under 400ft a few minutes into the flight I was not even 200ft away I did get a high wind warning. I started to bring the magic down to around 225ft and stayed under 200ft from home base. Out of nowhere I lost all satellites and got a compass error. Mavic started flying backwards across the river and I had no controls at all. I switched to sport mode and immediately got responsive controls. I was able to land at home point manually but was scared to take it up any distance again. I did check everything over and put it back up to 125ft in elevation and everything seemed fine but I was afraid to fly away from home point. Any ideas on what causes you to totally lose satellite signal with absolutely nothing around? Also I dont know how to upload my flight logs?
 
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#6
As stated before there is absolutely nothing around this area for at least 10 miles, only trees and the river with one road going through the federal forest here
 

sar104

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#7
DJI Flight Log Viewer - PhantomHelp.com

Thanks for any help. I did land it check everything over and then put it right back up but didn't fly away from home point.
There's no mystery about what happened here. You didn't lose GPS at all - a discrepancy between the IMU yaw, calculated from the rate gyros, and the magnetic yaw, from the compass, caused the inappropriately named GPS health value to drop to zero and the FC to switch to ATTI mode (flycState = 0).

2018-07-21_[16-49-52]_01.png

The aircraft continued to respond appropriately to your stick inputs but, if you are not practiced at flying in ATTI mode where centering the sticks does not cause it to hover, the aircraft will have seemed difficult to control.

The cause of the yaw discrepancy is most likely to have been local magnetic interference at the location where you powered up the aircraft.
 

Irish-apple

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#8
There's no mystery about what happened here. You didn't lose GPS at all - a discrepancy between the IMU yaw, calculated from the rate gyros, and the magnetic yaw, from the compass, caused the inappropriately named GPS health value to drop to zero and the FC to switch to ATTI mode (flycState = 0).

View attachment 42524

The aircraft continued to respond appropriately to your stick inputs but, if you are not practiced at flying in ATTI mode where centering the sticks does not cause it to hover, the aircraft will have seemed difficult to control.

The cause of the yaw discrepancy is most likely to have been local magnetic interference at the location where you powered up the aircraft.
Your not human lol ..
 

Lake_Flyer

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#9
OP:
It is better not to calibrate where you can expect ferric magnetic rock like in the mountains. Usually a previously known good calibration is good enough to keep (forever) until a firmware update or far travel. A seemingly good calibration in a magnetic environment leads to Atti mode once up in the air, free from that magnetic radiation.

Edit: I just assumed you were in an area with with rocks and mountains, but you didn't write that, I realise now. And I also can't know if you calibrated or not. But anyway, good advice for if you wouldn't know already.
 
Last edited:
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#10
Thanks, I didn't recalibrate (should I do an IMU recalibration at home as a precaution?) and this was really thick woods and an open area by the cabin. I will for the fun of it post the link of the video. I do actually fly in sport mode quite often once I'm above the tree lines and clear of everything. But thanks for the help. I guess one thing to note on the magnetic interference is that upper Wisconsin area where I was has very dense bedrock. There used to be a military base about 5 miles from here (now closed down). It was an ELF (Extremely Low Frequency) base where they used the bedrock to send signals to submarines in the great lakes area. It was an experimental base for many years and that area was picked because it was one of the only areas in the Midwest that had this type of dene rock base. This is an area where we go frequently for hunting and fishing, so should I just assume that I'll need to use sport mode once in the air to prevent this in the future, so I can keep flying it up there? Doing a little research on my own the Mavic did have a lot of compass issues as far as with magnetic interference and eratic controls in the past. I've had my mavic for almost a year now and I love to take it with me wherever I go. I'm getting a lot better at trying to avoid my own flight mistakes but being new it is a learning curve.

Flyaway starts at around the 4:30 mark. I didn't let it get to far before switching to sport mode and bringing it back.
 
Last edited:

Canuk

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Apr 19, 2018
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#11
Is this a fly away or wind drift from being in atti mode . Big difference I think
 

Mossiback

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#13
...Out of nowhere I lost all satellites and got a compass error. Mavic started flying backwards across the river and I had no controls at all. I switched to sport mode and immediately got responsive controls...
I would like to know how switching to sport mode would suddenly give you responsive controls. Another interesting thing I saw on the video was the tilted horizon when control was lost. Perhaps it is a clue for someone more enlightened than myself.
 
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sar104

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#15
it wasn't wind drift I had no controls, I've had wind drift before
I'm sorry but that is not correct - the aircraft responded to your inputs throughout the flight, including in ATTI mode, which started at 280 s and lasted 60 s as shown in post #7. To illustrate, below is a plot of your elevator stick inputs and the corresponding aircraft pitch, which is the flight characteristic that the elevator stick controls, from just before the onset of ATTI to the end of the flight.

2018-07-21_[16-49-52]_02.png
 
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Canuk

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#16

If I put a magnet or steel near the open app it shows up fast . Works well
 

sar104

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#17

If I put a magnet or steel near the open app it shows up fast . Works well
I'm confused - did you mean a different app? That one is just an app to display NOAA's forecast for geomagnetic storms - it doesn't appear to have any functionality related to detecting local magnetic fields. There are plenty of other apps that do take data from cell phone compasses, however.
 

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