Satellite signal lost, erratic flying, almost lost Mavic!

daithi23 · Mar 4, 2017

Hi all, had a real "Oh ****" moment today, after flying for a couple of minutes the Mavic went into ATTI mode, top left of app which usually said GPS connected or whatever said something like No GPS signal even though next to the satellite icon was "20". So using the map box in the bottom corner of the app I turned it around to face me and started heading back only to realise after a little bit it hadn't gotten any closer but stayed in the same spot according to the map. I was now truly lost! It was also really hard to control, like there was high winds pushing it around (dead calm in reality). The distance from me was changing though, don't know if it was real time or intermittent but tried to use that to figure out if I was flying it away or towards me when I saw a house. Was trying to bring it down there and really battling with the "drift" when GPS popped backed in, immediately pressed RTH to at least get it pointed towards me but it came back all the way anyway, flew really weird back though, not facing forward, slightly off to one side. Had noticed some drift the last week, thought maybe it was the firmware update.
The other thing, don't know if it's coincidence or part of the problem: I had just flown it at the base of a mountain cliff amongst trees, good and stable, no problem then brought it to a close by car park to get more clearance and better view but I lost my dedicated drone phone on the way to the car park and instead used my personal phone, saw a prompt for new firmware (I'm on x.x.0400) but ignored it as the last one took ages. After I got it back I also saw a prompt for new DJI go app (4.0.3 I believe), since plugging in the phone and connecting the WiFi it automatically updated and now says 4.0.4 so don't know what one it actually was one. Anyway don't know if there was some FW/app conflict or if it's just coincidence but Im thinking coincidence, just want to give all info...
Anyway, glad to still have it, heart was in my mouth for what seemed like an eternity today! Does anyone have a link to instructions on how to upload the Log? Never did it before... Anyone experience something like this before or know what happened? GPS lost I could put down to one fault but the drift and flying home at an angle was something else...

Other notes : The arrow in the map box turned after the GPS went and I was trying to initially orientate it towards me just now all the way leading me to believe there was still some connection even though the app wasn't showing this. Also, distance from me was changing, isn't this based on home point vs GPS position of drone?

P.S. A bit off topic but this was a replacement as my first Mavic had gimbal issue, also had watercolour problem which I wanted to test to see if it was resolved (did see some watercolour but not as bad as before). Just wondering if the P4P a more stable platform?

P.P.S. Inb4 I should have had line of sight and updated firmware. ;-)

daithi23 · Mar 4, 2017

Video comments : noticed signals lost approx 45 secs at the top of the hill. Looking at it, think it was drifting to the right on the way up there then notice the tilt @ 45 secs just before I turn it round (this was when I thought the map representation was still working)
You notice the drift after this when I fly it straight back to me or so I thought and when I'm over the building, I'm not actually moving it, it's just drifting mad.. After that is when GPS returns and you see on the RTH it's not flying straight...

msinger · Mar 4, 2017

daithi23 said:
Does anyone have a link to instructions on how to upload the Log?

You can find instructions to upload and view your log online here. After uploading it, please post a link back here if you'd like other people to review it and comment on it.

daithi23 · Mar 4, 2017

Newest file in folder DJI/dji.pilot/Flight record is a couple of months old.. Possible to get it from the drone?
Edit: think i found it, wait...
Edit! Here it is: Phantom Log Viewer - PhantomHelp.com

Edit: here's the DAT ~~FLY044.DAT@17-03-04_03-06-36-683~~ DJI_ASSISTANT_EXPORT_FILE_2017-03-05_12-56-15.DAT

Mavicsailor · Mar 4, 2017

daithi23 said:
Hi all, had a real "Oh ****" moment today, after flying for a couple of minutes the Mavic went into ATTI mode, top left of app which usually said GPS connected or whatever said something like No GPS signal even though next to the satellite icon was "20". So using the map box in the bottom corner of the app I turned it around to face me and started heading back only to realise after a little bit it hadn't gotten any closer but stayed in the same spot according to the map. I was now truly lost! It was also really hard to control, like there was high winds pushing it around (dead calm in reality). The distance from me was changing though, don't know if it was real time or intermittent but tried to use that to figure out if I was flying it away or towards me when I saw a house. Was trying to bring it down there and really battling with the "drift" when GPS popped backed in, immediately pressed RTH to at least get it pointed towards me but it came back all the way anyway, flew really weird back though, not facing forward, slightly off to one side. Had noticed some drift the last week, thought maybe it was the firmware update.

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The other thing, don't know if it's coincidence or part of the problem: I had just flown it at the base of a mountain cliff amongst trees, good and stable, no problem then brought it to a close by car park to get more clearance and better view but I lost my dedicated drone phone on the way to the car park and instead used my personal phone, saw a prompt for new firmware (I'm on x.x.0400) but ignored it as the last one took ages. After I got it back I also saw a prompt for new DJI go app (4.0.3 I believe), since plugging in the phone and connecting the WiFi it automatically updated and now says 4.0.4 so don't know what one it actually was one. Anyway don't know if there was some FW/app conflict or if it's just coincidence but Im thinking coincidence, just want to give all info...
Anyway, glad to still have it, heart was in my mouth for what seemed like an eternity today! Does anyone have a link to instructions on how to upload the Log? Never did it before... Anyone experience something like this before or know what happened? GPS lost I could put down to one fault but the drift and flying home at an angle was something else...

Other notes : The arrow in the map box turned after the GPS went and I was trying to initially orientate it towards me just now all the way leading me to believe there was still some connection even though the app wasn't showing this. Also, distance from me was changing, isn't this based on home point vs GPS position of drone?

P.S. A bit off topic but this was a replacement as my first Mavic had gimbal issue, also had watercolour problem which I wanted to test to see if it was resolved (did see some watercolour but not as bad as before). Just wondering if the P4P a more stable platform?

P.P.S. Inb4 I should have had line of sight and updated firmware. ;-)

Best to also download the DAT file directly from the Mavic using DJI Assist. Use Dropbox or similar to post to this thread. GPS health has been a fairly common post.

grizzard · Mar 4, 2017

Wind changes in speed and direction (as much as 45 degrees) as you change altitude ... also, I agree with your PPS. I don't see anything unusual though given all the circumstances. I've had 4 or 5 similar.

daithi23 · Mar 4, 2017

grizzard said:
Wind changes in speed and direction (as much as 45 degrees) as you change altitude ... also, I agree with your PPS. I don't see anything unusual though given all the circumstances. I've had 4 or 5 similar.

What's PPS? There was literally no wind. I've had it flying in high wind warnings and it didn't act like that, it had something to do with the satellite, maybe more..

daithi23 · Mar 4, 2017

Mavicsailor said:
Best to also download the DAT file directly from the Mavic using DJI Assist. Use Dropbox or similar to post to this thread. GPS health has been a fairly common post.

Will do tomorrow, gotta get some sleep now

TestPilot · Mar 4, 2017

I noticed this issue before. Sudden loss of signal and then disconnection. Luckily, it happened just as I was taking off....and it was still very much responsive. Landed it back down without any issues....

This kind of disconnection issue is always a risk.

frankiez · Mar 4, 2017

I always have fear/nervousness that this will happen on EVERY flight. Too bad we can't visually see interference in the air.

I guess I need to calm down and realize that it is insured so...

AlanTheBeast · Mar 4, 2017

frankiez said:
Too bad we can't visually see interference in the air.

Maybe you need new glasses?

grizzard · Mar 4, 2017

daithi23 said:
What's PPS? There was literally no wind. I've had it flying in high wind warnings and it didn't act like that, it had something to do with the satellite, maybe more..

Your launch point appeared to be where trees surrounded you which would buffer any wind on the surface. Also ... just because there is no wind on the ground does not mean that there is no wind at altitudes. The sun was out and you're in a mountain area. The sun heats the ground and air rises moving up the slopes ... in the evening it cools and air comes down the canyons. Also .... if you're down in the trees the drone to the controller signal is going to be reduced. Just a few things to think about.

daithi23 · Mar 4, 2017

Here's the DAT : ~~FLY044.DAT@17-03-04_03-06-36-683~~ DJI_ASSISTANT_EXPORT_FILE_2017-03-05_12-56-15.DAT

daithi23 · Mar 4, 2017

@grizzard You need to actually read what I wrote and look at the video I provided as well as the flight log, wind was not an issue. If you had similar issues and you're happy with them that's fine, I look forward to reading your thread on how you lose your Mavic.

grizzard · Mar 4, 2017

daithi23 said:
@grizzard You need to actually read what I wrote and look at the video I provided as well as the flight log, wind was not an issue. If you had similar issues and you're happy with them that's fine, I look forward to reading your thread on how you lose your Mavic.

Ok ... no problem. I didn't mean to sound condescending if you took it that way, but was only meant as a few things to consider. As a pilot I can take off with zero surface winds and get aloft and find I have noticeable headwinds. FYI ..... I've already crashed my Mavic twice ... once inside into a basement wall where is screwed itself right down into the floor (3 broken props) and the second time outside in misty fog from the props icing up and the Mavic came straight down in a vertical descent, broke off a prop and threw off one leg extension, and then bounced up to landing altitude on 3 /1/2 props and then landed. Gimbal stayed intact. I've also had one incident where I changed the Home Point when the Mavic ran low on battery and then it took off on it's own back 1/2 mile where I launched because it failed to recognize the new Home Point. And I have totally lost connection a couple of times and panicked ... but then connection was re-established. But your point is well taken and I look forward to Msinger reading and publishing the flight. We're all here to learn ... including me.

Robbyg · Mar 4, 2017

daithi23 said:
Here's the DAT : FLY044.DAT@17-03-04_03-06-36-683

That is not the right DAT file.
You need to plug the drone into your PC and use DJI assistant 2 to extract the file. It should be around 450MB long.

daithi23 · Mar 4, 2017

Sorry @grizzard I thought you were just trolling, my bad, I've seen a few too many smart-arse unhelpful posts here so I presumed you were doing the same. Full apology and retraction.
@Robbyg Here's the correct DAT (I hope!): DJI_ASSISTANT_EXPORT_FILE_2017-03-05_12-56-15.DAT
@BudWalker I've seen you show some interest in similar posts if you want to jump in?

daithi23 · Mar 5, 2017

I've been playing around with the csvview and GPS health does indeed drop dramatically and unexpectedly. I'm not an expert at this but that would seem to explain the ATTI mode, any idea what would cause the GPS health to suddenly drop off like that?

Mavicsailor · Mar 5, 2017

daithi23 said:
I've been playing around with the csvview and GPS health does indeed drop dramatically and unexpectedly. I'm not an expert at this but that would seem to explain the ATTI mode, any idea what would cause the GPS health to suddenly drop off like that?

Really hard to say. Each one if these GPS Health drops/ATTI events is a bit different. In your case, it looks like you were giving strong elevator and throttle up to about 10 seconds before what appeared to be a small case of TBE. This strong elevator and throttle decrease appeared to be the start of a difference between YAW and YAWmag.

It dropped into Atti when YAW and YAWmag were the greatest difference. The timing on this is when the AC appeared to be in TBE.

From there, it drifted a distance until it regained GPS health, where you eventually told it to come home, after decending to possibly make an emergency landing. A drop of GPS health seems to be sometimes related to a large difference in YAW and YAWmag, or at least an unexpected change, and appears to sometimes occur in conjunction with TBE.

The question here is what caused the large difference in YAW and YAWMag that appears to have ultimately lead to TBE and GPS health drop? The only thing I see just prior to this is strong elevator and throttle at the same time. GPS health drops seem to occur more frequently with more aggressive flying, although I wouldn't call holding down 2 sticks at once necessarily aggressive, at least not in GPS mode, and this was several seconds prior to the TBE. Maybe others can take a look and give their thoughts on what might have caused the TBE/ GPS health drop/ATTI.

daithi23 · Mar 6, 2017

Thanks for spending the time analysing this. You're correct just as I reached the high point of the hill the RC vibrated and I let the sticks back to neutral position (all that had happened is that I had reached max flight altitude). Strange that YAWMag would deviate from YAW like that and precede the GPS health drop. I've contacted DJI and they want me to send it in to get checked, they may just send me a replacement and never explain what was going on but at least Mavic was retrieved and the DAT is there for us to analyse and learn from.