ATTI mode mid flight - causing the Mavic to almost crash

[m0j0]

Will calibrating the compass over a grassy surface lock in the calibration for good

Yes if you fly in that area all the time you will not have to calibrate.. read the compass thread a number of times so that you understand when to calibrate and where to do it. It is incredibly important. Once you have a good calibration you should leave alone unless there is a change in location (70+ miles), significant change in terrain or you prompted to do so..

If you observe a compass error prior to flight.. move your launch location it could be that you are over metal which is skewing your compass readings. 9 times out of 10 the issue is interference from your launch location.


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[erkme73]

@mattmjm - sucks doesn't it? When something like this happens, it kills your confidence - and most of the joy/excitement of having a new drone. I had a very similar experience yesterday evening. It was too dark to get a good visual on what was happening, but looking at the flight path it flew, the rotations it made, and the drifting - all without any stick input - has left me spooked. I just purchased the Refresh plan today. I also sent an email to [email protected] with the cloud-synced flight data description. I was hoping my issue was operator error - something I could learn to avoid in the future. But I'm starting to think there may still be some bugs left in the design/software that need squishing.

 

[The Editor]

Learning lesson: Now, I am realizing I should have done the compass calibration and should probably continue to calibrate the compass before every single flight from now on.

TLDR; Didn't calibrate compass, took off, aircraft went into ATTI mode, went wild, barely managed to land safely and in one piece. Calibrate the compass before every single flight.

No - absolutely not DO NOT calibrate your compass before every flight. This is bad advice and very well documented on here now and over on InspirePilots.
By doing so you increase the risk of unknowingly introducing a bad calibration (which is what it appears you had with your experience of a bad flight)
Calibrate it a known good position or well away from anything (middle of a field), not wearing watches, belt buckles, anywhere near a car or concrete (which can have rebar in - nor on a beach where the geological makeup of the rocks can have a magnetic flux)
Once you have got that calibration LEAVE IT ALONE!
Do however check your mod values before every single take off - if they are out, don't fly. Move a few feet/meters and check them again.
Do not however recalibrate every flight or everytime you move.

 

[Wacker2611]

I don't want to sound mean as you've obviously had a scare, but the fact that you had to calibrate before every flight should have raised alarm bells and is very abnormal. I assume you're a new user, but the forums are choc full of compass advice so the reality is that you shouldn't have flown it in the first place. Assuming you haven't got a faulty unit the solution is really simple. As has been said, you must get that solid calibration in an open space, ideally an open field. As an additional precaution, move your phone, car keys, watch etc away from the quad and also put your rc on your bag where you can see the screen but it is away from the Mavic. Once you've got that good calibration that should be it....You might never have to do it again!
Also, I always check the compass in app ( in sensors) before most flights. If the 2 compasses are both showing in green, you should be good to go in 99.99% of cases.


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[mattmjm]

Thank you for your replies and recommendations guys. I plan to calibrate in an open field tomorrow afternoon and I'll post a more detailed reply then (Wednesday, November 23rd).

However, this looks to be a bigger problem and other pilots are experiencing it too:

Four separate pilots (in the same thread) report the same exact GPS signal loss issue that I had tonight:
GPS lost mid flight (single incident, possible geographical problem)

Some guy on YouTube caught it happening live:

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After reviewing my logs, I had 18 satellites locked on when signal was lost and it went into ATTI mode.

 

[J-Dub]

So, if I read this thread accurately, if you live in a City, surrounded by Concrete and Asphalt, and you find a small grassy area that's far enough away from "metal" to get a successful compass-cal, you are still going to be screwed because you can't take off from anywhere but the grassy spot??

 

[msinger]

Asphalt should be an okay surface to launch from.

 

[J-Dub]

Asphalt, no metal, check. Thanks, msinger, you seem to be the expert. Whenever, if ever I get my Mavic, I'm using your threads and links etc before I take off on my first flight. I went thru these growing/learning pains back with the P2+. Now I can fly a little Hubsan in all directions around my livingroom, so that should help. This time I will have a camera on my forehead, and one on a tripod about 20feet away to capture my first flights. Do you recommend Litchi because it can record your device's screen? Would/Do you use both Apps?

 

[The Editor]

Thank you for your replies and recommendations guys. I plan to calibrate in an open field tomorrow afternoon and I'll post a more detailed reply then (Wednesday, November 23rd).

However, this looks to be a bigger problem and other pilots are experiencing it too:

Four separate pilots (in the same thread) report the same exact GPS signal loss issue that I had tonight:
GPS lost mid flight (single incident, possible geographical problem)

Some guy on YouTube caught it happening live:

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For more detailed information, see our cookies page.

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After reviewing my logs, I had 18 satellites locked on when signal was lost and it went into ATTI mode.

The number of satellites is pretty immaterial. Everybody gets hung up on 'oh I had 15 satellites'
It is the HDOP/VDOP that is important not number of birds your GPS/Glonass RX can 'see'. This is indicated by the small bargraph display next to the number. DJI will say in the manual this is a 'signal strength' - it isn't. It is the quality of the positioning derived from timing errors.
12 or 16 sats with poor HDOP/VDOP is worthless.
DJI actually removed the number from the Go app around 14 months ago but so many people complained because they needed their number back that they reinstated it (wrongly in my opinion) since it gives a false sense of security.
If there are a large cluster of sats low on the horizon then then you will have a large horizontal dilution of precision and hence the positioning errors (or worse for some, the aircraft drops into Atti).
Pay attention to the bargraph/signal strength style display not some meaningless number.

 

[msinger]

Do you recommend Litchi because it can record your device's screen?

The Apple version of Litchi can record the screen. If you're going to use DJI GO, then try one of these screen recorders.

I own Litchi, but I don't use it often since DJI GO meets my needs. You'll need DJI GO to register your Mavic, update the firmware, and setup some other settings not available in 3rd party apps, so give it a shot before you try anything else. If you really get into flying waypoint missions, then a 3rd party app like Litchi would be worth considering.

 

[generaltso]

I had a similar experience today, which scared me. I've flown the Mavic plenty of times without any issues other than gimbal judder sometimes in Sport Mode. I did a chat with DJI Support about the gimbal judder, and they said to do an IMU calibration and a gimbal calibration. So I did both of those and took it out for a test flight. I didn't immediately see the judder, so I think that may have fixed that issue. However, after flying around for about 10 minutes, the Mavic suddenly switched to Atti mode and started drifting with the wind. I was high enough that I didn't have to worry about hitting anything, but I was struggling to get it back to the home point. On my way back to home, it switched back to GPS mode and a breathed a sigh of relief. But it was short lived because it switched back to Atti mode about 10 seconds later, and this time it stayed that way. It was a struggle and scary, but I was able to get the bird back to me and land it without crashing. Right after I landed, it switched back to GPS mode. I took off and flew back and forth right in front of me a little bit, and it stayed in GPS mode fine. Now I'm kinda spooked. I've never flown in Atti mode, so the drifting at 350 feet was a real challenge for me. Not having any map or direction data sure didn't help.

The Mavic had a clear open view of the sky and locked on plenty of satellites before it had issues. Is it bad that I didn't calibrate the compass after calibrating the IMU and gimbal? Could that have caused the loss of GPS? I sure hope so because at least then I'll know what caused it and won't need to worry about it happening next time.

 

[m0j0]

I'm a stay away from calibrating the IMU guy. I'm a leave the compass alone guys as well.. but... if you calibrate the IMU you should calibrate the compass. Check the compass calibration thread. There is a lot of useful info in there.


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[generaltso]

I'm a stay away from calibrating the IMU guy. I'm a leave the compass alone guys as well.. but... if you calibrate the IMU you should calibrate the compass. Check the compass calibration thread. There is a lot of useful info in there.

I usually stay way from calibrations as well, but since DJI specifically told me to do an IMU and Gimbal calibration, I did. In hindsight, I know I should have done a compass calibration as well, but is it likely that skipping the compass calibration after an IMU calibration would cause GPS issues?

 

[flumpet]

Concrete typically. But other times, just a gravel driveway or road.


Yes, and I typically have to move far away from them for compass calibration to complete successfully. I've noticed even a small drain pipe cover in the ground can affect the results of the calibration. I also make sure to remove my phone and keys from my pockets.

Best place to calibrate is over organic soft ground like a grass patch. Avoid roads and pavements as there are lots of metal and rebar contained within them.

 

[Mako79]

I had a similar experience today, which scared me. I've flown the Mavic plenty of times without any issues other than gimbal judder sometimes in Sport Mode. I did a chat with DJI Support about the gimbal judder, and they said to do an IMU calibration and a gimbal calibration. So I did both of those and took it out for a test flight. I didn't immediately see the judder, so I think that may have fixed that issue. However, after flying around for about 10 minutes, the Mavic suddenly switched to Atti mode and started drifting with the wind. I was high enough that I didn't have to worry about hitting anything, but I was struggling to get it back to the home point. On my way back to home, it switched back to GPS mode and a breathed a sigh of relief. But it was short lived because it switched back to Atti mode about 10 seconds later, and this time it stayed that way. It was a struggle and scary, but I was able to get the bird back to me and land it without crashing. Right after I landed, it switched back to GPS mode. I took off and flew back and forth right in front of me a little bit, and it stayed in GPS mode fine. Now I'm kinda spooked. I've never flown in Atti mode, so the drifting at 350 feet was a real challenge for me. Not having any map or direction data sure didn't help.

The Mavic had a clear open view of the sky and locked on plenty of satellites before it had issues. Is it bad that I didn't calibrate the compass after calibrating the IMU and gimbal? Could that have caused the loss of GPS? I sure hope so because at least then I'll know what caused it and won't need to worry about it happening next time.

I know, If the compass is out whack or gets heavy interference mid flight (close to fences etc), then the Mavic will switch into ATTI to stop the fly-away. The bad compass data and GPS data is now conflicting and to prevent the confliction/fly-away, DJI has made it switch to ATTI.

Like everyone has said, recalibrate your compass in an open grassy field. And try taking off from an elevated card board box if you think the ground is full of rebar etc.

 

[Mr Spock]

Does the mavic have course lock like the p3a p3ps? In atti mode would help get it back easier?

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[generaltso]

Does the mavic have course lock like the p3a p3ps? In atti mode would help get it back easier?

It does, but I don't think any of the flight modes can be used in atti mode.

 

[younumpty]

Z. . B !.!b. !.! MbzzzzybzbbbbxlxlxlldA,aaasSas,seessdSessafsasasaSsASS


Fly safe and within the law. Protect our hobby... [emoji482]

 

[generaltso]

So, is it likely that calibrating the IMU without calibrating the compass is what caused me to switch to atti mode mid-flight? If I calibrate the compass before the next flight, is it unlikely to happen again?