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LOST MAVIC PRO - Why?
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2926 62 2017-12-27
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VANDAN
lvl.2
Flight distance : 10600 ft
South Africa
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Hi all. I recently lost my Mavic Pro and wanted to understand why since I honestly believe I did nothing wrong. I took off and within 50 seconds, the drone lost GPS signal and lost connection to my remote controller. It subsequently went on ATTI mode and flew away with the wind. Since it lost connection to my RC, I had no way of controlling it and flying it back to me.

What can I do to understand what went wrong - I'm a newbie.

Thanks!
Vandan
2017-12-27
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jcgoobee
First Officer
Flight distance : 476119 ft
United States
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There are some points that you should be aware of before taking off.

- How many SATs were seen before you took off?
- Did you enable Precision Landing when taking off?
- Did you do a compass calibration prior to taking off?
- If your drone was brand new, first flight, did you calibrate the IMU?

ALl these four base points could be the contributing factors to your drone flying off.
2017-12-27
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4WDaus
Captain
Flight distance : 1187257 ft
Australia
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Have you tried analysing the flight data on http://airdata.com ?
2017-12-27
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DroneFlying
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I recently lost my Mavic Pro and wanted to understand why since I honestly believe I did nothing wrong.

You may not have done anything wrong, but there's no way to know without more information. Please upload the TXT file (flight log) from your mobile device to PhantomHelp using these instructions and provide a link to it here. You may also choose to upload to AirData as 4WDaus suggested, but PhantomHelp provides quite a bit more useful information about the flight than AirData. In fact, PhantomHelp is specifically intended for looking at cases like this while AirData isn't.
2017-12-27
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4WDaus
Captain
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Australia
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DroneFlying Posted at 2017-12-27 18:26
I recently lost my Mavic Pro and wanted to understand why since I honestly believe I did nothing wrong.

You may not have done anything wrong, but there's no way to know without more information. Please upload the TXT file (flight log) from your mobile device to PhantomHelp using these instructions and provide a link to it here. You may also choose to upload to AirData as 4WDaus suggested, but PhantomHelp provides quite a bit more useful information about the flight than AirData. In fact, PhantomHelp is specifically intended for looking at cases like this while AirData isn't.

Thanks for the pointer on phantumhelp!
2017-12-27
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Kevin_d
lvl.4
Flight distance : 4219 ft
United States
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jcgoobee Posted at 2017-12-27 13:56
There are some points that you should be aware of before taking off.

- How many SATs were seen before you took off?

Hi JC... some questions for you or anyone that can answer.

- How many SATS are required? Why would the drone take off just because there's a lack of or no satellites? Can't the drone be flown without GPS?

- How does precision landing contribute to a fly-away?

- Would a bad compass cal cause the drone to ignore RC commands and just take off?

Finally, is the drone so sensitive and misbehaving that it will just take off? That sounds kind of scary to me. Why wouldn't the drone try to return home or simply try to land if it lost RC?
2017-12-27
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Woe
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Phantomhelp is a great resource
2017-12-27
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DroneFlying
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Kevin_d Posted at 2017-12-27 18:36
Hi JC... some questions for you or anyone that can answer.

- How many SATS are required? Why would the drone take off just because there's a lack of or no satellites? Can't the drone be flown without GPS?

How many SATS are required?

The number of satellites isn't as important as the "GPS health", which is represented in the app by the green bars. You need at least four of the possible five to fly in P-mode.

Why would the drone take off just because there's a lack of or no satellites?

If by "take off" you mean drift, it could happen because without GPS the drone has no way of knowing where it is or how to stay in the same spot.

Can't the drone be flown without GPS?

Yes, but ATTI mode takes a little more attention and skill.

How does precision landing contribute to a fly-away?

I can't think of any way that it would / does.

Would a bad compass cal cause the drone to ignore RC commands and just take off?

Bad compass data can cause the aircraft to fly erratically because the aircraft can't hold its position if it doesn't know which direction it should fly in to do so. That would more often be caused by magnetic interference on the ground, though, and not a bad calibration.

Finally, is the drone so sensitive and misbehaving that it will just take off?

Very few people have lost their Mavics in this way, so in general, no.

Why wouldn't the drone try to return home or simply try to land if it lost RC?

By default it will try to return home, but again, if it doesn't have both good compass and GPS data then it won't know how to do that. Also, if the wind is too strong for it to do so then the quality (or lack of it) of the data won't matter.
2017-12-27
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jcgoobee
First Officer
Flight distance : 476119 ft
United States
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DroneFlying has answered most of your questions but I want to take a moment to address the notion of  "How does precision landing contribute to a fly-away?"

It doesn't contribute to fly-away directly. HOWEVER, if your aircraft senses something has gone wrong and decided to initiate the fail-safe RTH, it would know exactly where it should be heading back, if Precision Landing has been initiated. This is why I always make it a habit to calibrate my compass in a new location, enable Precision Landing.

Hope this clarifies it.
2017-12-27
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$gambino$
First Officer
Flight distance : 1563980 ft
United States
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Jcgoobee why would he have to do imu or compass cal? Just because its new? No  he should do it if imu values are high or app tells him to cal compass otgerwise ge shouldnt mess with it
2017-12-27
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$gambino$
First Officer
Flight distance : 1563980 ft
United States
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Precision landing has nothing to do with compass or gps and how the drunk gets back all that does is precisely lanyard run where it initially took its snapshot at the beginning of the flight so instead of Landing in a two to three meter radius it will land within inches of where you took off. It's just using the bottom sensors. I think you have a few things messed up ....compass cal wont help with precision landing!
2017-12-27
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$gambino$
First Officer
Flight distance : 1563980 ft
United States
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Also precision landing does not activate until the craft is over the home point and is low enough to use its bottom sensors. so how would Precision Landing know where to head back?
2017-12-27
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DJI Thor
Administrator
Flight distance : 13602 ft
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Vandan, sorry to hear about the loss of your drone, it must be painful. Had you reported the case to our support? If you haven't, please contact our support and start a ticket, we will start a data analysis to find out the reason if the drone is under warranty period (12 months). Here’s the link to contact us: http://www.dji.com/support
If you had, please kindly leave me with your case number, I would like to check more details about it. Sorry again for your loss.
2017-12-27
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VANDAN
lvl.2
Flight distance : 10600 ft
South Africa
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jcgoobee Posted at 2017-12-27 13:56
There are some points that you should be aware of before taking off.

- How many SATs were seen before you took off?

- How many SATs were seen before you took off?
There were 14 satellites based on the flight log.

- Did you enable Precision Landing when taking off?
I don't think so. I did set the home point for RTH though.

- Did you do a compass calibration prior to taking off?
No I didn't. Should I be doing this before every flight? I thought it would prompt me before I take off if the compass needs to be calibrated? This was my 6th/7th flight and I calibrated before I used it for the first time.

- If your drone was brand new, first flight, did you calibrate the IMU?
I calibrated when I got it in the first week of December.
2017-12-27
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VANDAN
lvl.2
Flight distance : 10600 ft
South Africa
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Hi everyone. This is the link to my flight analysis on PhantomHelp:

http://www.phantomhelp.com/logviewer/G3GYDWOJBEAOBM9AXBX2/

I'm new to all of this and really appreciate all your help!
2017-12-27
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VANDAN
lvl.2
Flight distance : 10600 ft
South Africa
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DJI Thor Posted at 2017-12-27 22:10
Vandan, sorry to hear about the loss of your drone, it must be painful. Had you reported the case to our support? If you haven't, please contact our support and start a ticket, we will start a data analysis to find out the reason if the drone is under warranty period (12 months). Here’s the link to contact us: http://www.dji.com/support
If you had, please kindly leave me with your case number, I would like to check more details about it. Sorry again for your loss.

Hi. Thanks for your message.

My ticket number is 905651

I bought the drone on 24 November 2017 so it definitely is within the warranty period.

To make it clear this is what I think happened (you can clarify this based on my flight analysis). I took off, set the RTH point. I had full connection to 14 satellites when I took off. 2 things happened: the drone lost connection to the GPS signal  (and went to ATTI mode) and the drone lost connection to my RC (and as a result I couldnt fly the drone back to me and hence it got taken away by the wind in ATTI).

My view is if the GPS signal was lost but I still had connection to my RC, I could've flown in back to me. Similarly if the RC connection was lost but I still had GPS signal then it would've RTH.

I feel frustrated because I feel I did nothing wrong and there was an issue with the drone. Please can you follow up so we can resolve this issue.

Thanks
Vandan
2017-12-27
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Jos A
Captain
Netherlands
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Well this is the well known major fault  from Last FW and dji go 4 app.
You read it many times now!
2017-12-28
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Nelsonlee
First Officer
Flight distance : 1958609 ft
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Malaysia
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This is how i lost my mavic.....

2017-12-28
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Jos A
Captain
Netherlands
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well you know now how far you can fly
2017-12-28
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Rooivalk
lvl.4
Flight distance : 4764767 ft
South Africa
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VANDAN Posted at 2017-12-27 23:56
Hi. Thanks for your message.

My ticket number is 905651

Sorry to hear about you're loss. Do you know the wind direction when you lost the drone?  If it was North Westerly then it would drift out to see into the bay, but with south easterly wind, it will be over land. I am on the other side of Walker Bay. In you're flight record it shows "yaw error" and what I could find is "Magnectic field interference". Where there any metal close to the drone at take off?
2017-12-28
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Nees
Second Officer
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Belgium
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jcgoobee Posted at 2017-12-27 13:56
There are some points that you should be aware of before taking off.

- How many SATs were seen before you took off?

And again someone giving false info. IMU should not be calibrated unless the devices asks for it (confirmed several times by DJI, doing it might even make things worse) I have never done it since I have mine, just keep an eye on the sensors before takeoff.

Doing compass-calibration is also a bad thing if you don't know what you are doing. For example: In my home, when I have mine on the floor, it will scream MAGNETIC INTERFERENCE due to cables under the floor. When I lift it, it is gone, so I don't care about that. This is why, when you get a compass error, you should not immediatly calibrate, as when you will be airborn, the compass will return normal with a good calibration. There is no metal in the air! So doing a compass calibration with interference under the floor without knowing it, might give a good compass on the ground but a BAD ONE in the air as the conditions change, suddenly no metal/interference. So I lift off about 2m in the air. Check compass, if all are at minimum, I fly.

The reason the RC disconnected has nothing to do with IMU or Compass. This should NOT happen for any reason. I have taken off with lower sats and kept it steady why it was gaining more sats and while it does, you will notice small reactions from the craft as it gets more and more precise. So again, should not be a problem as long as you have RC connected.
2017-12-28
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M.C. Pilot
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$gambino$ Posted at 2017-12-27 19:48
Jcgoobee why would he have to do imu or compass cal? Just because its new? No  he should do it if imu values are high or app tells him to cal compass otgerwise ge shouldnt mess with it

100% agree.
2017-12-28
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M.C. Pilot
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Nees Posted at 2017-12-28 01:00
And again someone giving false info. IMU should not be calibrated unless the devices asks for it (confirmed several times by DJI, doing it might even make things worse) I have never done it since I have mine, just keep an eye on the sensors before takeoff.

Doing compass-calibration is also a bad thing if you don't know what you are doing. For example: In my home, when I have mine on the floor, it will scream MAGNETIC INTERFERENCE due to cables under the floor. When I lift it, it is gone, so I don't care about that. This is why, when you get a compass error, you should not immediatly calibrate, as when you will be airborn, the compass will return normal with a good calibration. There is no metal in the air! So doing a compass calibration with interference under the floor without knowing it, might give a good compass on the ground but a BAD ONE in the air as the conditions change, suddenly no metal/interference. So I lift off about 2m in the air. Check compass, if all are at minimum, I fly.

Nees posted - "IMU should not be calibrated unless the devices asks for it (confirmed several times by DJI, doing it might even make things worse) I have never done it since I have mine, just keep an eye on the sensors before takeoff."


True. Bought a P4P recently and right out of the box it flew perfectly. No calibrations needed - still hasn't ask for it either.

2017-12-28
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fanse6566494
lvl.4
Flight distance : 152411 ft
Malaysia
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Pilot error / mistake! Flied too far and did not have enough battery juice to reach home point.
2017-12-28
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DroneFlying
Captain
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VANDAN Posted at 2017-12-27 23:36
Hi everyone. This is the link to my flight analysis on PhantomHelp:

http://www.phantomhelp.com/logviewer/G3GYDWOJBEAOBM9AXBX2/

I recently lost my Mavic Pro and wanted to understand why since I honestly believe I did nothing wrong.

It looks like there were a couple of factors that contributed to the loss: the disconnections and the switch to ATTI mode.

The disconnections started happening almost immediately; the first one took place 10 seconds into the flight while the Mavic was still right in front of you. If I encountered that I'd end the flight right away, but that's partly because I've flown a bit and know that it isn't normal. On the other hand, a new Mavic owner wouldn't necessarily recognize that behavior as a problem, and since it technically shouldn't occur anyway I'm not sure what DJI's position will be. I do know that we regularly see posts from people who have disconnection problems, some of which are resolved by switching the phone to airplane mode.

The other part of the problem was the switch to ATTI mode. The Mavic is still very flyable in ATTI mode, but as you noted, without a connection there was no way you could control it. As best I can tell, the ATTI  mode change was in no way your fault, as it occurred (as you pointed out) about 50 seconds into the flight. Offhand I'd guess that a compass calibration might have prevented it, but that's just speculation on my part.

The ATTI mode problem was arguably the bigger factor in the loss, as the disconnection should have caused the Mavic to RTH instead of being blown away by the wind. Unfortunately, having a fully charged battery actually worked against you, because with 96% of the battery's capacity remaining on last contact it could have drifted a while. It might also have eventually reverted back to P-mode and attempted to RTH, but there's no way to know what happened unless you happen to find it (or someone else does and contacts you).

Anyway, good luck with your DJI case and please let us know how it turns out.
2017-12-28
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jcgoobee
First Officer
Flight distance : 476119 ft
United States
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Guys, I only mentioned about IMU calibration when operating the aircraft the first time, NOT every time. The Aircraft was manufactured from overseas and shipped to wherever the pilot's home location. A lot of things could have happened. A full reset of IMU and compass calibration should be initiated. Please correct me if I'm wrong.

Based on what VANDAN has elaborated, I don't think this fly-away is the user error. DJI should study the flight log and see what they can do.
2017-12-28
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HomePoint
First Officer
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Most people have not read the most recent change as when to calibrate in the updated manual?
2017-12-28
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Griffith
First Officer
Flight distance : 98537 ft
United States
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It appears that the GPS count was always high throughout the flight (although that doesn't mean that the received signal was strong).  The cause of going into ATTI mode was an apparent  consistent yaw error that started 49 seconds into the flight at 177 ft altitude and 120 feet distance.  Interestingly, there is very little change in recorded yaw (~142 degrees)  during the entire flight  - which corresponds to no rudder commands after the  4.2 sec mark, although throttle and elevator commands were received - wrong stick, OP ???

The AC was moving (backwards) approximately north - with Mavic pointed SW -  at 27 mph with NO throttle - so there must have been a helluva headwind.  I don't know it that would have caused the "YAW ERROR".  With the lack of any compass errors, I would surmise that was the case.

The downlink wasn't lost long enough (in the brief log) to initiate RTH.  I think the Mavic still had sufficient GPS to RTH -  but the yaw error was obfuscating the flight control system.
2017-12-28
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W1zzard
Second Officer
Russia
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Griffith Posted at 2017-12-28 08:18
It appears that the GPS count was always high throughout the flight (although that doesn't mean that the received signal was strong).  The cause of going into ATTI mode was an apparent  consistent yaw error that started 49 seconds into the flight at 177 ft altitude and 120 feet distance.  Interestingly, there is very little change in recorded yaw (~142 degrees)  during the entire flight  - which corresponds to no rudder commands after the  4.2 sec mark, although throttle and elevator commands were received - wrong stick, OP ???

The AC was moving (backwards) approximately north - with Mavic pointed SW -  at 27 mph with NO throttle - so there must have been a helluva headwind.  I don't know it that would have caused the "YAW ERROR".  With the lack of any compass errors, I would surmise that was the case.

This messages:

Yaw Error
Compass Error. Exit P-GPS Mode; Yaw Error
Yaw Error
Yaw Error
Yaw Error
Yaw Error
In Flight, working IMU encounters heading exception,please switch to atti mode if craft behave abnormally; Yaw Error

Looks like compass fails first, and inflict yaw error, but anyway atti should work.

also as Griffith mention speed changed from 5mph to 30mph in 6 seconds without any controller stick input, that is strange.

2017-12-28
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Griffith
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W1zzard Posted at 2017-12-28 11:12
This messages:

Yaw Error

speed changed from 5mph to 30mph in 6 seconds without any controller stick input, that is strange.

That was most likely wind.  From the log information, it looked like the AC was flying backwards at that point.  I saw no indication that OP tried to correct direction (i,.e. no rudder commands - only intermittent throttle and elevator - but there were several downlink failures during that time).
2017-12-28
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VANDAN
lvl.2
Flight distance : 10600 ft
South Africa
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Yes. The reason there weren't any rudder commands was because i barely had time to control it with my RC as it was losing connection all the time.

Regarding the winds, yes there were winds but I got no warnings about excessive winds on my RC - upon takeoff the Mavic was holding strongly against the wind. The day before (25 December) I flew it in stronger winds and had no issues (I got a warning to make sure it was in my line of sight due to the winds but got no such warning on the day I lost it).
2017-12-28
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VANDAN
lvl.2
Flight distance : 10600 ft
South Africa
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DroneFlying Posted at 2017-12-28 06:41
I recently lost my Mavic Pro and wanted to understand why since I honestly believe I did nothing wrong.

It looks like there were a couple of factors that contributed to the loss: the disconnections and the switch to ATTI mode.

When the disconnection happened, according to the flight plan, did the RC connection come back briefly? I don't recall the RC getting connection again?

Eitherways, when the RC lost connection (and before the GPS signal was lost), shouldn't the Mavic have returned to home?
2017-12-28
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VANDAN
lvl.2
Flight distance : 10600 ft
South Africa
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DJI have been in touch and have asked for the necessary flight details. I'll keep everyone updated as to the outcome. Hopefully this can be a learning experience for everyone.

Still don't have a clue why the RC connection was lost and why the GPS signal was lost (given the satellite connections).
2017-12-28
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DroneFlying
Captain
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VANDAN Posted at 2017-12-28 12:05
When the disconnection happened, according to the flight plan, did the RC connection come back briefly? I don't recall the RC getting connection again?

Eitherways, when the RC lost connection (and before the GPS signal was lost), shouldn't the Mavic have returned to home?

when the RC lost connection (and before the GPS signal was lost), shouldn't the Mavic have returned to home?

Normally yes, but without the ability to navigate by GPS -- which is essentially what happens in ATTI mode -- it had no idea how to return home.
2017-12-28
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W1zzard
Second Officer
Russia
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Ok, so, what i understand for now, i begin from end to beginning:

- RC connection lost and drone blown away by wind (but it should not happen normally because of failsafe)
- failsafe GPS mode was disabled (because of some compass error)

Main questions is:
what happen with compass that it unexpectedly failed (as i know mavic has 2 compasses exactly for such case if one is fail)?

What happen with RC signal? Because that distance about 500ft looks not very far. However after i check log and map closely..
Vandan, do you start flying from the bottom of the shore inside this stone walls?  And drone started to lose signal after it was behind that stone "walls"?
It could block signal very well and only possible direction for signal is open sea where no obstacles for signal to bounce back to drone like in city.
2017-12-28
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Gunship9
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W1zzard Posted at 2017-12-28 20:47
Ok, so, what i understand for now, i begin from end to beginning:

- RC connection lost and drone blown away by wind (but it should not happen normally because of failsafe)

Yeah, I was wondering if he lost RC link when he flew it behind the walls/cliffside in ATTI mode.  You have to fly it back to you when in ATTI and not fly in a way that will cause you to loose the radio link.
2017-12-28
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Satish
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South Africa
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Hi Vandaan. Sorry for your loss.  Looking forward to finding out why this happened.
2017-12-28
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VANDAN
lvl.2
Flight distance : 10600 ft
South Africa
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W1zzard Posted at 2017-12-28 20:47
Ok, so, what i understand for now, i begin from end to beginning:

- RC connection lost and drone blown away by wind (but it should not happen normally because of failsafe)

Vandan, do you start flying from the bottom of the shore inside this stone walls?  And drone started to lose signal after it was behind that stone "walls"?
It could block signal very well and only possible direction for signal is open sea where no obstacles for signal to bounce back to drone like in city.


The drone lost signal while it was in my line of sight (i.e. it didn't go behind any of the "cliffs"). I literally took off, took the drone up at a safe height and around then it lost connection. Here is the link to the cached video, you can see the point where the wind takes it away: https://www.dropbox.com/s/4zpq80 ... %2055%2005.mp4?dl=0

There was a small "cliff" next to me but I never flew it behind the cliff. i.e. there wasn't anything that was in between me and the drone.
2017-12-28
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VANDAN
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Flight distance : 10600 ft
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Gunship9 Posted at 2017-12-28 21:14
Yeah, I was wondering if he lost RC link when he flew it behind the walls/cliffside in ATTI mode.  You have to fly it back to you when in ATTI and not fly in a way that will cause you to loose the radio link.

The flight log will give the full details but by the time it got in ATTI mode i had lost RC connection hence couldnt do anything.

Also, in my view, I didn't fly it in a way that will cause me to lose radio link (as it was in my line of sight and nothing was in between me and the drone)
2017-12-28
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KabirTheSpark
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Flight distance : 68163 ft
South Africa
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VANDAN Posted at 2017-12-28 23:03
Vandan, do you start flying from the bottom of the shore inside this stone walls?  And drone started to lose signal after it was behind that stone "walls"?
It could block signal very well and only possible direction for signal is open sea where no obstacles for signal to bounce back to drone like in city.

Scary video. Based on the flight logs, this is quite clearly not a user error as I don't see any reasonable thing the pilot could have done to prevent this flyaway. Let's hope DJI will come to this conclusion too! Going to be following this closely
2017-12-28
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