Mavic Air fly-away with no luck to find it. SOLVED

[InvisibleName]

It's really unfortunate that doing the Yaw check before launch isn't mentioned in any DJI documetation. It's been mentioned in these forums and the DJI forum several times so, hopefully, most pilots are aware of this check.


I think the one you want to look at is the red triangle heading indicator on the map display.
View attachment 39014

No, I mean this:

 

[BudWalker]

No, I mean this:

But, with this don't you have to use a handheld compass, know the geomagnetic declination and then apply it? At least for me it's a lot easier to look at the heading indicator on the map and compare that to what I can see.

 

[MustangPhil]

You may have pointed that already, but would’t it be possible for the App to compare the compass ‘guessed heading’ that may be wrong due to magnetic distorsion with the GPS heading (compare last known gps position with actual gps position)
If the compass says ‘going south’ and the Gps says ‘going north’ it would trigger a function ‘something_stinks’ that would engage a kind of error warning and a ‘auto-land with Gps info only’ ?

 

[sar104]

You may have pointed that already, but would’t it be possible for the App to compare the compass ‘guessed heading’ that may be wrong due to magnetic distorsion with the GPS heading (compare last known gps position with actual gps position)
If the compass says ‘going south’ and the Gps says ‘going north’ it would trigger a function ‘something_stinks’ that would engage a kind of error warning and a ‘auto-land with Gps info only’ ?

The compass isn't the primary source of yaw data - that comes from the rate gyros. In flight the compass is rarely wrong - it's the rate gyro data that is incorrect due to incorrect yaw initialization on the ground (where the compass was wrong). But your basic point is correct; it is actually the disagreement between the IMU yaw from the rate gyros and the compass data that leads to the yaw and compass errors and, eventually, a switch to ATTI mode. In the meantime, before that happens, the GPS data tell the FC that it is moving in the wrong direction when it is in fact moving in the right direction (relative to the aircraft), leading to the inappropriate corrective actions by the FC and unstable flight.

 

[BudWalker]

You may have pointed that already, but would’t it be possible for the App to compare the compass ‘guessed heading’ that may be wrong due to magnetic distorsion with the GPS heading (compare last known gps position with actual gps position)
If the compass says ‘going south’ and the Gps says ‘going north’ it would trigger a function ‘something_stinks’ that would engage a kind of error warning and a ‘auto-land with Gps info only’ ?

Something similar to this already happens on the Mavic. The Flight Controller keeps track of expected location vs the GPS location. When they don't match a "compass error" in the form of a GPS_POSITION_NONMATCH, SPEED_ERROR_LARGE,YAW_ERROR_LARGE, or COMPASS_ERROR_LARGE error will be issued.

 

[BudWalker]

The compass isn't the primary source of yaw data - that comes from the rate gyros. In flight the compass is rarely wrong - it's the rate gyro data that is incorrect due to incorrect yaw initialization on the ground (where the compass was wrong). But your basic point is correct; it is actually the disagreement between the IMU yaw from the rate gyros and the compass data that leads to the yaw and compass errors and, eventually, a switch to ATTI mode. In the meantime, before that happens, the GPS data tell the FC that it is moving in the wrong direction when it is in fact moving in the right direction (relative to the aircraft), leading to the inappropriate corrective actions by the FC and unstable flight.

Oops, cross posted.

 

[sar104]

Oops, cross posted.

That's fine - between us I think we have it covered.

 

[InvisibleName]

But, with this don't you have to use a handheld compass, know the geomagnetic declination and then apply it? At least for me it's a lot easier to look at the heading indicator on the map and compare that to what I can see.

Sar, step in if I’m wrong. When you initialise the Air the red arrow represents the direction it thinks it’s pointing. If you then compare this by physically looking at your drone, they should align - there’s no need to use a magnetic compass. The problem that Sar is talking about should be avoided if you ALWAYS check for this alignment before takeoff. If they are not aligned, you can almost guarantee a problem in flight.

 

[BudWalker]

Sar, step in if I’m wrong. When you initialise the Air the red arrow represents the direction it thinks it’s pointing. If you then compare this by physically looking at your drone, they should align - there’s no need to use a magnetic compass. The problem thar Sar is talking about should be avoided if you ALWAYS check for this alignment before takeoff. If they are not aligned, you can almost guarantee a problem in flight.

I think we're in agreement that we're trying to detect if the FC's idea of Yaw is correct - I've been saying this for a couple of years now. The question is what is the easiest way to determine that. I get it now that the radar display can be used for that but it requires that the tablet compass data be used. There aren't any assurances that the tablet compass data is accurate or calibrated. I tried using the radar display just now and it has an error of 15° to 20°.

IMHO using the map display heading indicator is the most robust method. It relies on the least data and that data is accurate and calibrated. Also, it's not necessary to align the tablet with the Mavic. But, you should do what you're most comfortable with

 

[MustangPhil]

Ok, now it’s much clearer. Thanks to all of you for clarifications.

 

[alexbutenkofi]

Now if you still interested whats the result of this story, read following....
So this is the answer I received from dji after I have sent them as much info and files as I could.
DJI:
"For the unfortunate incident happened to your drone, we have confirmed it as a warranty case according to our analysis.
We would like to offer you a replacement, Mavic Air(Arctic White) without charger and remote. Please kindly inform us below:
Shipping address:
Contact name:
Phone number:
----------If the model is incorrect, please let us know.
----------Sorry that it is not available to offer another model even if you will pay the different, or to credit the value to your account.
Should you have more question, please reply to this email directly within 15 calendar days. Then we will contact you via email in 2-3 working days.
"
ME:
"Hello, I am glad to hear it! I was thinking that there will be a lot of troubles and discussions around my case, but no and thank you for your fast and professional work!
Can you clear up for me and describe the reason of current "fly away" case, so that I could avoid this to happen in future? Thank you!
I agree with your offer and will be glad to receive a new Mavic Air(Arctic White). Can you confirm that one battery is included? Thank you!
"
DJI:
"For your case, the incident was caused by possible compass interference. Tall structures and large metal structures may affect the accuracy of the onboard compass and GPS system. Please pay attention to the flight environment and better to calibrate the compass regularly.
Many thanks for the information.
The replacement of Mavic Air(Arctic White) without charger and remote would be arranged by the logistics department later. And there will be one battery included.
I have informed my colleagues to follow up on your case and they will assist you directly. "

That's all for now. I am glad to get a new drone, but what's your thoughts on reason DJI have mentioned and their flight suggestions?

 

[InvisibleName]

Now if you still interested whats the result of this story, read following....
So this is the answer I received from dji after I have sent them as much info and files as I could.
DJI:
"For the unfortunate incident happened to your drone, we have confirmed it as a warranty case according to our analysis.
We would like to offer you a replacement, Mavic Air(Arctic White) without charger and remote. Please kindly inform us below:
Shipping address:
Contact name:
Phone number:
----------If the model is incorrect, please let us know.
----------Sorry that it is not available to offer another model even if you will pay the different, or to credit the value to your account.
Should you have more question, please reply to this email directly within 15 calendar days. Then we will contact you via email in 2-3 working days.
"
ME:
"Hello, I am glad to hear it! I was thinking that there will be a lot of troubles and discussions around my case, but no and thank you for your fast and professional work!
Can you clear up for me and describe the reason of current "fly away" case, so that I could avoid this to happen in future? Thank you!
I agree with your offer and will be glad to receive a new Mavic Air(Arctic White). Can you confirm that one battery is included? Thank you!
"
DJI:
"For your case, the incident was caused by possible compass interference. Tall structures and large metal structures may affect the accuracy of the onboard compass and GPS system. Please pay attention to the flight environment and better to calibrate the compass regularly.
Many thanks for the information.
The replacement of Mavic Air(Arctic White) without charger and remote would be arranged by the logistics department later. And there will be one battery included.
I have informed my colleagues to follow up on your case and they will assist you directly. "

That's all for now. I am glad to get a new drone, but what's your thoughts on reason DJI have mentioned and their flight suggestions?

OMG!!! Not much else I can say! I'm speechless!!!!

 

[Tinmania]

OMG!!! Not much else I can say! I'm speechless!!!!

I don't see what is so surprising. It wasn't pilot error. DJI, who is known to reject even slightly bogus warranty claims, didn't think it was the pilot's fault, and will replace the Mavic. That was the right thing to do.

DJI needs to fix their FC logic to switch to ATTI faster and/or make it well known to check actual heading before flight. On another level they might want to rethink that vision compass idea.


Mike

 

[InvisibleName]

I don't see what is so surprising. It wasn't pilot error. DJI, who is known to reject even slightly bogus warranty claims, didn't think it was the pilot's fault, and will replace the Mavic. That was the right thing to do.

DJI needs to fix their FC logic to switch to ATTI faster and/or make it well known to check actual heading before flight. On another level they might want to rethink that vision compass idea.


Mike

You misunderstood me, it wasn’t that he didn’t deserve a replacement, it was the fact that DJI gave him one that has me speechless!

 

[Tinmania]

You misunderstood me, it wasn’t that he didn’t deserve a replacement, it was the fact that DJI gave him one that has me speechless!

Even a broken clock gets it right twice a day.



Mike

 

[Canuk]

Dji is a strange bunch for sure . Our local hobbie store sold a Air to a fire fighter from town . On his very first flight he was about 10 minutes in and
Over the local river taking pictures of the town when 2 motors on one end quit without any warning . It did a flip and went splash . Dji told the guy it will be 3 months before they make there decision if it will be replaced . That’s a long freaking time to wait . People would lose there minds if there car broke down and was told wait 3 months before we decide if it’s warranty or not

 

[sar104]

Now if you still interested whats the result of this story, read following....
So this is the answer I received from dji after I have sent them as much info and files as I could.
DJI:
"For the unfortunate incident happened to your drone, we have confirmed it as a warranty case according to our analysis.
We would like to offer you a replacement, Mavic Air(Arctic White) without charger and remote. Please kindly inform us below:
Shipping address:
Contact name:
Phone number:
----------If the model is incorrect, please let us know.
----------Sorry that it is not available to offer another model even if you will pay the different, or to credit the value to your account.
Should you have more question, please reply to this email directly within 15 calendar days. Then we will contact you via email in 2-3 working days.
"
ME:
"Hello, I am glad to hear it! I was thinking that there will be a lot of troubles and discussions around my case, but no and thank you for your fast and professional work!
Can you clear up for me and describe the reason of current "fly away" case, so that I could avoid this to happen in future? Thank you!
I agree with your offer and will be glad to receive a new Mavic Air(Arctic White). Can you confirm that one battery is included? Thank you!
"
DJI:
"For your case, the incident was caused by possible compass interference. Tall structures and large metal structures may affect the accuracy of the onboard compass and GPS system. Please pay attention to the flight environment and better to calibrate the compass regularly.
Many thanks for the information.
The replacement of Mavic Air(Arctic White) without charger and remote would be arranged by the logistics department later. And there will be one battery included.
I have informed my colleagues to follow up on your case and they will assist you directly. "

That's all for now. I am glad to get a new drone, but what's your thoughts on reason DJI have mentioned and their flight suggestions?

Good result, and noteworthy that they decided that a lost aircraft after a yaw initialization error was a full warranty issue. Not everyone has been so lucky with their response to the same situation.

 

[BudWalker]

Good result, and noteworthy that they decided that a lost aircraft after a yaw initialization error was a full warranty issue. Not everyone has been so lucky with their response to the same situation.

Unheard of would be the way I'd describe it.

 

[sar104]

Unheard of would be the way I'd describe it.

I wasn't sure whether there had been none, but I certainly can't remember one of these incidents where they replaced the aircraft.

 

[Timbo~SYD]

The only exception I can recall recently was an aircraft with a broken z-axis gyro, which is a hardware failure that leads to exactly the same kind of yaw error.

Would that have shown up in the sensor status display or elsewhere? Or was this something that you were able to deduce from flight data?

Btw I really appreciate the effort that you, and other similarly talented members, put into forum. It is very generous!