Theory explaining how Mavic could drop down from skies... Your thoughts, please...

[Alex ROV]

Please guys... It might be very important...

I have developed a theory that explains why and how the Mavics are dropping down from the skies... I would like to hear your thoughts and contributions, please...

I have read lots of flight data logs that were published by its unffortunate pilots, trying to find any points in order to clarify what had happened, there 2 or 3 details that all events have in common, but there is one that highlight my attention since the first reported case: the last system message is always "MAVIC HAS LANDED"

Normally, in any other case of crashing, the last message is "LOST CONNECTION"... Even in case of battery disconnection, the app and remote controller loose connection with aircraft and "LOST CONNECTION" is the last recorded message in the log, which is correct. But with the dropping down events this message is never recorded, instead the last one says that the aircraft has landed and that means the end of a normaal regular flight.

My theory: the system thinks that Mavic has landed, or in other words, Mavic is touching a surface, then, when the pilot commands to go down, the motors go to shutdown, as is designed to happen.

Now, lets think: how does Mavic know that she has landed? Using her barometer... The air pressure given by altitude is given to the system by her barometer, and the computer uses this data to maintain her altitude. So, saying this, how does the computer know that Mavic is touching the ground (landed)? Because the pilot moves the stick down and the Mavic altitude DOES NOT change, in other words, the data that computer receives from her barometer DOES NOT change...

And what happens after, when the pilot keeps the stick down after landind? Motors shutdonw!

Long story short, my theory is that the barometer freezes its data in middle flight, middle air, making the computer assume that Mavic has landed... Then the motors shutdown as expected with stick down command.

I really would like to hear from DJI about this theory...

Now, in order to try to avoid this serious issue... Could we avoid that if we leave the Landing Protection feature always ON? I believe that in this case the system would ask the pilot to confirm the landing...
I would like to move from theory to practise... I will try to simulate that, holding the Mavic from the top, with my hand, not allowing her to go down... Then I will command the stick down. She will think that has landed and shut down the engines after short seconds. If that experiment happens, I believe we prove the cause of the problem.

Please, sorry by the very long text... But I would like to hear your thoughts... And if any of you guys could make contacts and forward this message to DJI techs, it would be much appreciate.

Many thanks!

UPDATE:

- Thanks everybody for the comments... Lets keep it, please, and try to reach DJI techs... Another piece of advice I believe we can take from here:
NEVER DO FULL STICK DOWN DURING THE FLIGHT...

- Yes! Mavic does shutdown the motors "thinking" that has landed when hand catched... So, if a glitch happens in middle air and the sensors dont update the altitude the Mavic will assume that has landed and possibly shutdown the motors... That's my theory...

- Combination Stick Command in middle flight would be shown on logs... But I have never seen CSC in these events...

 

[msinger]

But with the dropping down events this message is never recorded, instead the last one says that the aircraft has landed and that means the end of a normaal regular flight.

My theory: the system thinks that Mavic has landed, or in other words, Mavic is touching a surface, then, when the pilot commands to go down, the motors go to shutdown, as is designed to happen.

Can you post one log that shows an example of this?

 

[Anthony Viscomi]

I must be living in a vacuum, because I haven't been aware of any widespread issues of Mavics "dropping out of the sky". With that said, there are a fair amount of reports that the Sparks have this issue.

 

[Kilrah]

The only "motor shutdown in flight" events I've seen discussed were complete power losses.
No idea where you're pulling that from. Document with evidence if you want a discussion.

Of course sensors stopping to update would be likely to cause that, but would also be apparent in many other ways. Even without motor shutdown it would pretty certainly lead to a crash anyway.

 

[Alex ROV]

Can you post one log that shows an example of this?

Thanks! I'm looking at my browser on my devices but as I work offshore in a vessel I had private browsing all the time... Most of reports I saw on Facebook groups, some here... Of course I'm not counting those that seemed to be be pilot error...

 

[mpa]

the mavic is super complicated, so there are thousands of faults and permutations of failure modes possible.
once such example is the battery dislodging from its clips or prop failure. which have happened before but are generally due to user error

 

[msinger]

Thanks! I'm looking at my browser on my devices but as I work offshore in a vessel I had private browsing all the time... Most of reports I saw on Facebook groups, some here... Of course I'm not counting those that seemed to be be pilot error...

I've reviewed lots of logs and never saw one like you're describing above. When you find a log, please post it here. I'm assuming it'll be easier for you to track one down since you seem to be indicating this is occurring often.

 

[Alex ROV]

The only "motor shutdown in flight" events I've seen discussed were complete power losses.
No idea where you're pulling that from. Document with evidence if you want a discussion.

Of course sensors stopping to update would be likely to cause that, but would also be apparent in many other ways. Even without motor shutdown it would pretty certainly lead to a crash anyway.

Power loss was also my first thought but there will be a "Lost Connection" message recorded on the logs... I have never seen that... If only the sensors in charge for altitude (barometer, sonar, accel. or any combination) freeze for some seconds maybe that would not cause a crash, maybe just instability for seconds... The pilot would not "sense" or realise that...

 

[Kilrah]

The entire vertical control of the aircraft depends on the baro - if it froze your aircraft would either shoot up or down full speed anytime the stick isn't dead center.

 

[gnirtS]

A few things, firstly I'm very unconvinced that mavics are falling from the sky with any sort of regularity. Of the few incidences you can find online most boil down to user error it them failing to understand how the mavic works.

Secondly, a stuck barometer would be very very easy to see in the txt logs or the. Dat file and I haven't heard of a single example of it.
It's a theory but so far from what I can see lacks any evidence (or evidence of an actual problem in the first place)

 

[BudWalker]

Please guys... It might be very important...

I have developed a theory that explains why and how the Mavics are dropping down from the skies... I would like to hear your thoughts and contributions, please...

I have read lots of flight data logs that were published by its unffortunate pilots, trying to find any points in order to clarify what had happened, there 2 or 3 details that all events have in common, but there is one that highlight my attention since the first reported case: the last system message is always "MAVIC HAS LANDED"

Normally, in any other case of crashing, the last message is "LOST CONNECTION"... Even in case of battery disconnection, the app and remote controller loose connection with aircraft and "LOST CONNECTION" is the last recorded message in the log, which is correct. But with the dropping down events this message is never recorded, instead the last one says that the aircraft has landed and that means the end of a normaal regular flight.

My theory: the system thinks that Mavic has landed, or in other words, Mavic is touching a surface, then, when the pilot commands to go down, the motors go to shutdown, as is designed to happen.

Now, lets think: how does Mavic know that she has landed? Using her barometer... The air pressure given by altitude is given to the system by her barometer, and the computer uses this data to maintain her altitude. So, saying this, how does the computer know that Mavic is touching the ground (landed)? Because the pilot moves the stick down and the Mavic altitude DOES NOT change, in other words, the data that computer receives from her barometer DOES NOT change...

And what happens after, when the pilot keeps the stick down after landind? Motors shutdonw!

Long story short, my theory is that the barometer freezes its data in middle flight, middle air, making the computer assume that Mavic has landed... Then the motors shutdown as expected with stick down command.

I really would like to hear from DJI about this theory...

Now, in order to try to avoid this serious issue... Could we avoid that if we leave the Landing Protection feature always ON? I believe that in this case the system would ask the pilot to confirm the landing...
I would like to move from theory to practise... I will try to simulate that, holding the Mavic from the top, with my hand, not allowing her to go down... Then I will command the stick down. She will think that has landed and shut down the engines after short seconds. If that experiment happens, I believe we prove the cause of the problem.

Please, sorry by the very long text... But I would like to hear your thoughts... And if any of you guys could make contacts and forward this message to DJI techs, it would be much appreciate.

Many thanks!

UPDATE:

- Thanks everybody for the comments... Lets keep it, please, and try to reach DJI techs... Another piece of advice I believe we can take from here:
NEVER DO FULL STICK DOWN DURING THE FLIGHT...

- Yes! Mavic does shutdown the motors "thinking" that has landed when hand catched... So, if a glitch happens in middle air and the sensors dont update the altitude the Mavic will assume that has landed and possibly shutdown the motors... That's my theory...

- Combination Stick Command in middle flight would be shown on logs... But I have never seen CSC in these events...

It isn't the barometer that determines the AC is on the ground. The barometer is way to imprecise. It's the IMU (accelerometers) that determine this by sensing a lack of acceleration which would normally be caused by changes in motor speed. During a hand catch if the AC is moved only slightly the motors won't shut off.

 

[Alex ROV]

I've reviewed lots of logs and never saw one like you're describing above. When you find a log, please post it here. I'm assuming it'll be easier for you to track one down since you seem to be indicating this is occurring often.

I'm sure that you have seen much more logs and naturally can make a much better statistic sample for studies purposes... Have you seen the "lost connection" message on cases like that? Do you agree that a battery dislogged would give this message? What are your thoughts about this "false landing detection" theory?

Another friend says it has occured/reported more often with Spark... The way Sparks are designed would make more likely to happen with them! It looks like it matches the theory.

One case that comes easier to mind is a pilot in Israel... He was really piss off with that "Mavic has landed" and did not like when I highlighed this message... General assumption by then, including myself, was a precise shot by israeli security forces...

Many thanks!

 

[msinger]

What are your thoughts about this "false landing detection" theory?

I'm thinking it never happened. That's why I'm asking you to post a flight log that supports your first post above.

 

[Anthony Viscomi]

I'm thinking it never happened. That's why I'm asking you to post a flight log that supports your first post above.

 

[Alex ROV]

It isn't the barometer that determines the AC is on the ground. The barometer is way to imprecise. It's the IMU (accelerometers) that determine this by sensing a lack of acceleration which would normally be caused by changes in motor speed. During a hand catch if the AC is moved only slightly the motors won't shut off.

Very good tech contribution! If we forget about the "name" of the device or subsystem in charge for providing the indication that a landing has happened, lets say, in the rare case or possibility of this subsystem glitches for a few seconds, just enough to produce a "false landing" indication... Would the motors shut down? What catches my attention is the logs showing a regular end of flight, without "lost connection" warnings or messages...

Many thanks!

 

[msinger]

What catches my attention is the logs showing a regular end of flight, without "lost connection" warnings or messages...

Where are these logs though?

 

[geigy]

Interesting. I for one appreciate the effort that Alex ROV has put into this, whether or not it turns out to be true or not, this kind of analysis is an example of what is great about this board. Our own expertise and motivation are far superior to anything DJI can or will provide on an ongoing basis..

This brings up the issue of keeping a tally of log files, and various causes of crashes. I wonder if the healthy drone site does this sort of analysis. They would be in a great position to do a statistical analysis, since they collect thousands of log files.

 

[Anthony Viscomi]

Interesting. I for one appreciate the effort that Alex ROV has put into this, whether or not it turns out to be true or not, this kind of analysis is an example of what is great about this board. Our own expertise and motivation are far superior to anything DJI can or will provide on an ongoing basis..

This brings up the issue of keeping a tally of log files, and various causes of crashes. I wonder if the healthy drone site does this sort of analysis. They would be in a great position to do a statistical analysis, since they collect thousands of log files.

I too think that its admirable work done by Alex ROV, but I'm still perplexed on where the "Mavics dropping from the sky" derives from. I've been lurking on these forums for quite some time and never seen wide-spread "mavic dropping from sky issues", Karma..yes. Spark...yes. In regards to DJI providing us (the consumer) with any data pertaining to failure rates is ludicrous. What other consumer product(s) manufacturer publicly publishes failure rate information.

 

[Alex ROV]

Where are these logs though?

When I find anyone again of them I shall post it, not a problem... But if you find any showing "lost connection" or anything diferente than a regular end of flight for this "drop down" reported events you can post it as well, I believe your database is much bigger than mine... At end of the day that is what I'm kindly asking for, contributions for the case...

 

[Alex ROV]

I too think that its admirable work done by Alex ROV, but I'm still perplexed on where the "Mavics dropping from the sky" derives from. I've been lurking on these forums for quite some time and never seen wide-spread "mavic dropping from sky issues", Karma..yes. Spark...yes. In regards to DJI providing us (the consumer) with any data pertaining to failure rates is ludicrous. What other consumer product(s) manufacturer publicly publishes failure rate information.

I thank you for your support and apologize if I might have made it look a "wide-spread issue"... That is not, definitely, but I was just making reference to the reports that I have seen... If only ONE that I could discard pilot error, I still would be worried about...

Many thanks!