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Phantom 3 Adv dropped from the sky today. Trying to understand why.
254 23 11-17 08:21
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lemieszek
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Flight distance : 12959 ft
Brazil
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Hi all,

Was doing a flight test earlier today and my Phantom 3 Advanced just started spinning and dropped on the ground. Total loss.

Here's the flight log. Quite a few warnings towards the end. It began with "Not enough force/ESC Error".

Any ideas?

https://app.airdata.com/share/CrYGfZ

Thanks!
11-17 08:21
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DJI Stephen
Super Moderator

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Hello and good day lemieszek. I am sorry to know what happened to your previous flight with your DJI Phantom 3 Advanced. Since this unfortunate incident happened on the said drone I would recommend you contact our support team to start up a ticket at https://www.dji.com/support?site=brandsite&from=nav for us to be able to assists you further. We have the professional team who would do their best to find out the reason of the incident and then the corresponding resolution would be provided. Just a friendly reminder the please note that DJI will not perform data analysis for cases occurring after the expiry of the warranty period; otherwise, valid charges will apply. Again I am sorry for the trouble and thank for your support.
11-17 08:26
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lemieszek
lvl.1
Flight distance : 12959 ft
Brazil
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DJI Stephen Posted at 11-17 08:26
Hello and good day lemieszek. I am sorry to know what happened to your previous flight with your DJI Phantom 3 Advanced. Since this unfortunate incident happened on the said drone I would recommend you contact our support team to start up a ticket at https://www.dji.com/support?site=brandsite&from=nav for us to be able to assists you further. We have the professional team who would do their best to find out the reason of the incident and then the corresponding resolution would be provided. Just a friendly reminder the please note that DJI will not perform data analysis for cases occurring after the expiry of the warranty period; otherwise, valid charges will apply. Again I am sorry for the trouble and thank for your support.

Hi Stephen and thanks for your reply.

The product was well out of warranty. And it doesn't look like support is available here in Brazil.

My main goal is to understand what happened and make sure it doesn't happen again - the drone was well maintained and the propellers were almost new, and original.

Thanks again.
11-17 09:47
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Mark The Droner
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Flight distance : 2917 ft
United States
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Sorry for your loss.

The following is a better site for examining logs

https://www.phantomhelp.com/LogViewer/0C26W5ARVNVVVUUIGKJA/

I see you launched with less than a fully charged battery.  That's not a good idea.  

Looks to me like you must have hit the tall building nearby.  

Somebody else may offer their opinion soon as to what happened.  

Good luck
11-17 10:54
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lemieszek
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Flight distance : 12959 ft
Brazil
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Mark The Droner Posted at 11-17 10:54
Sorry for your loss.

The following is a better site for examining logs

Hello and thanks for your reply. Interesting website indeed. Some useful info there.

I had 81% on launch because I did a short (and uneventful) flight right before that one. Had 51% when it crashed, so I don't think the battery would be relevant here.

The drone was at an altitude of 160m and the tallest building anywhere near its path is maybe 30m tall. Hitting a building is certainly out of the question.

Maybe attacked or hit by a large bird?
11-17 11:53
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Goldenseal
Second Officer
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United States
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I have looked at your air data and I don't think there is enough information to show the cause. We can only guess. If you down load your flight data from your drone that would be much better.
11-17 12:20
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Labroides
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Australia
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lemieszek Posted at 11-17 11:53
Hello and thanks for your reply. Interesting website indeed. Some useful info there.

I had 81% on launch because I did a short (and uneventful) flight right before that one. Had 51% when it crashed, so I don't think the battery would be relevant here.

It's a little difficult to properly investigate the incident because it was a waypoing plight and we can't tell how the flight was programmed.
But we can see that at 7:43.3 your drone begins slowly rotating anti-clockwise (but maintaining height).  The pitch begins to swing backwards and forwards.
At 8:04.4 it starts to lose height and is still spinning and it begins to tumble.
The error messages following that are due to the spinning and tumbling as it falls.

The cause will be either the loss of a prop, a motor or the ESC that controls a motor.
11-17 13:23
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Mark The Droner
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lemieszek Posted at 11-17 11:53
Hello and thanks for your reply. Interesting website indeed. Some useful info there.

I had 81% on launch because I did a short (and uneventful) flight right before that one. Had 51% when it crashed, so I don't think the battery would be relevant here.

Were all four props still attached to the drone?  
11-17 14:19
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RedHotPoker
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Canada
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Sorry to read about this. Hope the answers are available.



RedHotPoker
11-17 14:33
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cheddar-man
lvl.2
Flight distance : 44062 ft

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At 8m 9.5s you started getting speed errors.
Any chance you can upload the .DAT file??
Ahhhh, hang on, you posted this on the Phantom Forum. The conclusion there was either the front left ESC or motor.
11-17 14:48
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lemieszek
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Flight distance : 12959 ft
Brazil
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cheddar-man Posted at 11-17 14:48
At 8m 9.5s you started getting speed errors.
Any chance you can upload the .DAT file??
Ahhhh, hang on, you posted this on the Phantom Forum. The conclusion there was either the front left ESC or motor.

I'll upload the .DAT file when I get the chance.  Haven't downloaded it yet.

I did not post this elsewhere... would you mind pointing me to the thread?

Thanks!
11-17 15:31
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lemieszek
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Brazil
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Mark The Droner Posted at 11-17 14:19
Were all four props still attached to the drone?

Hard to say. It was not a short fall, and when I got to the site a dude had it and was picking it apart. One of the motors didn't have a propeller but he might have took it off for some reason.

FWIW, I attached them firmly before taking off (and it flew for close to 10 minutes... weren't they supposed to be self tightening?)
11-17 15:34
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Labroides
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cheddar-man Posted at 11-17 14:48
At 8m 9.5s you started getting speed errors.
Any chance you can upload the .DAT file??
Ahhhh, hang on, you posted this on the Phantom Forum. The conclusion there was either the front left ESC or motor.

All of those error messages are because the drone was falling, spinning and tumbling.
They don't indicate any cause of the incident.
11-17 16:05
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Mark The Droner
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lemieszek Posted at 11-17 15:34
Hard to say. It was not a short fall, and when I got to the site a dude had it and was picking it apart. One of the motors didn't have a propeller but he might have took it off for some reason.

FWIW, I attached them firmly before taking off (and it flew for close to 10 minutes... weren't they supposed to be self tightening?)



So you took four props home - 3 on their motors, one not on the motor.  Correct?   
11-17 16:16
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lemieszek
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Mark The Droner Posted at 11-17 16:16
So you took four props home - 3 on their motors, one not on the motor.  Correct?

Correct, if you count the fractions of props. Two of the attached ones are broken on one side.

One of the props came home attached to the motor but the motor was not attached to the drone

So, props 1 and 2: attached but broken
Prop 3: detached (dude detached it?)
Prop 4: attached to a detached motor I found on the sidewalk
11-17 16:38
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lemieszek
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I think I have a big clue.

Look at the marks on the shell left by the front propellers.



It's visible on the left and it even made a hole on the shell on the right.

I know the shell was not out of place when it took off. Maybe the front motors were tilting back more than they should for some reason?
11-17 17:14
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Bashy
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the fold marks are indicative of an impact, the hole is indicative of the prop melting and slicing away at the shell, hence the grooves and right angle on the edge leading towards the center of the shell
11-17 18:35
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Labroides
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lemieszek Posted at 11-17 17:14
I think I have a big clue.

Look at the marks on the shell left by the front propellers.
Maybe the front motors were tilting back more than they should for some reason?
That cannot happen, and would not have given data like yours.

Bashy's comment is correct.

The spinning while losing height indicates loss of thrust from one of the propellers.
That could be caused by loss (or breakage) of a propeller or a fault with a motor or its ESC.
11-17 18:46
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fans0195750a
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Labroides Posted at 11-17 18:46
Maybe the front motors were tilting back more than they should for some reason?
That cannot happen, and would not have given data like yours.

What he have:

- At least one propeller was touching the shell during the flight. Enough that it punched a hole on it
- The bird flew for quite a while after this became a problem. Counterclockwise motion starting at a little over 7 minutes, then a straight line, then counterclockwise motion again and finally a drop

So:

- It seems the propeller touching the shell might have contributed less and less to the bird's flight, which manifested as CCW motion at some points and finally a drop. Maybe it got more and more stuck in the groove it created and at some point it finally didn't spin anymore.

Is that a good theory?

In any case, what would cause a propeller to touch the shell? The motor was bent for some reason? The shell was out of place? None of those factors were present at takeoff...

Here's the last photograph I took of it, on the eve of the crash. Everything seems in place...?

Anotação 2019-11-18 135325.png
11-18 08:54
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Labroides
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fans0195750a Posted at 11-18 08:54
What he have:

- At least one propeller was touching the shell during the flight. Enough that it punched a hole on it

Is that a good theory?
It's a very good theory.
But it's WRONG.
In any case, what would cause a propeller to touch the shell? The motor was bent for some reason? The shell was out of place?
Nothing would cause that in flight.
The thin, soft propellers can't cause damage like that and the shell doesn't fold up in flight.

The damage all happened on impact with the ground.
11-18 12:02
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fans0195750a
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Labroides Posted at 11-18 12:02
Is that a good theory?
It's a very good theory.
But it's WRONG.

But you said Bashy's comment is correct...?

"the fold marks are indicative of an impact, the hole is indicative of the prop melting and slicing away at the shell, hence the grooves and right angle on the edge leading towards the center of the shell"

The prop certainly didn't melt and slice away at the shell after impact...?
11-18 12:08
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Mark The Droner
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fans0195750a Posted at 11-18 12:08
But you said Bashy's comment is correct...?

"the fold marks are indicative of an impact, the hole is indicative of the prop melting and slicing away at the shell, hence the grooves and right angle on the edge leading towards the center of the shell"

Often after a crash, the drone will find itself on the ground upside down.  From there, assuming the battery is still intact, it would try to right itself, meaning the props would spin crazily at high speed and continue spinning while on the ground.  They won't stop until you it runs out of battery or you find it, turn it right side up, and use the controller to stop the motors.  So it's clear what happened is your motor mount broke or bent during the crash causing a tilted motor and so the props shaved away at the top of the drone.  Another possibility is the motor overheated while spinning and so the plastic motor mounts melted and loosened causing the same thing.  The latter has happened to me personally once after I crashed in the woods.  

I think the last sentence in post #8 is the best guess as to why you crashed - motor or ESC.  It seems unlikely a prop flew off if you found all four props near the crash site.  I would guess motor has a better chance of failure than an ESC during a free flight.  ESCs really don't fail during flight - they fail from the motor being locked up after a crash.  It's possible a tiny piece of gravel was in one of the motors causing it to lock up or become intermittent during flight.
11-18 12:14
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fans0195750a
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Mark The Droner Posted at 11-18 12:14
Often after a crash, the drone will find itself on the ground upside down.  From there, assuming the battery is still intact, it would try to right itself, meaning the props would spin crazily at high speed and continue spinning while on the ground.  They won't stop until you it runs out of battery or you find it, turn it right side up, and use the controller to stop the motors.  So it's clear what happened is your motor mount broke or bent during the crash causing a tilted motor and so the props shaved away at the top of the drone.  Another possibility is the motor overheated while spinning and so the plastic motor mounts melted and loosened causing the same thing.  The latter has happened to me personally once after I crashed in the woods.  

I think the last sentence in post #8 is the best guess as to why you crashed - motor or ESC.  It seems unlikely a prop flew off if you found all four props near the crash site.  I would guess motor has a better chance of failure than an ESC during a free flight.  ESCs really don't fail during flight - they fail from the motor being locked up after a crash.  It's possible a tiny piece of gravel was in one of the motors causing it to lock up or become intermittent during flight.

By all accounts, the drone stopped moving once it hit the ground. So if it's true that the hole on the right was caused by the propeller hitting it continually, it happened in the air. Maybe after something hit it? Might be. But the CCW motion the drone showed over a minute before it fell tells me whatever failed, failed gradually...
11-21 10:34
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Mark The Droner
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The motor would have to be loose, or the wing would have to be bent.  I don't think a bird collision would result in either of those scenarios.  I suppose if the screws suddenly began falling out of your motor while in flight, something like that is possible.  Seems unlikely though - DJI uses thread lock on those screws.  Have you loosened those screws yourself at some point prior?  Were screws missing from the motor when you found it?  

I think you'd have to look at the onboard log to research your theory further.  

Good luck
11-22 04:31
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