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DJI Mavic Pro span out of control and crashed into the sea

Chris9393

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Hi,

I'm currently on vacation in Fiji and have just been flying my Mavic Pro in and around the beach. I have owned my drone for 2 years so I am not a novice flyer.

I flew my drone approximately 40m into the air and flew it out over the sea around 200m away to take pictures of my friends snorkeling just off the reef.

My drone was 100% fully charged and was connected via GPS to 18 satellites. The weather conditions were perfect clear blue sky with minimal wind. As I flew my drone out over the sea in sport mode, to bring the drone to a stop I let go of the controls.

As I let go of the controls, the drone immediately started spiralling out of control and crashed into the sea. At no point were there any error messages displayed or connection issues. Nothing like this has ever happened to me before. I was also not able to retrieve the drone as it was simply too deep to recover.

I wasn't recording at the time however the flight log has saved to my account.

I've contacted DJI and low and behold, as the drone is now out of warranty there's nothing they can do. They won't even conduct any analysis to establish what exactly happened.

I'm hoping if there's something on this forum that could kindly establish what went wrong.

I've attached the flight log below.

Regards,

Chris
 

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old man mavic

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two things spring to mind for a cause and i base them on flying in sport mode, and letting go of the sticks which would bring the mav to an abrupt stop.

(1) battery came loose
(2) a prop broke or came off

and if anyone can give you a educated reason it is @sar104
 

Ds67888

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two things spring to mind for a cause and i base them on flying in sport mode, and letting go of the sticks which would bring the mav to an abrupt stop.

(1) battery came loose
(2) a prop broke or came off

and if anyone can give you a educated reason it is @sar104
i was in sport mode; released sticks... jammed camera; i learned 'don't do that' agina
 

Thomas B

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two things spring to mind for a cause and i base them on flying in sport mode, and letting go of the sticks which would bring the mav to an abrupt stop.

(1) battery came loose
(2) a prop broke or came off

and if anyone can give you a educated reason it is @sar104
Wonder what the chances are that the drone flipped over during a rapid sport mode stop?

It would be helpful to see the analysis of the controlling device logs as was requested above.
 

sar104

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What on earth is up with these aircraft the last few weeks? I have no idea what is going on with this one.

Attitude_comp.png

It all goes south at 376 seconds, but the txt log and the DAT log disagree wildly on attitude when it happens. The txt log has it rolling left upside down, while the DAT log shows it pitching forwards. I had always assumed that the txt and DAT log files were assembled from the same data stream, so that's strange.

The motor data don't seem to help:

motors.png

Apparently the left front motor stops briefly at 376 seconds and then again later, which would cause left roll and forwards pitch. The cause is unclear. The event stream doesn't indicate a motor problem - just some post hoc statements of the obvious:

376.143 : 22266 [L-FDI][CTRL]: fault on , tilt_ctrl_fail​
376.160 : 22267 [L-RC]craft ctrl failed!!!​
376.562 : 22287 [L-FDI][CTRL]: fault on , height_ctrl_fail​

There is an unusual (i.e. I don't recognize it) entry 16 seconds earlier that may or may not be important:

360.805 : 21499 [L-FMU/LED]action changed. aircraft install warning!:aircraft vibration err(3)​

I can't see any other clues. The left front motor speed excursions were not commanded by the FC, so perhaps an ESC fault?
 

Thomas B

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What on earth is up with these aircraft the last few weeks? I have no idea what is going on with this one.

View attachment 82294

It all goes south at 376 seconds, but the txt log and the DAT log disagree wildly on attitude when it happens. The txt log has it rolling left upside down, while the DAT log shows it pitching forwards. I had always assumed that the txt and DAT log files were assembled from the same data stream, so that's strange.

The motor data don't seem to help:

View attachment 82295

Apparently the left front motor stops briefly at 376 seconds and then again later, which would cause left roll and forwards pitch. The cause is unclear. The event stream doesn't indicate a motor problem - just some post hoc statements of the obvious:

376.143 : 22266 [L-FDI][CTRL]: fault on , tilt_ctrl_fail​
376.160 : 22267 [L-RC]craft ctrl failed!!!​
376.562 : 22287 [L-FDI][CTRL]: fault on , height_ctrl_fail​

There is an unusual (i.e. I don't recognize it) entry 16 seconds earlier that may or may not be important:

360.805 : 21499 [L-FMU/LED]action changed. aircraft install warning!:aircraft vibration err(3)​

I can't see any other clues. The left front motor speed excursions were not commanded by the FC, so perhaps an ESC fault?
It would be nice.to know what that last warning was about, but with the uncommanded motor speed excursions and and the vibration error I think about things like something getting into the motor... like one of the prop retainer tabs... or a failed bearing in the motor. Of course that’s just speculation by me.
One last thought.... wonder if that left front arm folded up partially?
 
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Ken Nash

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I don't if its me but a lot of people think that the sea is some kind of Bermuda Triangle personally I think not but I would hazard a guess is that the aircraft was unfit to fly before take off in one form or another. I flown over the sea many times without coming across the Bermuda Triangle. I always check my aircraft prior to take-off and in hover mode for a minute to make sure I'm good to go.
 

BudWalker

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What on earth is up with these aircraft the last few weeks? I have no idea what is going on with this one.

View attachment 82294

It all goes south at 376 seconds, but the txt log and the DAT log disagree wildly on attitude when it happens. The txt log has it rolling left upside down, while the DAT log shows it pitching forwards. I had always assumed that the txt and DAT log files were assembled from the same data stream, so that's strange.

The motor data don't seem to help:

View attachment 82295

Apparently the left front motor stops briefly at 376 seconds and then again later, which would cause left roll and forwards pitch. The cause is unclear. The event stream doesn't indicate a motor problem - just some post hoc statements of the obvious:

376.143 : 22266 [L-FDI][CTRL]: fault on , tilt_ctrl_fail​
376.160 : 22267 [L-RC]craft ctrl failed!!!​
376.562 : 22287 [L-FDI][CTRL]: fault on , height_ctrl_fail​

There is an unusual (i.e. I don't recognize it) entry 16 seconds earlier that may or may not be important:

360.805 : 21499 [L-FMU/LED]action changed. aircraft install warning!:aircraft vibration err(3)​

I can't see any other clues. The left front motor speed excursions were not commanded by the FC, so perhaps an ESC fault?
Looks to me like a propulsion problem with the leftFront or leftBack or both. (Whew! I thought at first it was another Yaw problem!!) It starts at 356.5, about 20 secs before the pilot releases the sticks and can then see there is a problem. Looking at the integrated gyro data the MP begins to tumble backwards (increasing totalGyroY) and CCW rolling (decreasing totalGyroX) which indicates a leftFront problem.
1569331083785.png
But, there is CCW rotation (decreasing totalGyroZ) that is consistent with a leftBack problem.

At the same time the data in ctrl_horiz_ang_vel_debug "goes crazy"
1569331578638.png

360.805 : 21499 [L-FMU/LED]action changed. aircraft install warning!:aircraft vibration err(3)

Interesting. I think that entry may be an indication that the AC has started to vibrate.
1569331792026.png
 
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sar104

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Looks to me like a propulsion problem with the leftFront or leftBack or both. (Whew! I thought at first it was another Yaw problem!!) It starts at 356.5, about 20 secs before the pilot releases the sticks and can then see there is a problem. Looking at the integrated gyro data the MP begins to tumble backwards (increasing totalGyroY) and CCW rolling (decreasing totalGyroX) which indicates a leftFront problem.
View attachment 82326
But, there is CCW rotation (decreasing totalGyroZ) that is consistent with a leftBack problem.

At the same time the data in ctrl_horiz_ang_vel_debug "goes crazy"
View attachment 82328


Interesting. I think that entry may be an indication that the AC has started to vibrate.
View attachment 82329
The left front motor speed data do suggest a problem with that motor.
 
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BudWalker

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The left front motor speed data do suggest a problem with that motor.
Agree, but the CCW rotation about the Z axis is a little odd. Also, PWM:LBack seems to be commanded higher than the others.
 

METIOR

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There were cases of destruction of propellers when flying in sport mode. Were the propellers very old?
 

Chris9393

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Thank you all for taking the time to assist me with establishing what exactly happened.

I had replaced the rear propellors with another set of DJI one's about a year ago. As I'm from the UK, we have something called the Consumer Rights Act 2015 whereby goods should last for a reasonable amount of time regardless if your warrant has expired. Has anyone had any experience in claiming under this legislation?

I'm wondering whether I do have a case to answer as in my opinion a drone of this quality and price, should last longer than 2 years. Especially since I fly it a few times a year, its not as if I've been flying it every day and in this case it has not been pilot error. The drone itself has malfunctioned?
 

dannybgoode

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Thank you all for taking the time to assist me with establishing what exactly happened.

I had replaced the rear propellors with another set of DJI one's about a year ago. As I'm from the UK, we have something called the Consumer Rights Act 2015 whereby goods should last for a reasonable amount of time regardless if your warrant has expired. Has anyone had any experience in claiming under this legislation?

I'm wondering whether I do have a case to answer as in my opinion a drone of this quality and price, should last longer than 2 years. Especially since I fly it a few times a year, its not as if I've been flying it every day and in this case it has not been pilot error. The drone itself has malfunctioned?
I think you’d struggle under this legislation without being able to prove that it was a fault with the flight computers or the like.

For example it could have been a prop failure which would not be covered by the legislation, they could argue that a motor seized due to poor maintenance or any number of other get-outs.

Sadly it is for you to prove the goods were faulty and without the drone you will struggle to do that. The legislation looks good in a newspaper headline but when you drill down into it, it’s not just a case of rocking up at the shop and demanding a replacement.

It’s worth a try I guess but I very much doubt you’ll get anywhere. It would almost certainly end up being a small claims court hearing as I suspect the shop and/or DJI would hold out otherwise.
 

Ds67888

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What on earth is up with these aircraft the last few weeks? I have no idea what is going on with this one.

View attachment 82294

It all goes south at 376 seconds, but the txt log and the DAT log disagree wildly on attitude when it happens. The txt log has it rolling left upside down, while the DAT log shows it pitching forwards. I had always assumed that the txt and DAT log files were assembled from the same data stream, so that's strange.

The motor data don't seem to help:

View attachment 82295

Apparently the left front motor stops briefly at 376 seconds and then again later, which would cause left roll and forwards pitch. The cause is unclear. The event stream doesn't indicate a motor problem - just some post hoc statements of the obvious:

376.143 : 22266 [L-FDI][CTRL]: fault on , tilt_ctrl_fail​
376.160 : 22267 [L-RC]craft ctrl failed!!!​
376.562 : 22287 [L-FDI][CTRL]: fault on , height_ctrl_fail​

There is an unusual (i.e. I don't recognize it) entry 16 seconds earlier that may or may not be important:

360.805 : 21499 [L-FMU/LED]action changed. aircraft install warning!:aircraft vibration err(3)​

I can't see any other clues. The left front motor speed excursions were not commanded by the FC, so perhaps an ESC fault?
where do you find these logs? dave
 

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Sand in the motors. During flight it ground away the motor internals.
I had a friend do the same with his phantom 3. Even though he was careful about getting sand on the P3, it crashed. He was able to retrieve it. When he took the motor off and apart, the inside of the motor was severely ground away.
 
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Bob4131

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Sand in the motors. During flight it ground away the motor internals.
I had a friend do the same with his phantom 3. Even though he was careful about getting sand on the P3, it crashed. He was able to retrieve it. When he took the motor off and apart, the inside of the motor was severely ground away.
My drone normally doesn't land/takeoff in sandy environments but it has on occasion. Any warning ahead of time of this type of failure? Would the motor / prop spin less freely for example? I would appreciate your feedback. Thanks
 
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