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Mavic Air 2 crash and lost. Error: "Motor is Blocked. Not Enough Force/ESC Error"

hypershade

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Hello,
  • I have been reading those forum, and it would appear many people have had crashes due to ESC errors.
  • I was hoping an expert can look at my log files and tell me what happened. In essence, my drone just fell out of the sky on a clear day without wind. I could see the drone and no birds attached it. I was flying over marshes and despite a search and rescue, I was unable to locate the drone.
  • I already contacted DJI and they are investigating, but I assume they will try to find an excuse in case it was a drone malfunction.
  • I was hoping somebody here could tell me if this was a hardware/software malfunction.
Log files (from RC only) attached.

Thank you very much!

PS: my previous post did not show up. Sorry of double posting.
 

Attachments

  • 2020-11-08_16-48-36_FLY095.DAT
    4.8 MB · Views: 8
  • DJIFlightRecord_2020-11-08_[16-49-07].txt
    879.2 KB · Views: 8

Meta4

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  • I was hoping an expert can look at my log files and tell me what happened. In essence, my drone just fell out of the sky on a clear day without wind. I could see the drone and no birds attached it. I was flying over marshes and despite a search and rescue, I was unable to locate the drone.
Here's what that flight data looks like: DJI Flight Log Viewer - PhantomHelp.com
You were flying backwards and things were going smoothly until 7:31.1 when the drone suddenly leveled and then pitched backwards much more than the normal limit.
At the same time it rolled >90° to the right, started spinning anti-clockwise and losing height as it tumbled from the sky.
This indicates losing either a prop or motor.
If the props were all attached, it would be a motor or the esc that drives it.
  • I already contacted DJI and they are investigating, but I assume they will try to find an excuse in case it was a drone malfunction.
DJI don't usually work that way.
They examine the data and if it shows a DJI fault, you are covered for a warranty replacement.
Without the wreckage for them to examine, things can be difficult.
But yours didn't lose power and was able to record the crash.
That should be enough for DJI to see what happened and I would think you would have a good chance at a replacement.
 
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slup

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Reading off the DAT log shows clearly that the culprit is the Right front, both looking at the AC movements from 451,6sec where it pitches front down, rolls to the right & rotates CCW ...
Black = your right stick full backwards command), Blue = yaw, Purple = roll, Yellow = pitch & Red = height.

(Click on all graphs below to make them larger)
1605446130368.png

... and checking off that motor's RPM that goes from approx 7000rpm to 100rpm in 1,5sec & at the same time the current spikes high with a FC command to go to 100%. This says that the right front motor gets jammed (HW failure, debris inside?) & comes to a stop.

Have here below kept the Purple graph (roll) as a reference ... Red = RPM, Blue= current & Green = FC command percentage.

1605446542802.png
 
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hypershade

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Here's what that flight data looks like: DJI Flight Log Viewer - PhantomHelp.com
You were flying backwards and things were going smoothly until 7:31.1 when the drone suddenly leveled and then pitched backwards much more than the normal limit.
At the same time it rolled >90° to the right, started spinning anti-clockwise and losing height as it tumbled from the sky.
This indicates losing either a prop or motor (rear left?).
If the props were all attached, it would be a motor or the esc that drives it.

Thank you for taking the time to review. I indeed had a look at the txt, dat in the relevant apps/sites. I also studied KML on google earth trying to find the cause of the crash. During my preflight check, I always pay very close attention to the motors and rotors and they were clear. I also took of from a landing pad, exactly to avoid dust or grass getting in the motors; so I am very curious what caused the blockage. Is there any way to know the cause of the blockage based on the data?
 

hypershade

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... and checking off that motor's RPM that goes from approx 7000rpm to 100rpm in 1,5sec & at the same time the current spikes high with a FC command to go to 100%. This says that the right front motor gets jammed (HW failure, debris inside?) & comes to a stop.

Hello Slup - thank you very much to look at the data. Is there anyway to know what caused the jam? If it was indeed hardware failure?

Thank you kindly.
 
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slup

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Hello Slup - thank you very much to look at the data. Is there anyway to know what caused the jam? If it was indeed hardware failure?

Thank you kindly.
Unfortunately it could have been due to a number of different reasons ... debris blown up from this or earlier take offs/landings, a prop attachment tab that suddenly broke off & ended up inside the motor jamming it or just that the motor seized up.

Hard to judge if it's pointing to HW=manufacturing fault or Pilot error=not inspecting the motors/prop attachments enough. It will be up to DJI I'm afraid ... it possibly had been easier if you have had the AC to inspect.
 
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slup

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Bird strike?
Nothing in the logs indicate that at all ...

The top 3 graphs in the chart below show the acceleration in X-axis (forward/backwards), Y-axis (right/left) & Z-axis (down/up) (axis explanation further below) ... when the incident starts with a sudden major roll (red graph) to the right the accel values is & have been constant in all axis, the first change seen is a positive change in the Z-axis (yellow graph) that shows an downward acceleration that later is somewhat restored as the other motors counteract trying to keep the AC airborne. So no ... nothing hit the AC causing this.

1605457243080.png

1605457367689.png
 

hypershade

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Nothing in the logs indicate that at all ...

The top 3 graphs in the chart below show the acceleration in X-axis (forward/backwards), Y-axis (right/left) & Z-axis (down/up) (axis explanation further below) ... when the incident starts with a sudden major roll (red graph) to the right the accel values is & have been constant in all axis, the first change seen is a positive change in the Z-axis (yellow graph) that shows an downward acceleration that later is somewhat restored as the other motors counteract trying to keep the AC airborne. So no ... nothing hit the AC causing this.

Slup - thanks again. In your experience, what is the most common cause for an incident like this?
Also what application do you use to get these graphs, I would like to study them closer up.

Thanks!
 
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slup

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...what is the most common cause for an incident like this?
Also what application do you use to get these graphs...
As said earlier, it's hard to judge, have seen cases with the AC recovered where debris or pieces of prop attachments have been found inside the motors ...

I use CsvView to decode both the .TXT & .DAT logs (free download here --> CsvView Downloads , credit goes to forum member Budwalker. It requires a bit knowledge though ... you need to pick the data you want to look at by yourself so some knowledge is required regarding what data that should be chosen & what it indicates.

If you're interested in log reading I recommend you to start with reading the first post here --> Mavic Flight Log Retrieval and Analysis Guide , credit for this goes to forum member sar104.
 

hypershade

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Quick question about DJI's latest reply about this case - see below:
  • Why do they keep asking the date of the crash when it is clearly visible in the logs?
  • Why do they need the data from all flights, including the cached videos?
Thanks!
Good day.

For your claimed case CAS-5453219-W4Z6W5, our analysis team were analyzing it for you and found that the flight records stored inside your phone are needed for a better analysis:

Please confirm the exact date of the flight incident. Then export the Whole FlightRecords Folder including the MCDatFlight Records Folder and the Video Cache Folder/DJI Records from the phone used during the incident. Attached file is for the instruction. Use Google Drive or Dropbox to upload all the files and give us the link on this email.
 

slup

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Quick question about DJI's latest reply about this case - see below:
  • Why do they keep asking the date of the crash when it is clearly visible in the logs?
  • Why do they need the data from all flights, including the cached videos?
Thanks!
As they want you to export the whole folder with all logs inside they want to know the date to pinpoint which logs that are from the incident ... & the cached video can be a good piece of the forensic puzzle, with a video available it's much easier to interpret what's happening.
 

hypershade

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As they want you to export the whole folder with all logs inside they want to know the date to pinpoint which logs that are from the incident ... & the cached video can be a good piece of the forensic puzzle, with a video available it's much easier to interpret what's happening.
Thanks, that makes sense - but:
  • I already told them twice I was not recording video during the crash.
  • They also know the date of the crash, because the case was opened with only the logs of the flight that crashed.
  • I guess I can only wait and see....
Thanks again Slup - you are most helpful - much appreciated.
 

pilotstever

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Hello Slup - thank you very much to look at the data. Is there anyway to know what caused the jam? If it was indeed hardware failure?

Thank you kindly.
You also can't overlook the obvious. The drone is not built to any standard that meets airworthiness or safety. The motors do fail and bring down aircraft regularly. I tend to only get reports about larger public safety drones but here is a similar incident with a Matrice 210. DJI Matrice 210 – Accident – 2020-06-25
 
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