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Help- dji mavic pro 2 crashed into 130m building

HlaaDrone

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Hi guys,

I've been flying drone in park and lost signal, alt 120m and distance 2000m. After loosing the signal it tried to return home but then it it crashed onto the building on the way home. Before it crashed the I change the to position mode, should've the sensors stopped it from crashing? I contacted dji and told me send the drone for investigation, before I send it I want to make diagnostic on damages, some people reported that dji repair guys try to rip off. Any guides on how how I can do it or some one can help me? I had a look at the flight log and sent that to DJI and told me they've found nothing.


Thanks
 

Ansia

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OA should have worked and stopped your drone from meeting the building. I suggest you upload the logs in here, in hopes that one of the gurus can dissect and anaylize you logs. Hopefully finding fault on the drone and you get a free repair. Prices on repairs are standard, and I believe you can find them online. I know I've seen them somewhere. Hope it helps.
 

JAW

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I'm asking this because I don't know the answer:
If you're flying in S mode and lose signal are you able to switch to P mode?
 

Ansia

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I'm asking this because I don't know the answer:
If you're flying in S mode and lose signal are you able to switch to P mode?
No. If you don't have any connection with the drone, then even if you do switch to P mode, the drone will not receive the command.
 

JAW

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Thanks. If you're in S mode and suffer loss of connection and RTH is initiated, will the drone automatically activate OA?
 

old man mavic

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if you can get the logs for @sar104 to look at maybe he can tell you what went wrong
 

HlaaDrone

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OA should have worked and stopped your drone from meeting the building. I suggest you upload the logs in here, in hopes that one of the gurus can dissect and anaylize you logs. Hopefully finding fault on the drone and you get a free repair. Prices on repairs are standard, and I believe you can find them online. I know I've seen them somewhere. Hope it helps.
Here is the log, DJI Flight Log Viewer - PhantomHelp.com
 

HlaaDrone

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No. If you don't have any connection with the drone, then even if you do switch to P mode, the drone will not receive the command.
I think it did send switch command and after that it lost the connection.
 

Ansia

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The logs your provided are from the DJI Go 4 app. The end exacly where it disconnected from the drone. Can you provide the Dat file from the drone?
 

sar104

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The logs your provided are from the DJI Go 4 app. The end exacly where it disconnected from the drone. Can you provide the Dat file from the drone?
Unfortunately the onboard DAT file from the Mavic 2 is only readable by DJI.

In terms of this event I haven't yet looked at the log data but the cause of the problem seems very likely to be disabled OA on RTH.
 
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JAW

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If you're more than 2km away when connection is lost, the drone will fly in a straight line back to the home point rather than retrace the original flight path for 60 seconds. OP said he was 2km away but maybe it was a bit more than 2km in which case it would fly in a straight line and possibly encounter the the 400'+ building which he avoided on the outbound flight. Assuming OA WAS working, will the Mavic ascend to more than 400' agl to avoid an obstacle during faillsafe RTH? While it's legal to climb higher than 400' to avoid and obstacle (provided you remain within 400' laterally,) does the Mavic 2 know this while performing failsafe RTH?
(granted, I'm just spitballing here. The logs will provide the answers.)
 
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Ansia

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Unfortunately the onboard DAT file from the Mavic 2 is only readable by DJI.

In terms of this event I haven't yet looked at the log data but the cause of the problem seems very likely to be disabled OA on RTH.
I didn't know that. I thoughr it was like the Phantoms. Thanks for the info.
 

HlaaDrone

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If you're more than 2km away when connection is lost, the drone will fly in a straight line back to the home point rather than retrace the original flight path for 60 seconds. OP said he was 2km away but maybe it was a bit more than 2km in which case it would fly in a straight line and possibly encounter the the 400'+ building which he avoided on the outbound flight. Assuming OA WAS working, will the Mavic ascend to more than 400' agl to avoid an obstacle during faillsafe RTH? While it's legal to climb higher than 400' to avoid and obstacle (provided you remain within 400' laterally,) does the Mavic 2 know this while performing failsafe RTH?
(granted, I'm just spitballing here. The logs will provide the answers.)
The distance is exactly 1741.627m, Alt was 120m. All the surroundings buildings are 80m except that building which crashed into. I can provide you the log, which log are after? thanks I've downloaded dji assistant and exporting the logs, there is 3gb of log file. is it this?
 

Ansia

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If you're more than 2km away when connection is lost, the drone will fly in a straight line back to the home point rather than retrace the original flight path for 60 seconds. OP said he was 2km away but maybe it was a bit more than 2km in which case it would fly in a straight line and possibly encounter the the 400'+ building which he avoided on the outbound flight. Assuming OA WAS working, will the Mavic ascend to more than 400' agl to avoid an obstacle during faillsafe RTH? While it's legal to climb higher than 400' to avoid and obstacle (provided you remain within 400' laterally,) does the Mavic 2 know this while performing failsafe RTH?
(granted, I'm just spitballing here. The logs will provide the answers.)
I am amazed how different the Mavic is to the Phantom in this area, but he never reached 2Km.
 

Ansia

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The distance is exactly 1741.627m, Alt was 120m. All the surroundings buildings are 80m except that building which crashed into. I can provide you the log, which log are after? thanks I've downloaded dji assistant and exporting the logs, there is 3gb of log file. is it this?
I'm sorry. I didn't know the Mavics where different from the Phantom series on the log department. I came here to learn about Mavics, before pulling the trigger on Jan 2020, but I thought they were like the Phantoms. It seems, you only get 1 set of logs.
 

HlaaDrone

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I'm sorry. I didn't know the Mavics where different from the Phantom series on the log department. I came here to learn about Mavics, before pulling the trigger on Jan 2020, but I thought they were like the Phantoms. It seems, you only get 1 set of logs.
I managed to get the dat file tryint to open using the CsvView/DatCon
 

RWD

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First off - fair warning, I am a complete rookie at analyzing flight logs, but here is what I can see in . I expect @sar104 to be able to give you far more detailed view after he looks at the file. And yes - this is a LONG note, I tried to relay everything that may be of interest from the files.....
  • manual takeoff, home point recorded.
  • full throttle and full elevator for first part of flight
  • at 2 minutes 23 seconds into the flight, you reach maximum altitude of 400 feet.
  • from there you proceed with full elevator, level flight, crossing the A12 motorway.
  • at 2 m 45 s, shortly after crossing the A12 you get a high wind warning, and are advised to fly with caution. You are already a long ways from the park.
  • at 3 m 50 s, you have crossed Watenden Road, and are almost 5,000 feet from takeoff point. Here you get a warning that you are approaching a No Fly Zone, and that RTH may be affected. There does not appear to be any immediate change in your input via the RC.
  • about 1.5 seconds later at 3 m 51 s you get a second message - that "your aircraft is at a boundary of an Authorization Zone, please fly away."
  • abut 4 seconds later you start some left rudder input, until you have completed approximately a 90 degree left turn.
  • a few seconds later at 4 m 18 s, you ask for a change to Sport Mode, but it appears that communication is lost, so my guess is that the drone never received that command.
  • about 6.8 seconds later (4 m 25 s) you get a message that downlink has been restored, after being lost for 6.8 seconds. You get a second warning about high wind speeds and are advised to land ASAP. Aircraft mode is still P.
  • flight continues with full elevator input for another 27 seconds or so, and then you get a final warning about signal: "Weak signal. Avoid blocking the antennas and keep the antennas parallel to and facing toward the aircraft during flight.".
  • That is the last transmission I can see in the log, and places the aircraft over what looks like a parking garage over top of a rail station. You say that it flew into a building - the log does not show that. At the time of last transmission, the bird was 1745 m from launch point (as the crow flies), and had covered a distance of 2345 m in the flight.
  • I can't see any indication that RTH was ever initiated, either automatically or by your command, or that the bird ever turned back towards the launch point. Also, the log seems to indicate that the flight was in P mode the entire time.
  • I see no indication that the flight ever exited the Authorization Zone, so not clear to me what impact that might have had on the RTH function. We saw a case in the USA last week where a Temporary Flight Restriction came into effect during a flight and that caused the drone to land immediately - into the water. I do not know how that works in Europe.
  • I don't know what variables to look at in the verbose CCVS file to understand status of the optical sensors, but in P mode, I believe they default to on.
That is nowhere near a nice an analysis as @sar104 will undoubtedly produce, and lacks the graphical representation of the different variables in the log file.

A few questions - did you recover the drone, and if so, can you share lat/long where you recovered it? What leads you to believe that it flew into a building, it would have been challenging to see the drone given its distance from you (assuming you stayed at the takeoff point)??

To the experts - I am more than happy to have your view of this analysis. Like I said up top, I am new to this, and am interested in learning to get better at it.......

Thanks...