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Crash out of nowhere, what?
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1355 59 7-3 13:16
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Niftiest
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Can these things be trusted? I read so many stories about them basically crash landing in to water out of nowhere, now my drone has just crashed out of nowhere in a basic flight. LUCKILY it happened when it was almost back to me, and I could find it relatively quickly. Just wow.
VIDEO:



FLIGHT DATA:
https://app.airdata.com/share/pkLAKh

As you can see, it straight up dropped out of the sky. It gave "motor is blocked, motor is stuck" errors. There was no obstructions, there was nothing above it that could have dropped in to it, it was fairly high up in comparison to the dunes. I recovered the drone, cleaned it off, put another battery in and let it hover for 10min with no issue, but now I'm too afraid to fly this thing at any serious distance/height.

Note for curiosity (I use return to home sometimes for cinematic smooth flying, so when you see those in the notification area of the log, that's what those were for).

Anyone have any clue what...the..heck...happened?
7-3 13:16
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itchyeyeballs
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Really looks like it was hit by a bird but I guess that's impossible as you were looking right at it.

This crash looks much different from all the other uncommanded decent videos I've seen, level flight to falling in a split second.
7-3 15:38
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Niftiest
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itchyeyeballs Posted at 7-3 15:38
Really looks like it was hit by a bird but I guess that's impossible as you were looking right at it.

This crash looks much different from all the other uncommanded decent videos I've seen, level flight to falling in a split second.

No birds around at all. It literally just .. dropped straight down, was so wild to watch. Usually I don't record the return flight, I'm so glad I did this time.
7-3 16:37
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Labroides
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Anyone have any clue what...the..heck...happened? NOT what the log says it was, because NOTHING was above it or beside it, or within area to get in the motor and make it straight drop dead like that.

** This post is completely wrong **
Assessment was made without realising that the pilot was using a non-standard flight mode.
Correct analysis is further down the page.

I have a few clues.  
Video is useless for analysing this flight incident but the story is very clear in the flight data.
Here's what your data really looks like: https://www.phantomhelp.com/LogViewer/Q5MHNYU3LGF7LOEU7D3M/

Your Mini had the same old uncommanded descent problem that's plagued this model since it was released.
Yours was running Firmware 1.0.5 which was supposed to fix it but cases like yours still show up.

Your Mini showed very poor altitude stability and control for much of the flight.
I'm surprised you didn't notice it much earlier.
There was plenty of evidence of a serious problem well before the crash.

There's too much to list every incidence so here's what I see from halfway through the flight.

From 7:06.5, left stick full down but the drone climbs from 17 ft - 330 ft.
From 7:44, left stick full forward, drone fails to climb
From 7:54.9, left stick full forward, drone fails to climb, then loses altitude from 370 ft - 222 ft
From 8:49.5, left stick full forward, drone fails to climb
From 9:24.4, drone sinks while hovering
From 9:34.6, left stick full forward, drone fails to climb
From 9:49.1,  left stick full forward but drone loses height from 226 ft - 143 ft
From 10:05.9, left stick full forward, drone fails to climb until 11:00.7
From 11:00.7, left stick full forward but drone loses height until 11:34.3
From 11:49.3, left stick full forward but drone loses height
From 12:09.7, drone sinks while hovering until 12:13.2
From 12:28.9, drone sinks while hovering
From 12:47.6, left stick full forward but drone loses height until 12:53.3
From 13:18.6, left stick full forward but drone loses height from 269 ft - crash
13:48.6 - crash


7-3 17:41
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Niftiest
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Labroides Posted at 7-3 17:41
Anyone have any clue what...the..heck...happened? NOT what the log says it was, because NOTHING was above it or beside it, or within area to get in the motor and make it straight drop dead like that.

I have a few clues.  

Thank you for the response. By "not what the flight data says" I was passively joking as the notifications stated the obvious (motor stopped). I really appreciate your analysis, I oddly didn't notice a single issue with it (which says something about me, too). Well crap. Now that I know this is a known issue, think I'm giving up this hobby and returning it. Thank you for verification!
7-3 19:09
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GaryDoug
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Sounds like a hardware failure to me. Doesn't look like the typical Mini failure. Just MHO.

At this stage, maybe a loose/intermittent connection? I have seen intermittent connections plague many electronics devices of the last 45 years in my career as a failure analysis test engineer.


I have two Minis and an MA2 and have never seen anything like that. I would not give up.

7-3 19:10
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itchyeyeballs
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GaryDoug Posted at 7-3 19:10
Sounds like a hardware failure to me. Doesn't look like the typical Mini failure. Just MHO.

At this stage, maybe a loose/intermittent connection? I have seen intermittent connections plague many electronics devices of the last 45 years in my career as a failure analysis test engineer.
agree, it really doesn't look like the uncommanded descent issue, in every instance of that I have seen reported the drone descends in a stable manner, this one tumbles out of the sky.
7-3 23:56
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Bjord
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Sounds like you got a bum unit. Maybe a bad ESC or something.
7-4 00:12
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Labroides
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itchyeyeballs Posted at 7-3 23:56
agree, it really doesn't look like the uncommanded descent issue, in every instance of that I have seen reported the drone descends in a stable manner, this one tumbles out of the sky.
** This post is completely wrong **
Assessment was made without realising that the pilot was using a non-standard flight mode.
Correct analysis is further down the page.

it really doesn't look like the uncommanded descent issue, in every instance of that I have seen reported the drone descends in a stable manner, this one tumbles out of the sky.
Read my post above.
This Mini descended in stable flight many times, sometimes falling a few hundred feet.
The last descent was from 269 feet and only started to tumble when it got down to 17 ft.
The tumbling only lasted for 1.8 seconds before the Mini came to rest.
I'd say this was just like many uncommanded descent incidents, except that it kept going for much longer before finally crashing.

7-4 02:12
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EHEA
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If I read the log correctly, that drone made some ground-hugging (to negative altitude wrt home-point altitude) passes over that sandy terrain. Is it possible that sand got blown into one of the motors which later made it block or fail  (the final crash indeed looks like a complete motor failure, doesn't it). You would not be able to tell post-crash because then, of course, you will have found sand in the motors, right?
I guess video footage of these low altitude fly-overs might be useful to access whether there was indeed a risk of foreign-object-damage, so to speak.

> From 7:06.5, left stick full down but the drone climbs from 17 ft - 330 ft.

Look closely:
As for comments on the stick movement: the left/right sticks here seem to be swapped wrt the "default" configuration: left stick seems to control horizontal movement  and the right one yaw and climb/descent. e.g when you notice the drone climbing despite left stick full down, actually it's flying backwards at full throttle and climbing because the other stick is full up! Nothing suspicious here, and an explanation why the pilot didn't notice anything strange either at that point in the flight.

Fly safe
HB
7-4 05:26
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virtual
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Was the Motor stuck warning displayed in the air or after the crash? Because of the rolls during the fall I would suspect motor or propeller failure...
7-4 06:40
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GaryDoug
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I think the key difference here is the repeated warnings of "Motor is blocked. Motor Stuck." I don't remember seeing those in previous reports of the uncommanded descents. <<<Rubbish

And as stated above, the remote appears to be in the Mode 3 setting. That is further confirmed by watching the log file when the drone is turning....again Mode 3. <<< Just repeating what EHEA posted above

7-4 06:43
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virtual
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GaryDoug Posted at 7-4 06:43
I think the key difference here is the repeated warnings of "Motor is blocked. Motor Stuck." I don't remember seeing those in previous reports of the uncommanded descents.

But at the map it looks like they came at the crash site (after hitting the ground?)...
7-4 06:53
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GaryDoug
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virtual Posted at 7-4 06:53
But at the map it looks like they came at the crash site (after hitting the ground?)...

******Ignore the following ;-) ******

I don't see that. They start at a Baro altitude of 19 feet. The crash altitude appears to be -49 feet.
7-4 06:57
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Labroides
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GaryDoug Posted at 7-4 06:43
I think the key difference here is the repeated warnings of "Motor is blocked. Motor Stuck." I don't remember seeing those in previous reports of the uncommanded descents.

And as stated above, the remote appears to be in the Mode 3 setting. That is further confirmed by watching the log file when the drone is turning....again Mode 3.
the remote appears to be in the Mode 3 setting
Well spotted ... I'll have to reassess the incident.
Sometimes you miss something in a spreadsheet with >8000 lines.
Why do people do that?  It makes it much harder to read the data.

I think the key difference here is the repeated warnings of "Motor is blocked. Motor Stuck."
They start at a Baro altitude of 19 feet. The crash altitude appears to be -49 feet.
Motor is stuck messages mark the crash.
It was at approx -17 ft.
The launch was from up on the dunes above the beach and the crash was down on the beach.
The drone moved very little after 13:50.4, as confirmed by the pitch, roll and yaw data hardly changing.

Speed and altitude data after that is false and due to the IMU affected by the impact.

7-4 07:51
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virtual
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GaryDoug Posted at 7-4 06:57
I don't see that. They start at a Baro altitude of 19 feet. The crash altitude appears to be -49 feet.

Not sure if I see all the data (I´m not registered member at Airdata) but it looks that at 13m48s AC crashed.
7-4 08:09
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Labroides
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Labroides Posted at 7-4 07:51
the remote appears to be in the Mode 3 setting
Well spotted ... I'll have to reassess the incident.
Sometimes you miss something in a spreadsheet with >8000 lines.

** Reassessment of flight data with the correct flight mode **
The flight was normal until near the end.
From 13:22.2 at 259 ft, the elevator was full forward and the throttle was full down.
The drone descended at 3 m/s (normal speed) and was moving forward at 9 m/s.
The aileron was released at 13:46.5 and forward speed slowed.
13:47.9 (altitude 25 ft) the Mini started to rotate clockwise without any rudder input.
At 13:48.5 the drone had rotated 180° and it also started to roll heavily to the left while it first pitched forwards and then backwards.
The final tumbling descent had accelerated to about 7 m/s.
At 13:50.3 the spinning stopped when the drone crashed at an indicated altitude of about -17 ft.

The spinning and falling, suggests the loss of either a motor or a prop.

Motor is stuck messages mark the crash.
It was at approx -17 ft.
The launch was from up on the dunes above the beach and the crash was down on the beach.
The drone moved very little after 13:50.4, as confirmed by the pitch, roll and yaw data hardly changing.

Speed and altitude data after that is false and due to the IMU affected by the impact.
7-4 08:18
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GaryDoug
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Labroides Posted at 7-4 07:51
the remote appears to be in the Mode 3 setting
Well spotted ... I'll have to reassess the incident.
Sometimes you miss something in a spreadsheet with >8000 lines.

Where are you getting this crash altitude of -17 feet? After and before that Baro height the altitude still drops at the same rate (about 1-2 foot/sec) and there are still 13 sats counted. After that the home distance reverses and slightly increases (falling backwards?).

Now that I see the terrain a bit, it does not look like a difference of 40+ feet.


To me it looks like the main fault occurs at 13:50.7 when the battery voltage drops temporarily....

edit 10 hours later ^^^^^  what a bunch of rubbish that is ;-) Come on Gary...

7-4 09:05
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Labroides
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GaryDoug Posted at 7-4 09:05
Where are you getting this crash altitude of -17 feet? After and before that Baro height the altitude still drops at the same rate (about 1-2 foot/sec) and there are still 13 sats counted. After that the home distance reverses and slightly increases (falling backwards?).

Now that I see the terrain a bit, it does not look like a difference of 40+ feet.

Where are you getting this crash altitude of -17 feet?
It's where the pitch, roll and yaw data stabilises.
That's where the drone came to rest.
Everything after that is junk (shaded grey).
It's common to see crazy altitude and speed data after a crash impact.

Cr1.jpg
7-4 09:33
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Niftiest
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Sorry on not specifying that I do indeed use a different control mode than default. This is correct. After I found it, cleaned it off, etc, it flew properly, letting it hover with no erorrs, then flew a bit more normally (I did a few quick shots then left) but or course I didn't take it far. As for the erorrs I saw absolutely no errors prior to the crash. As you can see in the video at that point I was looking at it, not the screen, but no audible errors, no. It just.... Dropped/swirled down to the ground. I'm sure that doesn't help but fig I'd mention. If this were to happen outright and I'm unable to recover it, would DJI replace it? I unfortunately can't afford to just lose $535 that quickly. I have th DJI refresh program but of course that requires you be able to retrieve the device. I'm not sure what to do currently.
7-4 10:22
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Sean-newbie
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Is it possible some sand got into the motors at or before launch and worked its way into a position to jam a motor?  Are the motor speeds available in any of the posted data, I can't seem to find them?
7-4 11:17
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hallmark007
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Sean-newbie Posted at 7-4 11:17
Is it possible some sand got into the motors at or before launch and worked its way into a position to jam a motor?  Are the motor speeds available in any of the posted data, I can't seem to find them?

Motor obstruction is normally the first sign you will see on a flight log that tells you this was point of crash. If there was sand in motor your warning is more likely to be Motor speed error.
7-4 11:37
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Labroides
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Niftiest Posted at 7-4 10:22
Sorry on not specifying that I do indeed use a different control mode than default. This is correct. After I found it, cleaned it off, etc, it flew properly, letting it hover with no erorrs, then flew a bit more normally (I did a few quick shots then left) but or course I didn't take it far. As for the erorrs I saw absolutely no errors prior to the crash. As you can see in the video at that point I was looking at it, not the screen, but no audible errors, no. It just.... Dropped/swirled down to the ground. I'm sure that doesn't help but fig I'd mention. If this were to happen outright and I'm unable to recover it, would DJI replace it? I unfortunately can't afford to just lose $535 that quickly. I have th DJI refresh program but of course that requires you be able to retrieve the device. I'm not sure what to do currently.

If this were to happen outright and I'm unable to recover it, would DJI replace it?

DJI will replace .. even if the wreckage cannot be retrieved, but only if the data clearly shows a DJI fault.
7-4 16:23
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GaryDoug
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Labroides Posted at 7-4 09:33
Where are you getting this crash altitude of -17 feet?
It's where the pitch, roll and yaw data stabilises.
That's where the drone came to rest.

Very interesting. I guess I will download the csv file next time to see that data. And, of course, forget what I said about the battery voltage. I see that going high and low on several occasions in the last few seconds. Thanks for the explanation.
7-4 19:41
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m80116
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Small wonder the drone couldn't keep its attitude with a -motor blocked-.

I can just assume the OP did take off from the sandy area and collected some in the process which is very likely.

I can personally confirm that by sheer dust alone at least two of my MM motors were already showing signs of increased resistance (before I dusted and lubed every single one with good quality silicone oil).
7-5 00:32
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Labroides
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m80116 Posted at 7-5 00:32
Small wonder the drone couldn't keep its attitude with a -motor blocked-.

I can just assume the OP did take off from the sandy area and collected some in the process which is very likely.

* * * * *
7-5 05:19
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EHEA
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Edit: Sorry, this was wrong (Well the "motor blocked" warning happened only as the drone hit the ground).
But it really looks like the crash was caused by a sudden underperformance of one of the motors. It would be an interesting excercise for the pros here to analyse which motor it was, given the initial pitch down, yaw right movement, I'd say it was front left??
I also cannot find the motor rpms in the csv data (???) it would be nice to see whether the Front Left motor showed any signs of abnormal performance at some part of the flight. Maybe it ingested an insect, or sand? The drone was flying below the dune top rather close to the ground at times.

Fly Safe
HB
7-5 05:38
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JJB*
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Niftiest Posted at 7-4 10:22
Sorry on not specifying that I do indeed use a different control mode than default. This is correct. After I found it, cleaned it off, etc, it flew properly, letting it hover with no erorrs, then flew a bit more normally (I did a few quick shots then left) but or course I didn't take it far. As for the erorrs I saw absolutely no errors prior to the crash. As you can see in the video at that point I was looking at it, not the screen, but no audible errors, no. It just.... Dropped/swirled down to the ground. I'm sure that doesn't help but fig I'd mention. If this were to happen outright and I'm unable to recover it, would DJI replace it? I unfortunately can't afford to just lose $535 that quickly. I have th DJI refresh program but of course that requires you be able to retrieve the device. I'm not sure what to do currently.

Hiya,

Hope DJI will help you out.

Seeing your video and log : during the last part of your flight one of the motors was blocked.
This when flying, as seen in the video few meters above your head, so no crash into the sand but it dropped into the sand.

First error before is tumbeld down:  "Motor stuck. Check for objects blocking motor or contact DJI Support for assistance | Motor unable to rotate. Check for objects blocking motor or contact DJI Support for assistance".
If you like post a link to your DAT file for this flight (FLY008.DAT on your mobile device), possible more info to be found in there about about the blocking motor.
Amazed that after some cleaning it did fly again, so why a temporarily block on a motor?  mayby in the dat file....(DAT files includes motor RPMs)

See the chart where you can seen the different values for your mode3 flight.

cheers
JJB


analysis1.png
7-5 05:59
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GaryDoug
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Hmmmm. In the video it takes about 2 seconds to go from stable operation to resting on the sand. In the log file the first motor warning is at 13m 48.3 seconds. The drone seems to come to rest on the sand at 13m 50.4 seconds, just about 2 seconds later. probably not a coincidence.
7-5 09:55
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JJB*
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GaryDoug Posted at 7-5 09:55
Hmmmm. In the video it takes about 2 seconds to go from stable operation to resting on the sand. In the log file the first motor warning is at 13m 48.3 seconds. The drone seems to come to rest on the sand at 13m 50.4 seconds, just about 2 seconds later. probably not a coincidence.

Hi Gary,  ofcourse no coincidence. Data in the log  is showing too what happend in this flight.
In flight a motor become "unable to rotate", so drone dropped out of the sky.

Great to see not only the log but the video as well.

cheers
JJB
7-5 10:42
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Niftiest
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JJB* Posted at 7-5 05:59
Hiya,

Hope DJI will help you out.
[Image]

Hi, thank you for your feedback. I've uploaded the log (I think this is the one). Please let me know if you need anything else!

FLIGHT LOG:
https://drive.google.com/file/d/15cPz5zg3QXRa4L9JZ0Bl1sIG-fMjDcy0/view?usp=drivesdk
7-5 10:58
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Sean-newbie
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If this is the correct bit of the log something wierd seems to be going on, the speed of all the motors plummet
7-5 11:29
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Sean-newbie
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I can't seem to delete the image in the post above so here's attempt 2
If this is the correct bit of the log something wierd seems to be going on, isn't it? The speed of all the motors plummet

left motor slows volts vs speed.png
7-5 11:45
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JJB*
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Niftiest Posted at 7-5 10:58
Hi, thank you for your feedback. I've uploaded the log (I think this is the one). Please let me know if you need anything else!

FLIGHT LOG:

Hi Niftiest,

Yes, this DAT is the correct one.

Looking into it, see the error log and some motor rpm values.

All 4 motors reduced their speed at same time. Some motor more than the others.
If all motors were reduced in the same way i suspect an sw error or batt error. Not in this case.
An impact in air is in the log.



cheers
JJB
analysis1.png
analysis2.png
analysis3.png
7-5 11:57
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GaryDoug
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From the dat file, here is a graph of the motor speeds before, during and after the failure.   ooops, redundent charts ;-)  See above

7-5 12:09
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GaryDoug
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Motor speeds for the entire flight

7-5 12:15
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Niftiest
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JJB* Posted at 7-5 11:57
Hi Niftiest,

Yes, this DAT is the correct one.
[Image]

I can assure you 1000% there was nothing that impacted it prior to the drop, If it did, it was too small to be seen by my eye. Not sure if that's what you're saying or how I interpreted but if it helps, to my eyes, absolutely nothing was near it during the return flight or any of the flights (can share all flight videos from that day nps! Just lmk!)
7-5 15:44
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The Saint
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I always try to wear a GoPro and keep it rolling while I am flying.  just strap on one of those chest mounts and it should record for a few hours.  I can think of a dozen good reasons to have video from your perspective while operating your drone.  in addition, I try to have a tripod-mounted camera (yes, it's a Osmo action) setup in a nearby vantage point to record the general area where I wander around, sorta like a third person view.  not paranoid, just cautious.

btw, the birds were attacking like crazy; had to pack it in early.  sorry I can't help with the crash details; sounds like you are getting alot of good feedback.
7-5 17:36
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Bloodied_Mini
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I'm not a pro here but once I was flying my MM and was absorbed by reading the telemetry (especially trying to read white font over light blue sky) on my drone that I failed to notice the drone was being harrassed by a group of swallows. As luck have it my wife was watching and filming it next to me and called out the attack and I pulled up... flew back and landed. A review on the footage did show the swallows swooping around and charging at the MM. After that incident, decided to buy an action cam and a compatible cap to film the drone when I was alone (so far didn't work as intended as when I was squinting at the telemetry, it's just focused on the... remote/ground). Still, in cases like yours while you're looking at your drone's approach, it might help. The bright side is, the flight logs shows you don't really have something in your motor.
7-5 17:37
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Guorium
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It does appear to be a motor speed issue the left and right are not very matched. But i have no idea why it would shut the motors suddenly. Lucky you had it back. This is not common. Do not give up on flying. Open a case with DJI. Upload the log and video as they ask, they will ask for the drone to be returned and give you a repair or replacement. But I do recommend you to keep close contact as sometimes dji gives bogus repair description that does not seem to be related to the problem (your propulsion system). Try to reason with them to get a replacement unit if they plan to give you unconvincing repair. It is the best solution for you to avoid more troubles down the line. And very importantly, do not use dji replacement program, it does not seem to be user error from your description of the crash.
7-5 18:29
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