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Drone just drops out of the sky.

Crouching Leopard

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I realise this is a mavic forum, but I know there are some real savy data file gurus on here so I thought I would give it a try.

I normally fly Mavics, but 2 weeks ago purchased the Avata. Today, I was flying at about 5.5 metres height, and slowly, on my way back to the takeoff point, roughly 49% battery, no prior high speed maneuvers. It was just a quick fun, no frills flight before dinner.

Suddenly, the drone just fell out of the air onto some very soft, tall, grass. I tried using turtle mode to right it, but it did not work.

On finding the drone using the esc beep, I noticed that the drone it was still transmitting video, but that the battery connector was partially out. However, some power was still getting to the drone, but it would not respond to any commands, not even pressing the controls on my fpv goggles V2 to bring up the menus worked.

No damage but a prop was completely missing, although the screws holding it in place were still there, fully seated and tight. It looks like the prop may have sheared in half at the base, whether in the sky or on impact. I saw no sign of bird collision and no "jolt" which would be associated with one. I could not find any part of the prop.

I have reviewed the drone sd card video, and there is nothing obvious to indicate what caused the failure.

Could someone look through the attached flight file and give some advice on what may have happened. There were three files on the drone all taken around the relevant time, but I think the attached file is the correct one.

I am interested to know if it was a partial power failure which caused the crash and the prop came off on impact, or was there a sudden motor surge (prop loss?, bird or other strike) which caused the impact and the battery partially popped out. Thanks

Link to crash video

 

Attachments

  • DJIFlightRecord_2022-12-06_[07-14-13].txt
    1 MB · Views: 11
I'm not the flight log guy on the forum, but I just thought I would mention my experience with drones. I have had quite a few due to crashes for some reason or another. I have had 2 DJI's fall from the sky for no apparent reason and 2 Autel Evo series drones do the same over the past 4 years. I just had them repaired or used their care refresh programs and got replacements. I sold one for scrap.

Is it Meta4 that evaluates flight logs or is it Sar? I can't remember.
 
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I am interested to know if it was a partial power failure which caused the crash and the prop came off on impact, or was there a sudden motor surge (prop loss?, bird or other strike) which caused the impact and the battery partially popped out. Thanks
The data just ends with the drone still in stable, slow flight.
These incidents are frustrating because the data doesn't show what caused the incident.
If there was a collision or a broken prop, that wouldn't stop the data recording.
But losing power does.
 
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The data just ends with the drone still in stable, slow flight.
These incidents are frustrating because the data doesn't show what caused the incident.
If there was a collision or a broken prop, that wouldn't stop the data recording.
But losing power does.
As always, thanks for your log assessments.
 
What stands out to me is your estimate of ~ 5.5m alt at that point of flight issue, which does correlate to the log in general (17.7' or 5.4m) at the end of the data record.

Did you get the estimated alt of the aircraft from the screen telemetry and remember it, or did you look at the report prior to uploading the TXT ?

It just seems at the point the flight goes pear shaped, the drone looks a lot higher, perhaps triple that.
I'm basing that on estimated size of the trees nearby, and relative to the size of the people walking their dog early in the video.

The cell deviation yellow shading in the log is off, and it appears you had good battery reserve at 41%.
It is recorded you took off with a less than fully charged battery at 73% . . . was that a fresh charge, or was it perhaps slightly discharged and cell balance / voltage might have been erroneously reported in the app ?
 
What stands out to me is your estimate of ~ 5.5m alt at that point of flight issue, which does correlate to the log in general (17.7' or 5.4m) at the end of the data record.

Did you get the estimated alt of the aircraft from the screen telemetry and remember it, or did you look at the report prior to uploading the TXT ?

It just seems at the point the flight goes pear shaped, the drone looks a lot higher, perhaps triple that.
I'm basing that on estimated size of the trees nearby, and relative to the size of the people walking their dog early in the video.

The cell deviation yellow shading in the log is off, and it appears you had good battery reserve at 41%.
It is recorded you took off with a less than fully charged battery at 73% . . . was that a fresh charge, or was it perhaps slightly discharged and cell balance / voltage might have been erroneously reported in the app ?
It was the second flight of the evening on that battery. The previous was a few minutes before. I have learnt my lesson previously on taking off with non full batteries, especially FPVs.😓

The height is correct (give or take a small amount. The trees in that area are around 11 metres high and I had dropped height after flying through their canopy.
 
a prop was completely missing, although the screws holding it in place were still there, fully seated and tight
Did the entire prop fly off? Or was the center of the prop still attached and the blades somehow sheered off?

Were you flying with OEM DJI props or 3rd party props?
 
The data just ends with the drone still in stable, slow flight.
These incidents are frustrating because the data doesn't show what caused the incident.
If there was a collision or a broken prop, that wouldn't stop the data recording.
But losing power does.
Thanks for your assessment. The connector was partially out when I found the drone, although some functions such as esc beep were still working, and the drone did record itself going down. Also, in the goggles, I had no response to such things as entering menu modes, viewing video before loss, or anything else, just the live video feed was still working, So I am thinking partial power loss. I usually push the connectors hard in and check before flying, but I could have missed it this time. I also always check props and didnt see anything out of place.

Although I believe the record I uploaded is the correct one, there was a flight shortly before the crash flight, and I did turn the drone on after the crash to see if it was still "booting up". These logs are close together but my pc is showing the same time and date for all. Might I trouble you to have a quick look at the first and last logs to see they are not the ones for the crash. The cash flight was the longest and I did reach altitudes of around 28-30 metres.

Again, I really appreciate your help on this.

Although I will put this down to partial power loss, I am beginning to think this drone was released to early. I have owned an avata for a little over 2 weeks and have had 3 issues. The first issue was with 2 out of 4 brand new, fully charged batteries going from 95% charge to almost zero in just a few seconds (DJI admitted faulty batteries), then a couple of days later, a couple of seconds after taking off, the drone went wild, flew around in a left hand very tight yaw at great speed, did 3 laps around me and crashed. I had no right hand sticks control, the video went blank, my left sticks would only allow left yaw, up and down (but not land) and the brake button did not work. It was a very scary 15 or so seconds. I also lost video transmission and the data file did not record. I sent it in for assessment. DJI reported an IMU and telemetry board faults and replaced the drone under warranty. One more incident and this drone is going back!!

As for this issue, and am probably going to put it down to partial power loss. Another good reason for flying within the rules.
 

Attachments

  • DJIFlightRecord_2022-12-06_[07-09-33].txt
    720 KB · Views: 5
  • DJIFlightRecord_2022-12-06_[10-09-01].txt
    548.4 KB · Views: 4
the 2022-12-06_[07-09-33] log = DJI Flight Log Viewer - PhantomHelp.com
the 2022-12-06_[07-14-13] log = DJI Flight Log Viewer - PhantomHelp.com
the 2022-12-06_[10-09-01] log = DJI Flight Log Viewer - PhantomHelp.com

I would repeat Msinger's question, was there absolutely no remnants of the propeller's hub left on the motor?
To be honest from the photos I have seen the props look flimsey enough (they appear to be semi tranparent) that I would suspect that anything that would snag a blade with enough force to break the blade would rip the blade off the hub and leave the hub largely intact.

Personally I would be inclined to post this on the DJI forum ........ hoping to get them to ask for the DAT from the drone ..... if the Avata creates one on the drone. The logs we mere mortals can access are recorded whist the motors are running and the recording device is connected to the drone. The DAT on the drone (which we most likely CAN NOT read) is recorded whilst the drone is on. Your video shows the drone suddenly yawing anti clockwise and then rolling to the left.
I can't imagine how a partial power failure would cause that, I can imagine that a prop failure on the left might.
The DAT on the drone, if recorded would probably give DJI the means to check for a prop failure i.e. increased motor speed if nothing else
 
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the drone did record itself going down.
How do you know this?
Is there any data?
So I am thinking partial power loss.
A complete power loss
These logs are close together but my pc is showing the same time and date for all.
The file times for these two are 7:09 and 10:09, the first one posted was 7:14
Might I trouble you to have a quick look at the first and last logs to see they are not the ones for the crash.
Both are complete flights and ended in safe landings.
 
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the 2022-12-06_[07-09-33] log = DJI Flight Log Viewer - PhantomHelp.com
the 2022-12-06_[07-14-13] log = DJI Flight Log Viewer - PhantomHelp.com
the 2022-12-06_[10-09-01] log = DJI Flight Log Viewer - PhantomHelp.com

I would repeat Msinger's question, was there absolutely no remnants of the propeller's hub left on the motor?
To be honest from the photos I have seen the props look flimsey enough (they appear to be semi tranparent) that I would suspect that anything that would snag a blade with enough force to break the blade would rip the blade off the hub and leave the hub largely intact.

Personally I would be inclined to post this on the DJI forum ........ hoping to get them to ask for the DAT from the drone ..... if the Avata creates one on the drone. The logs we mere mortals can access are recorded whist the motors are running and the recording device is connected to the drone. The DAT on the drone (which we most likely CAN NOT read) is recorded whilst the drone is on. Your video shows the drone suddenly yawing anti clockwise and then rolling to the left.
I can't imagine how a partial power failure would cause that, I can imagine that a prop failure on the left might.
The DAT on the drone, if recorded would probably give DJI the means to check for a prop failure i.e. increased motor speed if nothing else
Yes, there was absolutely nothing left of the pop or its base, just the screws.
 
How do you know this?
Is there any data?

A complete power loss

The file times for these two are 7:09 and 10:09, the first one posted was 7:14

Both are complete flights and ended in safe landings.
No data as such, just the video I posted of the drone going down, and the continued transmission to the goggles of the upside down drone on the ground, plus the ability to turn on the esc beep from the controller There is a couple of minutes of uneventful video before the last few seconds, which I edited out for expediiency.

I go for complete power loss, but as can be seen from the video, it was recording as it went down, and responded to the ESC beep command. The video is from the drone sd card.

Here is the full video
 
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I just checked the battery connector base on the drone. On the right hand side 2 small pins, the top one seems to be located in further into the assembly than the bottom mini pin by about 1.5 mm. On the battery they are both located to the same depth. I cant see any logical reason for the difference, but it would make it easier to lose contact on the top pin if there was a minor incorrect insertion of the battery. I will check out other drones at the dji repair centre tomorrow.

I have labeled it "" pushed in", but it could be manufactured that way, although, as someone who spent time on electroinic systems design, I cant see why.
 

Attachments

  • Pin further in.jpg
    Pin further in.jpg
    1.5 MB · Views: 51
Last edited:
the 2022-12-06_[07-09-33] log = DJI Flight Log Viewer - PhantomHelp.com
the 2022-12-06_[07-14-13] log = DJI Flight Log Viewer - PhantomHelp.com
the 2022-12-06_[10-09-01] log = DJI Flight Log Viewer - PhantomHelp.com

I would repeat Msinger's question, was there absolutely no remnants of the propeller's hub left on the motor?
To be honest from the photos I have seen the props look flimsey enough (they appear to be semi tranparent) that I would suspect that anything that would snag a blade with enough force to break the blade would rip the blade off the hub and leave the hub largely intact.

Personally I would be inclined to post this on the DJI forum ........ hoping to get them to ask for the DAT from the drone ..... if the Avata creates one on the drone. The logs we mere mortals can access are recorded whist the motors are running and the recording device is connected to the drone. The DAT on the drone (which we most likely CAN NOT read) is recorded whilst the drone is on. Your video shows the drone suddenly yawing anti clockwise and then rolling to the left.
I can't imagine how a partial power failure would cause that, I can imagine that a prop failure on the left might.
The DAT on the drone, if recorded would probably give DJI the means to check for a prop failure i.e. increased motor speed if nothing else
 
No data as such, just the video...
If doing as usual with DIY FPV quads where no log exists in a similar way as for the DJI drones ... video analyzing of the incident.

The video shows that the Avata start to rotate CCW, then shortly after rolls over to the left... how it's pitching is hard to say due to the gimbal.

1670403037703.png

1670402981342.png

The Avata have a "props in" rotation configuration... meaning that the front props have a rotation direction towards the front & the rear props a rotation towards the rear. As the pic below...

1670401769978.png

As the Avata starts to yaw CCW this indicate that a CW torqueing corner fails (either rear left or front right)... & as the roll is towards the left, both indicate that the rear left corner suddenly lose thrust.

As you earlier (on the FPV forum) confirmed that the broken prop was where the usb connection is (near rear left prop)... all this tells me that the primary reason for the crash was a failing prop, the other indications like log recording that stopped, a partial connected battery & that you couldn't re-connect was secondary & possibly caused by the touch down.
 
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