Unexpected loss in altitude

atsphenomenon · Jan 4, 2020

sar104 said:
Some background to log analysis is linked in my signature.

Thanks! That's quite exhaustive!

TDZHDTV · Jan 4, 2020

sar104 said:
Very interesting pitch and roll oscillations just before the uncommanded descent started:

View attachment 89730

This looks like a firmware bug to me.

Hi Sar, would you relate this to the issue were some people believe simply changing the propellers solves the decent issue? I find it hard to believe changing props is a solution.

sar104 · Jan 4, 2020

TDZHDTV said:
Hi Sar, would you relate this to the issue were some people believe simply changing the propellers solves the decent issue? I find it hard to believe changing props is a solution.

This is clearly an intermittent fault, which superficially doesn't seem consistent with it being a problem with the props - they are presumably not going to change significantly during the flight. However, they could be out of specification and causing intermittent problems with the flight controller in certain situations.

atsphenomenon · Jan 4, 2020

sar104 said:
This is clearly an intermittent fault, which superficially doesn't seem consistent with it being a problem with the props - they are presumably not going to change significantly during the flight. However, they could be out of specification and causing intermittent problems with the flight controller in certain situations.

Though the props i have are ALMOST pristine; I did buy the flymore combo and have an extra set of propellers. Would you guys recommend i change em and give it a try. My reservation is that in 71 flights with 8 hrs of fly time, this is the first instance of this anomaly. So I'm not sure how long would i need to test with the new props to know for certain that the culprit were the props.

On the other hand, this was my first flight with the new firmware, and i faced this error. I'm willing to put my money on the firmware being the issue, purely because of this. More experienced folks would know better.

atsphenomenon · Jan 5, 2020

Fly Dawg said:
There have been a few instances when the .dat wasn't recorded for whatever reason that is. But it is odd that there are not any .dat files at all. Let me see if @sar104 can add to this.

While I haven't been able to recover the previous dat files, i did want those for subsequent flights. Tried uninstalling and reinstalling the app multiple times to no avail. What's finally worked is uninstalling the app + deleting the DJI folder from the phone + reinstalling. The dat logs seem to be getting created 100% of the times. Hope this helps someone.

TDZHDTV · Jan 5, 2020

atsphenomenon said:
Though the props i have are ALMOST pristine; I did buy the flymore combo and have an extra set of propellers. Would you guys recommend i change em and give it a try. My reservation is that in 71 flights with 8 hrs of fly time, this is the first instance of this anomaly. So I'm not sure how long would i need to test with the new props to know for certain that the culprit were the props.

On the other hand, this was my first flight with the new firmware, and i faced this error. I'm willing to put my money on the firmware being the issue, purely because of this. More experienced folks would know better.

This issue was reported before the latest firmware was released, therefore I firmly believe it’s a bug that DJI will resolve as there are more instances starting to show up on the DJI forum. I’m not 100% convinced props are the issue, mine are worn with a small piece missing and it still fly perfect with around 40 flights. I guess it a personal judgement call, I’m taking my mini to the mountains next month weather permitting, I’ll probably swap the props for that visit

sar104 · Jan 5, 2020

atsphenomenon said:
While I haven't been able to recover the previous dat files, i did want those for subsequent flights. Tried uninstalling and reinstalling the app multiple times to no avail. What's finally worked is uninstalling the app + deleting the DJI folder from the phone + reinstalling. The dat logs seem to be getting created 100% of the times. Hope this helps someone.
View attachment 89856

Thanks for reporting that you managed to fix that. I'm surprised that simply uninstalling the app didn't delete the app directory. I'll add a note about that to the logs guide.

Eka · Jan 6, 2020

Another similar case

Woodie_07 · Jan 12, 2020

Eka said:
Another similar case

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It looks quite cold in that video and the props could have iced up, causing the drone to not have enough thrust and start falling down. Could this be what happened?

new2mavic · Jan 12, 2020

Icing can well be the reason. There has been a report by a local pilot that he attempted to fly through the cloud and ended up in the drone falling out of the sky. Subsequent analysis by DJI revealed that the motor / prop had iced up in the process.