Erratic Descent On Return To Home

[rkwingo]

I am an experienced drone pilot with about 50 hours on a new (6 months) Phantom 4. The unit has the latest firmware updates (as does the controller). IMU and Compass are accurately calibrated. I have never had prior issues with interference, and always fly away from houses or other structures.

This afternoon I was descending from 300 ft after engaging the return to home routine. At about 150 ft the drone went out of a controlled descent and moved at high speed to the right. I quickly brought it under control, but I have never seen it do that before.

Any idea what could have caused this to happen?

 

[Meta4]

This afternoon I was descending from 300 ft after engaging the return to home routine. At about 150 ft the drone went out of a controlled descent and moved at high speed to the right. I quickly brought it under control, but I have never seen it do that before.

Any idea what could have caused this to happen?

Looking at the flight data is usually the way to get an understanding of what's happened in a flight.
Go to https://www.phantomhelp.com/LogViewer/Upload/
Follow the instructions to upload your flight record.

 

[rkwingo]

Thanks! I was able to upload all of my DAT files from my Phantom 4 to my PC. When I try to upload the most recent DAT file using the LogViewer/Upload utility I get an error "Site Can't Be Reached'. Any idea why that's happening?

 

[rkwingo]

i was able to watch my flight on the DJI App on my IPad. at approx 100 Ft, the screen says: 'Locating Landing Point'. It is at that exact moment that the horizontal speed went from 0 to nearly 7 mph. That's the exact point I took over control and landed the Phantom. Any ideas what may be causing that to happen?

 

[Meta4]

i was able to watch my flight on the DJI App on my IPad. at approx 100 Ft, the screen says: 'Locating Landing Point'. It is at that exact moment that the horizontal speed went from 0 to nearly 7 mph. That's the exact point I took over control and landed the Phantom. Any ideas what may be causing that to happen?

If you follow the instructions in post #2 to upload the .txt file from your phone/tablet you'll see exactly what was happening with no need to guess.
Post a link here if you need help.

 

[rkwingo]

I was successful in uploading the .txt file and discovered that at ~60 Ft I received a warning message that the gimbal had reached its "movement limit". What would cause that?

 

[Meta4]

I was successful in uploading the .txt file and discovered that at ~60 Ft I received a warning message that the gimbal had reached its "movement limit". What would cause that?

Post a link

 

[rkwingo]

This is the file I as viewing

 

[Meta4]

This is the file I as viewing

Here's the flight data.
You were descending in autoland, using the precision landing feature.
But if Google Earth is a good indication of the flying environment, you were landing onto a plain grass surface which would have been a problem for the precision landing system.
It needs recognisable features to be able to find the launch spot.
I'm guessing it started to wander because it couldn't find a pattern in the grass and maybe GPS counteracted that.
The data shows it wandering a little from 3:11-3:20 with no joystick input.
And wandering faster from 3:22 - 3:38 while you were trying to counter it with some joystick input.
Here's what the manual says about limitations for precision landing:

Test it again on a good landing surface and if it comes down straight and steady, that clear up the mystery.
And if landing where/when conditions aren't good for precision landing, cancel and land manually to avoid a repeat.

 

[rkwingo]

Thank you very much.