MP1 RTH wont respond in the normal manner

[mereflyer]

I am a long term X large scale RC model aircraft pilot, having owned and enjoyed my MP1 with no real problems for more than 2 years .

But now I have this problem - MP1 RTH wont respond in the normal manner since these last three flights.

I use both Litchi and DJI Go4 Flight Control Apps and the problem appears equally on either of them.

Before this I had no problem with accuracy of Auto Returning to Home with fairly good and consistent landings.

For no reason, these last three flights on separate days and at different locations, RTH failed to trigger normally with the usual long button press.

The RTH started to activate at slow speed for about 5 seconds, the drone then climbed slowly. Kept repeating this sequence of slow forward (toward home point) then climbing each time until the voice finally announced "You have reached maximum altitude 120 meters" then continued to travel very slowly forward (1 -2 Kph). After which I took over and landed the MP manually, to preserve the battery.

I had previously calibrated both IMU and Compasses, with all green lights, and did a repeat calibrations when the problem first appeared.

The only constant is that the weather has remained cool and overcast on each of the 3 events. Trying to remember how many Sats on the screen - maybe 5 - I think!

Seeing this happening on the last three separate landings has me very puzzled and not sure how to fix it, so if anyone can help with any ideas or suggestions,I would be very appreciative.

 

[old man mavic]

sounds like you were not getting enough sats locked to get a good home point location on my MPP i have the precision landing tick box does the MP1 have this feature

 

[Kilrah]

Likely the MP was erroneously detecting an obstacle in front of it.

 

[kndll]

How often do you use RTH ? Does the same thing happen when you use the on screen RTH option ?

 

[Flycaster]

5 sats?, that sounds low, not knowing the terrain tho.
Sounds like a cross between terrain following and obstacle avoidance issue?
No other warnings popped up?

 

[mereflyer]

Post the flight logs, I'm sure some of the clever people on here could help.

Flight log retrieval and analysis guide

Thanks for the suggestion - I will get to that shortly!

 

[mereflyer]

Likely the MP was erroneously detecting an obstacle in front of it.

Thanks for that, but very certain - no objects in either of the three flights!

 

[mereflyer]

How often do you use RTH ? Does the same thing happen when you use the on screen RTH option ?

I normally use RTH for end of Waypoint flights with the Litchi App and most often with FPV/Go4 flights as well. I have not used the "On Screen" option, only ever used the controller button.
Those last three flights had to be manually RTH and landed.

 

[mereflyer]

5 sats?, that sounds low, not knowing the terrain tho.
Sounds like a cross between terrain following and obstacle avoidance issue?
No other warnings popped up?

I must confess to not actually being certain about the number of Sats when RTH was triggered - either when auto triggered, or manually selected. Could try again today sometime and take a good look!

 

[mereflyer]

5 sats?, that sounds low, not knowing the terrain tho.
Sounds like a cross between terrain following and obstacle avoidance issue?
No other warnings popped up?

I must confess to not actually being certain about the number of Sats when RTH was triggered - either when auto triggered, or manually selected. Could try again today sometime and take a good look!

Post the flight logs, I'm sure some of the clever people on here could help.

Flight log retrieval and analysis guide

One of the three problem flights can be viewed here: DJI Flight Log Viewer - PhantomHelp.com You will see the variations in speed and altitude as the MP returned home - and the several mentions of obstacles to be avoided - Excepting that at the recorded altitudes no obstacles were sighted, so maybe this could be something to do with a faulty obstacle sensor? - would that be an issue?
Any suggestions?

 

[sar104]

I must confess to not actually being certain about the number of Sats when RTH was triggered - either when auto triggered, or manually selected. Could try again today sometime and take a good look!

One of the three problem flights can be viewed here: DJI Flight Log Viewer - PhantomHelp.com You will see the variations in speed and altitude as the MP returned home - and the several mentions of obstacles to be avoided - Excepting that at the recorded altitudes no obstacles were sighted, so maybe this could be something to do with a faulty obstacle sensor? - would that be an issue?
Any suggestions?

That is unusual behavior - the aircraft repeatedly starts and stops in RTH mode:



In fact the vertical behavior is the clue to the reason:



The uncommanded periods of climb between the RTH stops indicate that the aircraft is repeatedly spuriously detecting an obstacle and then attempting to climb over it. Strangely, RTH OA, and OA generally, is marked as disabled, but that's clearly what seems to be happening.

 

[FoxhallGH]

Just an idea - but at this time of the year the sun is low on the horizon. Were your RTH attempts aiming the Mavic at the Sun???
This can sometimes upset the sensors and make the Mavic think it's seeing a wall!

 

[sar104]

Just an idea - but at this time of the year the sun is low on the horizon. Were your RTH attempts aiming the Mavic at the Sun???
This can sometimes upset the sensors and make the Mavic think it's seeing a wall!

The aircraft was flying due north.

 

[mereflyer]

Just an idea - but at this time of the year the sun is low on the horizon. Were your RTH attempts aiming the Mavic at the Sun???
This can sometimes upset the sensors and make the Mavic think it's seeing a wall!

No Sun - was quite overcast sky with only slight breezes

 

[mereflyer]

That is unusual behavior - the aircraft repeatedly starts and stops in RTH mode:

View attachment 94727

In fact the vertical behavior is the clue to the reason:

View attachment 94729

The uncommanded periods of climb between the RTH stops indicate that the aircraft is repeatedly spuriously detecting an obstacle and then attempting to climb over it. Strangely, RTH OA, and OA generally, is marked as disabled, but that's clearly what seems to be happening.

Thanks for the analysis Sar. Yes you can clearly see the events on the graphs. The problem for me now is how to fix it - any idea's??

 

[sar104]

Thanks for the analysis Sar. Yes you can clearly see the events on the graphs. The problem for me now is how to fix it - any idea's??

I would do a sensor calibration if you haven't already done that.

 

[mereflyer]

I would do a sensor calibration if you haven't already done that.

Yes - I was thinking this would be the next step - will need to find info as have never done sensor calibration before. So Off to search for the best way to do this!

 

[mereflyer]

Use the DJI Assistant PC program. DJI Assistant 2- DJI Download Center- DJI

Connect the drone to the PC by USB and follow the instructions.

Thanks for that Gobuchal,
DJI Assistant 2 Updates (not available for my op sys) - I use Linux Mint 19.3 exclusively... No access to Windows or Mac, so will have to make other arrangements...

 

[Bekanne]

Likely the MP was erroneously detecting an obstacle in front of it.

Three times though; could it be a damaged front sensor causing it to think there is an obstacle?

 

[mereflyer]

You need WINE and you can run Windows stuff on Linux.

How to run Windows software in Linux: Everything you need to know

Thanks Gobuchal - Yes I am aware of the Windows/Linux connection through Wine. Certainly worth pursuing, since I dont have any answers yet to the problem.
Flew again today after disabling forward obstacle sensors, still same fault.