https://www.phantomhelp.com/LogViewer/5H5CH9HHFR2LFZ181OQ0/

Hello all,

I was flying my drone in a zone with altitude restricted to 30m. There was a building about ~35m high, which I tried to fly around, however I lost the signal and RTH was activated. Then the drone flew in a straight line into the builiding, without allowing me to disactivate RTH (signal was lost for the whole time <- edit: the point is I caught the signal at least once for a brief second, but it was not enough to disactivate RTH). I am quite shocked that the drone didn't recognize the obstacle. I have already requested drone replacement using DJI Care Refresh, but I want to analyze this situation to prevent it from happening in future. I will greatly appretiate some tips. Should I maybe set RTH high to > 30m to bypass highest building's height, even if the zone does not allow it?

Here is the video of the last seconds before impact, on which you can clearly see drone not reacting to the obstacle: https://www.youtube.com/watch?v=WHmuP3Vgx-s

Sorry, but I just want to check, are you seriously suggesting you do not know what happened and why it happened, you answer your own questions in you story .......... or is this thread a joke?

"I am quite shocked that the drone didn't recognize the obstacle. "  
In terms of obstacle avoidance the Mini 2 SE does not have horizontal sensors with which to see ANYTHING, the only 'obstacle sensors' are the downwards looking VPS sensor.
In other words the drone is blind to obstacles in its flight path.

"I lost the signal and RTH was activated. Then the drone flew in a straight line into the builiding, without allowing me to disactivate RTH (signal was lost for the whole time). "  Taking your original story at face value i.e.to be true, then my response was ''Uuum for you to be able to cancel an RTH the controller must be connected to the drone, since it was disconnected it couldn't do that.''
But the log seem to tell a somewhat different story and you need someone better than me to interpret it, JJB* perhaps.
Why? Firstly I don't really see what triggered the RTH. Download the csv from Phantom help and open it with a speedsheet program. Go over to the far right and look at the messages section, there are plenty of message about weak signal and disconnections.Looking at the PH flight track and RC.downlinkSignal  &  RC.uplinkSignal columns in the csv the connection starts to go bad almost as soon as that building gets in the way of the signal, around 13:11.7 but what interests me that there are 4 '' Downlink Restored '' messages with disconnection time stamps and NONE of those times stamps is longer than 9 seconds, 11 seconds is the trigger threshold for failsafe behaviour. At 13:44.5 the message is ''Downlink Restored (after 0m 8.5s)'' and at 13:49.5 the message is Downlink Restored (after 0m 3.5s). The other two reconnections were much earlier in the flight and not relevant.
Strictly speaking the 8.5 second and the 3.5 second disconnections do not, on their own, meet the required disconnection period and each, on its own would not, I think, have triggered failsafe. Maybe their being so close to gether caused the drone to sum them (12 sec) or something, but, to my mind, that is an interesting question.  
Then we come to the RTH flight into the building. There was data getting from the drone to the controller, as can be seen by the flight track, distance & speed.
I am left wondering if you might have had some control ? If the ''upload'' signal refers to data transmission to the drone i.e. commands then maybe not, it was weaker than the download signal strength, see the PH csv.

With regards to height, I still stand by what I said ''are you saying that the system, or something else, told you that the area had a drone flying height limit of 30m above the ground which may be a legal height limit? If so are you asking ''should I have set an max ceiling & RTH height that broke tha height limit?'' ''.  
If that is a legal hight limit then the answer to  your question about whether or not you should bave breached that ceiling is NO.
What should have done is NOT FLOWN BEHIND THE BUILDING IN THE FIRST PLACE.''
However I would add two points
1) it is possible that if you were flying UNDER a restriction zone then it may have been impossible for you to increase the drone's maximum ceiling and the set RTH height, simply because they were already JUST below the bottom of that restriction zone and the drone will not let entry to a restriction zone that the drone, knows about.
2) you can not set an RTH height that is higher than the drone's maximum height setting in the app. If somewhere in the future you happen to reduce the Max height setting to below the RTH height setting then the RTH height setting will be reduced to equal the max height setting.

Here is a graphical representation of the end of the flight that you might find useful, it is generated by processing the Phantomhelp csv with CsvView https://datfile.net/CsvView/downloads.html

I am sorry it seemed like for you that the thread I've created was a joke. This is my first drone, some things were not obvious for me despite reading manual (apparently not very carefully).

In terms of obstacle avoidance the Mini 2 SE does not have horizontal sensors with which to see ANYTHING, the only 'obstacle sensors' are the downwards looking VPS sensor.
In other words the drone is blind to obstacles in its flight path.
Thank you very much for pointing this out. I was not aware of it. I didn't pay enough attention for this feature.

If that is a legal hight limit then the answer to  your question about whether or not you should bave breached that ceiling is NO.
What I meant with this question was if a drone resque manner, such like RTH can breach the ceiling limit, as this is an emergency procedure. Now I see that it was a stupid question and I feel ashamed.

Mini 2 SE does NOT have Obstacle Avoidance. That's why you set RTH height above tallest obstacle in the area. Pilot error 100%

beznick Posted at 7-31 15:52
I am sorry it seemed like for you that the thread I've created was a joke. This is my first drone, some things were not obvious for me despite reading manual (apparently not very carefully).

In terms of obstacle avoidance the Mini 2 SE does not have horizontal sensors with which to see ANYTHING, the only 'obstacle sensors' are the downwards looking VPS sensor.

The edited version of my post#2 is available, you might like to read it.

Hi, there beznick. I'm sorry about what happened with your drone. But I'm glad it's already being handled by our team. If you want to see the progress of your request, you can use this link: https://repair.dji.com/us/trace/list. Hopefully, you get some awesome tips and recommendations from your fellow DJI pilots. Have a great day ahead.

Thank you Sean-bumble-bee for detailed analysis and the chart. Next time when flying in low altitude zone, I will set to hovering option, instead of RTH in case of signal lost. It's interesting that the chart shows I had control during RTH (green zone). I didn't have image updates during that time and I was trying to desperately cancel RTH, which I'm 100% confident was first time triggered automatically. I am aware that by clicking on RTH button multiple times can lead to  sequential canceling and retrigering RTH, but how could I know if my command to cancel it reached the drone, if the image was stucked? Maybe if there was a way to set in software a button that cancels RTH, but does not allow to retrigger it after? (in case you press the same button again)

beznick Posted at 8-1 14:02
Thank you Sean-bumble-bee for detailed analysis and the chart. Next time when flying in low altitude zone, I will set to hovering option, instead of RTH in case of signal lost. It's interesting that the chart shows I had control during RTH (green zone). I didn't have image updates during that time and I was trying to desperately cancel RTH, which I'm 100% confident was first time triggered automatically. I am aware that by clicking on RTH button multiple times can lead to  sequential canceling and retrigering RTH, but how could I know if my command to cancel it reached the drone, if the image was stucked? Maybe if there was a way to set in software a button that cancels RTH, but does not allow to retrigger it after? (in case you press the same button again)

" but how could I know if my command to cancel it reached the drone, if the image was stucked?"
That's an interesting question to which I do not have an answer.

Usually when the pilot is confused about whether or not an RTH is taking place, the pilot WANTS an RTH to take place, so the answer is to switch the controller off.
That assumes that the failsafe option is RTH. The idea is that if the RTH had been previously cancelled the disconnection would cause the failsafe behaviour to start and result in an RTH. If the drone WAS doing an RTH at the time of the disconnection my guess is that the disconnection would cause the on-going RTH to be stopped, the drone would then start the failsafe behaviour and ultimately start another RTH.

I am deaf so I can't answer the question I am about to pose, does the controller or phone make any audible announcements about RTH?

In general I would suggest you avoid flying behind ANYTHING that blocks you line of sight to the drone.
Why?
1) it may block the control signal and result in disconnection,
2) you can not see what is happening to the drone,
3) if may constitue breakining VLOS
And all the more so if you do not have the RTH height to fly over the over the building or obstacle.