My first 'Aircraft disconnected'.. but no clue to the reason

[Niky]

Hallo wise and seasoned pilots, this morning I experienced an 'aircraft disconnected' situation. I was nearer to the home point than in the initial part of the flight, the bird was high and with no obstructions between RC and its position (I was on top of a mountain...) and it happened all of a sudden, without any message or similar. Luckily it got back home via failsafe RTH, but I wasn't able to reconnect no matter what I did (close DJI GO, switch RC off and back on) even when the bird was descending on top of my head. Yes, antennas were correctly pointed (even when it was overhead). Finally when it was at 8m height and 6m distance it reconnected, so I was able to move it away the fundamental couple of metres out of a tree... Anyway, I know it can happen so I was curious to understand why it has this time, so to learn and avoid possible pilot or situational errors next time. I opened an account on Airdata, upload txt, and as far as I can understand from the reports there was nothing strange, flight records simply stops at 9:22 even if RC signal was still full bars. I was recording the video, I retrieved it from the SD and it shows all, including when AC turned and headed back to my arms.
I uploaded the CSV to PhantomHelp, here is the link:
DJI Flight Log Viewer - PhantomHelp.com

Forgot to say: Phantom 3 Pro with latest firmware (1.11.20), RC fully charged with latest firmware (1.9.2), DJI Go app latest version (3.1.15).

Can anyone help me discover what the reason of disconnection and so difficult reconnection might have been?
Thanks a lot in advance.

 

[Niky]

If it is useful, here the link to the other (final) part of the flight, after my P3P reconnected to RC
DJI Flight Log Viewer - PhantomHelp.com

 

[Niky]

And finally the link to Airdata info
Airdata UAV - Flight Data Analysis for Drones

 

[Numone]

Hi Niky.
When you say you were in the top of a mountain, was the AC above or below you?
I've whizzed through the log and I cant see any warnings or problems.
I had a similar situation on the one and only occasion that I lost connectivity and then the RTH kicked in. I was quite a long way out and it took a couple of minutes to regain the signal. But, using the app and the radar, I kept the RC pointed toward the AC as best as I could and I'm sure that helped regain connection. I didn't get too deeply concerned about it - it was my fault and the kit did exactly what DJI designed it to do.

 

[Niky]

Hallo Numone, AC was more or less 100m above home point (where I was standing), and distant around 500m. I knew perfectly where it was (you can see the flight path was roughly straight), and in fact I was very calm while waiting for the return, expecting to reconnect any moment. I started worrying when I saw it approaching in the distance and then starting to autoland, and nothing was happening on the RC... so I switched off the RC and then back on, but it still took 90m or so of descent before the reconnection. The take off was from a free area of around 10m diameter in the middle of trees, and the GPS precision tolerance was letting it land on one of the trees at the border of the area... you can imagine how shaky were my legs when I finally was able to control its landing point...

 

[solentlife]

A little bit concerned that you say a 10m hole in middle of trees ... does that mean you were surrounded by trees ? Were they a bit more dense in direction of AC from the RC ?

Personally I try to avoid all obstructions between myself and AC ... I like a clear area in front of me widening out so the AC is totally without any obstacle back to controller.
I know its not always possible - but at least I ensure area around me is clear for large amount so any angle of sight from RC to AC is clear for entire flight ...

Nigel

 

[Numone]

Yeah, taking off in the centre of a tree clearing isn't the best of ideas. Whilst it's OK initially, the further you go out, the lower it falls against the horizon, so more of the signal gets absorbed by the trees. That could've been your problem.

 

[Niky]

Trees were three or four on each sidee of a country road and no more than 6 or 7 metres high, I went more than 500m distant at 100m altitude before disconnection, but I have no problem with the reason, it's obvious that the angle of elevation decreases when distance increases if you don't increase altitude, so at around 480metres distance I lost LOS. My doubt is with the fact that until that moment I had full RC bars (100% confirmed by Airdata report) and connection dropped suddenly without any warning of interference, loss of video before control, or similar early indicator.
My biggest concern is with the reconnection that did not happen at all until the bird was less tham 10m away and after having had it il LOS for most part of its return flight.

 

[Numone]

Trees were three or four on each sidee of a country road and no more than 6 or 7 metres high, I went more than 500m distant at 100m altitude before disconnection, but I have no problem with the reason, it's obvious that the angle of elevation decreases when distance increases if you don't increase altitude, so at around 480metres distance I lost LOS. My doubt is with the fact that until that moment I had full RC bars (100% confirmed by Airdata report) and connection dropped suddenly without any warning of interference, loss of video before control, or similar early indicator.
My biggest concern is with the reconnection that did not happen at all until the bird was less tham 10m away and after having had it il LOS for most part of its return flight.

Hmmmm. What I find odd is that there is no red loss of signal warning on the flight log. Anyway, something was interfering with the signal, Niky, that's for sure, so you can go back and try again in the same location and see if it reoccurs, or just forget it and move on. I actually did both (!) firstly, on the single occasion I had the RTH kick in (it's hasn't since!) and secondly when I had a compass error and the AC went into ATTI mode and I had to bring it home. That's never happened again either, but I always practice flying in ATTI during a session just in case it does....

 

[RodPad]

Hum,+1

Yes nothing shows loss of signal or signal restored. Only thing I can think of is your mobile device stopped working.
If the cable from the remote to the mobile device failed it still should have reported a disconnection in the log.

I think you still had control of the Phantom. You didn't know it so your turned off the remote, which then activated RTH.
Finally your mobile device started working after everything connected back up.

Airdata you only shared the first part of the flight.

You stated:
"I uploaded the CSV to PhantomHelp"

Usually it is a .txt file from DJI-GO, .csv usually comes from Litchi, I confused here.

Rod

 

[Niky]

Sorry RodPad, my mistype of course, I uploaded TXT files.
And here the link to the other Airdata logs:
http://app.airdata.com/main?share=POqeTy

My iPad was working fine, actually I got the red "aircraft disconnected" message in DJI GO on its screen and immediately looked down at the RC led that in fact had turned red. Before doing anything I waited patiently for around one minute expecting aircraft reconnection when I saw it coming back in the distance (meaning it had again clear LOS). Nothing was happening, so I firstly closed DJI GO (swap upwards) and relaunched it, entered the camera view but it coherently had the same empty screen as when you don't have the AC turned on, so only at that point I switched RC off and then on. Still no reconnection (in the meantime the bird had almost arrived on the vertical), same when descending until finally at around 7 or 8 meters altitude RC led turned green and GO woke up.
Mystery...

I am not familiar with the kind of info contained in birds' CSV files, are they more detailed as to the possible reasons of this behavior? I haven't yet searched the forum to find info on a suitable viewer/analyser, but if might not worth doing if the info are the same of the TXTs
Thanks, ciao

 

[RodPad]

The .csv files are how Litchi flight logs are saved, so actually you wouldn't have any.

Your disconnection issue is so odd to me, it really is like DJI-Go just stopped working.

The light on the remote turning red, remote is not getting a signal from the Phantom.
You lost signal from the Phantom and app crashed at the same time.

You could download the .dat files from the Phantom before they get overwritten, there are some here that can analyze them, I have downloaded some from the past but never went any farther.

Rod