Almost a flyaway

[rscheff]

I fly the Mini with Samsung S21 phone. I use DroneLink to create missions. I have approximately 4,500 minutes of flying time so I am not a total Newbie. On 10/12/22 and 10/14/22 I encountered two issues which I have never had exactly like these. On the 12th I was flying a routine mapping mission and I ran out of juice (20%), happens all the time, this day was a little windy so it caused more power to be used. Normally RTH is initiated and the drone comes back and lands within 10 feet of launch. This time RTH was initiated and it started back to home but just kept going until it was approximately 200 feet away. It was at 400 feet altitude and I lost physical sight of it but when I looked at the controller I could see it was way beyond home. I immediately shut off RTH and started using the sticks to manually return and it was fighting me the whole time as if it wanted to go elsewhere, but I don't know where. I finally landed it with about 8 % power left.

I flew another mapping mission on the 14th. About 400 feet away I lost contact and the DroneLink program shut off and returned my phone to the regular desktop. I re-started the Dronelink program but it would not hookup, the wheel just kept spinning. I shut that program down and turned on DJI Fly, it also would not connect. By now several minutes had elapsed and I had no idea how high, how far, or where the drone was going. I knew the general direction and could hear it but could not see it. I had somewhere around 50% battery so I was not panicked (as much as I was two days ago) so I waited another minute or so to see if I could spot it. So now I guess about 3 minutes had past, but I know how time flys (no pun intended) but at least a minute had passed. The DJI manual says RTH is initiated after 11 seconds of lost connection. I reviewed the flight logs and they were strange. At 79% power log said battery at max distance (556') and then on a second log it said battery at max at 48% (415'). I eventually had to manually initiate RTH and it had returned without issue. I believe there were two logs because it had lost connection and created a second log. Looking at both log entries it appears that my guess of 3 minutes loss of contact may be right because the first entry ended at 6 min and 30 seconds and the second entry started at 8:26 and RTH was initiated at 9:31, 3 minutes and 1 seconds difference. Can anyone make heads or tails of this?"C:\Users\rsche\Dropbox\DJIFlightRecord_2022-10-12_[17-53-23].txt" "C:\Users\rsche\Dropbox\DJIFlightRecord_2022-10-14_[15-49-10].txt" "C:\Users\rsche\Dropbox\DJIFlightRecord_2022-10-14_[15-57-48].txt"

 

[slup]

Seems like you're trying to share the dropbox folder on you local C:\ drive ... will not work, instead attach the logs with the "Attach files button" in the bottom of a "new post" window.

But just a couple of reflections...

In the first flight were it passed your location on it's RTH ... did you verify that the HP was in the correct place?

In the second flight... as the log is created by the app & stored on your mobile device nothing will be created if the app stops working... that doesn't mean that the controller itself have disconnected with the craft. If something happens with the app during a flight that prevents a continuous log creation & later the opportunity occurs to continue the log from a still airborne craft it will start up a second log file.

Then a tip... if you've lost sight of your craft & the app crashes & you're not certain if the control connection also have failed & not sure if a failsafe RTH have been initiated... it's good to actually turn the controller off, in that way you can be certain that a failsafe RTH will be started (if that's your set failsafe)... it's always a risk that you wait for something to happen & you eventually press the RTH button on the controller & instead of initiating RTH you maybe stops an ongoing RTH by pressing that button.

 

[rscheff]

I thought you would be able to load from my dropbox, I did it that way when I sent them to DJI so maybe they did not get them. I almost always take off from the exact same place, my deck, I even having a landing pad I built, so I know where the RTH spot is. So again, why did it go beyond my home by a couple hundred feet and why couldn't I just fly it straight back, you can see the squiggly lines in the flight record.

On the second flight you are suggesting the Dronelink app may have crashed causing the disconnect? What about the DJI app, that would not load either, so it seems too much of a coincidence that bot apps would not load, well let's put this way, they would not connect. DJI app came on and went to the screen saying that aircraft was not connected. So I shut both apps off, by the "close all" apps button and waited approximately one minute to manually hit RTH. Your suggestion to shut off the controller is a good one, and I have done this before (experimenting) and it did return to home. But I roughly new where the drone was, I could hear it and it wasn't getting closer or further away so I felt safe just trying to wait out the automatic RTH to happen. Maybe looking at the flight records will help. You will see that there was a 3 minute period between the first record and the second one but the second record says there was a 10.7 second loss off contact. Now that I am thinking it through it seems that even though both apps were off the RC was still on and in contact for the whole time except for 10.7 seconds which is under 11 so RTH would not be initiated automatically. Don't know why I would lose contact only 400 feet away, but it's kinda scary that both programs can crash and the drone will not return home, after all at this point I am blind as a bat. The only reason I could not see it was that my eyes had not had time to focus on it while moving, you know how it seems to just appears to you all of a sudden. But if these theories are true then that explains that one, but I am not liking it. I still don't understand why the first flight went 200 feet beyond home and was difficult to fly back manually.

 

[slup]

Mmm yeah ... took a look at the flight where the craft continued after reaching the HP (Oct 12:th). This I'm afraid, wasn't a near "Fly Away" ... this was a near "Blow Away"

If we first look at the actual wind conditions up on the height where your Mini was... up on approx. 290ft.

This is your log in Airdata.com & their wind calculations... have highlighted the point where your Mini flies past the HP with a direct tail wind, the wind speed is a tad below 10m/s there & the whole way until you took over the control & descended. Your Mini's max air speed in both the RTH & ordinary GPS mode is 8m/s... in Sport it can achieve 13m/s.



And here averages from the whole flight on each height segment...



So with this it looks like your Mini must have needed to Brake the whole way from where the RTH started until it reached the HP... it does that by pitching up (a positive pitch angle)... & when it drifted past the HP it must have tried again to back it's way toward the HP, again by pitching up. But as the wind speed was faster than what your Mini could achieve it was drifting away from the HP.

If looking into the log data this is easily seen on the pitch angle (fat grey graph)... the chart starts to the left, exactly when the low battery RTH starts, there the blue thin graph shows how the Mini yaw's around aiming on the HP... a couple seconds later the heading speed starts to increase (fat orange graph) up to about 18-19mph... note that the pitch angle (grey) is positive, meaning the Mini is forcefully trying to keep the max specified speed (8m/s or 17,9mph) by braking (this as it's a strong tail wind).

At about 12m 20s into the flight it reaches the HP (fat red graph) & tries to brake to start a descent, this by pitching nose up to the max allowed 20 degrees ... but the speed just slowly decreases & the Mini shoots over the HP & all the time after that it tries to reverse back but fails as the wind is too strong... the Mini is blowing away. The data also shows that it wasn't trouble free for you to manually fly the Mini back either... you managed it in the end as you descended.

So in the end this wasn't a mystery at all ... just a pilot error flying in to strong winds.




The other 2 logs (Oct 14:th) from where you had app & re-connection troubles doesn't show anything useful... nothing odd in that, this as if the RC isn't connected to the Mini or if the app doesn't work nothing is recorded... have yet to see a log that reveals a reason for connection troubles.

 

[rscheff]

I used airdata to look at logs and I don't have access to the information you have, at least I can't find it. I see what you are saying about the wind, it picked up for a brief period over the maximum suggested of 8ms. That happens quite a lot in my area but it usually just gusts and the drone goes off course but has always adjusted. It was not windy on the ground and the drone did fly most of the mission without going off course. I will have to be more careful but it is the first time this has happened to me.

 

[slup]

I used airdata to look at logs and I don't have access to the information you have...

The wind information is part of their payed subscription.

 

[FLDave]

The wind information is part of their payed subscription.

And well worth the cost to analyze after each flight, along with take-off point measured surface wind.