Crashed Mavic after loss of RC Control

[Tac52]

Hello all... wondering if anyone has any insight onto what I might could have done to fix this.

Had my Mavic out at the shooting range. We have an outdoor range that has a covered area from the bullet trap to about the 25 yard line. The covered area is like a "pole barn" with large sliding barn doors that were open.

Launched the Mavic from the open, and after takeoff, it immediately lost connection with the RC. I shut the RC down and fired it back up, and it got connection again. Landed the mavic, restarted everything.

Took it off again, and had no issues until I had loss of controller connection again after a few minutes of flying. The drone was at altitude, and in line of sight (91 feet away, 497ft altitude). I got control quickly after that and continued flying. Flight lasted another 11 minutes with no issues....until....

I flew down the side of the covered area to the targets, then turned around and was very slowly making my way back to me to land. I could see the drone, it was only about 100 feet away and maybe 10 feet off the ground.

To my terror, it lost connection again. I ran up to try and get connection....but not before RTH initiated and it smashed into the roof, lost a prop, and then smashed into the concrete. It is destroyed....on day 2.

Any idea why the RC/Mavic connection was dropping off?

Looking back, I realize that before I took it under the cover I should had changed the RTH protocol to hover as oppose to RTH. Lesson learned. Any other tips you guys have?

I have refresh, and the thing is getting sent off. So, at least I am not out $1000 bucks. I wonder if they will give me a break due to the loss of control connection - or say I should have been smarter about my RTH settings...

 

[CashCache]

A few guys here could take a look at your DAT file and give you a ton of information - that is, unless you sent it back already.

 

[Tac52]

Well. ****. I just dropped it off. I thought the files from my phone we're the ones in question. They show the loss of signal (on healthydrones) that happened prior to the crash, but not the final one....

Pretty odd. It was within line of sight, and where I was flying there should be little to no RF interference at all, not even wifi out there. The disconnect was completely without warning.

Thanks for the reply.

 

[sekine12]

Sorry about the crash. There are at least two instances of operator error here that we can all learn from:

- Flying in/around lots of metal can lead to signal multipath, RC/Aircraft interference, GPS issues, IMU/Compass issues, and other various performance problems, be careful in these situations. Losing connection isn't surprising based on your description of the structure. Flying further away after experiencing signal issues is also not a good idea. Interference isn't usually a fluke, and it doesn't get better with distance. Either there's an environmental issue causing problems (likely in your case) that will get worse with distance; or, there's a software issue causing a flaky connection, that won't just resolve itself. Either way, if you experience connection issues, stop flying until you can identify the cause and resolve it.

- Understanding your drone's behavior and expected behavior is critical, especially when you're already experiencing signal loss issues. RTH is expected behavior, ascending to RTH altitude is expected behavior on loss of signal. Your Mavic did precisely what it was programmed to do, and precisely what you as its pilot should have been prepared for it to do based on your configuration at the time.

It's unlikely that DJI will cover this as a warranty issue unless you get lucky. On the bright side, you have care refresh, and you can learn from this incident!

 

[Tac52]

The RTH is on me. I'm not so sure about the signal loss. I flew it in the morning with no issues. The buildings in question are wood, not metal. And, after the first loss of signal, I brought it closer. The crash happened 100 feet away, maybe closer as I was flying back toward myself.

Either way, I shall adjust the rth behavior when necessary when I get back in the air.

 

[sekine12]

The RTH is on me. I'm not so sure about the signal loss. I flew it in the morning with no issues. The buildings in question are wood, not metal. And, after the first loss of signal, I brought it closer. The crash happened 100 feet away, maybe closer as I was flying back toward myself.

Either way, I shall adjust the rth behavior when necessary when I get back in the air.

Is the roof of that building wood as well?

 

[Tac52]

Is the roof of that building wood as well?

Yes. Wooden trusses with plywood on top, wood poles, no walls....It experienced a loss of connection two minutes prior to the flight with the crash when it was in open error, directly after takeoff. The first loss of connection resulted in the Drone taking off and hovering about ten feet above me until I got the controller shut off and then reconnected.

I had flown it a couple times earlier in the day and had taken it up to about three-quarters of a mile away from my location. All of the losses of connection that I had in this case on the drones last two flights were all well within line-of-sight. Either way, the rth setting failure is my fault I'm just wondering if there's any wisdom on why it would continually drop the RC connection.

I appreciate your thoughts.

 

[sekine12]

Hrrrrmmmm... Alright, nevermind about the expecting interference due to metal then. Sounds like you were having some intermittent issues that may actually be defect related. I stand by my point about continuing to fly with unresolved intermittent issues though.

Hopefully DJI concludes for you that this was a defect, this does indeed sound like erroneous behavior.

 

[TrayBoz]

Call me crazy, but if I were having any kind of connection issues with my mavic, the last thing I would do is fly it under any kind of cover.

Sorry for your crash.

 

[Tac52]

So what would you have done? Clearly what I did had an unintended bad outcome.

My intent in flying under the cover was to check it out prior to recording some training under there. And, honestly, I wasn't expecting an issue with the thing 10' off the ground and only 100' away.

How would you have troubleshot the connection issues? What do you think might have been the causes? Have you had this happen in the past? What did you do?

 

[TrayBoz]

I appreciate your thoughts.

My thoughts: The mavic uses GPS to maintain it's position. GPS reception is blocked or partially blocked when it is under any kind of cover. Flying under cover when I'm already having connection issues does not sound like a good idea.

That is all. I've not had connection issues, so I'm not qualified to tell you what the best troubleshooting steps are.

 

[Tac52]

My thoughts: The mavic uses GPS to maintain it's position. GPS reception is blocked or partially blocked when it is under any kind of cover. Flying under cover when I'm already having connection issues does not sound like a good idea.

That is all. I've not had connection issues, so I'm not qualified to tell you what the best troubleshooting steps are.

Thanks. I get that. However, the connection was lost between the RC and the drone. It said "connecting" on the RC. If it had switched to atti mode due to gps loss of signal, I could have just landed it. Anyway...I'm still trying to figure why I'd have a random RC loss in the open at very close range.

 

[tomakava]

What was your Mavic firmware version?

I had exact same problem in my first flight after upgrading to v01.03.0600 just in my case outcome was not so bad.
It was a short flight in empty beach and just after 2 minutes RC connection was lost, while I was standing just 3 meters away. DJI GO 4 shown "Aircraft disconnected" and I could swear RC was stuck showing "GPS mode" but it was not controlling Mavic. After 3 seconds Mavic started to RTH and I ran to home point trying to regain control. After rebooting RC I regained full control and I canceled RTH landing. After 4 minutes it happened again and reboot of RC fixed it once again. It never showed any interference or weak signal warnings.

Later that day I made another flight in different place and there was no problem so I attributed it to some kind of interference. But in previous flights I never lost connection without warning and gradual video downlink degradation. So maybe after all it is a firmware bug.

 

[Tac52]

What was your Mavic firmware version?

I had exact same problem in my first flight after upgrading to v01.03.0600 just in my case outcome was not so bad.
It was a short flight in empty beach and just after 2 minutes RC connection was lost, while I was standing just 3 meters away. DJI GO 4 shown "Aircraft disconnected" and I could swear RC was stuck showing "GPS mode" but it was not controlling Mavic. After 3 seconds Mavic started to RTH and I ran to home point trying to regain control. After rebooting RC I regained full control and I canceled RTH landing. After 4 minutes it happened again and reboot of RC fixed it once again. It never showed any interference or weak signal warnings.

Later that day I made another flight in different place and there was no problem so I attributed it to some kind of interference. But in previous flights I never lost connection without warning and gradual video downlink degradation. So maybe after all it is a firmware bug.

It was the .O6 firmware. I only had the thing for a day, so it made me update latest firmware. Thank you for your thoughts.

 

[tomakava]

What mobile device you were using? From the log you provided in DJI forum I see it was Android.

In my case I was using Samsung S7 Edge updated to Android 7.0
I analyzed logs from my Mavic DAT and see something interesting.

In this flight both times before loosing RC connection it lost app connection just some milliseconds or seconds before:
124.325 : 1149078284 : 12520 [L-SEND DATA]app connect changed:last(1) != current(0)
125.087 : 1152505267 : 12558 [L-RC]rc_connect:1=>0
125.087 : 1152505485 : 12558 [L-RC]rc_func_disable @ [256112 ms]
128.545 : 1168068935 : 12731 [L-FMU/LED]action changed. rc completely lost: (0)
199.343 : 1486658532 : 16271 [L-RC]rc_connect:0=>1
199.345 : 1486666551 : 16271 [L-RC]rc_resume @ [330370 ms]
200.045 : 1489818563 : 16306 [L-SEND DATA]app connect changed:last(0) != current(1)

366.605 : 2239337869 : 24634 [L-SEND DATA]app connect changed:last(1) != current(0)
370.325 : 2256076470 : 24820 [L-RC]rc_connect:1=>0
370.325 : 2256076724 : 24820 [L-RC]rc_func_disable @ [501350 ms]
374.145 : 2273268676 : 25011 [L-FMU/LED]action changed. rc completely lost: (0)
400.623 : 2392418376 : 26335 [L-RC]rc_connect:0=>1
400.625 : 2392426450 : 26335 [L-RC]rc_resume @ [531648 ms]
400.705 : 2392788449 : 26339 [L-SEND DATA]app connect changed:last(0) != current(1)

In both cases it reconnected just after me rebooting RC.

Also there was some more app connection loses, but without loosing RC connection:
413.025 : 2448228232 : 26955 [L-SEND DATA]app connect changed:last(1) != current(0)
416.025 : 2461727539 : 27105 [L-SEND DATA]app connect changed:last(0) != current(1)

419.325 : 2476577015 : 27270 [L-SEND DATA]app connect changed:last(1) != current(0)
422.025 : 2488727745 : 27405 [L-SEND DATA]app connect changed:last(0) != current(1)

699.645 : 3738018329 : 41286 [L-SEND DATA]app connect changed:last(1) != current(0)

Whats more, last time it lost app connection just before final landing and I remember DJI GO app totally hanged my mobile device. I had to hold buttons to force reboot it.

Next flight same day there were no such problems in the log. And when I was flying longer range (about 600m) and behind obstacles it started loosing connections as expected.
But every time RC and app connections were lost and reconnected at exactly same time:
663.185 : 3348562386 : 36933 [L-RC]rc_connect:1=>0
663.185 : 3348562624 : 36933 [L-RC]rc_func_disable @ [744125 ms]
663.185 : 3348564173 : 36933 [L-SEND DATA]app connect changed:last(1) != current(0)
663.625 : 3350543070 : 36955 [L-RC]rc_connect:0=>1
663.625 : 3350543454 : 36955 [L-RC]rc_resume @ [744565 ms]
663.625 : 3350544874 : 36955 [L-SEND DATA]app connect changed:last(0) != current(1)

So what I think is happening, that bad USB mobile connection sometimes causes RC to hang and lose connection.

 

[J3ffrey]

There have been 5 posts in the past 24 hours with this exact same thing happening. It has nothing to do with METAL - I wish we could squash that wives tale.. I fly mine around metal and have never calibrated it and it does fine.

Someone should make a post with all the links to people having controller disconnects I know there have been 5 or so this weekend and I'm thinking there's no way I'm updating firmware or app until these posts stop happening.

 

[Tac52]

I am using android (just updated a few days ago to the latest OS...whatever version they are on now) DJI Apps were all the latest firmware, as it asked me to do so when I unboxed it on thursday.

I was using a GalaxyS5 that is no longer used as a phone (an extra one laying around after upgrading to S7s in our house). I was using the supplied connector that goes in the side of the remote control. I have heard there is, perhaps, a more robust connection to be made if I connect through the bottom of the remote control instead of in the side. I might try that when I get back in the air.

Thanks very much to folks that have replied....

 

[smithlaw]

Sorry this happened to you. I am one of the other guys that had mine destroyed from loss of connection as well.

 

[Rnl]

What firmware are you running

 

[Rnl]

I too had this with new update I too lost connection and it drifted into a tree.