Day 2 on Mavic - failure and crash

[Chipfatbob]

Hi all,

So, day 2 with my brand new Mavic. Flew it yesterday with no issues - firmware updates were fine. kept it low to begin with. 2 flights this afternoon were fine. Then, at about 6, I took it out with a mate who was flying a P3. I had mine up for about a minute - RTH was set, good connection - then the app started dropping in and out of connection and before I could bring it back, it dropped like a stone, onto concrete. I was flying with the gimbal cover on, which has (hopefully) absorbed most of the impact. the cover was totally smashed. Cosmetic damage to the top and underside.

I was flying with a Samsung S7 edge as my screen. I have a second, identical phone which I switched to and tested fine. When I re-installed the app on the original phone, once again it was fine. I've taken it out for a test flight and all seems to be functioning. Flight log is here:

Phantom Log Viewer - PhantomHelp.com

I'd appreciate any thoughts before I raise this with DJi. I understand there are issues with the android app but I was also under the impression that if the drone lost connectivity with the controller, it would wither hover or RTH.

Sincerely,

Gutted from Gloucester!

 

[Robbyg]

If the battery came lose it would drop like a stone. Did you clip it on properly?

Second thought is what was the battery level when you hit RTH and what did you have it programmed to do. You might have had it set to hover but that still does not explain the sudden fall. It would have hovered until 10% battery and then descended and landed. I will look at the log and get back to you.


Rob

 

[Cyberpower678]

I'll be honest this is literally the 3rd thread about a Mavic dropping out of the sky within the last 24 hours. This is turning into a trend here.

 

[Chipfatbob]

Thanks, Rob. Can confirm - battery was totally secure both pre and post accident. Mavic didn't seem to loose power as all nav lights remained on.

 

[Robbyg]

You where really flying pretty low, it was at about 6M up from the ground relative to your take off altitude.

Battery power was fine and I see nothing to indicate why it would just fall out of the sky. All data stops very suddenly. Since you say you could see it just fall out of the sky it really looks like the battery was not latched down properly.

OK I posted the above as you were writing your reply.
Your saying all the lights where on when you got there, wow that is strange. Can you upload the DAT file from the Mavic itself to a hosting site?

Rob

 

[Robbyg]

I'll be honest this is literally the 3rd thread about a Mavic dropping out of the sky within the last 24 hours. This is turning into a trend here.

Yeah it is kind of strange. I really doubt DJI changed anything, with the latches. it could just be coincidence.

Rob

 

[Cyberpower678]

Thanks, Rob. Can confirm - battery was totally secure both pre and post accident. Mavic didn't seem to loose power as all nav lights remained on.

This definitely needs to be looked at. We're going to need the DAT file from the Mavic's flight data recorder.

 

[Robbyg]

Cyber I am seeing that just before the crash he pulled down hard on the elevator. It seems he was flying very low and just got too low to the ground and then pulled down on the elevator and slammed it into the ground. It might have been simple pilot error. Lets wait and hear what he thinks.

Rob

 

[Chipfatbob]

OK. I have the DAT file. any ideas where I can host it would be appreciated. Re the flight controls, any movement on the elevator came after the mavic lost power. I was purposefully flying low while I was getting used to the Mavic's characteristics. I am new to the Mavic but not new to drone flying . I also had an experienced flyer with me, who witnessed the loss of power.

 

[Cyberpower678]

Cyber I am seeing that just before the crash he pulled down hard on the elevator. It seems he was flying very low and just got too low to the ground and then pulled down on the elevator and slammed it into the ground. It might have been simple pilot error. Lets wait and hear what he thinks.

Rob

Unfortunately, with just my Mac, I cannot fully analyze TXT files beyond PhantomHelper and AirData. I can look at the CSVs, but the software on the Mac is missing a vital component the Windows version has. I wonder if @BudWalker has an update on this.

 

[Cyberpower678]

OK. I have the DAT file. any ideas where I can host it would be appreciated. Re the flight controls, any movement on the elevator came after the mavic lost power. I was purposefully flying low while I was getting used to the Mavic's characteristics. I am new to the Mavic but not new to drone flying . I also had an experienced flyer with me, who witnessed the loss of power.

A dropbox will do.

 

[Robbyg]

Cyber i have to head out for two hours. If I am not back in time I think if you look at the control inputs just before he crashed versus that altitude and then super impose them on google maps with terrain height it will probably solve the mystery.

Rob

 

[Chipfatbob]

Hi Cyber,

Try this link Dropbox - DJI DAT

 

[Andrew F]

Cyber I am seeing that just before the crash he pulled down hard on the elevator. It seems he was flying very low and just got too low to the ground and then pulled down on the elevator and slammed it into the ground. It might have been simple pilot error. Lets wait and hear what he thinks.

Rob

I have a theory that maybe the DAT files will debunk. If he was full stick down and the Mavic believed it was on the ground already, it would shut down the props but lights would remain on. So both elevation streams should be reviewed. I've had this happen to me but only from 18 inches. I was flying indoors so visual only.

 

[BudWalker]

Unfortunately, with just my Mac, I cannot fully analyze TXT files beyond PhantomHelper and AirData. I can look at the CSVs, but the software on the Mac is missing a vital component the Windows version has. I wonder if @BudWalker has an update on this.

Unfortunately not. The fact that the Mac version of CsvView can not accept .txt files probably won't change.

 

[Lapeer20m]

Since the battery apparently stayed in the mavic after it crashed my bet is that "improperly seated battery" is not the problem.

From my understanding, the other mavics with suspected improperly seated battery issue, the battery was found separate from the machine on the ground.

 

[Robbyg]

Chipfatbob uploaded the file.

Just looking on this flight I am hesitant to make any judgement calls on it. The Mavic crashed in clear view 39ft from him.




As you can see he was going up a hill yet the last input was for down elevator. Yet I see this and scratch my head when I also see the VPS saying 4m off the ground just a second before impact.



Looking at it in more detail now. I may call on Budwalker for some advice.

Rob

 

[Robbyg]

Just got back some info from Budwalker who IMHO is the absolute Guru of log analysis and he pointed me right at the problem. The logs show that the battery lost connection for a moment and the drone powered down in mid flight.

I saw the Motor volts on my first sweep and lacking the skills of Budwalker I just assumed that the end of the graph was the motors shutting down on impact.



When Budwalker suggested I sample the data at a higher rate and zoom into the actual shutdown you can actually see when the battery wiggles loose and then the motor voltage drops low enough that the drone cuts power to the motors.



Wow three of these in one day!
I am not sure if this is a new problem with the latches or the connector or just people not putting the battery in properly.
Unfortunately DJI will almost certainly say the battery was not clipped in properly.

Rob

 

[Gary cato]

Seriously these things are dropping so fast you guys have your hands full.

I also just can not believe how many Mavic losses there are going on now.

mind you for 9 weeks i never saw a drone in the sky except mine, now i have seen everything from nanocopters to Mavics all flying around each other.

seems the whole world is buying drones.

 

[Chipfatbob]

Many thanks for all the efforts - hugely appreciated.

I bought the drone with the extra flight pack, which included 2 additional batteries. Luckily, I numbered them as they came out of the box. Battery number 2 was being used during the crash flight. I've tested all three batteries and while batteries 1 and 3 click in and seat immediately, battery 2 has a slightly faulty catch on the right hand side which doesn't click in properly and required an additional push. Due to the faulty catch, it is also under load which means it has a propensity to pop out on the right hand side.

I will take this up with DJI. Frankly, having just spent a huge (to me!) wedge on this drone, I was diligent in checking everything before flight. If there is an issue with batteries not seating properly in the Mavic, when they visually (and audibly) seem to be, this is a design flaw and at the very least needs to be issued as a notice of awareness by DJI.

I'll keep you posted with their response.

Best,

Jon