Mavic Crash in Water.... hoping someone can help

[ronniefastback]

Hi, hope someone can lend some assistance. My Mavic crashed a couple months ago and I wasn't sure what to do until a friend mentioned this site and that people can look at logs and perhaps figure out what happened. I uploaded a log and the link is below. I bought it about 1.5 years ago along with DJI Care Refresh. My warranty coverage is gone and I did not renew DJI Care after the 1st year (dumb dumb dumb).

Basically, I was on my boat on a lake and decided to fly my drone. It's not the first time I've done it and have flown it over my local lake and the ocean multiple times. I had to calibrate it first and after that, I set it down on the rear swim platform on my boat. Took off and backed up a couple feet from my boat and got it about 5 feet above the water. Then, it made some high pitched beeping noises, flipped upside down and crashed into the water. From takeoff to crash it was only a couple seconds. No warning or anything, just the beeping noise and it went upside and into the water. It happened 4-5 feet from the back of my boat. The water is brown and you can't really see much.

There's not much more to explain.... it all happened so fast. I did contacted DJI and they said sorry/. They did offer to review the logs if I paid them to help make their products better. Why would I pay them to review logs with my drone at the bottom of a lake...???

Here's the file. I hope someone is willing and able to take a look and see if you find anything? Thanks!!!

 

[srnolten]

Did you have a good GPS lock ? Maybe the experts from this forum can say something about this ?

 

[slup]

Hi, hope someone can lend some assistance. My Mavic crashed a couple months ago and I wasn't sure what to do until a friend mentioned this site and that people can look at logs and perhaps figure out what happened. I uploaded a log and the link is below. I bought it about 1.5 years ago along with DJI Care Refresh. My warranty coverage is gone and I did not renew DJI Care after the 1st year (dumb dumb dumb).

Basically, I was on my boat on a lake and decided to fly my drone. It's not the first time I've done it and have flown it over my local lake and the ocean multiple times. I had to calibrate it first and after that, I set it down on the rear swim platform on my boat. Took off and backed up a couple feet from my boat and got it about 5 feet above the water. Then, it made some high pitched beeping noises, flipped upside down and crashed into the water. From takeoff to crash it was only a couple seconds. No warning or anything, just the beeping noise and it went upside and into the water. It happened 4-5 feet from the back of my boat. The water is brown and you can't really see much.

There's not much more to explain.... it all happened so fast. I did contacted DJI and they said sorry/. They did offer to review the logs if I paid them to help make their products better. Why would I pay them to review logs with my drone at the bottom of a lake...???

Here's the file. I hope someone is willing and able to take a look and see if you find anything? Thanks!!!

Hi there & welcome to the forum ? ... even though it's under unfortunate circumstances.

Looking at your Airdata link it seems that you uploaded the mobile device DAT log named FLY068.DAT in the end & with that conversion made at Airdata not much useful is left.

Every flight with your Mavic Air creates 2 different log files stored in the mobile device you flew with ...

One ending with .TXT containing telemetry transmitted from the aircraft to the RC & battery data, gimbal and camera data, flight status and error flags. This log runs from motor start to stop. The log naming convention is DJIFlightRecord_YYYY_MM_DD_[hr-min-sec].txt

The second log ends with .DAT ... these contain most of the raw sensor data & motor data. This log runs from power on to off. The log naming convention is YY-MM-DD-hr-min-sec_FLYXXX.DAT

Go here and read up on how to retrieve them --> Mavic Flight Log Retrieval and Analysis Guide (read under section 3.)

Once retrieved attach the .TXT & the .DAT log here in a new post. (the DAT log ends probably with FLY068.DAT)

 

[ronniefastback]

Thanks for the reply!

Strangely, there is no .TXT file with the right date in the "FlightRecords" folder. It's just not there. Plenty of others from previous dates but not the right date. In that folder, there's a folder called "MCDatFlightRecords" and I found another .DAT file that you correctly identified (2020-05-03_12-57-25_FLY068.DAT). I uploaded that to Airdata and attached a link.

I searched the entire DJI folder for "2020-05" and here's all that showed up. No .TXT file, other than the upgradeLog files and I don't think that's of interest.

 

[slup]

Thanks for the reply!

Strangely, there is no .TXT file with the right date in the "FlightRecords" folder. It's just not there. Plenty of others from previous dates but not the right date. In that folder, there's a folder called "MCDatFlightRecords" and I found another .DAT file that you correctly identified (2020-05-03_12-57-25_FLY068.DAT). I uploaded that to Airdata and attached a link.

I searched the entire DJI folder for "2020-05" and here's all that showed up. No .TXT file, other than the upgradeLog files and I don't think that's of interest.
View attachment 111454

You need to attach the actual DAT log directly into a new post here ... going through Airdata will not do, their conversion mess it up.

 

[ronniefastback]

OK, here it is

 

[slup]

Thank you, that's the one ...

Well, this flight was short for sure ... you started up everything by trying to calibrate the compass, 3 failed attempts but the fourth goes through. You placed it for take off & started the take off through the apps auto take off button as no stick CSC can bee seen in the log. Immediately you filled in both a positive throttle & a positive elevator command, this probably due to quick get some distance away from the boat.

Nothing odd so far ... but only 3,7sec after take off the MA1 pitch severely up, rolls over to the left & yaw clock wise as seen here below in the chart. This pattern of movement usually mean that the AC have lost thrust from either side. If the AC pitch up it point to lost thrust from either of the rear sides ... if the AC at the same time rolls left it indicate that it's a problem with the left side ... rear. The only anomaly is the clock wise rotation as the rear left is torquing clock wise, so by loosing the left rear the AC should have rotated counter clock wise instead.



The movement is so abrupt & severe that the flight controller command motor shut down at 4,15sec ... very similar as you can do during a hand catching when you flip the AC upside down.



Spinning further on the suspected lost thrust ... Looking into the motor data one thing stands out & that is how the flight controller command the rpm's for the motors. In the chart below we see that the left rear motor get's commanded to 100% at 3,8sec (magenta graph) ... just a tenth of a second after the severe movement have started. It's definitely something going on with the rear left side. So is it a lost prop or a failing motor there? Well, it's hard to say here during the short time span ... if it's a lost prop we should have seen max rpm's as an answer to a 100% command, but we don't. If it was a jammed motor we should have seen a spiking current draw for that motor, but we don't.



So in the end we only have a stronger indication towards a lost thrust from the left rear side ... this made the AC flip so severely that the flight controller shut the motors off at 0,81m ultrasonic height.

 

[ronniefastback]

I really appreciate you going thru all of this and providing an explanation. Not sure I totally understand it all..... sounds like for some reason 1 motor went to 100% and that made it flip. What does "AC" stand for?

In your opinion, is there anything in what you can see that gives me leverage with DJI? Software bug? Known issue from a few months ago? As I mentioned before, I'm out of warranty but have heard of people getting replacements if something was "their fault" and not mine...??? I didn't see any props fly off. I just heard that high pitched beeping and then it pancaked into the water.

I'm going to see if my credit card will cover it. I have a good card and get an additional year of coverage. Gonna be a battle with them I imagine.

Again, thanks for sharing your insight. Really appreciate it. If anyone else has additional thoughts, I welcome any and all input!

 

[slup]

... sounds like for some reason 1 motor went to 100% and that made it flip.

Nothing besides the flight control command to the left rear went to 100% ... an answer to that, in either increased rpm or a higher current draw wasn't seen from that motor though, this possibly due to the short time between that command & the aircraft going into the water & ending the log. What made your MA1 flip was a loss of thrust, due to either a lost prop or a motor that stopped turning. Usually a 4 prop drone can't keep itself airborne with only 3 working, it will roll, pitch, turn & fall down.

What does "AC" stand for?

AC = aircraft

... is there anything in what you can see that gives me leverage with DJI? Software bug? Known issue from a few months ago?

No ... unfortunately. A lost prop or a failing motor can fall on the pilot ... neglected prop care, flying with nicked props from past flights together with a skipped visual inspection before flight can mean disaster later on. Micro cracks that break up making the prop split or attachment tabs that break off ... a lot of thing's can happen with the props not directly pointing to DJI's fault. It's not uncommon that debris is blown up from a dusty ground during take off or landing either ... & fall into the motor, that debris can then suddenly jam the motor, again hard to point that towards DJI.

Have also a MA1 & I haven't heard of or noticed any SW bugs or issues that make it lose thrust from either side.

You can of course contact DJI ... but being out of the warranty period & not having the drone for them to inspect makes it hard to get any kind of leverage.

 

[Dave Maine]

This is not a software bug, or it would have been seen by others with the same pattern. It is some electronic or mechanical failure on the specific drone. Lost prop, dirt in the motor, faulty cable from the esc to motor, esc board hardware internal failure.

 

[ronniefastback]

Appreciate the feedback..... sucks! Hope my credit card insurance will cover it. Want to buy another one but think the boss, I mean my wife, will squash that idea.

 

[hiflyer201]

bummer...if it had been dry land you could have just walked over and picked it up. Good luck with the claim and the boss..DJI could possibly offer a discount... I've been able to get discounts. Of course nothing is ever my fault

 

[skunky1]

Considering dirt in the motors may cause failure, whats the best way to keep it clean?

 

[maelstrom]

Considering dirt in the motors may cause failure, whats the best way to keep it clean?

Using some kind of take-off/landing pad is a good idea as it reduces the chances of localised dust, grit or vegetation getting into the motors and props.

 

[JMTremblay]

Hey sorry to hear about your situation. If you get another drone you may want to consider a drone life-preserver. Check out drone-retriever.com they have a product which I use. They also have excellent insight into what to do after a water crash.

 

[ronniefastback]

Hey sorry to hear about your situation. If you get another drone you may want to consider a drone life-preserver. Check out drone-retriever.com they have a product which I use. They also have excellent insight into what to do after a water crash.

Thanks, never even knew those existed.