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Crashed after 'max motor speed reached' - what to do?
1332 32 2018-12-28
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Rushish
lvl.2
Germany
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Hi community,

a few weeks ago I bought a  Mavic Air and have really fun with it. Today the clouds were hanging  very low so I wanted to get a short view above them. I turned on the  mavic and started climbing straight up in sport mode. At about 120m the  warning began to pop up: 'max motor speed reached' followed by 'motor  obstructed'. I started immediately to decrease before something more  wors happen. The messages did not stop popping up alternately.

I  managed it to get the drone back to about 10 meters, then all motos  stopped and my drone is fallen like a stone straight onto the field.
The night was very rainy so the ground was soft. The drone is ok.

After  that crash I checked if the motors are still able to rotate. I could  turn every one very easily, just normal. So I tried to reconstruct what  happend and started again in very low altitude.

It  seem, that this problem occures only in Sport mode where the motors  drain more current and delivers more power. Specially in the case of  fast moving in any directions the warnings are popping up. As I wanted  to land, agian all motors stopped.  I felt that one motor was very hot  and smelled like aburned old transformer. This was the right back motor.  


I did nothing  to the drone, only changed one propeller, but not the one of the hot motor.

So what could have happened here? Do I have any possibility to check the flight logs? I read that the DAT-files are encoded.


Is there any one who can help me or advice me what to do in this situation.

Thank you very much,
Konrad





2018-12-28
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JJBspark
Captain
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Hi Konrad,

If you like others to comment and mayby advice you on your log do upload your flightlog ; https://www.phantomhelp.com/LogViewer/Upload/

cheers
JJB
2018-12-28
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Rushish
lvl.2
Germany
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Hi,
I already found this website, too. But it tells me that i shall upload an txt-file. But what I get out of the DJI Assistence tool are DAT files. So where to encode them ?
2018-12-28
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BudWalker
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There is a .DAT file on the device running the DJI Go App. It's not encrypted. Here are some instructions about retrieving it.
http://datfile.net/DatCon/retrieveV3DatfromTablet.html

It will probably have the info you're looking for. If you want others to take a look you'll need to upload it to a public sharing site like Dropbox or GoogleDrive and then provide the link to the uploaded file.
2018-12-28
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JJBspark
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Rushish Posted at 12-28 06:40
Hi,
I already found this website, too. But it tells me that i shall upload an txt-file. But what I get out of the DJI Assistence tool are DAT files. So where to encode them ?

Flightlogs are stored at your mobile device, see the link for where to find them on your device.

for android: // root/dji/dji go/flightrecords/*.txt

cheers
JJB
2018-12-28
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Rushish
lvl.2
Germany
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Thanks for your reply.

I downloaded the logs from my phone and tryed to look what DatCon can do with it. But for some reason it generated only the appropiated file names but with no content or with just the headers.
I uploaded the DAT files of my phone to my ftp. Maybe someone can have a look at them and if possible upload a decoded version of them in the same folder?

Server:   ftp://fharjwf7l4snfege.myfritz.net:42842/
user:    dji
login:   MavicAirCrash
2018-12-28
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HedsIc
Second Officer
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United States
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Wonder if the motor that was hot didn't get water inside of it because of the clouds. causing it to malfunction
2018-12-28
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Bart B
Second Officer
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Rushish Posted at 12-28 08:14
Thanks for your reply.

I downloaded the logs from my phone and tryed to look what DatCon can do with it. But for some reason it generated only the appropiated file names but with no content or with just the headers.

The .dat files wont do much good you need to post the .txt flight logs. In the link below there instructions how to locate the files on both android and ios


https://www.phantomhelp.com/logviewer/Upload/
2018-12-28
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Rushish
lvl.2
Germany
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Ok, I have uploaded the txt files and die files from phantomhelp now on my ftp.

@HedsIc
I think this should not be a problem because the copper wire that the winding inside the motor is made of is painted. Otherwise the whole winding would be an short circuit. You can run a brushless motor under the water and nothing will die. Sure, the controller shall not be under the water ,-)
2018-12-28
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Rushish
lvl.2
Germany
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I am wondering why the cell voltage is droppins sometime about 0.1V from one second to another... that could be an indication for a blocking motor. but the blocking messages don't appear in this lines
2018-12-28
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OneDoesNotSimply
First Officer
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Paste the link from Phantomhelp instead of your FTP.
2018-12-28
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Zigenbock
lvl.4
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I bet you the props iced up.....
2018-12-28
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jacksonnai
Captain
Malaysia
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Sorry to read that mate
2018-12-28
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Rushish
lvl.2
Germany
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https://www.phantomhelp.com/logviewer/JO8YFIGJE02NE70AZXP2/
2018-12-29
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sioh4
lvl.3
Flight distance : 3845 ft
Germany
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Hi Rushis

I guess you experienced the same I did yesterday. Foggy and cold outside (around 0°C) so i went out to get a look over the fog into the sun above.

I startet my MA and hoovered for a minute at 1-2m to get it on operating temperature - then the motor current warning appeared and after a few seconds the motors stopped and the drone fell
like a stone.

Like you i had the luck to be at wet grass, so nothing was damaged but when i looked closer i saw that the propellers were iced up.

Repeated that 2 times with holding the drone in my hand - always ice building and motor shut off shortly after a warning.

So we have to be more careful about our environmental conditions

Good luck for your flights
2018-12-29
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Rushish
lvl.2
Germany
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Maybe, but then they would just be heavier and provoke an unbalanced rotation that the drone can compensate. So that they do not rotate at all, the engine would have to freeze, and since they are warm due to the high current, it is almost impossible.
2018-12-29
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sioh4
lvl.3
Flight distance : 3845 ft
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Hi
In my case battery and engine were quite warm, but the ice appeared at the front edge of the props and the flight / hoovering was very stable without any unintentional turns or moves.

Just my experience as i flew the thing at lower temp without problems (but on dry air conditions).

2018-12-29
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Rushish
lvl.2
Germany
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Hm...
I can not say that my battery and all the hardware was cold becaus I had it at home, so the temperature was about 21°C ;-)   I can not imagine that the temperature in the flight sinks rather than to rise because the drone runs relatively quickly warm.

Did anyone looked at the log ?
2018-12-29
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JJBspark
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Rushish Posted at 12-29 03:08
Hm...
I can not say that my battery and all the hardware was cold becaus I had it at home, so the temperature was about 21°C ;-)   I can not imagine that the temperature in the flight sinks rather than to rise because the drone runs relatively quickly warm.

Hi,

yes, looking....

Your DAT file 18-12-28-10-50-02_FLY006.DAT is only 1 KB, no data in there. The following DAT starts at the end of the 'crash'flight. So with only the flightlog i cannot see motor status, temp, revs etc.

cheers
JJB
2018-12-29
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bjr981s
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JJBspark Posted at 12-29 04:13
Hi,

yes, looking....

The spec for the Mavic is 0 to 40 C.

But you must remember to be able to fly at low temps you must warm the batteries first.

A cold Lipo cannot deliver current so it will show as a Max Motor speed reached.

If you get this error load immediately and warm the batteries. There are a number of battery warmers on the market.

Cheers Brian

2018-12-29
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JJBspark
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bjr981s Posted at 12-29 04:34
The spec for the Mavic is 0 to 40 C.

But you must remember to be able to fly at low temps you must warm the batteries first.

Hi Brian,

yes, in cold temps warm the lipos. Seen a flight where a batt temp started low (13 degrees C) so a warning in the app, but during flight in cold temps the batt temp raises to 28 degree C.
So flying in cold is not sucha problem, but i will never use Sports mode for  long period in the cold.

cheers
JJB
2018-12-29
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BudWalker
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I looked at 18-12-28-10-54-16_FLY006.DAT. It appears that both the rightFront and the rightBack were having problems. At time 97 secs just full throttle was applied. Although the motor speeds remained close the rightFront and rightBack had to work harder as can be seen in the motor current data.
Rush1.jpg

This can also be seen in the eventLog stream that shows ESC1 (rightFront) and ESC4 (rightBack) stalling.

98.287 :   28714 [L-FMU/MOTOR]fault on , esc(4) is stall
98.458 :   28724 [L-FDI]propulsion Spd-Cur fault:0
98.491 :   28726 [L-FMU/MOTOR]fault on , esc(1) is stall


I can only speculate the cause. Are all 4 props the same brand/type?

You could try swapping rightFront/leftBack and rightBack/leftFront and see if the problem changes to the left side.

2018-12-29
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BudWalker
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The motorCurrent data is consistent with ice building up on the props. As the flight progresses there is a noticeable increase in current
Rush2.jpg
2018-12-29
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JJBspark
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BudWalker Posted at 12-29 06:36
The motorCurrent data is consistent with ice building up on the props. As the flight progresses there is a noticeable increase in current
[view_image]

Hi BudWalker,

Nice data, but it is from the next flight after the crash. But guess the same happend to the flight before.

I have seen now 2 flights with looks the same, but why does the logging stops so suddenly ? i would think that the falling down (as it is still connected) would be seen in the data.

Curious, isn`t it?

cheers
JJB
2018-12-29
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BudWalker
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JJBspark Posted at 12-29 07:23
Hi BudWalker,

Nice data, but it is from the next flight after the crash. But guess the same happend to the flight before.

You're right. Is there a FLY005?

The tablet .DATs can sometimes be flakey. Mostly, I think it's due to the fact that it depends on the AC->RC->Go App link.
2018-12-29
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JJBspark
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BudWalker Posted at 12-29 07:52
You're right. Is there a FLY005?

The tablet .DATs can sometimes be flakey. Mostly, I think it's due to the fact that it depends on the AC->RC->Go App link.

Yes, there is another 006 18-12-28-10-50-02_FLY006.DAT, only 1 kb.
This one, when filled, should have the crash data in there.
Mayby a copy/paste error, if not than infortunately really empty 1 kb DAT file.
2018-12-29
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Rushish
lvl.2
Germany
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@JJBspark

Yes there is another one with 2,6MB But that should be the second flight on low altitude to see if the motor blocks again. And this flight was only about 1 minute...  (but this file is bigger than the one of the longer flight?)

@bjr981s
As I said... I had the batteries at home so at about 21°C

@BudWalker
What tool did you use for the visualisation and where can I find the eventLog? The props are all original form DJI, the one of the FlyMore-Combo.
I noticed that there are two FLY006, but no 005. Please see the screenshots an my FTP

How about the DAT files from the drone and the DJI Go App? Are they identically?
Furthermore I created a new directory with the logs I got out of the DJI Assistant. I did not download the gimbal and navigation logs because they are not important I think.

2018-12-29
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BudWalker
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Rushish Posted at 12-29 11:33
@JJBspark

Yes there is another one with 2,6MB But that should be the second flight on low altitude to see if the motor blocks again. And this flight was only about 1 minute...  (but this file is bigger than the one of the longer flight?)

What tool did you use for the visualisation and where can I find the eventLog? The props are all original form DJI, the one of the FlyMore-Combo.


I use CsvView to visualize the .DAT file. It's free and can be obtained here
http://datfile.net/CsvView/downloads.html

To see the eventLog you'll need to use DatCon which can be obtained here
http://datfile.net/DatCon/downloads.html

The tablet .DAT will sometimes be split as it was here. The 1st FLY006.DAT is just the DatHeader and the 2nd is the part actually containing the data. So, that means the 2nd .DAT doesn't have a DatHeader. You'll need to CsvView or DatCon that an invalid or missing DatHeader is OK.
Rush3.jpg

Or, you can merge the two parts with something like this
$bash> cat 18-12-28-10-50-02_FLY006.DAT 18-12-28-10-54-16_FLY006.DAT > FLY006.DAT
then tell CsvView or DatCon to use the FLY006.DAT that was created
2018-12-29
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BudWalker
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Rushish Posted at 12-29 11:33
@JJBspark

Yes there is another one with 2,6MB But that should be the second flight on low altitude to see if the motor blocks again. And this flight was only about 1 minute...  (but this file is bigger than the one of the longer flight?)

How about the DAT files from the drone and the DJI Go App? Are they identically?

Although they have the same format the drone .DAT has more fields and a higher sampling rate. But, more to the point the Mavic Air .DAT is encrypted and can't be used.
2018-12-29
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A.V.hiflyer
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zero degree's and visible moisture is the recipe for icing...sometimes a little and sometimes a lot ...airmanship 101 but I'm not being snide..It's easy to forget and sometimes the clouds are dry enough that you can get away with it.  Hope you are able to fix the antenna..I sent mine back to the factory for the over-center spring on the antenna and it was costly. 170 I think
2018-12-30
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EdisonW1979
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A.V.hiflyer Posted at 12-30 23:39
zero degree's and visible moisture is the recipe for icing...sometimes a little and sometimes a lot ...airmanship 101 but I'm not being snide..It's easy to forget and sometimes the clouds are dry enough that you can get away with it.  Hope you are able to fix the antenna..I sent mine back to the factory for the over-center spring on the antenna and it was costly. 170 I think

Agreed, even with the Mavic 2 series with its -10c flight rating, that’s only if it’s a dry sub-zero without visible moisture... If you’ve watched any documentaries, or are a fixed wing pilot otherwise, you’ll know that any moisturized air travelling over a metallic, composite, or plastic surface at sub-zero has a much higher chance of forming ice crystals and bonding to the aircraft, which can spell disaster.

In fact, DJI I believe specifically state not to take the AC thru any clouds or fog banks, as even if the temperature is above freezing, the chances of the moisture getting into the aircraft electronics and/or motors and causing issues during flight is much higher than in standard flight.
2018-12-31
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Zigenbock
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Rushish Posted at 12-29 01:26
Maybe, but then they would just be heavier and provoke an unbalanced rotation that the drone can compensate. So that they do not rotate at all, the engine would have to freeze, and since they are warm due to the high current, it is almost impossible.

This is the same as a plane flying - the engine does not ice up because it is hot - the props on the MA are NOT heated and therefore ice builds up.... Anything below 10 degrees C with visible moisture can cause icing.
2018-12-31
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Rushish
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Yes sure! But in the case of an obstructed motor, something must be blocking. But there is nothing that could be blocked. The only thing that can happen is that, as you said, the props ice up.
So, could it be that there was so much ice on the props that they could not reache enough boost ? The electronic don't know if there is ice on the props or not. It just see that there is not enough boost and thus increase the power on the appropriate motor. If there is on max. rpm still not enough boost, the remote says "max. motor speed reached".
But what behavior caused the controller to say "motor obstructed" if there are no parts that can obstract at all.
Could it be the unbalanced rotation due to uneven ice distribution on the props?
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