Mavic mini uncontrolled spin and crash

[DanMan32]

The flight replay uses the TXT logs. Don't let the extension fool you, it's not human readable.
The TXT file can be quite useful but its more of a summary with less detail than the DAT file.

 

[Fly Dawg]

@miker570 The flight replays do not really do anything for you. The motor errors you see are well after the spin started from the interaction with the trees. We really need the .dat ( FLY074 ) to tell you much more than that.

 

[miker570]

Yes all there errors were from the events of the crash. If you watch the video from the MM in the first post it confirms that I was several feet over the tree top. I’m still puzzled by the sound I heard that sounded like a grouse ruffling it’s feathers as it passed over the tree tops on the first pass. I flew back and listened and watched closely for anything unusual but the MM was stable and the responded to the controls normally so I continued back out to the lake. I am thinking the downward sensors might have picked up the trees as I was passing over and changed the motor speed causing the sound I heard. On the next pass the sensors might have picked up on the trees at the highest point, and something then went very wrong. I had updated to the latest firmware the day it was released a couple days ago.

 

[Fly Dawg]

I am thinking the downward sensors might have picked up the trees as I was passing over and changed the motor speed causing the sound I heard. On the next pass the sensors might have picked up on the trees at the highest point, and something then went very wrong.

I can say it was not your downward sensors.

 

[miker570]

If you watch the replay as I was taking off, at about 9 feet there was a brief sensor error that flashed. What might that be?

 

[DanMan32]

I've gotten that too once in a while. I suspect it has to do with the downward sensors being dark. With the MM having such low ground clearance, they could be blocked in daylight but would be OK once off the ground.
But I can't be sure if I'm right. Message isn't clear enough and I haven't found any documentation about it.

 

[Fly Dawg]

If you watch the replay as I was taking off, at about 9 feet there was a brief sensor error that flashed. What might that be?

Can't be 100% positive on that, but by viewing your flight in the CSV there was a GPS POSITION NO MATCH at roughly that time.
Here is a better view and similar to the video you posted. That is the only error I can find that early in the flight. I will say that message has been seen quite often accross all platforms and generally does not affect the flight. See this link:

Flight View

 

[miker570]

I received a response from DJI support regarding the shipping instructions for my DJI Care return. They want only the MM and RC in the original box but no battery or accessories. I uploaded my proof of purchase with the case I opened, but they asked to include another copy of that as well. It will be shipped via UPS to a CA address in the LA area.

 

[miker570]

Can't be 100% positive on that, but by viewing your flight in the CSV there was a GPS POSITION NO MATCH at roughly that time.
Here is a better view and similar to the video you posted. That is the only error I can find that early in the flight. I will say that message has been seen quite often accross all platforms and generally does not affect the flight. See this link:

Flight View

Wow lots of details in that replay.. thanks!

Seems like it dropped from 85 ft to below 80 ft in less than a second as it crashed. I did nothing to change altitude and tried to maintain level flight while I was passing over the tree line.

 

[Fly Dawg]

I did nothing to change altitude and tried to maintain level flight while I was passing over the tree line.

Correct, with only one exception. You were yawing around when the spin began. Below is when you were at the tree tops when the spin occurred.

 

[miker570]

Correct, with only one exception. You were yawing around when the spin began. Below is when you were at the tree tops when the spin occurred.

Yes that is correct, I think I sensed something was wrong and I tried to turn around and come back home but she dropped like a rock. I see I tried left stick up full trying to recover without success. Happened so quick that the replay is very good to see all events leading to the crash. Thanks again!

 

[HiTec]

I suspect the sudden movement caused either left or right front propeller to hit the drones front body. When the prop bends during the quick movement/wind, it can hit the drones frame, possibly leaving black marks. It also does the strange sound. I know because my Mavic Mini had this problem before i swapped in new propellers to front right corner. I almost crashed mine when the props bent so badly that they hitted to the front frame corner and it slowed down the motor so much that the drone tilted and the DJI Fly gave an motor error code.

It also might be possible that the same prop hitting the frame problem could cause some kind of gimbal vibration/shake/jello effects that some people are experiencing. Because my drone vibrated like crazy with out of the box setup. The whole right front arm vibrated so much in quick movements/wind that i was affraid that its going to tear off.

 

[miker570]

It is possible that the props were hitting the side, but before this last flight I had never seen that behavior. I did not notice any scuff marks on the side after the crash, but I didn’t suspect any issue with the props. I did read about that strange behavior in a few posts here.

DJI care has my MM and its currently in the evaluation step, and I should hear about their findings in the next 3 business days.

 

[miker570]

Received good news from DJI today. Their evaluation determined that the failure will be fully covered under warranty, and they are shipping a new (or like new?) replacement at no charge.

They did not share the root cause of the failure, but I’ll be happy to get back in the air soon!

 

[easyheimer]

Received good news from DJI today. Their evaluation determined that the failure will be fully covered under warranty, and they are shipping a new (or like new?) replacement at no charge.

They did not share the root cause of the failure, but I’ll be happy to get back in the air soon!

That's great news. So you didn't need to use an incident from your DJI Refresh?

 

[miker570]

Good question. I am not sure, but it sounds like it was replacement under warranty. I received an email with the shipment tracking info, including the serial numbers of my new MM and RC.
The new s/n is not registered yet, so I’ll need to follow up with support to get the new MM under my DJI Care refresh plan. Also wondering if I will receive a new sealed box with, including accessories. Getting another battery out of the deal would be nice. I should receive it Monday or sooner according to the tracking info.

 

[Fly Dawg]

They did not share the root cause of the failure,

Would have been nice to see the .dat file. That would be more conclusive of the cause. DJI rarely tells you the findings.

 

[miker570]

I received my replacement Mavic Mini today. It appears to be brand new.
DJI returned my same RC and new MM in my original box. Nothing else included. New MM paired with my RC fine, and downloaded the updated FlySafe DB, and MM firmware updated from v1.0.0 to v1.0.3 successfully. It only required compass calibration.
I Just completed a short indoor test flight and it is working great.

Also waiting for an email response from DJI support about how to transfer the new MM to my DJI Care Refresh, and remove the replaced MM from my acct.

 

[JAW]

Also waiting for an email response from DJI support about how to transfer the new MM to my DJI Care Refresh, and remove the replaced MM from my acct.

I believe they should do that automatically. Check your DJI account to verify.

 

[miker570]

I suspect the sudden movement caused either left or right front propeller to hit the drones front body. When the prop bends during the quick movement/wind, it can hit the drones frame, possibly leaving black marks. It also does the strange sound...

It also might be possible that the same prop hitting the frame problem could cause some kind of gimbal vibration/shake/jello effects that some people are experiencing. Because my drone vibrated like crazy with out of the box setup. The whole right front arm vibrated so much in quick movements/wind that i was affraid that its going to tear off.

Looking at my new MM, I don’t see how the front props could get so low that they hit the side. I see many people are tying their props down when storing them or putting them in a case, which might warp the props downward over time? Another possibility is the front arms get bent up changing the angle might possibly do it.

Here my new MM, which show about half inch clearance above the frame.