Mavic Mini uncommanded descent tests

[TDZHDTV]

On every drone or just on Mavic Mini?

Mini

 

[JAW]

Next up:
3 bladed props. Can they be far off?

 

[MrBongo]

Mines at dji care at this very moment as straight out the box was having back props warning and auto Descent to a
Landing for safety then on a circuit round the house it just dropped out of the sky luckily it was only at 1.5m called dji tech they told me to send it in for assessment.
Still waiting further info.

 

[MrBongo]

Well the data is in propulsion error issues esc modular board repair. Repair under warranty. So there was an issue with the ESC modular board causing the propulsion errors glad I questioned it and sent it in now.

 

[mm crashed]

I wish this was the case. I had an uncommanded descent last week while in C taking some video of a local harbor. Unfortunately being at a harbor you can guess what happened next.

Luckily DJI have concluded that it is a warranty issue and are sending me a new MM but it is certainly something that needs to be fixed soon given the amount of posts about it!

I had somethign similiar happen to me. Any suggestions on dealing with DJI?

 

[MrBongo]

I had somethign similiar happen to me. Any suggestions on dealing with DJI?

I bought my mavic mini about June/May time had prop issues and auto descents and then it took a 2m dive after switching off and heading for the deck going round my house . Luckily I complained to dji sent it in and they replaced under warranty claiming a board issue needing replacement after analysing my flight data. But sent me a whole replaced mavic mini since then no repeats and I’m still storing with a rubber band type clasp round the props so it’s not storage issue. It appears to be a fault in one of the micro boards inside the mini.

Defsend your flight data to dji and ask there opinion.

Regards

Les Frith

 

[Zbip57]

I’m still storing with a rubber band type clasp round the props so it’s not a storage issue.

Have a look at this earlier post, and following discussion, and see if this may actually still be a storage issue.

mavicpilots.com/threads/motor-speed-error-mavic-mini.86130/page-13#post-1038101

 

[chiangmaicharlies]

I bought my mavic mini about June/May time had prop issues and auto descents and then it took a 2m dive after switching off and heading for the deck going round my house . Luckily I complained to dji sent it in and they replaced under warranty claiming a board issue needing replacement after analysing my flight data. But sent me a whole replaced mavic mini since then no repeats and I’m still storing with a rubber band type clasp round the props so it’s not storage issue. It appears to be a fault in one of the micro boards inside the mini.

Defsend your flight data to dji and ask there opinion.

Regards

Les Frith

i"m very pleased to see that DJI seem to respond positively to quite a few of the problems I've seen here. Unfortunately most companies these days can hardly be bothered to reply to queries and problems. Once they have a sale that's it. Congrats to DJI.

 

[warmax356]

sorry to crash into the thread, just stumbled upon this site as i was googling the issue, if i may ask how did you full the flight logs from the drone, its my first dji and its now its 8th flight, but i keep getting props to fast then esc beep, the props dont look bent or twisted to me, though the feel flimsy, i happen to own the fly more combo, should i just swap the props or should i send it into dji?

 

[Zbip57]

how did you pull the flight logs from the drone?

Check this thread:

mavic-flight-log-retrieval-and-analysis-guide

 

[spsphotos]

since this is caused by warped props when storing, wouldn't it be advisable to just remove the rear props when storing it?

 

[FoxhallGH]

since this is caused by warped props when storing, wouldn't it be advisable to just remove the rear props when storing it?

In theory - yes - that would do the trick. However, the Mini does not have the same twist-lock props that the big-brother Mavic's have, so if you were to screw/un-screw the prop blades for every flying day, you'll risk damaging the threads where the screws are put in to hold the props - and making a more expensive problem!
Personally - I remove the prop's from my Mavic Pro when I store it, but it has a twist-lock system that makes that easy to do - and there is nothing to wear out.

 

[new2mavic]

since this is caused by warped props when storing, wouldn't it be advisable to just remove the rear props when storing it?

There is no need to do so. The original combo storage case has space dedicated for accomodating the props. Just make sure that the props are positioned as indicated on the sticker. A bit of care has to be taken because the props can swing freely so they can move out of the wanted position easily.

 

[FoxhallGH]

There is no need to do so. The original combo storage case has space dedicated for accomodating the props. Just make sure that the props are positioned as indicated on the sticker. A bit of care has to be taken because the props can swing freely so they can move out of the wanted position easily.
View attachment 115325

Oh for goodness sake! This whole thread is dedicated to telling everybody why this method of storage is responsible for the warping of the prop's in the first place!
Due to the outward cantering of the rear motors on the Mini - if you mesh the prop's like this they bend and flatten. When the prop's flatten, they loose pitch and that's what makes them ineffective! If you stow the Mini like this after a flight when the body of the Mini is warm, it makes it worse due to the warmth softening the plastic blades and making them deform and hold the deformed shape as they cool.
I know this is a long thread, but please have a look through it before you comment further ...

 

[new2mavic]

I know this is a long thread, but please have a look through it before you comment further ...

I have studied the issue quite deeply by myself as detailed in this thread : The problem of un-commanded descent by Mini reproduced so you can rest assured that I did have taken a good look into it and I know how much flattening or pitch change is required to trigger uncommanded descent.

Due to the outward cantering of the rear motors on the Mini - if you mesh the prop's like this they bend and flatten.

This theory does not make sense to me. The props are just lightly pressing against each other when folded up in that way and if there is any bending at all, it's barely noticeable and I just cannot see how that can result in the amount of pitch change required to trigger uncommanded descent. What's more convincing to me is that the if the props are NOT folded up in that way, the inner side of the storage case will be pressing onto the prop with a much bigger force. The chance of getting the props flattened will be much higher.

 

[FoxhallGH]

This theory does not make sense to me. The props are just lightly pressing against each other when folded up in that way and if there is any bending at all, it's barely noticeable and I just cannot see how that can result in the amount of pitch change required to trigger uncommanded descent. What's more convincing to me is that the if the props are NOT folded up in that way, the inner side of the storage case will be pressing onto the prop with a much bigger force. The chance of getting the props flattened will be much higher.

The prop's are not just lightly pressing against each other though. The motors are cantered outward at about 5 degrees from the vertical and that means that to mesh as per the DJI diagram, 3 of the 4 blades must bend downwards (in toward the body of the drone). You can best see this by folding the Mavic Mini up, putting it on its back, and then swinging the two rear prop-sets outward away from the body of the drone. You'll immediately see how they angle downward on both sides and do not sit on a horizontal plane. Swing the blades in as per the DJI diagram, and now you are forcing the blade sets into each other, with the one on the bottom having the most force applied, and the one on top (which will angle away from the others), having the least pressure. When you bend the plastic blade it ends up adopting a shape where it keeps that downward-pointing angle (i.e. in comparison to a new blade it will appear to 'droop'), and more importantly, the pitch/curve of the blade will flatten.
While the drone is cold, there is a better chance that the prop-blades will return to near original shape when the Mini is unfolded - but if it's warm after a flight, then the heat will help the deforming process and make it permanent.
The theory may not make sense just to read it, but have a look at your Mini and see how those props need to 'bend' to get into that DJI 'mesh' as per the diagram - and also know that I have seen a lot of feedback through this and other Facebook forums, that indicates that when Mini owners purchased new rear props and a replacement for the Flymore case, that had cut-outs that allow the props to be stored by folding them north-south along the motor arms, rather than east-west across the drone body - the problems disappeared.
The answer is NOT to fold the drone differently and put it in the same DJI Flymore case - you can't do that ... Unfortunately the answer is to get a different kind of storage case ...

 

[new2mavic]

... this and other Facebook forums ...... Mini owners purchased.... a replacement for the Flymore case, ..... the problems disappeared.

View attachment 115350

This only confirms once again that social media is indeed a very powerful means to advertise products.

My experience is the opposite. I only use the original flymore case for storing my Mini and it never exhibited the uncommanded descent problem.

As described in my thread on the subject, I have intentionally flattened the props to create the problem so I know how much stress is needed. This knowledge is first-hand and acquired through hands-on practice, not hear say on "this and other Facebook forums".

There is absolutely NO ways that the tiny stress created by folded props pressing lightly against each other can create the following pitch difference which is about the minimum needed to make uncommanded descent happen :

 

[maelstrom]

Oh for goodness sake! This whole thread is dedicated to telling everybody why this method of storage is responsible for the warping of the prop's in the first place!

But even if it did (and that's by no means certain), would that automatically lead to undemanded descents? The logic would say that it would be more likely to initially cause speed errors for the motors with flattened blades as they compensate for the different blade pitch. If this was really causing the descents, almost everyone who used a Fly More case would be experiencing them and that doesn't seem to be happening. Until recently, I stored my Mini in the Fly More case all the time without issues. It seems odd that DJI would recommend storing them like this if it was known to cause problems.

 

[FoxhallGH]

But even if it did (and that's by no means certain), would that automatically lead to undemanded descents? The logic would say that it would be more likely to initially cause speed errors for the motors with flattened blades as they compensate for the different blade pitch. If this was really causing the descents, almost everyone who used a Fly More case would be experiencing them and that doesn't seem to be happening. Until recently, I stored my Mini in the Fly More case all the time without issues. It seems odd that DJI would recommend storing them like this if it was known to cause problems.

Well actually - that's what started this whole thing ... The rear motors would show speed errors and the Mini would fall out of the sky.
DJI would have to acknowledge that this was the cause of the problem - but to date, they have not.
If you are not having problems using the FlyMore case - then OK ... Carry on using it.
All I'm saying is that in this thread, and another [MOTOR SPEED ERROR MAVIC MINI] there has been a lot of testing, theorising and work done to come to this conclusion ... Do with it what you will ...

 

[maelstrom]

All I'm saying is that in this thread, and another [MOTOR SPEED ERROR MAVIC MINI] there has been a lot of testing, theorising and work done to come to this conclusion

But my comment still stands - if the case was causing these problems, why isn't everyone who uses it getting them? The problem is more likely caused because some people don't fold the blades exactly as recommended in the DJI diagram.