The update wasn't the problem, and the problem hasn't gone away - it's just that .400 doesn't warn you about it. Ignorance is bliss.
MOTOR SPEED ERROR MAVIC MINI
- Thread starter RyanDG
- Start date
The update wasn't the problem, and the problem hasn't gone away - it's just that .400 doesn't warn you about it. Ignorance is bliss.
Generally speaking, as a software guy who used to write this stuff, I'd have to say restoring to an older version of anything should be the option of last resort. I could go on about why that is but won't, just trust me. Ignore the screen errors if you can't fix them physically at the time. Chances are they won't reappear next time you start up from scratch.
Fix any damaged blades first though.
It's a bug, or more probably, lousy (or more accurately 'lazy') exception handling on the part of the programmer(s). Personally I would have fired them, unless someone above me was gonna fire me for firing them and my mortgage payment was due, you know how that goes.
Fix any damaged blades first though.
It's a bug, or more probably, lousy (or more accurately 'lazy') exception handling on the part of the programmer(s). Personally I would have fired them, unless someone above me was gonna fire me for firing them and my mortgage payment was due, you know how that goes.
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FoxhallGH
Well-Known Member
Please take the time to read this thread. The software is NOT bad! All you are doing by downgrading is removing the warning. The prop distortion problem described in the 13 pages of this post is caused by how the Mavic Mini is folded & stowed. If you remove the warning, all you will do is have the Mini fall out of the sky at some point, without giving you a clue as to what it's about to do!
FoxhallGH
Well-Known Member
... and then fold and stow the Mavic Mini in a way that the rear prop-set isn't meshed and under pressure - making the blades distort.
SSG Rock
Member
Posted about the motor speed error problem on May 20 after only flying my new mini less than 30 min. After reading all of the posts about the update I refreshed it via Assistant 2 and flew without a problem for about 40 min. then it was back. Changed the props on left rear (the bad actor) and stopped using the Fly More case. 5 hrs. of trouble free flying. Life is good.
Air Dog Two
Member
Due to various life circumstances, I've not flown my mini for quite a while. It's been stored in the fly-more case supplied by DJI when I purchased it. Now I see that this very case and my lack of attention as to how the props were positioned in the case has caused my mini to report a prop speed problem.
I guess it makes sense because the props are fairly fragile but it's more than a bit irritating to me that the supplied case ends up being the cause of problems with my mini. I'll go back and look thru the documentation - I'm curious where & how DJI stresses the importance of how to store the mini and props.
I'm curious - are the other DJI quad models & props this susceptible to storage problems?
I guess it makes sense because the props are fairly fragile but it's more than a bit irritating to me that the supplied case ends up being the cause of problems with my mini. I'll go back and look thru the documentation - I'm curious where & how DJI stresses the importance of how to store the mini and props.
I'm curious - are the other DJI quad models & props this susceptible to storage problems?
It's not only the Fly More case that's causing the prop deformation. It's also the original plastic shell which non-Fly More Minis are shipped in. Common to both is the way the blades are crossed when stored.
The latest firmware (v01.00.0500) introduced a new feature that alerts you to excessive motor speeds and instructs you to replace the prop blades on the identified motor. The reason the warning is sometimes triggered even on brand new Minis, and even on Minis with recently replaced propellers, is due to how the blades are bent while stored in the crossed position.
The label in the Fly More case shows the left-rear blades (A&B) folded under the right-rear blades when the Mini is stored with arms folded.
First off, that label is already inaccurate as it is impossible to position them like this (with A under B) since the leading edge of A cannot be forced under the trailing edge of B.
Regardless of that particular inaccuracy, the Mini is shipped with both left-rear blades (A&B) folded under the right-rear blades. That is why the Motor Speed Error most often first identifies the left-rear blades as needing replacement, even on brand new Mavic Minis.
My Mini was always stored (with blades crossed) in its Fly More case, and I was never aware of any prop issue until my first flight after updating to the latest firmware. The new Motor Speed Error instructed me to replace the left-rear prop blades.
Here's a photo comparing the new left-rear blades versus the old original right-rear blades. Note how the fresh left blades are straight and now stand higher than the old right blades. The right-rear blades easily slide under the left blades when crossed.
Next is a photo with both the left-rear and right-rear props replaced with fresh new blades. Now you can see how both sides cross, with neither side wanting to fit under the opposite side when folded together. Blade #1 is straight and un-deflected, while blade #2 has to be bent down in order to force it to nest under the opposite side's blades.
Here is someone else's photo of a Mini still in its plastic shipping tray, with DJI's paper band securing the prop blades in their stowed crossed position.
And this is the how the rear prop blades look, straight out of the box, with the paper band still keeping the blades fixed in their "proper" stowed configuration. Clearly the left-rear blades are bent to fit under the right-rear blades like this.
That is why the left-rear blades are almost always the first to trigger the Motor Speed Error warning. If you store yours the other way around, with the right-side blades bent under the left-side blades, then you'll likely have the Motor Speed Error identify the right-rear motor first.
So why do the front motors hardly ever trigger a similar warning? It's because of the way the motors are mounted canted at different angles. The rear motors are canted outboard, whereas the front motors are not. The fronts are instead canted rearward.
With the arms folded, you can see how much the rear motors are canted outboard. That means the propeller blades must cross when nested inboard across the body. New prop blades can only be forced to stow nested together if one side or the other is forced to bend under/over the other side.
The front motors instead are level with each other, not canted outboard.
The front propeller blades can therefor be stowed nested together without imposing any bending stress on the blades.
Air Dog Two
Member
Thank you for an excellent description of the issue. The photos and your comments make perfect sense.
I'm glad DJI came up with the software update to detect the issue. I wonder if they have a plan to redesign a better storage solution? I definitely won't be storing in the fly-more case any longer. I'm hesitant to even use it short term for transport.
FoxhallGH
Well-Known Member
Absolutely stunning description and photo gallery ... Well done ...
I'd like to suggest that you take the content of this post, and make a new thread with this as the first post in it ... I'm not sure what you should call it, but something like "Cure the Mavic Mini overspeed problem!" ... I'm coming across a lot of Mini owners on Facebook groups, and I cut & paste a pre-written monologue about this problem - but it would be great to be able to point them at a short, definitive thread providing the reasons and answers... What you have put in this thread is top class. By pointing people at your new thread, we'd;
a) provide the info about the problem and the answer for a lot of MM owners
b) Give you the deserved Kudos for the work done to describe and illustrate the issue
c) attract Mavic Mini owners to a decent source of info (to join Mavic Pilots Forum) rather than trying to get answers from bickering and unprofessional Facebook forums!
Air Dog Two
Member
Based on Zbip57's excellent photos and discussion, I examined my MM carefully and did see that my rear right A prop was slightly bent up compared to the B prop. "A" being the prop on top compared to B.
I decided to see if I could "fix" it. I DO NOT recommend my method to anyone here. Please don't try this on your MM based on my method.
That being said, I very carefully and gently bent (no photos sorry, and no, I don't know how much I bent it, certainly not 45 degrees, probably closer to 15 or 20 degrees) the A prop and held it in place for maybe a minute, maybe less. After bending, the A prop contour follows the B prop much more closely. So, out to the yard for a test.
No more error message and the MM flew for ~10 minutes w/o an error popping up. I have no idea if it will stay "fixed", but I do know that I won't be storing it in the fly-more case any longer.
(Again, try this at your own risk - I don't want anybody to mess up their props based upon my totally unscientific methods.)
I decided to see if I could "fix" it. I DO NOT recommend my method to anyone here. Please don't try this on your MM based on my method.
That being said, I very carefully and gently bent (no photos sorry, and no, I don't know how much I bent it, certainly not 45 degrees, probably closer to 15 or 20 degrees) the A prop and held it in place for maybe a minute, maybe less. After bending, the A prop contour follows the B prop much more closely. So, out to the yard for a test.
No more error message and the MM flew for ~10 minutes w/o an error popping up. I have no idea if it will stay "fixed", but I do know that I won't be storing it in the fly-more case any longer.
(Again, try this at your own risk - I don't want anybody to mess up their props based upon my totally unscientific methods.)
Thanks everyone, but credit for first bringing this to our attention goes to @rumitcu who started the thread "MM Folded Rear Prop Bending per DJI Instructions" all the way back in April.
You can use a direct url link to that particular post (#247) in this thread as:
mavicpilots.com/threads/motor-speed-error-mavic-mini.86130/post-1038101
FoxhallGH
Well-Known Member
Yes indeed - that works. Thanks.
I have a theory that the prop distortion may be made worse if the MM is folded and stowed in the FlyMore case immediately after flying it. The bottom heat-sink plate of the MM will still be warm, and the folded/deformed prop blades [that sit right next to the belly of the MM] will soften and then cool to keep their distorted shape. In other words, stowing the MM in the case warm or cold could also make a difference - I think ...
The other thing to take into consideration is that the prop distortion is not just about the angle of the blades ... If you have one set of blades pushed under the other, then the blades that are pushed down will flatten ... In other words, the pitch will decrease on those blades. That means the blade will need to be spun at a higher rpm to get an equivalent lift to a new blade.
Exactly.
And that increased rpm is what is detected by the new v01.00.0500 firmware to trigger the Motor Speed Error warning telling you exactly which motor to inspect. If the warning is ignored, or the lift capacity of the propeller blades becomes severe enough, the motor eventually reaches a limit beyond which it is no longer able to increase rpm to produce the required lift. Then we get into the dreaded Uncommanded Descent.
Of course there are still people out there who insist the warning is a software bug and a better "solution" is to downgrade to the previous firmware firmware version in order to remove the annoying new Motor Speed warning. Sheesh. ?
I'm having a eureka! moment reviewing this thread and the earlier one from @rumitcu. I believe you may have all the pieces of this problem laid out now.
It seems to me that one- or many of these discrete issues may be in play for a given in-flight occurrence. Which makes it a very slippery problem to nail down since we naturally tend to look for a single cause.
Well done everybody, and my personal thanks for your dogged pursuit of the facts and attention to detail.
It seems to me that one- or many of these discrete issues may be in play for a given in-flight occurrence. Which makes it a very slippery problem to nail down since we naturally tend to look for a single cause.
Well done everybody, and my personal thanks for your dogged pursuit of the facts and attention to detail.
That, in fact, is the critical detail.
The Motor Speed Error message tells you to inspect the propeller blades on the affected motor. On mine, there was nothing visibly wrong with the blades. They looked perfectly fine to me. It was only after replacing the left-rear blades that I could see the obvious difference compared to the right-rear blades. Note how high the tips of the new left blades sit, compared to the droop in the tips of the right blades.
If you were instead expecting to see obvious cracks or chunks missing out of the blades, the difference in prop shape is quite subtle and easily overlooked, So people tend to take only a quick glance at the props, see nothing obviously wrong, and they dismiss the warning as an annoying firmware defect that should be ignored.
A conclusive method of measuring for yourself whether the propeller blades actually have degraded lift efficiency is to do a simple hover test. Press auto-takeoff, allow the Mini to stabilize in a hover for a couple of minutes, then auto-land, all without touching the control sticks. Doing it indoors is preferable as it minimizes the influence of wind. Then access the flight log DAT file to plot the motor speeds using CsvView.
For example, this is a plot of my motor speeds on the flight that first triggered the Motor Speed Error warning for me. The lines jump all over the place because it was a windy day and I was flying the Mini back and forth. The only thing to note in this plot is that the left-rear motor (blue line) is turning consistently much faster than the others, reaching a peak of 16,000 rpm.
Next is the plot of the hover test after replacing the left-rear (blue) propeller blades. Note the improvement in the blue line, and that now the right-rear motor (yellow line) is the one spinning consistently fastest.
Next I replaced the right-rear (yellow) prop blades. Note how the blue, red, and yellow lines are now fairly even, while it is the left-front (green) running consistently the fastest.
It wasn't a critically big difference, just a noticeable and obvious consistent difference in motor speed. The left-front (green) props didn't need to be replaced, but for the sake of scientific experiment I also swapped in a set of new left-front prop blades.
Here is the result of a hover test with new props, all except the right-front (red) which is still the original set.
Even though this hover test was done indoors, the propwash is enough to cause turbulence so that the flight controller needs to make small corrections to hold the Mini in a stable hover. That creates minor motor speed fluctuations in the plotted lines. If you do this test outdoors on a windy day there will be greater fluctuations in the lines. What you're looking for in any case is any significant difference in one motor running consistently faster than the others.
At hover, with new props installed, the motors should all be turning at near equal speed around 9600 rpm.
The point is, even if you can't visibly detect anything wrong with the propeller blades identified by the Motor Speed Error (ESC) warning, this hover test will conclusively demonstrate whether there is an issue or not.
The graphs above document an obvious difference between the motor speeds running on old versus new propeller blades. How much of a difference you are willing to tolerate is up to you. But if any of your motors are running at such an elevated speed sufficient to trigger the new Motor Speed Error warning, then it's certainly something you should pay attention to.
Do not trust people telling you the props are fine as-is, or that the Motor Speed warning is merely a firmware bug. Do NOT downgrade to a previous firmware version to prevent the warning message from ever reappearing. Test the props for yourself. Do the hover test, plot the data, and then decide for yourself based on real evidence.
vindibona1
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What a great explanation of why the problems occur in flight. Forgive me, I have some reading issues, so with all the information I missed if you supplied the recipe for the CORRECT way to fold the rear props in to avoid distortion. If you did, could you please repost (just the proper folding instructions). TIA
FoxhallGH
Well-Known Member
The rear prop-set should be aligned with the motor arms. In other words, both sets of rear props should point directly forwards when the MM is folded for storage - but note that it is not possible to put the MM into the FlyMore case when it is folded this way - you'd need a different design of storage case ...
YES the left motor. changed the blades twice and stills happened. Now I do not do any thing about it, I do not have any performers problems.
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