Prop Overspeed

[W5CI]

Occasionally I get a Propeller Overspeed Warning. What may be causing this My Mini has very low flight time on it

 

[Deleted member 103366]

You could try a search for deformed props, overspeed and warning (the search is accessed via the magnifying glass to the RHS of the 2nd line of this page). You will, I am sure, find quite a bit of interesting reading material.

 

[billiam1]

Make sure that you fold the props exactly like the diagram that's in the case...I was getting the warnings, but since then....no issues whatsoever

 

[W5CI]

thanks, I had never noticed that

 

[boblui]

Mini's props are prone to deformation if not properly stored. Quite a number of reported crash cases of the Mini are believed to be caused by this reason. The "solution" by DJI is giving a warning to the user instead of making the prop stiffer.

 

[W5CI]

Mini's props are prone to deformation if not properly stored. Quite a number of reported crash cases of the Mini are believed to be caused by this reason. The "solution" by DJI is giving a warning to the user instead of making the prop stiffer.

I just replaced the Rear Props in hopes that this will take care of the problem. thanks

 

[Zbip57]

Occasionally I get a Propeller Overspeed Warning. What may be causing this My Mini has very low flight time on it

What's causing prop deformation:
mavicpilots.com/threads/motor-speed-error-mavic-mini.86130/page-13#post-1038101

How to test prop blades:
mavicpilots.com/threads/motor-speed-error-mavic-mini.86130/page-13#post-1038918

How to prevent prop deformation:
mavicpilots.com/threads/motor-speed-error-mavic-mini.86130/page-14#post-1042991

 

[billiam1]

I had a few motor speed error warnings, but since I've paid particular attention to the diagram ( bottom props, left over right, top props right over left) ...no issues whatsoever

 

[DanMan32]

I don't think it matters if left is over right or right is over left. The point is that the back props face each other and front face each other when placing in FMC case. In this way, nothing is pushing on the props while in storage.

 

[Zbip57]

I don't think it matters if left is over right, or right is over left.

That much is true. However, whichever way you choose, fresh new and straight propeller blades on the rear motors cannot be nested together across the body of the Mini without bending one side under the other side, as illustrated in the first link I posted above.

The point is that the back props face each other and front face each other when placing in FMC case. In this way, nothing is pushing on the props while in storage.

The front props are probably fine. But even if stored "properly", crossed into the case's trough per the diagram in the bottom of the Flymore case without the weight of the Mini resting on the blades, the rear props are still being bent whenever forced to nest under/over the opposite side's blades.

If your rear props slide effortlessly over/under each other when crossed, with no apparent sign of bending, that only means they're already bent.

Whether that bending has produced any significant degradation of the blades' performance cannot be detected by merely looking at them. Do the hover test described in my 2nd link and plot the motor speeds. That will show whether there is any need to worry.

Certainly if you ever get the Motor Speed Error warning displayed, or Propeller Over Speed warning, that's a definite indication that your propeller blades are no longer producing sufficient lift and that motor is nearing its maximum rpm limit trying to compensate for the lack of lift.

 

[DanMan32]

Top or bottom (with respect to folded AC), both will have blades touching. Any possible bending to accommodate the overlap would be so slight as to be negligible. When properly folded across the AC body, the FMC case has baffles to make sure neither the case nor the AC has any contact with any of the props. It's putting pressure on the props that causes warping, which will happen with many of prop retainers, some cases, or not folding the prop properly when in the FMC case.

I realize it can be a little tricky preventing the bottom props from sliding out of place when placing the AC into the FMC case but if you keep the AC level, the props won't move.

 

[DanMan32]

Let's also not forget that the AC comes packed in the case from the factory with props already installed on the AC. If it was not possible to pack the AC in the case without potentially warping the props, then all FMC packages would have warped blades by the time you unbox it.

I have no flight issues and I do use the FMC case. I take care to be sure blades are across the body.

 

[Zbip57]

Top or bottom (with respect to folded AC), both will have blades touching. Any possible bending to accommodate the overlap would be so slight as to be negligible. When properly folded across the AC body, [...]

Have you actually looked at the posts in the links I provided above? If not, please do so.

Overlapping the rear prop blades does create significant bending.

When stored with the blades crossed like that, they will eventually become permanently deformed. A cursory visual inspection is often inconclusive. Deformed props may look perfectly fine, and they'll mesh together easily. But if you install a fresh set of brand new propeller blades, the difference is quite apparent.

Because of the way the rear motors are mounted on an angle canted outboard, straight new blades cannot be meshed together when folded unless one side is bent down to fit under the other side.



Here you can see how straight new rear blades form a crossed X when you try to fold them together. Note how high the tip of blade #1 stands when free, compared to how far down the tip of blade #2 must bend to fit under the blades of the opposite motor.

 

[Zbip57]

Let's also not forget that the AC comes packed in the case from the factory with props already installed on the AC. If it was not possible to pack the AC in the case without potentially warping the props, then all FMC packages would have warped blades by the time you unbox it.

Yes. That's exactly my point.

As mentioned (and illustrated) in the first link above, "What's causing prop deformation:", it's not only the Flymore Combo (FMC) Minis that are being affected. Regular non-FMC Minis display the exact same condition.

Of course, if you drop the Mini into the Flymore case without "properly" positioning the props into the space provided for them, then the weight of the Mini will be resting on the rear props. That's obviously not good. But even when "properly" stored, simply crossing the rear blades laterally across the body of the Mini is enough to bend the blades.

Here are a couple of examples. Brand new non-FMC Minis are shipped in a plastic tray with the arms folded and blades crossed. The blades are held in place by paper bands to ensure they remain "properly" folded in the box. Another guy (not me) posted these photos asking if it was normal to see the gimbal guard loose like this (it's not normal). But more interesting, note how far down the left rear blade tips are bent in order to fit folded under the opposite side's blades.








Here's another set of images posted by someone else. This is a brand new Mini straight out of the box. Note the obvious deflection of the left-rear blades. That's a pretty extreme example, but there's no telling how long it was in transit stored in its shipping box before he eventually unpacked it.

People have reported receiving the Motor Speed Error, or Propeller Overspeed, warnings on their very first flight with their Minis. The initial post in this thread says he's getting the overspeed warning even though his Mini "has very low flight time on it".

Your blades might not be as obviously bent. The deflection can be quite subtle. If it's not (yet) triggering a Motor Speed or Propeller Overspeed warning, then you can probably ignore any trivial bending.

However, if you're at all concerned, do the Hover Test and plot the motor speeds for comparison. With a healthy set of new fresh straight props, my Mini hovers with all four motors turning at equal speeds of ~9600 rpm. (See the 2nd link in my first post above.)