Mavic Mini uncommanded descent tests

[BokiFly]

I would check the flight data every time to make sure that the rear motors are not spinning at close to their limits during a static hover

What is their limit? What RPM numbers is call to concern?

Can rear blades be stored not East-West but something like this:

Left one: East - NorthEast
Right one: West-NorthWest

So that they don't overlap?

 

[lee82gx]

What is their limit? What RPM numbers is call to concern?

Can rear blades be stored not East-West but something like this:

Left one: East - NorthEast
Right one: West-NorthWest

So that they don't overlap?

I'm trying to help but I dont have a Mavic Mini, for the reason of this Uncommanded descent being improperly fixed by DJI for more than half a year.

The RPM for calm hover at rear should be around 10krpm for a fresh, good propeller. At 18krpm it will reach its limit and cannot go more to either give you a forward pitch, or static lift. I think for me, if reaching 12krpm on rear at calm hover / zero pitch is my limit to change props. But its a personal choice, because you know that in flight it can go up to 18krpm before hitting the limit.

 

[BokiFly]

Does any other Mavic drone have this problem with damaging props because of storage?

 

[lee82gx]

Does any other Mavic drone have this problem with damaging props because of storage?

My experience is limited to Mavic Air (no problem), Mavic Pro (No problem) and Mavic Air 2 (so far, no problem). Really, there is only the Mavic 2 that I dont have and I've not heard of it either.

 

[BokiFly]

Interesting. Is the way that these other drones props is stored very different from Mini's?

 

[lee82gx]

The propellers themselves appear to be weak. I think the discussion on the root cause of the propellers going bad is not complete (to my knowledge) as to whether its due to storage or just plain rotating or something else.
I can tell you that my Mavic Pro and Mavic Air 2 have storage to cramped that the props are surely stressed in storage. The Master Air screw props for Mavic Air 1 are so thin, even touching them bends them a lot. Of course, none of them are stored across each other, usually they are stored along the side of the drone. (North to south)

 

[sar104]

Does any other Mavic drone have this problem with damaging props because of storage?

I haven't seen this with any of the other models, but that's not particularly surprising since only the Mini uses noodles as propellers.

 

[BokiFly]

Considering Mini's popularity and considering how widespread this problem is company that accomplish to create quality props for Mini will get rich.

I hope that these companies will give their best to produce quality props for Mini. And soon.

 

[sar104]

Considering Mini's popularity and considering how widespread this problem is company that accomplish to create quality props for Mini will get rich.

I hope that these companies will give their best to produce quality props for Mini. And soon.

It should be easy enough to produce stiffer props, and so the fact that they are not yet available makes me think there may be additional subtleties involved. DJI may have cared about just the weight in order to stay under 250 g, but third-party manufacturers probably don't. I wonder if the additional mass required to stiffen them up causes problems for the motors, or if the amount of flexion (up to a point) is essential to the design.

 

[Zbip57]

Can rear blades be stored not East-West but something like this:
Left one: East - NorthEast
Right one: West-NorthWest
So that they don't overlap?

The Fly More case has a recessed area below the Mini into which the rear prop blades must fit. The blades have to be folded and overlapped in order to fit in there.

 

[BokiFly]

DJI may have cared about just the weight in order to stay under 250 g, but third-party manufacturers probably don't

You think so? I would like that be the truth, but I am afraid that increasing mass for stiffer props (and going over 250g) is maybe the main reason why they didn't hit the market yet. I would not have a problem if Mini go over 250g, but how regulations apply in this situation? Drone is labeled as under 250g, but someone can attach props that will push it over 250g. Will that break regulations? And if so, then props manufacturers can have a problem if people will be afraid to buy those props.

 

[slup]

You think so? I would like that be the truth, but I am afraid that increasing mass for stiffer props (and going over 250g) is maybe the main reason why they didn't hit the market yet. I would not have a problem if Mini go over 250g, but how regulations apply in this situation? Drone is labeled as under 250g, but someone can attach props that will push it over 250g. Will that break regulations? And if so, then props manufacturers can have a problem if people will be afraid to buy those props.

When it comes to fulfill weights according to regulations it's "in flight weight" that counts, not what a label on the AC say. Attach thing's to it & it will go over 250gr & will be considered as a done heavier than 250gr.

 

[Zbip57]

The propellers themselves appear to be weak. I think the discussion on the root cause of the propellers going bad is not complete (to my knowledge) as to whether its due to storage or just plain rotating or something else.

Everything on the Mini has been pared down to get its weight below the magic 250g limit. The prop blades are quite flimsy, but they function well as-designed.

Unless you're bouncing it off rocks and trees, I don't believe the prop degradation has anything to do with the way the Mini is flown. I agree the discussion is not yet complete or definitely proven, but I'm convinced the problem is in the way the props, especially the rears, are folded for storage.

Here's an example that was recently posted in the DJI forum. He says it hasn't been flown at all, it's brand new, came straight out of the box looking like this. Check the deformation on the left rear blades!

 

[sar104]

You think so? I would like that be the truth, but I am afraid that increasing mass for stiffer props (and going over 250g) is maybe the main reason why they didn't hit the market yet. I would not have a problem if Mini go over 250g, but how regulations apply in this situation? Drone is labeled as under 250g, but someone can attach props that will push it over 250g. Will that break regulations? And if so, then props manufacturers can have a problem if people will be afraid to buy those props.

When it comes to fulfill weights according to regulations it's "in flight weight" that counts, not what a label on the AC say. Attach thing's to it & it will go over 250gr & will be considered as a done heavier than 250gr.

That's technically correct but really is one of those marginal areas that I actually don't think would ever be an issue. If you are flying a commercial product that is certified as < 250 g, then even if something were to happen I cannot imagine the FAA getting out the scales and citing you for being at 255 g. Prop guards, strobes, motor covers, skins - any of the commonly added components will take it over 250 g, but I don't see anyone fretting about those.

 

[BokiFly]

The Fly More case has a recessed area below the Mini into which the rear prop blades must fit. The blades have to be folded and overlapped in order to fit in there.

I was referring to this orientation (second image).

 

[lee82gx]

Everything on the Mini has been pared down to get its weight below the magic 250g limit. The prop blades are quite flimsy, but they function well as-designed.

Unless you're bouncing it off rocks and trees, I don't believe the prop degradation has anything to do with the way the Mini is flown. I agree the discussion is not yet complete or definitely proven, but I'm convinced the problem is in the way the props, especially the rears, are folded for storage.

Here's an example that was recently posted in the DJI forum. He says it hasn't been flown at all, it's brand new, came straight out of the box looking like this. Check the deformation on the left rear blades!

View attachment 103231

Your theory may well turn out true, and the problem is while in storage and tumbling around it all it takes is for the props to stack and bend on top of each other, it could explain the intermittences of occurrence. That left rear out of box is too obviously a problem.

 

[slup]

That's technically correct but really is one of those marginal areas that I actually don't think would ever be an issue. If you are flying a commercial product that is certified as < 250 g, then even if something were to happen I cannot imagine the FAA getting out the scales and citing you for being at 255 g. Prop guards, strobes, motor covers, skins - any of the commonly added components will take it over 250 g, but I don't see anyone fretting about those.

Yeah ... my response was pure technical But somewhere the "line is drawn" & above is above. Big risk to get caught with 5gr overweight ..? Nah ... probably not big. But it's most probably the reason why DJI doesn't just beef them up giving the Mini that extra overweight already from factory.

 

[Zbip57]

That's technically correct but really is one of those marginal areas that I actually don't think would ever be an issue...

I used to work in regulation enforcement for Transport Canada, in their Motor Vehicle section. It's astounding how lawyers are able to twist words to suit their objectives whenever backed into corners.

Recently the UK proposed changes in the wording of their drone regs to clarify that the intent of the 250g limit applies to the aircraft in its "as flown" configuration. Here in Canada the wording instead refers to the aircraft's "maximum takeoff weight".

I've always wondered why that shouldn't simply say, "takeoff weight"? Why, "maximum takeoff weight"?

With battery and microSD card installed, the Mini takes off weighing 249g. All good. But it is also capable of taking off with the prop guards installed, in which configuration it weighs more than 250g. Doesn't that imply that its maximum takeoff weight is something greater than 250g?

 

[sar104]

I used to work in regulation enforcement for Transport Canada, in their Motor Vehicle section. It's astounding how lawyers are able to twist words to suit their objectives whenever backed into corners.

Recently the UK proposed changes in the wording of their drone regs to clarify that the intent of the 250g limit applies to the aircraft in its "as flown" configuration. Here in Canada the wording instead refers to the aircraft's "maximum takeoff weight".

I've always wondered why that shouldn't simply say, "takeoff weight"? Why, "maximum takeoff weight"?

With battery and microSD card installed, the Mini takes off weighing 249g. All good. But it is also capable of taking off with the prop guards installed, in which configuration it weighs more than 250g. Doesn't that imply that its maximum takeoff weight is something greater than 250g?

Agreed, but US law doesn't quote "maximum takeoff weight" - just "aircraft weight". And since DJI doesn't specify maximum takeoff weight it would be difficult to determine anyway, although obviously greater than 250 g for the Mini.

 

[Zbip57]

US law doesn't quote "maximum takeoff weight" - just "aircraft weight". And since DJI doesn't specify maximum takeoff weight it would be difficult to determine anyway, although obviously greater than 250 g for the Mini.

I'm pretty sure Transport Canada intended it to mean the same thing. It's the aircraft's weight as flown. But it's typically sloppy of them to publish regs that are open to misinterpretation.