120ccpm Posted at 4-8 12:32
I don't know the story behind this photo, but these two props look very different to the naked eye:

[view_image]

I saw something like that ou you tube and the problem was the way the drone is insert in the carriyng case, the props should be place the way there's not force apply on it, and if the prop are bent as little them seen, it will cause many flight problem.

A few things to add to this thread, JJB have reported that he used the same drone and same props to fly after the incidents and he did not have issues with subsequent flights. This points to possibility this have nothing to do with deformed props due to storage.

The question is, was the props deformed (or the arms deformed) in flight due to stress of wind or maneuvers?

Note: Just posting to keep this thread alive so DJI is paying attention to this problem.

Bloodied_Mini Posted at 4-21 20:42
A few things to add to this thread, JJB have reported that he used the same drone and same props to fly after the incidents and he did not have issues with subsequent flights. This points to possibility this have nothing to do with deformed props due to storage.

The question is, was the props deformed (or the arms deformed) in flight due to stress of wind or maneuvers?

Correct, had a flight yesterday (same props, batterty etc) in wind up and over the limit.

No problem at all. Only once a max power reached message, this at the end of the flight when the battery total volts < 6.6.

In my uncontrolled height drop i found a error in my DAT file, this error (height control fault) exactly at the moment of the height drop.

So i am looking for flightlogs and DAT files of such flights to see if there the same error is present in the flight.

BTWheight variations due to rapid stick moves are more present that in other drones, just a MM 'thing'and not the real problem.BTW
baro height indication changes due to wind the same, easy to check when fly fast few meters above flat ground (in VPS height range).
2 things ; sometimes MM actual ascends, sometimes only the indication indicate higher values that the actual height.

But the real problem is the uncontrolled height drop, and happens afaik only with low but not too battery values.

cheers
JJB

JJB* Posted at 4-21 23:20
Correct, had a flight yesterday (same props, batterty etc) in wind up and over the limit.

No problem at all. Only once a max power reached message, this at the end of the flight when the battery total volts < 6.6.

can you upload the log of your drop somewhere please?

Ice_2k Posted at 4-22 00:27
can you upload the log of your drop somewhere please?

Nope, some other things were checked also wich i do not want to publish.

JJB* Posted at 4-22 01:29
Nope, some other things were checked also wich i do not want to publish.

JJB, do you notice if there was a change in RPM from the motors when the MM dropped (or if the RPM data was even available)?

This is to know whether if the IMU decides to slowdown the motors for some reason thus causing the drop or if the motor still spins as fast but external factors cause the mini to drop.

Bloodied_Mini Posted at 4-22 22:06
JJB, do you notice if there was a change in RPM from the motors when the MM dropped (or if the RPM data was even available)?

This is to know whether if the IMU decides to slowdown the motors for some reason thus causing the drop or if the motor still spins as fast but external factors cause the mini to drop.

Wondering same thing, after reading elsewhere couple pilots talking about their MM still descending even though their MMs were being given full throttle ascent and log files confirming motors were at full speed.
Along with another member talking about how motors on MMs having descent problem not sounding same as his which has not suffered un-commanded descent problem.

Haven't been able to find four field entries, one for each motor, in verbose CSV flight log file; which show RPMs of motors or amount of power being applied to each motor.

Wondering now if there is any evidence that motors are actually turning at Max RPMs during un-commanded descent with pilots commanding a full throttle ascent?  

Bloodied_Mini Posted at 4-22 22:06
JJB, do you notice if there was a change in RPM from the motors when the MM dropped (or if the RPM data was even available)?

This is to know whether if the IMU decides to slowdown the motors for some reason thus causing the drop or if the motor still spins as fast but external factors cause the mini to drop.

Hi,

see#14

Engines were spinning down.

I have the habbit to upload my flightlog and DAT file to my PC before syncing with the DJI servers.
RPM data is to be found in the DAT file.So with only flightlog data it is not possible to know how the motors were acting at a uncontrolled down move.

cheers
JJB

Thanks JJB, was new to FRAPS and what it can do. If motor was spinning down, it further reinforce the fact that this drop is independent of the propellers deforming either by storage or by external factors. If barometer still shows the drop correctly and motor spins down, basically it meant the IMU was commanding the craft to drop -> Firmware bug somehow?

Bloodied_Mini Posted at 4-22 23:20
Thanks JJB, was new to FRAPS and what it can do. If motor was spinning down, it further reinforce the fact that this drop is independent of the propellers deforming either by storage or by external factors. If barometer still shows the drop correctly and motor spins down, basically it meant the IMU was commanding the craft to drop -> Firmware bug somehow?

Hard to make up a solid conclusion, i need to have more flightlogs and corresponding DAT files to 'know' if there is a common error to this.

I have still my original blades on my MM, craft performs great in lots of wind etc. Only once a height drop, this with low batt cell values and a error in the DAT.

Hope to have another height drop when i am flying for test (so i know i can recover MM from a large flat free area).

In the next version of FRAP the DAT file read-out is included, still working on it.  see chart1 wich includes a (app commanded) compass calib, as the last flight was 120 km away from this location.

Had a flight with lots of wind, only forward stick and yaw stick used. See how the baro indications shows his values against the more steady VPS height.  If i fly this with my MA both lines are more equal to eacht other.

cheers
JJB

JJB* Posted at 4-22 23:48
Hard to make up a solid conclusion, i need to have more flightlogs and corresponding DAT files to 'know' if there is a common error to this.

I have still my original blades on my MM, craft performs great in lots of wind etc. Only once a height drop, this with low batt cell values and a error in the DAT.
[Image]

Great news about FRAPS upgrade, very good program already but DAT files compatibility would be awesome! I store my logs to the computer too.

JJB* Posted at 4-22 23:48
Hard to make up a solid conclusion, i need to have more flightlogs and corresponding DAT files to 'know' if there is a common error to this.

I have still my original blades on my MM, craft performs great in lots of wind etc. Only once a height drop, this with low batt cell values and a error in the DAT.

Thanks for the explanations, a few questions (I'm a total rookie to drones or FRAPS):

1) How do I read the baro height from the graphs/tables vs VPS height? I do see VPS height on the top table but baro data?

2) You mentioned that this could relate to lower battery levels. So in order to help you pin this down, I guess it's better I fly around an open field until low bat, fly straight, stop and yaw to see if there's a uncommanded descent?

Bloodied_Mini Posted at 4-23 00:11
Thanks for the explanations, a few questions (I'm a total rookie to drones or FRAPS):

1) How do I read the baro height from the graphs/tables vs VPS height? I do see VPS height on the top table but baro data?

1) in the top table you can select any data column from a DAT into CVS file.

Don`t understand your question really
Barometric height info is from the baro sensor, this value is set to zero after takeoff.
VPS heigt indicates the true distance below the craft and ground, if the signal back is not disturbed in any way.  

So flying down from top of hill following the terrain you will see negative numbers for baro height and few meters for VPS height (if you can maintain few meters height following the down slope...)

2) No, i have flown many flight up to critical batt level and no problem, so low batt levels doesn`t mean always a height drop. But i think all the examples of height drop happend often with lower batt values, some more than average wind and few times after yaw turn.

cheers
JJB

Well because it looked extremely windy that might be your or djis problem.

JJB* Posted at 4-23 00:32
1) in the top table you can select any data column from a DAT into CVS file.

Don`t understand your question really

I think that it happens with low battery is pretty much a give away that it is not props that are at fault and I read many say it’s rear motors because of low battery, but if it were battery we would see low power across all engines not selectively to back engines, so unlikely the battery.

Mavic mini in strong wind gives clear warnings, LAND IMMEDIATELY this is backed up by vibration warning, maybe dji know a little more about this than they’re telling.

Maybe the installation of the new Mavic Mini firmware 01.00.0500 will solve some of the issues (hopefully)

* Improved flight stability in some scenarios.

hallmark007 Posted at 4-23 01:05
I think that it happens with low battery is pretty much a give away that it is not props that are at fault and I read many say it’s rear motors because of low battery, but if it were battery we would see low power across all engines not selectively to back engines, so unlikely the battery.

Mavic mini in strong wind gives clear warnings, LAND IMMEDIATELY this is backed up by vibration warning, maybe dji know a little more about this than they’re telling.

Not sure about the wind, i did few test with wind > 8 m/s   and my MM performed more than the specs.
Flying against wind with 10m/s MM in P-GPS reached forward speed of 8 m/s.

It just a mystery this height dropping!  But in my DAT file i found a sensor height error just before the unwanted descend started.  So no props to blaim, maby combination of low voltage and something else....
DJI should know by now, but they won`t inform MM users....

cheers
JJB

JJB* Posted at 4-23 04:09
Not sure about the wind, i did few test with wind > 8 m/s   and my MM performed more than the specs.
Flying against wind with 10m/s MM in P-GPS reached forward speed of 8 m/s.

Hopefully new FW will fix, I have just downloaded and flew one battery down to 18%, the wind is very low here so can't  confirm anything there.
Flying sport mode forward 50m altitude sudden stop craft going forward/back drops less than 1 metre and regains correct gps altitude.
At 1.3m altitude in sport mode over grass craft going forward will rise approx .2m flying back sport craft rises approx .3/4m. I flew really hard in sport mode at different altitude and very slight drops and increase were always followed by craft regaining correct gps altitude.

I was one of those who was not having any problems but I have noticed an improvement in all round stabilization of the mini, again I’ve tested in low wind but from 1.3m to 90m and all seems good.
I have never changed props original still on .

hallmark007 Posted at 4-23 04:26
Hopefully new FW will fix, I have just downloaded and flew one battery down to 18%, the wind is very low here so can't  confirm anything there.
Flying sport mode forward 50m altitude sudden stop craft going forward/back drops less than 1 metre and regains correct gps altitude.
At 1.3m altitude in sport mode over grass craft going forward will rise approx .2m flying back sport craft rises approx .3/4m. I flew really hard in sport mode at different altitude and very slight drops and increase were always followed by craft regaining correct gps altitude.

sounds good!  i will test this the next days!

JJB* Posted at 4-22 23:48
I have still my original blades on my MM, craft performs great in lots of wind etc. Only once a height drop, this with low batt cell values and a error in the DAT.

Would it be possible to see the curvature of your propellers (one or a few) ?

JGFly Posted at 4-23 06:33
Would it be possible to see the curvature of your propellers (one or a few) ?

well, hard to take a good picture for checking a blade to another.
My blades are the original ones, the spare set i bought are exactly the same.

So if you do not trust yours, buy a new set and compare or just use them

cheers
JJB

I had a low wind (insufficient power error) drone drop to the ground event today as well. I could not move forward without losing altitude. I noticed that I had insufficient power from the start of my flight. Even in sport mode I had slow speeds. I landed to check my propellers and when I went to finish my photoshoot, I lost altitude.  Trying another flight on a new battery.  

mattdswartz Posted at 4-23 10:47
I had a low wind (insufficient power error) drone drop to the ground event today as well. I could not move forward without losing altitude. I noticed that I had insufficient power from the start of my flight. Even in sport mode I had slow speeds. I landed to check my propellers and when I went to finish my photoshoot, I lost altitude.  Trying another flight on a new battery.

It was a max power load alarm. Sorry

mattdswartz Posted at 4-23 10:47
I had a low wind (insufficient power error) drone drop to the ground event today as well. I could not move forward without losing altitude. I noticed that I had insufficient power from the start of my flight. Even in sport mode I had slow speeds. I landed to check my propellers and when I went to finish my photoshoot, I lost altitude.  Trying another flight on a new battery.

Hi

could you upload your flightlog and DAT for this flight?

cheers
JJB

mattdswartz Posted at 4-23 10:54
It was a max power load alarm. Sorry

Replace props

JJB* Posted at 4-23 11:01
Hi

could you upload your flightlog and DAT for this flight?

Ok. I decided to update the IMU and compass . Once I got in the air the drone told me to replace my rear propeller. I did that, and everything is flying better. Amazingly, it even showed me which one by vibrating the one that needed changed.

mattdswartz Posted at 4-23 11:28
Ok. I decided to update the IMU and compass . Once I got in the air the drone told me to replace my rear propeller. I did that, and everything is flying better. Amazingly, it even showed me which one by vibrating the one that needed changed.

Wow, that must be the update.

JJB* Posted at 4-23 09:56
well, hard to take a good picture for checking a blade to another.
My blades are the original ones, the spare set i bought are exactly the same.

So if you do not trust yours, buy a new set and compare or just use them

I have the Fly more so also spare propellers, Thank you.

Here not had the opportunity to really test (too windy) therefore, impossible to compare one used for several hours versus the others included in the Combo.

No problem if you can't. I would still have liked to compare the curvature of a prop  having several hours of flight  with one not used yet  but no problem if you do not want..

If somebody else can, It would be interesting to see.

Cheers
JGFly

Seems to be 2 different reasons for the MM uncontrolled descent here:

1) The more common propellar deformed due to storage.
2) Height sensor error.

In JJB's case, it is clearly none propellar related. Thus it would be interesting to know what DJI have to say about the height sensor error at low batt. Especially when there's another thread that claims GPS error due to battery issues. Might or might not be related, but if so... looked to be more than a simple firmware update is required.