Hi all,

I'm running the latest firmware (re-installed using DJI assistant), I got the motor speed error initially but that disappeared without me having to change props and I've had several flights in lots of conditions with no issues or warnings.

Yesterday I took the drone to the beach, it was a bit windy for a big flight and I forgot my SD card anyway so I kept it low and was just playing chase with the dog in sport mode.

I noticed on several occasions whilst hovering (not when moving) I was getting prop strike on the front right, loud buzzing/clicking noise and front left landing leg vibrating a lot, visible marks on the body and one of the blades (not the other strangely), this would last 2 - 3 seconds then stop.

It was windy, 8 - 10 mph with 15 - 20 mph gusts.

At the end of the flight I left the drone hovering at about head height (2m). During a strong gust of wind the drone stayed on the spot but dropped from 2m down to just above the ground, I'm 99% sure I wasn't touching the sticks. It seemed to stop at the minimum height/ ground sensors kicked in, my feeling was that if it was over water it would have been swimming


Could someone have a look at my logs to confirm?

https://app.airdata.com/share/kmIZNx

Confirmed.... it is, and it's quite predictable. You were flying disregarding Strong Wind Warnings, coming to a stop from an hasty ride in Sport mode.

I am wondering if you read this forum or if you just believe the representatives of the Flying Integralist Drone Association. This kind of behaviour is most likely inbred into the Mini and will never change with firmware updates.
Btw: I know a hoard of DOWNVOTES will ensue... [shrugs] told you... face reality. Poeple have problems facing it... they were reacting the same way almost 6 months back when I was pointing out at the blades.


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m80116 Posted at 5-15 02:16
Confirmed.... it is, and it's quite predictable. You were flying disregarding Strong Wind Warnings, coming to a stop from an hasty ride in Sport mode.

I am wondering if you read this forum or if you just believe the representatives of the Flying Integralist Drone Association. This kind of behaviour is most likely inbred into the Mini and will never change with firmware updates.

I only disregarded the wind warnings as the drone was low over the sand and close to me the whole time, no risk of fly-away or water crash. Wind speed was below the spec in the manual

It hovered for a while before descending but was hit by a strong gust. I assumed it would hold the height and move sideways rather than stay on the spot and drop.

Eye-opening to know that a rogue gust on a calm day could lead to this happening
edit - forgot to say, thank you for taking the time to check and confirm

Do you still have the Dat file from this flight? Instructions for DAT

ABeardedItalian Posted at 5-15 03:17
Do you still have the Dat file from this flight? Instructions for DAT

Yes I do, I can upload but not sure if it contains sensitive info like SN?

I've had a look in CSVView, my rear left motor showing much higher speed than right but its always been like that. Not sure if I have added right things to the chart

itchyeyeballs Posted at 5-15 03:28
Yes I do, I can upload but not sure if it contains sensitive info like SN?

I've had a look in CSVView, my rear left motor showing much higher speed than right but its always been like that. Not sure if I have added right things to the chart

Yes if you could upload it that'd be great, as far as the SN is concerned that's already in your flight log.

While motor speed was one thing to look at I was trying to check for the UD, in another flight analysis program FRAP I couldn't see a UD so I wanted to check the Dat file since I know what it looks like there.

It's hard to see your graph but yes your Rear Left is experiencing much higher RPM, hearing that you've gotten the motor speed warning in the past confirms this. As of right now it's not enough to trigger the warnings but you are right on that line of it happening again, I would go ahead and replace the Rear Left to prevent any further incidents.

ABeardedItalian Posted at 5-15 03:39
Yes if you could upload it that'd be great, as far as the SN is concerned that's already in your flight log.

While motor speed was one thing to look at I was trying to check for the UD, in another flight analysis program FRAP I couldn't see a UD so I wanted to check the Dat file since I know what it looks like there.

The rear left has been like that since flight number 1, if its a defective prop its a factory issue but I will replace (along with the damaged front right)

Dat is here- https://drive.google.com/open?id ... d9TpE7ISRO4GI5NUFjZ

Appreciate your time and any insights you can find

itchyeyeballs Posted at 5-15 03:45
The rear left has been like that since flight number 1, if its a defective prop its a factory issue but I will replace (along with the damaged front right)

Dat is here- https://drive.google.com/open?id=1t4dQo65ZdUWjNd9TpE7ISRO4GI5NUFjZ

Unfortunately the tools I was going to use to check don't exist in my version of csvview, I've sent a pm to the user who has a more advanced version.

What I was able to see what but not confirm was you did experience a height loss to ground but i think it could of been lag. If you look at the graph below you can see you started to hold Stick Down for a second and resumed to center, but the drone seems to have kept dropping past the stick movement. I'm hoping JJB or Budwalker pops into this thread as they can tell you much more.

Thanks for looking

I had it hovering and not moving much, I was trying to look at the vibrations from the prop strikes (seemed like the leg was going to come off at certain points before the decent).

I definitely had the feeling it would have kept going down indefinitely if the ground sensors hadn't kicked in which is strange as it obviously had the physical ability to stop descending but the software was telling it otherwise.

It would be interesting to read the atmospheric pressure measurements during the uncommanded descent, but I suspect that might logged to the SD-card and no way to retrieve from a user standpoint.

If you have 5 minutes, please do the "hover test" we're doing on this thread, see around post #185. Basically: indoor (make sure you have good light for Vision System to work), auto takeoff, hover for 2-3 minutes without touching the sticks, auto landing, load the DAT in CsvView, look at motor speeds. You can also export to Csv, open in Excel and calculate averages for the 4 motor speeds with the following formula (remove spaces next to ":"):
=AVERAGEIF(DD : DD, ">8000")
Where "DD" is the column with the motors speeds you're averaging out.
We are seeing a significant variance in RPMs between props, it would be interesting to see what numbers you get, considering you got the Motor Speed warning at some point, and you're now getting some prop strikes (even if it's in extreme conditions).

120ccpm Posted at 5-15 08:43
If you have 5 minutes, please do the "hover test" we're doing on this thread, see around post #190. Basically: indoor (make sure you have good light for Vision System to work), auto takeoff, hover for 2-3 minutes without touching the sticks, auto landing, load the DAT in CsvView, look at motor speeds. You can also export to Csv, open in Excel and calculate averages for the 4 motor speeds with the following formula (remove spaces next to ":"):
=AVERAGEIF(DD : DD, ">8000")
Where "DD" is the column with the motors speeds you're averaging out.

Hi,

I've just run the test and will post the results in the thread you have linked to

As a quick update though, my visibly damaged front right prop (from the strikes) seems to be fine, the back left seems to behave very differently though, I could hear it making a different sound to the others. Was 100% like this from new (I have the logs)

Edit - To avoid doubt, I have been super careful about storing it correctly in the case from day 1, the props have never been under pressure or incorrectly aligned in the case or anywhere else.

Hmm, replaced front right and rear left props and got the following!



I will monitor closely going forward, seems the left-back was definitely dodgy when I received it. Feel more confident now I have changed but annoying that I have had to use two packs of props (does the Loctite go off when exposed to air, if so I may as well change the other two sets of props?)

itchyeyeballs Posted at 5-17 13:54
Hmm, replaced front right and rear left props and got the following!

[view_image]

I think we got one positive and one negative from your test. On the positive front, you were able to spot a prop (Left-Rear) that was performing worse than the others, spinning  2000 RPMs above the rest. You also saw the result of a new prop with your own eyes, so you know what to do in the future, should you have any doubts about props.
On the negative side, we did not see a correlation between prop strikes and high RPMs, because your Front-Right was doing just fine. As I mentioned recently on another post, scratches and dings make a prop look bad, but might have marginal effect on its performance, so I'm not surprised about that. But I would have guessed (hoped) that prop strikes were related to flattened props flapping around. Instead, your MM shows that's not that case.

As for the thread-lock, I don't know what type DJI puts on replacement screws. I personally re-used the old screws on a recent prop swap, and put a tiny bit of Loctite Blue (242) on them. Less than a drop, spread around with the tip of a finger. I'll let you know if it does not work... :-)

I'll keep a close eye on the props and the logs.

The prop strike must be related to the blades, only one of mine was hitting, if it was the arm at fault I would assume they would both hit?  

120ccpm Posted at 5-17 15:55
I think we got one positive and one negative from your test. On the positive front, you were able to spot a prop (Left-Rear) that was performing worse than the others, spinning  2000 RPMs above the rest. You also saw the result of a new prop with your own eyes, so you know what to do in the future, should you have any doubts about props.
On the negative side, we did not see a correlation between prop strikes and high RPMs, because your Front-Right was doing just fine. As I mentioned recently on another post, scratches and dings make a prop look bad, but might have marginal effect on its performance, so I'm not surprised about that. But I would have guessed (hoped) that prop strikes were related to flattened props flapping around. Instead, your MM shows that's not that case.

> scratches and dings make a prop look bad, but might have marginal effect

Can confirm this.. Most people would never start with how my props look like Starting in high gras, wasnt the best idea I ever had..

If I dont forget tonight, I will make the hoover test. Also take a photo of my props ;)

thE29 Posted at 5-28 00:48
> scratches and dings make a prop look bad, but might have marginal effect

Can confirm this.. Most people would never start with how my props look like  Starting in high gras, wasnt the best idea I ever had..

Why not start it from your hand? it's the easiest thing and does not damage the propeller. I take off and land from my hand when in nature, unless I have a very clean and stable ground, like concrete. It's so easy to do, and safe.

Daniella3d Posted at 6-10 05:35
Why not start it from your hand? it's the easiest thing and does not damage the propeller. I take off and land from my hand when in nature, unless I have a very clean and stable ground, like concrete. It's so easy to do, and safe.

I land quite often in my hand.. But I find it annoying to start in hand. But I start often from the fly more combo case.