Sigmo
 lvl.4
United States
Offline
|
This is a long tale, so bear with me. 
Before I even bought my Mini, I saw a couple of YouTube review videos where the YouTuber found that his Mini dropped towards the ground while he was trying to fly at a high elevation up in the mountains somewhere. Supposedly DJI worked with him and, after investigating the problem, supplied him with some new-style props AND new firmware. With the new props and firmware, he did more testing, and was able to fly well at a bit over 10,000 feet.
After I got my Mini, I've always wondered if it might have come with the "early style" props that are not as good at high elevations. I got mine fairly early, so it seemed possible.
Further, some people have reported that swapping out all of their propellers seemed to cure their "dropping" problems. So that adds to the evidence that "bad" or "old-style" props can be the cause of the infamous "dropping" problem.
I live at about 5150 feet of elevation. I have flown a lot indoors due to nasty weather here for the last couple of months. Naturally, I use the prop guards.
But the prop guards add considerable weight. And at this elevation, the Mini struggles anyhow. So the poor thing is on the edge of being able to fly at all at its best. I get only about 13 minutes max flight time with the prop guards installed, so that's good evidence that at my elevation, with the prop guards, and with the original props, my mini is really struggling just to fly. But it flies reasonably well, and I've had a lot of indoor flying with it, mostly where I work because it's a fairly large buiding.
So while the flight time is limited, I haven't had any serious trouble flying.
However, recently, I noticed that when I updated my phone, RC, and drone to 1.00.0400, the next two flights flew OK until around 50% battery level when the drone dropped down to right above the floor and was unable to rise up at all for the remainder of the battery's charge. The poor thing could barely hold itself a foot off the ground, maybe a bit less. I figured this was because "ground effect" was helping to hold it up. I could fly it forward and backward, left and right, and spin it ccw and cw, but nothing would make it rise up.
So this seemed a LOT like all of the "dropping" I've seen reported on this forum and looked exactly like what was shown in the YouTube video that was made at high elevation with the "old" props and "old" firmware.
But I didn't realize at that time that you are supposed to update the firmware in your batteries whenever you update the firmware in the Mini. And I didn't realize that ONE of my three batteries DID have the new firmware because the Mini automatically updates the one battery that's in it at the time you update the Mini itself. So I had ONE batery with the new firmware and two with something older.
So I replaced all four propellers because I've always been suspicious of whether or not my drone came with "old style" props. And lo and behold, with the new props, the drone flew just fine (considering my elevation and the weight of the prop guards) like it always has before. However, that flight also used the one battery that DID get updated! (But I didn't realize this at the time).
So THAT test made me think that it was the propellers at fault.
However, I THEN found out about the battery firmware thing. So then, as I thought about it, I felt that a reasonable cause for the sudden appearance of the "dropping" syndrome in my Mini, which coincided exactly with me updating to 1.00.0400, might be that I had NOT updated the two batteries that I used with the old props.
So because the drone flew OK with the new prop blades wasn't necessarily the cause because I was also then flying with the one battery that had happened to get updated. Crazy confusing, right?
So I theorized that if the battery firmware doesn't match that in the drone, some miscommunication or incorrect assessment of battery charge, etc., might cause the drone to lower power to the motors suddenly, even though the batteries were reporting a reasonable level of charge.
Several folks said that wasn't likely, but I thought I had this figured out. But to test it, I'd need to try with various firmware revisions, and with and without the batteries having matching firmware AND I'd want to test with the old prop blades and the new ones.
To add to the confusion, my old props did have some damage. This damage had happened on one of my first flights when the drone crashed. It had the prop guards in place, but it still managed to ding a couple of the blades a bit. It didn't look too bad to me, and I had flown it ever since then (at least 30 full-battery flights indoors with the prop guards and two outdoor flights without the prop guards). And it never flew funny or displayed any of the "dropping". So that was strong evidence that the prop damage was not the cause of the "dropping" that I saw after updating to 1.00.0400.
After all, how could I fly with those same slightly damaged blades for 30 flights with no issues, but then suddenly have the dreaded "drone drop" immediatly after doing a firmware update? That seemed highly unlikely.
Nonetheless. My testing showed that the problem was, indeed, the prop blades!
The only way I can explain this "dropping" being coincidental with the firmware update is that it really was a coincidence. And that for whatever reason, one of the blades split a bit more, perhaps with a crack forming and propagating back from a ding in the blade right during the first flight I made after doing the firmware update.
Swapping back and forth between the old and new blades, the issue follows the bad blades, and doesn't match with any firmware OR with any firmware mismatch between my batteries and the rest of the system. The only possibility that I can't test is if a battery with a firmware previous to 1.00.0200 might cause problems when used with firmware 1.00.0400 in the drone and controller. I can't test any firmware lower than 1.00.0200 because I don't see it available in the DJI Assistant 2.
Anyhow, what I've taken away from this is:
Do make sure to update the firmware in ALL of your batteries when you do a firmware update to the drone and RC. It might not be terribly important, but why risk it? It's not obvious that this needs to be done, but do it anyhow.
Do not fly with damaged blades. It may be OK, but then again, assuming my one blade did split from ding in it while flying, and that split then rendered the lift too low to allow the drone to fly well, that could be catastrophic if you're flying outdoors. I was lucky that it happened to me indoors with the drone close to me and under controlled conditions.
Also, if you're experiencing poor flight characteristics, you might want to swap out all of the blades that came on your Mini for new ones in case you did get "old style" blades, and they don't give as much lift as the "new style" blades do. Of course, it may well be that NOBODY has ever gotten the "old style" blades on their production Mini. But what if? The guy who posted the YouTube videos that talked about this issue has removed those two videos and replaced them with different ones. That seems sort of suspicious to me, but who knows?
Nonetheless, as cheap as replacement blades are, it makes sense to check that out if you're having problems. The blades are still hard to get from DJI, but I did get some from a large US vendor, and they came today. So I think DJI may be catching up on production of the blades.
Sorry for the long post. But this was a long set of experiments for me, and I want to set the record straight for everyone about what I found.
Check your prop blades.
|
|
lvl.2
DJI team
lvl.3
Second Officer
Core User of DJI
