Sigmo
Second Officer
United States
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Gu5s Posted at 1-26 22:44
It was meant to be a hyperbole... I had a pretty good Idea what went wrong and I knew I was doing something risky, the title was implying that the drone acted as if nothing was wrong during the fall... (Some members of forum, had to dig for a brief power warning and fluctuation of the Voltage) You would expect warnings, errors flashing left and right during that (right?) since it knew it knew it could not keep up the altitude from the sensors, but from the user perspective (looking at the dji fly app) it just seemed as if the mini "just gave up".
(BTW yesterday I saw a low temperature warning in one youtube video - I have never seen such warning in my flights)
I had my several "drop" incidents, flying indoors, at 5150' elevation, with the prop guards in place, and with damaged blades. This combination of things may have put the poor mini into a situation that might be similar to what you got with the icing on the blades. Basically, very high power required from the motors to be able to hold vertical position.
And what I noted was that I got NO warnings whatsoever. No extra load detected, no low battery, nothing like that. Instead, the Mini simply descended from where I was flying at about 1.5 meters above the floor down to within, perhaps, 15 CM (about a foot) above the floor. And from then on, for the remainder of these flights, I could not raise the mini no matter how much upward command I gave with the left stick. The Mini did not crash, and I could fly it back and forth, left and right, spin it CCW or CW, etc. And I was able to fly like this for another six or seven minutes. This sudden descent happened at about 50% indicated battery level.
Putting in a fresh battery, the Mini would do the same thing. I could fly normally until about 50% power at which point, the Mini would descend to just above the floor for the remainder of that battery's charge. About 6 or 7 minutes of "good flying" followed by the drop and about 6 minutes of "floor skimming".
I initially thought that this might have been caused by my having NOT properly updated the firmware in two of my three batteries when I had updated from 1.00.0300 to 1.00.0400. So I thought it might be some sort of miscommunication between the batteries and the Mini that caused it to either "protect" the batteries too soon, or something like that. But when I rolled things back, and tested with different combinations of firmware in batteries and the mini and remote control, etc., that hypothesis didn't pan out at all.
Instead, the conclusion I came to was that I had a nick in one of the blades which had suddenly propagated from that stress riser, turning into a split that then made that blade lose a lot of its former lift, and that was why this behavior appeared coincidentally with my update from 1.00.0300 to 1.00.0400. Coincidences are something to be very skeptical of when troubleshooting. But in this case, that's my best guess, because my tests of various battery firmwares in combination with various Mini firmwares didn't make any difference. What DID make a difference was replacing all of my props. With the old bad props, I got the problem. With the new, presumably good props, I never saw the issue no matter the firmware combinations.
But what is interesting to me about your incident when compared to mine is that in both cases, we got no dead battery indication. Yet the drones seemed to descend, but in a somewhat controlled way. I got the feeling with mine that the only thing that kept it from touching the floor was "ground effect" holding it up. It was as if the drone was protecting itself or the batteries OR the batteries were simply providing everything they had to give, but that was now not enough (between the loss of thrust and the battery level). And as I say, that happened to me at about 50% indicated battery level.
So I do think that when we have something happen where the poor Mini is being forced to work extra hard, AND the battery level is insufficient to meet that power demand, we're of course going to see the Mini drop down.
I don't know if there was any protection happening in my case, or things just reached the point where that's simply all the poor Mini (or its battery) had to give.
But regardless, it's interesting, and for me, it's a lesson that I need to be extremely careful to have all of the conditions correct when flying the Mini (or any drone). And with the Mini, at higher elevations, and certainly when flying with the prop guards mounted, things are very critical because I'm already flying at or beyond what the Mini was designed to do. I've seen a warning from DJI that says you should not fly with the prop guards in place at elevations over 1500 Meters. I'm right at or slightly above that level. So I can't complain about any of this.
All I'm offering here is that in my situation, I'm able to test the Mini right at its design limits. So perhaps I can do some tests for us all that might act as simulations of what people at lower elevations experience if they encounter something like this apparent icing you had. And maybe some of my flight logs could be helpful to the community. I have a situation where I could perform experiments in an indoor and controlled situation that might prove useful.
Plus, I'm bored because it's always so windy here that I can't fly outdoors much, so there's that. ;)
I think others could do similar testing by, for example, installing their prop guards and perhaps attaching small weights to it to get their Mini to be right at the limits, too.
Flying indoors here, with the prop guards on, I get flights of only 12 to 13 minutes before the battery is dead. So that gives an idea of how hard the Mini is working.
I'll bet with "iced" props, if you could maintain that in a constant way, you'd see something similar. I guess someone could stick bits of tape strategically to their props to simulate icing in a controlled and constant way.
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