I truly appreciate that some (most) of you guys are looking at this as the puzzle it is; the ones that are just quick to blame me for it weren't there, so I can't blame them for thinking it - but I would like to assure everyone here that this wasn't operator error, disorientation or insane circumstances. The scene could have very easily been a video shot of a wedding party at this location, with serious injuries and potentially a lawsuit with damages.
I encourage anyone that is even thinking of, or already in the process of using their P4 professionally to get both UAV insurance and Pilots Insurance. Anything can happen, and it doesn't have to be your fault, it just has to look like it is and you and the entire public view of UAV's are in big trouble.
I really hope this comes across as just that, a puzzle to be solved, and not the rants of some idiot with a fat wallet and time to waste. I'm trying to maintain an objective outlook on the puzzle and not get sucked into any drama, let me know if I do - I hate drama.
No RF interference? I'm not sure how you determined this and I personally have little experience with it, so I leave this one to someone who can read the logs better than I. But if you pulled back the stick in the proper config and got nothing? I wonder if you happened to notice the RC to UAV signal strength at the time, or if the logs indicate it.
Many people are askign for the logs, the logs are posted in the thread back there somewhere, not sure what to do with them past uploading them.
I should at least qualify myself in the RF department for future reference and questions about RFI:
I'm a FCC licensed radio operator (Old School, I know) in where I learned a great deal about Radio Frequency and Radio Electronics, which happened to be part of what introduced me to RC Helicopters and Cars. I am fortunately blessed with equipment that can tell me what frequencies are dominant at any given measuring point, and what the signal strength of any readings strong enough to cause any type of interference. I measure with the controller & UAV off, as it will detect their signals if I don't. It's a trick that is in use today by many professionals and other industries and now part of my PF Check. To quote someone here, "Still, the sticks should work." ; the only possible "reason" I can think of that makes sense for a "pull-back" NOT to work is RFI.
You mentioned that you can't do a VTOL off a metal picnic table, yet I use them in my VTOL exercises.
I spend a good deal of time in my neighborhood park doing control drill and flight control tricks, like VTOL's from an all-metal picnic table in A-mode. They have a perforated surface which nicely reduces down-wash by a small percentage. I even have done some video recordings of these exercises, but since they aren't really exciting, I may have tossed the footage. I'd be glad roll some video the next time I do the exercises. VTOL's from metal table to metal table, target landing, tight-area maneuvers (in, through, and under the playground equipment - which is built out of metal and plastic), 24" AGL tracking and FPV piloting, "Satellite POV" flight (camera pointed down) - ect.. I was planning on making some dumb you-tube videos of them, but who wants to watch that? Nowhere near a pro like those helicopter tricksters, but I've made sure I was confident that the craft could handle the scene flight path at 1MPh. The sticks should still work. That's going to be my new tagline here..
I enjoy challenges and I also needed to be able to trust that the P4 would tolerate sharing space with metallic objects before going out to do some video scenes for someone's family picnic. Not that I was actually booked for such, it was a mindset exercise, with my intentions to use the P4 professionally in the near future. Had this happened at a wedding, for instance, and the P4 would not respond to the controller, run into some fancy wedding decor and shoot full-tilt after the bride and groom, it would have been on the news. DJI would not want people knowing that their products have the potential to drop radio control randomly.
However, After all the facts have been laid out, I suspect what happened here was user confusion with orientation and lack of experience. If there was interference, then it certainly would have been from the powerlines! I mean seriously? Why are you even flying there?
Nice photos, and I appreciate that you've taken time to think this through. I know, most people would think exactly that - POWER LINES!! OMG, right?
I know a bit about electrical too, after enduring 2 years of working with the IBEW, where I came to understand that I don't fit in the Electrical Union simply because I don't hate my life, and a lot about the properties of live electrical industrial equipment, lines and systems. Many videos out there show and support that power lines are generally harmless objects unless you're out of range to compete with a 60hz signal or out of control. Some videos show UAV's getting snatched by lines, that's not "in-control" in anyone's book.
I've flewn over and under lines successfully many times, slowly and with great caution - always keeping a safe distance and sharp focus on my flight path - near impossible to avoid, so perfect practice makes perfect, right? I've never gotten even close to the red circles you've noted on the photo, that's too close and not safe, so good ilustration! I don't recommend or condone the intentional practice of making flight plans that include power lines, but just the same, if you live, play or work near any, then you won't be able to avoid learning how to NOT hit them.. I wouldn't dare to fly near or through a stack of lines, high-tension* lines or switch-yards* (*illegal without permits) unless I was contracted by the electric company to do it, and I was getting paid at least double what it costs to replace the UAV, pay the insurance deductible, and repair whatever potential collateral damage that might happen as a result of any incident. Local, 3&4 phase, single stack power lines should only pose a threat if you come into contact with them. If you live in the city, it's your landscape, so train and become an expert at navigating those vertically challenged eyesores.
Flying slowly, safely and cautiously under one set of power lines shouldn't have an effect on communications, unless you've flown far enough to weaken the signal to the point of easy RF "pollution". Staying close to your UAV ensures the controller has the dominant signal at all times. When you can't be with your UAV, don't do it unless you have no other option - in fact, if you don't have the confidence and control practice, it's time to land and fetch. Slow, safe & controlled is the only way to go when it comes to power lines; they teach you that at the electrical school and on the field.
Let's look at the clock-photo (article II). Not some crazy situation that one would be too concerned, like flying around a water-tower or doing an inner-city flight. Just a park, a clock and sure, power lines that were not directly over the flight path. The trees foliage did not encroach the circular concrete pad much at all, this photo has the illusion that there is a lot of foliage in the way, but it's a clear flight bubble of about 60' in diameter around the clock. Article III shows that the flight path did not go directly under the power lines. The incident started (I would estimate by the car sizes) more than 20' Vertically away from the power lines, not even close enough to corrupt a weak WiFi router signal.
I've logically ruled out power line "interference", anyone that poses statements otherwise haven't seen the many videos of people doing it.
That being the case, my focus is mainly on the possibility of the clock emitting a signal that "called" the P4 somehow. It would explain the P4's behavior, or at least give a solid reason for the controllers signal that was only 10' away to be ignored by an overpowering signal. I imagined that it would be possible that the park installed some WiFi device in the clock to make setting the time a matter of a computer command from a nearby laptop. Maybe public WiFi?
That hypotheses didn't pan out - no detectable signals.
Since the flight was relatively close to eye level and slightly overhead by only a few feet at the most, and where I was with the P4 the whole time ("walking it"), putting the controller less than 15' Vertically distanced at the most. There's no plausible circumstance that I can conjure to explain why the P4 did what it did, or more accurately, didn't do what I told it to do. RFI is even highly questionable at that close range, which is why I took RFI and Magnetic measurements AT and AROUND the clock. As the clock was the only thing that was closer to the P4 than the controller was - I had to see if it was emitting a signal that somehow caused a connection failure. I couldn't find any detectable signals, so I'm left with the most logical answer, the P4 ignored a stick-command and the incident took place. That makes me VERY nervous to even THINK about using the P4 professionally.
Orientation.. The P4 was facing the clock before I started the flight plan for the scene I wanted, I was facing the clock as well, standing about 3' to the left of the UAV, the tall bush was to its right, about the same distance and the craft was still and ready. I started the scene, the P4 took it from there. There's a few small prop marks that I'm going to buff-out.
At this point, I'm going to have to let a DJI tech analyze the data and flight video; they have a motor and shell casing to replace; unless they want a defective product out there to make them look randomly dangerous.
Yes, they are potentially dangerous, I'll tell anyone that all day - but "Randomly Dangerous" is far worse a thought.
Let the arjous journey of navigating tech support and warranty reps begin.. (i'm good at that too.. lol..)
I'll naturally keep this thread updated with DJI's considerations and resolution.
As for now, I have to get some work done - This puzzle isn't going to be solved without an MIT RF Programmer looking at it. LOL...
