I guess it's like motorcycles - not if you're going to crash, but when. Was flying my trusty CS8 yesterday and all was good for about 5 mins. Was doing a fairly speedy pull back for the 5th take in a row of the same shot and when I reached my end point, I threw the elevator forward effectively putting on the brakes. Except that's not quite what happened. It pitched forward for a moment, as it should have, but then just took on a mind of its own as it randomly pitched to the side. It responded to my stick control, but not as it should have so it was very hard to gain control of the thing. Thankfully I was able to safely crash land it and came away with not much more than one broken landing leg and the fried ESC. And thankfully nobody around was hurt and there was no other damage of any kind. But it freaked me out with imaginings of what could have happened as a much worse situation. I take really good care of my gear and safety check it all the time. Has anyone else had an ESC go out on them mid flight? Is there any way of monitoring the status of the ESC's to look for funky electronic stuff going on? The guy who put it together for me is convinced that it got zapped when I connected the battery power, sending a surge to it, weakening it to the point that I was able to get some good flight out of it until it just went kaput. Would love to hear any suggestions, previous experience with situations like this, any any other discussions relating to the safety of these things and how to manage expectations and things that can go wrong. I have had many, many perfectly safe flights with no problems whatsoever but this clearly raises a red flag that even in the best of scenarios, things can unpredictably go wrong.
Dan, Glad the damage was limited. I had something similar happen with my CS8 (running all Mikrokopter electronics) about 100 yards offshore over the ocean, and thankfully the redundancy of an octo saved me and my copter. I was able to land it without any problem. Here’s the thread: http://forum.freeflysystems.com/index.php?threads/motor-esc-failure-in-flight.2223/ The ESC that went out just bought the farm with no warning, and upon reading the telemetry data from the MK navi and flight control, there was no indication that anything failed...until it did. My best guess is a short from some moisture or other foreign material. The copter had at least 100 hours of flight time on it. Unfortunately, the DJI WKM (the other popular flight control system) has very little in the way of data recording.
Yes, I have had the exact same thing, very frightening and eye-opening at the same time. No warning, mine was likely caused by moisture as I was flying in on a foggy wet feeling morning and under some trees at the time. Probably got dripped on.
Gary - I'm running the Wookong FC and my ESC's are DYS 40A. If memory serves they are flashed with Simon K but I could be making that up. Running pairs of 5S @ 5000 mAh. Steve and Duane - I don't know if I'm a bit relieved that this hasn't happened to just me or the exact opposite. I was flying middle of a sunny day on a golf course so moisture could not have been a factor. Here's the F'd up part of the story: had the copter fully prepped just waiting for the green light to do the shots. Then lunch was called so I put it in the shade and threw my jacket over it just to keep it covered. Came back from lunch and a bird had crapped on one of the props. Laughing about it, I showed it to the actor who commented that it was good luck. I swear there was a part of me deep down that said, "uh oh" the moment he made that remark, but I figured, yeah, maybe it was good luck and we'd get some great shots. You know the rest. So is there anything we can do to protect ourselves from problems like this? Sounds like everything could check out fine and then poof! fail without any warning whatsoever.
Sadly, we're still in the prehistoric time of this technology. It has a long way to go, and failures such as that are unavoidable, and you can consider yourself lucky it didn't end worse.
As a follow up to my initial post, the guy who did the wiring for me is strongly suggesting I install a switch between the battery connection and the board in order to eliminate any possible surges when first connecting the batteries. I turned this option down when he first suggested it because I didn't want to incorporate one more thing that could possibly fail. Well...I'm putting in my order for that switch.
I doubt that switch will help, or that it will work at all. The surge isn't really a surge. I understand it is just a burst of current that charges up the capacitors in the ESCs. If you put in a switch, the surge will probably just happen in the switch. But maybe one of our electrically savvy folks will comment.
Back in 2007 Mk used to incorporate switches on their flight boards until they all started going bad due to current and surges.
Dan There's no way to reduce the current draw upon the initial connection because the capacitors on the power board charge and thus draw a lot current instantaneous. Each BL is rated to 40amp peaks and there's no way that your BL's are drawing anything near that upon initial connection. I would say 5 amps tops for each BL when connecting. In my opinion the BL's are very prone to moisture in the air. Spraying the boards like Andy instructs here http://rathergoodguides.com/images/...ds_With_Conformal_Acrylic_1-02_2012-10-22.pdf will help that.
I asked him about this and he said that while there is still a surge, it's greatly minimized because it's a much faster connection than doing it by hand. So hard to know what's right and what's wrong but I do know that all my connectors are charred from the sparking that has occurred from so many connections. But I imagine this is not much to worry about connection-wise as the contact in the connection is so much greater along the body of the connectors than just the initial point of contact at the tip. Howard - interesting about the nixing of switches on the Mk boards. This all leads me to wonder how common this issue is. Common enough that I should be paranoid about it or something that I just chalk up to an infrequent and unlucky incident? Dave - thanks for the link to the article. I have a Wookong FC so don't know anything about Mk boards but I imagine the info might still be relevant so I'll check it out.
Dan, as Howard said Mikrokopter used to have a switch as part of the FC board. They eliminated it due to induced failures and resulting crashes, at least that's what I understand from their wiki/forums.
Hmmm. I didn't realize there were broken links -- that said, I just moved the site (a week ago) back to an in-house server after a glancing encounter with GoDaddy (aka StopDaddy). This link should work (it may be the same as before and the issue was the transition of the web site): http://rathergoodguides.com/document-guides/rgg_spraying_mk_boards_with.pdf Andy.
Dan, What RC radio system are you using with your WooKong M? And what version of WKM firmware is loaded? I use fw 5.20 for over 120 flights to date without issue on my S800 clone and using a Futaba T8FG RC system. Multirotor Forums has extensive postings on WKM related issues including claims of issues with several firmware releases, newer and older.
Not sure what version of Wookong I'm using but I know I checked for the latest firmware just a couple of months ago. I'm also using Futaba. I have had many successful flights so this was totally unexpected. Maybe I just got a bad ESC that finally crapped out? Maybe there's something to the initial connection that sent an errant surge to that ESC and weakened it? Who knows. I'm just trying to figure out the best way to prevent this happening in the future. Does anyone know if there's some way to measure the health of an ESC? I don't know much about electronics but I have a multimeter and am pretty good at following instructions.
You would need one hefty switch or risk burning it up. To answer your question, unfortunately there is no in flight monitoring of your ESC's with WKM. Mikrokopter systems allow some inflgght monitoring in that you can monitor temperatures and currents with the MK blutetooth or Xbee or my preferred method of an On screen display. Even then it probably is not a hundred percent indication of a bad ESC if it the failure is abrupt. WKM with iOSD does not give you this data so there is no way to read the data. My thought is that it is not the initial surge of power at start up, as the ESC's are not under demand and not pulling much current. Most likely it is due to the abrupt control of the system putting a huge shock when hammering down the pitch stick. Its possible that your motors do not have the instantaneous throttle response due to prop inertia, stator and rotor size as well as the number of stator and rotors. What I have learned is that not all ESC's are created equal. Some are suited for motors that have a lot of poles and magnets and have to have shorter duty cycles. Other moors with lower number of poles and magnets require longer duty cycles. Though they may work well on powering the motors it possible that a rapid change in essence "stalls" the push on the motor out momentarily forcing the esc to pull more current until it gets synced again. Usually the ESC has protection circuit to prevent pulses but these things may not always work as advertised. The best prevention IMO is to apply smooth deliberate control. Think ahead of the aircraft, meaning be a few seconds ahead and plan for the change in rate. Ideally you know where you want the copter to slow down so you would smoothly apply opposite stick allowing for the system to not shock itself. These copters are not like the little sport quads where you can go from stop to stop rapidly and expect good results. Smaller quads with high KV motors have much better throttle response and can accept abrupt aircraft control movements, but heavy lift cinestars carrying large cameras not so much. Even though these are from Seattle they are not as reactive as the Seahawks more like the slow reaction of the Broncos last night. At least you brought it down safely and mitigated damage so all is not lost. Shaun
We can help if you can provide more information. I design MRs from the ground up beginning with motor speed/torque curves, using eCalc from Multirotors etc. Also I am quite familiar with DJI NAZA and the WooKong M but still learning the new A2. You can also get excellent support on MultiRotor Forums under the DJI WKM+A2 section. Some of the DJI dealers and tech support people frequently provide excellent help to people less familiar with DJI products. Other than that I have to say that the idea of a surge as the root cause is a bit of a surprise unless there is more to the story...... what are the specs on your batteries and are they in series or parallel? Also please provide ESC data. Was one recently replaced? If so, was it configured before flight? Many ESCs offer a simple $8 esc programming card which utilizes simple jumpers for programming. All ESCs have to beep when powered up to confirm they are AOK.
Actually there is a built in sd card inside the DJI iOSD and there is a way to download significant data including motor current and rpm etc. Granted mikrokopter provides more data.