It was pretty windy, probably 15-20 mph, lifting a heavy payload (Dragon.) This is (was) my back up with my new primary heli needing some diagnostics. Cinestar 8 with 500mm booms Tiger 4012-9 480 w xoar 15" beech Mk 2.5 w navi and gps i2c converter Freefly distro and 40A ESCs Movi M10 AUW approx 28 lbs About 5 minutes into the flight, we were done shooting and I started descending. All of the sudden the heli goes into a death spin. This wasn't your standard loss of yaw control, there was some significant wobble as you can see in the video. There was loss of power but I was able to slow the decent by giving it 90-100% throttle. The wind was blowing the craft away from the turbines, so I wasn't sweating it too bad. Where it went down was beyond a row of trees and down below a little incline. So I couldn't see it for it's last couple seconds of flight, or what I thought was it's last couple seconds of flight. When I thought it was on the ground I gave it the motor off command. I got the no connection beep (Graupner mx-20) Then we all ran to where we thought it should be. Four of us spent an hour until pitch dark circling an empty field and in the few trees looking for it. Finally I decided to just walk the direction the wind was blowing. I found it about 500 yards beyond where we thought it was crumpled from a hard impact. After reviewing the footage the heli actually made it to the ground at a controlled rate. And then (this is just speculation) knocked off one of the two batteries lightening it's load by 3.5 lbs. It was then light enough to take back off but the initial impact also knocked the voltage reg for my LEDs so I didn't see it climb back into the sky. Unfortunately the sd ejected somewhere in this event so no gpx. Either it went into failsafe and gps made it climb back up or my timing was off by quite a bit and I kept full throttle for too long. Either way, it climbed high enough that when I gave it 0% it did as told and fell to the ground far from where we thought it would be. I could only find one battery at the crash site. If I was still in Iowa I would go back and look for the battery and sd card. With the loss of power and the wobble, I'm thinking it was a motor out. If it was the i2c converter failing me on yaw I would have still had full power. All props were on tight. On inspection I found one of the the power leads on one of the ESCs had come un done from its bullet connector. It could have been a cold sweat and popped off from the trauma of the crash, or it got so hot it melted off. I have more time on these ESCs than any others, in the hundreds of hours. I was descending at the time it went haywire and it was a cool evening so it's hard to imagine it was overheating. I had just been flying the same setup in hot Reno and Moab with no heat issues. Time to rebuild... https://vimeo.com/110601943 p: wtf
Sorry to hear about this, Nick. Losing that microSD card is too bad -- it would give us a chance of seeing what failed and when. Losing a motor should not have caused the uncommanded yaw -- an 8 will survive that unless you're at maximum load (and there's no spare thrust left for yaw control). That battery connection, had it failed in flight, seems unlikely to have caused the yawing -- the other battery should have sustained the load (the fact that it appeared to climb back up suggests this was the case if the connection had failed). The I2C failing could have caused all sorts of control issues. By the way, what I do is put PVC tape across the exposed edge of the microSD card and tape it to the Navigation Control board to reduce the risk of it disappearing. Andy.
Wow, that must have been terrifying to watch and then to realize that the copter seemingly took off on its own like that. Man oh man... Do you know what version of the MK firmware you were running? There was a bug a while back that could cause a serious anomaly in the "come home" logic, that might explain the secondary part of this. As to what caused the spin...not sure. What gimbal are you running? I've often worried that an out-of-control gimbal could cause that kind of yaw, but the gimbal seems to have stayed true, so that seems unlikely. Still gasping for air. Yikes...sorry.
Hi Nick Sorry to hear. This is one reason why I never tried the abusemark I2C converter. Were you in PH mode? If so did you try to disengage PH? BTW: I think the 4012's are way too small for 28 pounds. You might want to consider the KDE ESC's and motors during your rebuild.
Thanks for the replies everyone. Andy- It was the ESC connection that failed not the battery. I was just speculating how it could possibly take back off after touching down at 100% My thought since one of the batteries couldn't be found is that one of them got knocked off. Then the craft was light enough to resume flight. I've had motor out before on this craft and it did OK. I did not have full control, but enough to get it to the ground. I believe it's possible that in the high winds what I was experiencing could have come from a motor out, esp with the loss of power. I2c converter failure is high on the list of possibilities as well. Yes I'm bummed I don't have a gpx file. I'm not sure if I'll return to MK yet but most likely will, if I do I will take your advice and tape the sd card. Steve- The FC 2.06 firmware This was the Movi M10. The guy operating it said just before it lost control he couldn't pan past a certain point. Perhaps you are onto something. Dave- I was in full manual mode, I didn't try switching modes, I was just happy at the time that I was slowing it's decent. My newest build has the kde 5215 435s with 55A ESCs. My plan was to build a fully redundant machine based off that, but I'm still not completely sold on it. I actually really like those 4012, I surprisingly had plenty of headroom at that weight. They were recommended to me by someone who builds for a living and are what is packaged with QCs HL RTF. I'm thinking about maybe trying KDE new 4215 465s. They're a lot lighter than the 5215s which is appealing to me.
Sorry to see this nick, I am wondering if those wind turbines caused some kind of emi problem? They are after all big magnets/turbines spinning around 40-50m in the air you where flying directly above them. I am only speculating though.
4012's rock. I have tons of head room on my CS8 HL and CS6 HL with them. Easily fly a Carbon dragon on the octo with a cine lens and the A7s/XA25 for 20+ minutes. Nick, any chance you had logging enabled on your Transmitter? Could be an RF interference thing, I had a test rig do something similar.
One battery or two? 1200 grams of thrust shows hover throttle of 50% which is just a tad over 21 pounds with flat 8 octocopter. I"m seeing 65% hover at 23.75 pounds with flat 8 octocopter and 2 QC batteries.
With 15x5's its 1550g/motor (16x5's bring it to close to 1900g, but are a bit risky on MK as the amp draw can get close to 19 at 100%). Dragon I run a pair of 6000 6s Tattu (800g ea 5-7 min flights) and depending on the client everything from a Canon 10-22 (I think 400g) to a Zeiss 35 CP (1000g) on a M10. I have been playing with the Canon 40/24 pancakes and they are great for dropping a ton of weight (150ish grams each). With a battery for the camera/M10 (300g) and the dragon (2150g with mag etc) its not where near the limits (max weight with the CP is around 9-10 lbs). AMP load per BL is around 13-15 in hover and takeoff with the CP is 50% hover is about 60%. I have not flown the camera in ages (since the I2C on my old flat) due to the BM4k being a much more cost conscious option in case of a crash, which.. it will survive. AWU is around 21.5 to 23.5 lbs depending on lens choice.
I'm running 22-23lbs with KDE 4012 motors and 16" props in an X8 config and get tons of airtime and lots of thrust. Not hungry for anything more. Motors are just warm after 10-15 minutes in the air.
Forgot that sarcasm does not translate on the interwebs =). I have yet to see the set I have testing get anything more then warm.
Are we talking about the same motor? I see the KV400 and KV480 motors that don't add up. Tiger does't even publish specs for the KV480's with 15 or 16 inch props.
Same motors. Just had to break out the test bench and do the numbers myself. Like I said, 16's are a bit much for MK but with a good 50-60 A esc I could see 18's possible on the Tiger 4012 (Lots of undue stress and more frequent bearing replacements). Test bench is a MK BL 3.0 single ESC with a 400mm boom and throttle up/down with 4-12s power from bench and batteries. Tigers numbers are a bit off, under by about 5-10% which I think is smart.
If found the Tiger 4120 specs right on the money as far as thrust goes compared to the hover throttle I was experiencing. I haven't tried the Tiger 4012's just the KDE 4012's (brand new version) and I haven't had much success with 23.75 pounds.
I have a set of 4120's and I LOVE them. They are currently on the Coax hex HL for testing and the KDE's are next~
Hi Ryan, Unfortunately I wasn't logging on my tx. I will from now on. You and Jason bring up a good point. It's a possibility for sure. But even if the FC got a wacky command to do a full yaw I'm not sure it would have spun that fast. The video is at 60fps so it was actually spinning twice as fast. Seems like it would take more than a bad command to pull that off, but I could be wrong. I've had signal loss twice, both times the helis did exactly what they were supposed to do. And in this instance I still had throttle control, for the other two it was a complete loss of control. I've flown around windmills before and didn't have an issue, and I've seen videos of Holger flying around them. But Jason you are right they are giant magnets creating a lot of electricity and they were pumping when this happened. Something to think about for sure. I was pretty nervous about turbulence on the lee side so I kept my distance. As for motors I did purchase the KDE 4215s and am working on the build this week. I can let you know how it goes if you'd like. It's gonna be a flat 8 with 17" props running the Herkules board. KDE is claiming 20KG of thrust at 50%
Nick, just seeing this for the first time today. Gnarly and very sad. That death spin was particularly brutal. I'm not as current on MK stuff as these guys so can't add much- but my gut feeling is that it's I2C related since it appears all rotors are powered throughout the descent. How bad was the damage to machine and camera? nick