The Copter:
Frame: Hobbyking X666 with double motor mounts
Motors: SunnySky X2212 980kv
ESC: Afro ESC 20A Simonk
Props: GemFan T-motor style 13x5.5’ Carbon
Battery: 2x Turnigy Nano-Tech 6000mAh [ 5700mAh measured from 4.2->3.6v]
FlightController: Pixhawk with Arducopter 3.1.4
Controller: 9XR
Reciever: FrSky D8R-II Plus + PPM Encoder
It was a never crashed build until today. It was moderately new, having between 4 to 5 hours of flight.
The Pilot:
I’ve started flying multis around an year ago, since Portugal has nice weather and I can fly at walking distance from home I’ve hundreds of flight hours already. I’m quiet used to build multis, I’ve built and flow quads, hexas, octos (I really need a tri!!).
Usually I fly with KK 2.0 boards (so used to Acro/Stabilized modes) or un-Autonomous boards of the sort, Pixhawk is the most advanced controller I’ve had the chance to fly. Due to my area of work/study I had no problems getting used to it and having it flying properly.
The Accident:
I flew around one of my usual spots for around 11minutes. Since I got the 30% battery warning and my voltage was already at ~10.6 I was heading home. The whole time I was flying the rig fpv. Neither the low voltage onboard alarm (set to 3.5v per cell) nor the Pixhawk voltage alarm (set to 10.6) made any sound.
What I felt was a loss of both power and attitude, I didn’t had fast enough reflexes to change from AltHold to Stab but I did give it full throttle. The craft went down either way. Luckily it felt in 1m high tall grass so not even a single prop broke, the only damage done was my home made aluminum landing gear and my GPS post, I ended up losing my FVP TX antenna top but who cares…
The video:
(Jump to the last few seconds to see the fall or enjoy the whole trip)
Comments about the video:
- Loss of power (no motor sound)
- Pixhawk turn on sound
- Motor rotate for a little bit (?!?)
- Puff ground.
After Crash Photos:
Some thoughts:
Upon inspection craft looked okish. Only thing that cough my eye was that my XT60 parallel connector was loose from the ESC input, I don’t know if it either happened because of the fall or it mid flight (less likely... do XT60 come loose ???).
When does the Pixhawk reboot? I’ve it powered by both the power module and the ESC UBEC to have power redundancy. If one of this power sources fail (for example the ESC UBEC) does the board reboot (this would be really weird...) or it keeps on running from the power module power?
I couldn’t find anything wrong on the logs and that’s worrying me...
Logs here:
https://www.dropbox.com/sh/h8cwwbet29twdyk/AADf2S2yHU3EhovAa2wXVcU5a
I need help analyzing this crash since for the first time I don't know for sure what went wrong.
Replies
MAX AMP OVER THE LIMIT OF ESC
MAX POWER OVER THE LIMIT OF MOTOR
You can accept or not but fact is you need bigger esc and bigger motors to carry that Lipos.....
I know you wanted to use principle biger props lower voltage what you see on some long endurance multis.....this motors KV with this props are ideal for 2S
check above calculations(and I must tell you can really trust ecalc with 10% margin) before you start to attack people who want to help you...
AND YES,I ALSO THINK THAT IS NOT VERY CLEVER TO USE 20a ESC ON THIS SETUP
You should always spec your ESCs for the max current draw of the motors no matter what. You shoul have 30a ESCs on there to add margin and a safety factor. ESCs don't like current induced heat.
I can't guarantee anything but it solved issues for me. Try first reformatting your current card. If you have another sdcard lying around, try it out. I know 3DR also had to change their initial shipments of Pixhawks due to bad (or slow) sdcards. Again, just a hunch.
I'll just put in my 2 cents worth probably not related. I've had problems with Pixhawk not booting up properly due to a bad or slow sdcard. Maybe the logs stopped recording because of that? I agree though, there was a reboot sequence.
Nic,thats Interesting...are you sure bad SD card can do that...now I am worried bcs I still have original one inside my Pix..?
Don't panic, no cause for alarm if your platform is stable. Just good to know if something weird happens.
power thru Power module and with dedicated 5V UBEC....disconnect ESC red wires from Pix....and no...in coaxial setup motors are working harder especially bottom ones..but that's another story discussed here so many times before......
As Paul mentions. I only use a stand alone ubec to power my flight controllers on Octo's. You should remove the red wire from your esc's. You do not have to cut the wire. You can remove it from the male plug by lifting the black plastic with a micro screwdriver and pulling the red wire.
And as Emin Bu proves your props are way to big.
On these motors the APC 10x4.7SF is the best choice on 3S.
Good luck with your rebuild.
P.S. Amazing scenery where you are flying. :)
Can you PM me the location. I will be in Portugal this summer.
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