Hi, I've just suffered a pretty bad crash with my hexacopter and am hoping someone can help me out in determining what went wrong. I had some successful flights (fairly new copter) but in about the 3rd test of the fpv equipment, it just dropped out of the sky from about 20m. Two arms were broken along with four props and a couple of motor mounts. Luckily the electronics seem to have survived. I won't go so far as to blame the APM 2.5, but this incident has seriously shaken my confidence in the board to the point I've even entertained the idea of switching to a Naza. I know APM boards require tinkering and tuning, but it seemed to me that I had done everything necessary.
I had the failsafe on the APM working and in land mode since I figured the 1.3GHz video may knock out the 2.4GHz control and possibly GPS so whatever happened seemed to be an onboard problem. The copter was in loiter mode during the crash so I first checked the barometer altitude: seemed fine throughout the flight. Next I checked the throttle input and it never seems to go down from where it was at loiter so I don't think the copter lost radio contact.
Beyond that analysis, I don't know what else to check. Please take a minute to help out a relative newby here. I know I can rebuild the copter and make it fly again, but it won't do me much good if the same thing happens again as soon as I do. Log files are attached, crash is at the end obviously.
Replies
I'm building a Hex with a Pixhawk. Flies great with two 5100 battery's. I took it up today with 1 and when I was bringing it down, it came down hard and I didn't have enough juice to slow it down. Those things are heavy and they don't like low voltage.
I'd use the battery still, but keep an aeye on it...maybe gove it a charge discharge cycle if your charger supports that to check capacity.
I've been caught out by my charger trying to be clever and terminating...If I set my charger to 4000mA, it will stop at 4400mAh annoyingly...especially if charging my 8000mA packs...so I have to hit them twice :(....germans trying to be clever :) (I like germans and work for a german owned company :))
and please use new forum at ardupilot.com for support :)
Map your ThrOut , BarAlt and Voltage to see this:
You start out at >21V , but when at line 8248 - your voltage is only 13.37v - and your alitude drops rapidly.
Assuming you started with a full battery, it was a 5S with 4.2V/cell - when it crashed, you had a cell voltage (if well balanced/quality cells) = 2,6 volt/cell only.
At 2.6 you not only deserved the crash, but also damaged the battery by going that low.
As most APM crashes, it's a clear user-error. - Configure some sort of voltage warning for yourself, many options are available.