Lesson from crash: check your power connections!

Check the video first:

So I'm flying up at 120m. What then happens is every RC pilots nightmare! Power cuts off from the APM!

Quad drops to about 90m before it wakes up again, then I take it down crazyfast but controlled to 20m, then at 20m it dies again and drops like a rock... hits pavement...3 broken props, all landing gear, 2 bent arms, cut cables and a broken Hero2. 

Why did this happen?
I had new and fancy LED strips connected directly to the LiPo between the LiPo and PDB. The connections were all with Dean connectors which should be ok. Well as this was a new build I had not yet shortened the cables to proper length. They where short enough to not even go near the props but long enough to have "wiggleroom". My theory is that the propwash made the cables wiggle just enough for the Dean connectors to cutoff enough to disturb the APM. This theory is supported with the fact that when I brought the quad down crazyfast and then stopped the decent by giving if full power the propwash must have been quite a lot. And that is exactly when the cutoff occurred the second time. Then on the ground after the crash the battery connection was still ok but when I wiggle the Dean connectors the power cuts off just enough that the APM boots.

Why no footage of the crash?

The camera is a GoPro Hero2 and it took the hit pretty bad. The case was cracked but the main camera was still in one piece. Battery and memory card had popped out. What I did was I started with powering it up to test if its still alive. It showed some weird picture on the LCD of a guy on a bicycle?? I pressed everything. Got it working again. Later I learn that IF the memory card would have been in when it powers up after a crash it should try to write the 5 sec buffer to the card and usually succeed... Dammit!

Craft:

3DR ArduCopter Quad-B

 

P.S. I know. I'm an idiot for taking my quad up to 120m with new stuff on it.

Views: 659

Comment by Rob_Lefebvre on November 8, 2012 at 3:07pm

Your APM rebooted mid-air, and resumed flying?!  It would have disarmed.  Did you arm it mid flight?


Developer
Comment by Jason Short on November 8, 2012 at 10:57pm

Most likely the RC link was lost and the receiver throttle is set to go low when that happens. Can you provide the logs? You can test that with the CLI by running test > pwm. Watch the PWM as you shut the transmitter off.

Jason

Comment by Jon von Weymarn on November 9, 2012 at 12:56am

I did NOT need to rearm.

Jason: So that the RC signal would have gone to failsafe mode? I have 9X with FrSky TX/RX and failsafe set up to RTL mode and, if I remember correctly, 50% throttle. There is a small chance that I reset the failsafe settings sometime in the field and had the throttle low while doing it...

However, I'm hesitant to believe this theory because when I drop the throttle in any mode but acro the quad has stayed upright and not flipped like in the video... 

I'll upload the logs later when I get to my laptop.

Comment by Peter Chaffe on November 9, 2012 at 2:24am

Always sorry to see crashes, looked to me that it was either a break in supply or you started a violent maneuver where the gyros couldn't catch up, I did this once, then the APM over compensates all the way to the ground!

Deans connectors are crap! Change them for XT_60's (end of connector problems)

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