Issues with Quad running APM 2.5 - Flip & Crash - Discussions

I just got my quad ready for initial flight testing today - everything works good at first, it's pretty solid, even with less than perfect weather conditions. However, after a few minutes of flying, it will flip over and crash upside down. (I didn't have it more than 3-6 feet up, so any flip would result in upside down crash.)

I am wondering if anyone has any suggestions?

Mode was "stabilize."

One thought - I noticed one of my ESCs is getting pretty hot even when the quad is not flying, just from the BEC functions I guess. (I have 4 linear ESCs tied together.) I am wondering if perhaps that ESC overheats and shuts down, causing a loss of power to one motor - and the quad to flip. The one thing about it is - after it's upside down in the dirt and I have reduced the throttle to zero, the motors are still trying to spin for a bit. If the BEC failed - could it cause a partial reset (while another BEC took over, or that one reset) resulting in this crash, and a few seconds to require the signal and detect zero throttle?

Next, I was wondering if it might be my radio tweaking out. I have a 2.4ghz FASST system, and a 900mhz 3DR telemetry radio. Think they may conflict? One thing, if I arm my ESCs, hold down the quad, and turn off the radio, the quad will "freak out." I would think a FASST system should not do that. Reminds me of the old 27mhz stuff.

Any other ideas/suggestions?

I've actually had something similar on APM2. I was flying the other day in stabilize (after attempting a mission in auto mode) and the copter flipped over and landed upside down with the motors still running (I had to unplug the battery to get them to stop). I fixed some of the damage (mostly plastic pieces and a prop) and checked out the copter real quick and then decided to try flying again and after hovering for a couple minutes, I attempted to switch to auto and the quad took off the wrong way. I then switched my transmitter to stabilize but couldn't control anything (the sticks didn't do anything). I tried to switch back to RTL and Auto and that didn't do anything either.

I fly with a separate BEC rated for 15A.

I have attached the 1 log file that contained data. None of the other flights appeared to have saved (possible culprit?). Initially couldn't connect on the terminal screen on the mission planner. I unplugged the sonar and xbee and was able to connect. I connected each separately and then together and haven't been able to reproduce that issue. The Terminal screen showed a bunch of ??? instead of the normal bootup. I guess right now I suspect that either the Xbee or dataflash card may be related to this problem.

2012-08-19 08-12 3.log

Replies

Troy August 20, 2012 at 7:31pm

I've actually had something similar on APM2. I was flying the other day in stabilize (after attempting a mission in auto mode) and the copter flipped over and landed upside down with the motors still running (I had to unplug the battery to get them to stop). I fixed some of the damage (mostly plastic pieces and a prop) and checked out the copter real quick and then decided to try flying again and after hovering for a couple minutes, I attempted to switch to auto and the quad took off the wrong way. I then switched my transmitter to stabilize but couldn't control anything (the sticks didn't do anything). I tried to switch back to RTL and Auto and that didn't do anything either.

I fly with a separate BEC rated for 15A.

I have attached the 1 log file that contained data. None of the other flights appeared to have saved (possible culprit?). Initially couldn't connect on the terminal screen on the mission planner. I unplugged the sonar and xbee and was able to connect. I connected each separately and then together and haven't been able to reproduce that issue. The Terminal screen showed a bunch of ??? instead of the normal bootup. I guess right now I suspect that either the Xbee or dataflash card may be related to this problem.

2012-08-19 08-12 3.log
AntimatterCrusader August 20, 2012 at 4:11pm

Update: I disconnected all the +5v wires and used another ESC I had laying around as a BEC... problem appears to be solved. Flew for several mins in loiter mode with no crash. :)
R. D. Starwalt August 20, 2012 at 9:58am

I suggest you simplify the installation and use just what is needed to fly, remove telemetry power/connections.

Battery --> PDB --> ESC (all of them) ---> APM2.x + Radio Rx.

I use the 3DR PDB and all 4 ESC are paralled out of it for the APM power (pretty sure - ohmed it out).

Glad you caught the failsafe mode. The documentation says in failsafe, if farther than X(?) meters from launch point, it should rise 30meters, RTL, and then land. I have Spektrum gear and there is also a TX loss failsafe mode for the receiver. Check your Futaba for something similar.

I have been using a tether system on my quad. If one leg is tethered, I can go about 10ft up. Two legs, 5ft. I just have to be aware of the cord and propwash during liftoff. It wouldn't do to suck that line up into the prop. :-O
Lloyd Breckenridge August 20, 2012 at 7:12am

(I have 4 linear ESCs tied together.)

This is not recommended.

There have been many discussions regarding powering the APM from a single ESC/BEC.
AntimatterCrusader August 19, 2012 at 8:26pm

Turns out the quad "freakout" when the radio gets turned off was caused by a failsafe being set to 20%... when it looses the signal, it will increase throttle to 20%. That is resolved. However, still wondering what the causes this problem in the first place. I am thinking an overloaded BEC causes one ESC to shut down for a second... causing the quad to flip as well as a momentary loss of power to the receiver, then after the crash it throttles to 20% due the failsafe until the receiver re-associates.

However, I have 4 ESCs.... if one browns out, wouldn't hte others take up the slack?

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