Yep, I know it sounds crazy, but here's what happened. I built a new F550 around the NAZA-M V2 and the E305 propulsion system. I've had about a dozen or so flights with different settings on level one and two warnings, and finally settled on one that gave me a little over 24 minutes flight time, and that's with about 70% aggressive flying. So I finally got all my FPV gear added and wanted to fly again, to see how much my additional 229 grams of gear reduced the flight time.
Everything was going normally, with a crisp OSD readout of voltage. About 10 minutes into the flight, I just happened to turn the nose toward home point (thankfully), and glanced at the voltage from my 4s 8000 mAh battery, and noticed it was at 15.9v. Plenty of juice left, right? So as I watched the monitor, I noticed I was heading straight for the tops of some 120-150' pines and wondered when I descended that low. I had just enough time to navigate away from them to the side into a clearing and tried to accelerate toward home.
Here's where the trouble started. I noticed the distance to home was NOT decreasing and the altitude was. Try as I might, I could not gain altitude, navigate in any direction, or maintain any control over the unit whatsoever. Another glance at the monitor showed that I still had 15.9v and was descending smoothly toward the ground. I had a soft landing, very similar to an RTH landing, except the mode on the OSD said GPS. The distance from home showed 225 meters with the nose pointed about five to ten degrees off dead center. I jumped on the four wheeler and found the bird on the ground in perfect shape with the props still spinning at idle speed, as if I had just armed the motors or just landed.
Now it gets really weird. Again the voltage is steady at 15.9v so I increased the throttle to take off again. I had very little if any response from the props. You could detect a slight RPM increase, but certainly not enough to take off or even tip over if one motor was weak. The video transmitter continued to transmit. The camera continued to record. It just sat there idling. So I shut her down and brought her home, no worse for wear and very happy it happened close enough to recover.
When I charged the battery back to full, I noticed it took 4819 mA to finish it off. So it appears I had used maybe 60% or so of the capacity. Since this happened with the first flight after adding all the FPV gear, I examined all the connections closely. The only thing I found that could remotely have caused a current drain, would be that one of the 5v solder pads (the + side) had some flux that had run over and onto the ground side of the 12v solder pad. It didn't appear that any solder was touching between these two, but I'm wondering if the flux could have created enough of a high resistance connection to drain the current and not the voltage. I know that sounds weird, but this whole event was weird.
So, in a nutshell, a bird that flew perfectly before adding FPV gear, now had a loss of power, but no corresponding loss of voltage. It couldn't maintain enough lift to hover, so it softly landed but would not take off again. I'm at a loss for what could possibly be going on here, but it's critical to isolate the cause before flying again. Or at least, fly very close to home in case this event repeats itself about 10 minutes into the next flight. I've just about ruled out interference, because I live in a rural area surrounded by swamp on three sides. That's another reason I was so relieved that it happened in a clearing and not over Smokey the Bear's den.
Please offer suggestions or theories as to what I might check or isolate to discover the problem. I've always received great assistance on this forum and am once again in need of your expertise. Thanks in advance...
Everything was going normally, with a crisp OSD readout of voltage. About 10 minutes into the flight, I just happened to turn the nose toward home point (thankfully), and glanced at the voltage from my 4s 8000 mAh battery, and noticed it was at 15.9v. Plenty of juice left, right? So as I watched the monitor, I noticed I was heading straight for the tops of some 120-150' pines and wondered when I descended that low. I had just enough time to navigate away from them to the side into a clearing and tried to accelerate toward home.
Here's where the trouble started. I noticed the distance to home was NOT decreasing and the altitude was. Try as I might, I could not gain altitude, navigate in any direction, or maintain any control over the unit whatsoever. Another glance at the monitor showed that I still had 15.9v and was descending smoothly toward the ground. I had a soft landing, very similar to an RTH landing, except the mode on the OSD said GPS. The distance from home showed 225 meters with the nose pointed about five to ten degrees off dead center. I jumped on the four wheeler and found the bird on the ground in perfect shape with the props still spinning at idle speed, as if I had just armed the motors or just landed.
Now it gets really weird. Again the voltage is steady at 15.9v so I increased the throttle to take off again. I had very little if any response from the props. You could detect a slight RPM increase, but certainly not enough to take off or even tip over if one motor was weak. The video transmitter continued to transmit. The camera continued to record. It just sat there idling. So I shut her down and brought her home, no worse for wear and very happy it happened close enough to recover.
When I charged the battery back to full, I noticed it took 4819 mA to finish it off. So it appears I had used maybe 60% or so of the capacity. Since this happened with the first flight after adding all the FPV gear, I examined all the connections closely. The only thing I found that could remotely have caused a current drain, would be that one of the 5v solder pads (the + side) had some flux that had run over and onto the ground side of the 12v solder pad. It didn't appear that any solder was touching between these two, but I'm wondering if the flux could have created enough of a high resistance connection to drain the current and not the voltage. I know that sounds weird, but this whole event was weird.
So, in a nutshell, a bird that flew perfectly before adding FPV gear, now had a loss of power, but no corresponding loss of voltage. It couldn't maintain enough lift to hover, so it softly landed but would not take off again. I'm at a loss for what could possibly be going on here, but it's critical to isolate the cause before flying again. Or at least, fly very close to home in case this event repeats itself about 10 minutes into the next flight. I've just about ruled out interference, because I live in a rural area surrounded by swamp on three sides. That's another reason I was so relieved that it happened in a clearing and not over Smokey the Bear's den.
Please offer suggestions or theories as to what I might check or isolate to discover the problem. I've always received great assistance on this forum and am once again in need of your expertise. Thanks in advance...