[I_drone_about_drones]

I have been flying my drone a few times in the last few days (After fixing a faulty motor). My problem is that every few minutes it drops out the air and then turns back on. It seems like it has a bad connection but surely it would fall more often if it was. It only falls every few minutes.
Any help would be appreciated.
Thanks



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[TheOtherCliff]

Does it only happen far away?    How are your RC and FC failsafe set?

What protocol does your receiver use?

If it sometimes happens close by, then it could be a bad connection.  It happened to me.

Do you have to arm it after it falls?  Or just give it throttle?  If you must rearm then the FC may have reset (bad FC?).

Are you using unflashed ESCs?  You must set the LVC to nicad or this will happen.  You have to time your flight or use a lipo alarm to avoid damaging your batteries by over discharging them.

Best way to know for sure is to log a flight with telemetry and a laptop GCS.  The reason will be there after some digging.  Did it go into failsafe?  Did the RC command it to fall?  Which signal wire came loose?

Another way is to assume that it is the FC failsafe.  The following is dangerous in that your quad could fly away if you don't adjust it correctly (so that it descends even with a fully charged battery).  You could set failsafe to an autoleveling flight mode and have it force throttle to be a little below hover on a fully charged battery.  If your falls change into float downs then you know the FC is going into failsafe and that is usually caused by loss of signal from the RC receiver.

[I_drone_about_drones]

I can't answer all your questions but I will answer a few.
It normally happens close by. (but I have never really flown far)
It falls out the air, turns back on and then I have to arm it.

[I_drone_about_drones]

I think it could be because my receiver's antenna is right under the top of the carbon fiber frame.
I bought my cc3d from hobbyking.

[TheOtherCliff]

If you have to arm it after the crash, then the FC lost power.  At least that's my understanding and is how my SBus quad works when I tested it just now.  I armed, unplugged the Rx (from FC) and plugged it back in and did not have to rearm.  This means you are not just loosing connection from Rx to FC.  It also means that an FC failsafe did not cause it, although it is possible that you have the Rx programmed to "drop out of the sky" on loss of signal, but it would still need to disconnect the FC power at impact for you to have to rearm.  That is too much coincidence for me.

Unless you have arming on a switch and momentary loss of signal causes a disarm due to your RC failsafe setup ...........

If you have telemetry and a laptop GCS, then after a power failure, you could look on the GCS Firmware page at FlightTime to see how long it has been since the FC was (re)booted.  If it lost power, the number will be lower than from when you plugged the battery in.

[I_drone_about_drones]

I think some history about the drone would help. I bought a drone with a plastic frame. I crashed it and broke the frame and one ESC. I replaced the frame with a carbon fiber frame. Unfortunately the one motor was not working properly and ever few minutes the drone would flip and fall. But I don't remember having to arm it again. I think it always flipped on the side with the broken motor. I bought a new motor and got it flying again but now it falls and I have to arm it. I think it is because the receiver is under the carbon fiber frame or that the FC is not getting power every few minutes.The problem with the theory that the Fc is not getting power every few minutes is that it only happens every few minutes.If there is a bad connection I would think It would fall every few seconds.

[TheOtherCliff]

I have had vibration cause bad connections twice.  Once in a PWM setup, one of the aux channels was intermittent.  I finally caught this one with a flight log and could see plainly that input pulse width went to 65534 when the problem happened.  The other time is an ongoing issue with a Nano in a PPM setup.  Several times now I have noticed (when it was obvious that it wouldn't arm) that the receiver didn't have power.  A slight push on the RcvrPort plug restored power to the receiver.  I am still evaluating fixes...

These were intermittent.  Most times I would get several flights or days in between issues.

Vibration is an issue that causes wiring failures over the long term, mainly at connectors for us.

If you have to arm after the crash, it really looks like the FC rebooted, could even be a different reason than an intermittent power connection.

What and how many sources of power does your FC have?  For instance, my ESCs have BECs (opto ESCs usually don't) so I have 4 sources of power on my quad.

If you have opto ESCs, could you add an additional source of power and see if the issue goes away?  A spare ESC that has a BEC would work.  Just plug it into an unused FC ESC output and get battery power to it somehow.

[I_drone_about_drones]

I've done a little more flying and it has happened a little more often. It turned off once and didn't turn back on at all, I had to unplug and replug it. I think it could be a bad connection between the battery lead and the power distribution board.

[I_drone_about_drones]

I did some flying and I'm pretty sure my PDB is cracked. Looks like I'm going to have to do some shopping.