3dr quad pixhawk drops from air repeatedly


My newish 3dr quad w pixhawk running 3.2.1 has fallen from the sky the last few flights. Battery is 4C 5000mah Turnigy and has 3dr power module. When I first started flying it when it was new, it worked normally. I could get 8-10 minutes if air time. I started having problems with it sky falling a while back and stopped flying it. Fast forward to now(5-6 months later) and I took it out today to see how it would fly and same thing. I was hovering it in front of me for a minute or two. Started to get comfortable and stated moving it around and it dropped to the ground from about 10-15 feet. I have looked at the logs myself for the usual suspects but things look normal up until things go dark I am a total noob but I did compare my logs to others on the forums and I seem to have plenty of power, just over 14v, when I free falled, all the motor channels seems to to doing the right thing. Desired vs actual movements are not contradicting each other. ThrIN and ThrOut look OK. But then it just drops.

I’m wondering if the power module could cause this? Any ideas on where I should look? By the time the quad is on the ground its powered up again. And to clarify, when it drops, it drops like a rock, absolutely no power to the props.

I’m definitely scared to fly this thing the way it is now. I may just attack it to something heavy and run it like that to see if it’s going to keep shutting down

Attached is log file


Looks like a dodgy connection on the power system.

For a quick check you could try removing the props, arm the quad and raise the throttle to get the motors spinning. While it’s sat on the bench with the motors going, try wiggling the cables and connections from the battery to the pixhawk and see if any point on the circuit repeatedly causes a shutdown.

Since the Pixhawk is powered from the power module it would have to be before that since the pixhawk loses power.
Also power to the Pixhawk seems to be jumping around as well. Maybe that connection is loose or not all the way in.


Thanks for the help.

I ran it without props and wiggled, jiggled, flicked, pulled, shook etc… Everything and not even a hesitation.
I did his til the battery died which was 20plus minutes.
I’m thinking of putting the props back on to put a load on it.
I’ll let u know how that goes.

I put props on, tied it to a dolly and ran 4 batteries through it(2 batts, each run twice). No problems.
Then I flew it.(1 meter over grass) Fell out of the sky 2 minutes into the 2nd batt.
Continued to fly 4 more times over a few days without a problem.
Then today, on the second flight, about 2 mins in, I’m hovering about 1 meter in loiter and switch to stabilize and, wait for it, the thing flips over in the air and lands not on the grass but the rock next to it. All 4 motors hit the ground at the same time.

I have attached the log file. I think I heard pixhawk starting up again after the landing so I’m wondering if it was the same problem and switching modes caused the lateral flip. Usually it just drops and lands nicely from 1 meter on grass.

Do the logs indicate that the pixhawk lost power again? Both of the last 2 failures were on the same battery. Could a battery just drop voltage and kill power to everything underlod then always balance charge fine?
At this point there is not much left to the quad. The frame needs new legs, 4 motors and pops. GPS has taken many hits but is probably ok? Not sure how sensitive they are to crash landing on the gps antenna. Think the compass might be in there too? Sounds like it could be sensitive.
If I was going to dump this quad(3DR DIY QUAD) and build a new one are there any items I could salvage and not have to worry about moving this problem to a new quad? What are the chances there is something wrong with the pixhawk?


Logs stop in mid air. Brown out again. Must be some lose component somewhere that is effected by vibration.


Thanks for chiming in Mike.
Could a bad battery cause this behavior? The 2 failures I had while testing were on the same battery and I was switching back and forth between 2 batts. The battery in questions takes a charge(balanced .02 variance between cels) without issue which makes me think its not the battery. I use a Turnigy accucel 8150 for charging.
I’m not sure exactly what takes place in the power module but I thought it played a roll in measuring draw on the battery. If there is something in there that is measuring current (component that measures is in series?) could that part be failing in power module? Causing an open circuit. Relay, over current protection?
Like I mentioned before I did a pretty through wiggle test and not a hiccup. I even took an IR thermometer and scanned all the wiring, connections etc… for signs of heat but nothing was over 100 degrees.

Do you think pixhawk could be failing and randomly rebooting or something to that extent?


Never heard of a battery just going dead or having a bad connection.

At this point it looks like the Pixhawk maybe rebooting in mid flight. Possible due to bad connection maybe on the Flight controller itself.


Based on what I heard and tests it seemed the most likely culprit was the power module. I cut the shrink rap off and found this. Hopefully you can make it out. Looks like a diode? exploded.

Oh Ya. How can that manifest itself as an intermittent problem?
Guess I’m pretty far off the log analysis topic by now…


Well it may have only been slightly fried and was opening due to vibration. At least now you have something to replace that you can easily get.