Crash after numerous flights without problems

[DUKE40]

I had a look again at some curves, and it looks like the quad flipped for some external reason, the AQ tried to get it stabilized back but was unable to do it and the touchdown caused the AQ to stop functioning. It was very windy and the Gimbal might have cuased a disbalance increasing the effect of the wind gusts.
I think a short or something similar can be excluded, as the SimpleGBC powered from the very same distribution circuit was still functioning and trying to level the gimbal when I found the Quad. And except the AQ ( and the ESCs, I did not test them now) everything else is working as it should.

[kinderkram]

Yes, looks like the board was still running after the flip and stopped working after the impact.
Strange thing is that there´s no obvious sign of a crack, ripped off trace or component.

So there might be a shortage of a circuit caused by the impact - but that´ll be hard to investigate if you don´t have the tools and/or knowledge. I´d look at the ESCs and see if there´s a sign of shortage somewhere in the wires, pins etc.
Even if the AQ was repaired you can´t be 100% sure that the bad component will not blow the FC again once plugged in...

Best option will be to send it in to Jussi for inspection, repair or replacement and in the meantime inspect and test all external components.

[joebar.rc]

As you don't have 12v as input on the recom and no 5v then probably the trace to the recom 12v line or anything in between might be the cause. Or... A short on that path.
Best is to take jussis offer obviously, or you must feel comfortable to do the tracing yourself

[DUKE40]

Hi,

I will take the offer of JussiH as soon as he has answered some questions, especially regarding where I should send my AQ to.
I will check tomorrow all ma ESCs and motors, as well as the wiring.
But could it be that all happebed because of the wind gusts? I was fliying forward against the wind at the time of the crash, and I have a gimbal at the front of the copter with a GoPro, resulting in higher weight on the front.
This is currently one of my suspicions, as according to th elog it was drawing less than 30A for all 3 ESCs and they are rated at 20A each. meaning I could have a global draw of 80A. from the video it looks like all motors were still running and the props are still not loose, so a loose prop can be excluded as cause for the crash.
I hope JussiH will be able to find the cause of the failure on the AQ and this could perhaps help find out what exactly happened.

[DUKE40]

I have again checked all ESCs and Wiring, and no short could be found, all my wires are in protective hoses.
I really think this might have been caused be the combination of flying forward against the wind, with an angle due to the forward flying (Nick) and wind gusts pushing the Quad front a little bit more down, and thus increasing the angle to an extend the AQ could not corrct anymore.

[DUKE40]

Today, I have performed my first flights with the new AQ with DIMU, and I do not know how to say it, but my confidence in the system is getting lower and lower.
The first flight about 45 seconds was good, no problem at all. a little bit short, the battery was quite quickly discharged, no idea why, it might have not been fully charged.

the second flight the nightmare began, again a few seconds hovering. Everythign looked good, and suddenly again the Quad flipped forward, fortunately this time it was only two or three meters above ground.

I checked everything, and could not see anything wrong. So I connected the battery again a tried to fly again, but after that:
* the telemetry was showing no GPS Lock, but an accuracy of 55cm.
* the quad was always yawing CCW and I had to put almost the stick full right to get it remain stable.
* the quad started to fly in any direction and was almost not really controllable, even in DVH mode I felt like I was flying a helicopter trying to keep it on the spot

Even after changing the battery and calibrating the gyros again this strange behaviour remained.

The weather was great, sunny, no wind at all.
I have not looked at the logs now, but I am not sure I will be able to find anything in it.
I have no idea what I will do next, I am quite frustrated.
I was flying so well before the first crash who caused an AQ to quit service. And since that day I have not been able to get it back in the air.

Currently I am flying my NanoWii copter, to not loose complete confidence in flying.

[aBUGSworstnightmare]

[DUKE40]

Hi Joerg,

I performed the onboard magnetic calibartion successfully.
I have setup my magnetic inclination and declination prior to it.
I have checked several times, that the craft is reacting as expected.
As mentioned, the first flight of about 45 seconds did not show any suspicious behaviour, so I decided to check DVH, as the craft was previously reacting as it should and I was sure about my magnetometer I double checked it with a compass to be sure there is no discrepancy.

As next step I will remove the gimbal, I do not think this is causing the problem, because prior to the first crash I had two or three successfull flights with it. But who knows.
I also removed the BT modul, but there were successfull flights with it before the crash.
I will have to go step by step, and this will take much time, because I have only very little time to testfly as I need to go to our RC-club, having no other possibility here.

[aBUGSworstnightmare]

Hi Duke40,

I don't think the BT module is making issues, but you should locate it far away from your receiver.

I was surprised how stable the craft flies with the DIMU with TARE only (level the ground, initiate TARE via TX (Throttle stick left/down, pitch stick left/down)) arm and take off.

I hoover (in manual mode) in 1.5 to 2m height to see if she's working as expected (only SHORT stick commands).
If something goes wrong you will be able to 'land' without risking too much damage.

When she flies in manual mode you can redo the onboard mag-calibration, and do some Altitude hold (increase NAV_ALT_SPEED_I if the craft can't hold the altitude)/position hold test, followed by RTH testings (I fly only 2 to 5m away from my home position when doing first testing). If this all is working you're save for some more advanced testings/tuning.

[JussiH]

I took a look at the previous log you posted. I notice several problems.

First of all your motors are running into saturation and is beeing clipped at the top end. This means you should work on your tuning or that you are possibly overloaded or both....

Part of the saturation is likely caused by a imbalance between Pitch and roll - Pitch is working harder - Likely a physical imbalance on the craft itself:

Both of the above are definately problems and you need to get this worked out and motors working in balance without running into saturation. I am willing to bet that will solve this problem.

Also, right before the flip, your channel 5 takes a sudden dip.But you didnt provide details about radio setup, so I cant judge if its significant....

But Again, we need more data about the craft. Total weight, powerplant, motors, ESC´s props, payload, parameters, firmware versions, etc --- Pictures tell a 1000 words...The more data you provide, the better the chance of someone beeing able to help you out!