Hey guys. First post here. Hope the is ok to post here.

I’ve been flying for about three months now. I have a Nazgûl V3 with upgraded 03 air unit. I had a gnarly crash the other day after hitting a power line. It broke an arm and a motor. I replaced the motor with a stick Xing-Epro 2207 1800kv motor to match the others. I also upgraded from a Zorro to a Boxer. When I take off now, it flies perfect for about 15 seconds, at which point it does a death roll always to the left and crashes. I thought it was based off % of throttle but it always seems to happy right at 15 seconds.


Trouble shooting -
1. Reflashed to known working version in betaflight
2. Check every solder and connection.
3. Added cap back that had come off during crash
4. Removed LEDs I had put on
5. Flashed different PID settings
6. Checked over betaflight for any odd settings
7. Used my zorro to verify it’s not the radio

I’m at a loss. Any suggestions would be amazing.
Thanks in advanced guys!!

Trying to post a video but it keeps timing out.

It can be so difficult to workout what causes this type of issue.  

I had something similar and it turn out to be one of the motors, and in your case it could even be one of the ECSs.

These may not be a real indicator (May not even be helpful   )

• When idling as on ARM before take off is any of you motors twitching?
  
• If your running Bluejay you could try flashing a different a different Mhz so if your running 24Mhz try 48Mhz, the plan is not actually to fly the quad as this different Mhz, usually the bad motor just will not start at all or be extremely glitchy.
  
• This is a pain, but swap the motors about from right to left side, see if your death roll happens on the opposite side.
  

Of cause this could be something else, at the time of the crash do you have a blackout -- indication the the FC is rebooting during flight for whatever reason.

Something to consider is that the new arm causes too much vibration such that the rpm filtering is overwhelmed.

You might not be able to see this visually. Hard to diagnose, but it sure looks like a possibility.

upload the video from another platform like yt, post the link inhere.


40% does sound like there failed one of two fets and it does desync therefor.
What battery do you use?

Desyncs by to low motor idle speed are mostly past issue, mostly on analog motorprotocols.
(To aim a general desync issue, these would matcht the route than.
Decrease startup/rampup power
Increase motor timing
Set demag compensation to high)

As it is always over the same axies, its a very strong sign for hardware issue. Plaster it by demag compensation to high could be a try, but i wouldnt hope..

My next step would be to move the front left motor with the front right motor and check if the issue stays by fall over front left or does wander to the front right with the motor. This will point to change the motor or replace the esc.

did you mix different motors?


Edit: as named "vibrations", check the stiffness of the arms by hand, add force and compare the flexibility. Unflyable arm should feel different in stiffness.

I had a death roll that was intermittent.. used black box to isolate the problem.. showed a motor going to 100%, I had discovered at one point I damaged the motor by using to long mounting screws.. the screw compromised the windings and when fail under load…

Here is what is going on
https://youtube.com/shorts/85zwfOg5U38?feature=shared

(24-Mar-2024, 11:49 PM)Cyberes Wrote: These may not be a real indicator (May not even be helpful   )

• When idling as on ARM before take off is any of you motors twitching?
  

Not really but there is a slightly loud squeak coming from one of the left motors at idle

• If your running Bluejay you could try flashing a different a different Mhz so if your running 24Mhz try 48Mhz, the plan is not actually to fly the quad as this different Mhz, usually the bad motor just will not start at all or be extremely glitchy.
  

Not running Bluejay

• This is a pain, but swap the motors about from right to left side, see if your death roll happens on the opposite side.
  

sounds reasonable  i will try this

(24-Mar-2024, 11:55 PM)segler999 Wrote: Something to consider is that the new arm causes too much vibration such that the rpm filtering is overwhelmed.

You might not be able to see this visually.  Hard to diagnose, but it sure looks like a possibility.

I did have an RPM Filtering error message for a while but it is gone now. 

(25-Mar-2024, 12:01 AM)hugnosed_bat Wrote: upload the video from another platform like yt, post the link inhere.
Uploaded on YouTube and posted here


40% does sound like there failed one of two fets and it does desync therefor.
What battery do you use?
I was using a Ovonic FPV 1000mAh 100C

Desyncs by to low motor idle speed are mostly past issue, mostly on analog motorprotocols.
(To aim a general desync issue, these would matcht the route than.
Decrease startup/rampup power
Increase motor timing
Set demag compensation to high)
Sorry Im not sure what this means.  I'm pretty new and learning a lot on the Betaflight side still


As it is always over the same axies, its a very strong sign for hardware issue. Plaster it by demag compensation to high could be a try, but i wouldnt hope.

My next step would be to move the front left motor with the  front right motor and check if the issue stays by fall over front left or does wander to the front right with the motor. This will point to change the motor or replace the esc.
Rodger I can do this!

did you mix different motors?
No  Same


Edit: as named "vibrations", check the stiffness of the arms by hand, add force and compare the flexibility. Unflyable arm should feel different in stiffness.
They all seem normal and stiff

(25-Mar-2024, 12:29 AM)Rob Axel Wrote: I had a death roll that was intermittent.. used black box to isolate the problem.. showed  a motor going to 100%,  I had discovered at one point I damaged the motor by using to long mounting screws.. the screw compromised the windings and when fail under load…

I wonder if my crash has damaged the windings and caused the same issue. How would i troubleshoot for this? 

Use back box, it’s been a couple years.. don’t remember how.. but I followed some YouTube videos ..

Desyncs by to low motor idle speed are mostly past issue, mostly on analog motorprotocols.
(To aim a general desync issue, these would matcht the route than.
Decrease startup/rampup power
Increase motor timing
Set demag compensation to high)

I just tried to name the esc ettings to solve a desync issue, bur as you dont have it by wrong settings, after a crash by hardware, its not where to look for a solution on the esc software.
Swap motors will bring the next usfull informations to proceed
Sorry Im not sure what this means. I'm pretty new and learning a lot on the Betaflight side still

https://youtu.be/DW5pX8jQE5s?si=W2Atu9DD6eA5F31p

Replaced the esc with a new one. Same issue persist! Now what!?