Spirit GT 4.0.3 – Sudden Tail Kick and Unexpected Power-Up Counter Reset

[senaka]

Helicopter setup:

* Helicopter: SAB Kraken 580
* FBL: Spirit GT
* Firmware: 4.0.3 (no recent upgrades)
* Tail servo: Savox SH-1290MG
* BEC voltage: 6.0 V
* Flight logging: 10 Hz
* Tail assembly grounded to the motor mount

The issue

During the 3rd flight of the day , after approximately 2 minutes of slow sports flying, I experienced a single, extremely brief and sharp tail kick to the left while hovering around 30 degrees clockwise. The nose moved rapidly, but the tail immediately corrected itself without any rudder input from me.

It wasn’t continuous tail wagging or hunting, just one sudden rapid movement followed by normal flight behaviour. Its so rapid its impossible to do manually via the Tx rudder stick.

I subsequently completed another test flight without reproducing the original tail kick. The heli is stable hands free hover and locked in tail. No stabilization was used throughout.


Servo and mechanical checks

I tested the Savox tail servo on the ground, and everything appeared normal:

* Smooth movement throughout its travel.
* No random twitching or hesitation.
* No noticeable binding in the tail linkage.
* Servo and BEC remained cool after flying.
* No unusual vibrations were noticed during the test hover.

Spirit GT logging and counter anomaly

When I connected the Spirit GT to my laptop to investigate, I noticed two unusual things:

1. Flight logging memory was 99% full, with logging configured at 10 Hz.
2. Both the System and User power-up counters were showing 7, although I would expect them to be in the hundreds.

Importantly, both counters were already showing 7 before I cleared the flight logs while I had 18 flight logs.

I checked the Spirit event log but couldn’t find any obvious errors associated with the tail kick. 10Hz interval may have not captured it on time, I have now set it to 25Hz.

My questions

1. Has anyone experienced a single, sharp, uncommanded tail kick with a Spirit GT that immediately corrects itself?
2. Could nearly full flight-log memory cause unexpected controller behaviour on firmware 4.0.3?
3. Has anyone experienced both the System and User power-up counters unexpectedly resetting?
4. Could the counter reset indicate a firmware or internal memory issue, and might it be related to the tail kick?

Configuration attached. I have now updated to 4.0.5. Did not fly on this version yet

Thank you.
-Senaka

[senaka]

Accelerometer data 15 -49 -2069

[ZeXx86]

Hello,

observed behavior is most probable strong electrostatic discharge where receiver connection can fail or result in a random input that was not yours. For belt drive models it is quite common and can develop over time and is also dependent on ambient condition. If this is the case you might observe Receiver data were corrupted in the Flight Log as Warning event.

For your Powerup reset counter it has likely no relation with this issue. Previously it could happen when Spirit unit did not powerup cleanly and re-rebooted during initialization for example during connecting a battery plug. This issue was addressed in 4.0.5 which will create backup settings/data for case like this.
So I recommend to check

[senaka]

Thanks for your reply.

Regarding flight log levels, do warnings get stored permanently? As the flight logs that I see are current events from the time the power is applied. I don’t seem to find any events from previous flights.