Hello,

if you are able to reproduce the odd servo movement on the ground, then try to initialize model without radio powered up.
Can the issue still be seen? If no, then you can be sure the issue is not caused by servos. If yes, then it is very likely a servo issue.
Can you see the problem is happening with a certain servo or it is random?

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Spirit System developer

Hello,

behavior you are describing is fortunately perfectly correct.
Once GeoLink will pickup signal from GPS/GNSS it will engage position hold or other feature you have engaged. It is engaged when your radio is off - this can be seen in the Diagnostic tab for example.

It will happen with any GeoLink and any model. We are looking for an unusual behavior, such as servos boucing, random movements, etc.
For good observation, please turn off GeoLink support or GeoLink feature that is engaged.

Is this what you have seen previously? If so, then this is not an issue. In the air behavior is very different, but without a movement unit is trying to reach desired position - but it is not possible obvously. For this reason you can see such movements.

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Spirit System developer

You're right, that was my lack of understanding of how the radio-off affects FBL+GeoLink

This time I turned GeoLink support off, and the servos kept constantly quiet after inizialization. I think servos are ok.


No this misunderstanding on my side was related to the radio-off test for determining the health of servos.
Strange behaviour appears mostly during flight, it seems as if commands (not from myself) are received by heli with tilting or tail impulse or pitch changes and occasionally even motor regime changes (governor should avoid that)

Do you have possibility to run the heli with a standard receiver connection (PWM)?

In this way we can verify if there is something wrong with SBUS.

Also with PWM static discharges will be more apparent. So if this is the case, the problem can be determined easily.

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Spirit System developer

Sorry for the long lack of messages, but I can now say PROBLEM SOLVED or, at least, my Trex 500L flies again perfectly.

After receiving the replacement of original tail boom, with no success, I made a last tentative: my heli supplier ,who followed and supported me along this very long story, had a Futaba receiver identical to the one installed, so we switched the receiving unit and bound it again. To our surprise the heli flew perfectly, no strange movements. Not believing the old receiver could be faulty, we revert back to the old unit and again the heli flew perfectly.

We don't have a clear explanation for this behaviour, only two possible clues about
1) binding again was the determining factor, the system was in an overall undetermined state.
2) connectors re-insertion corrected a non complete, intermittent electrical continuity

I do not trust the above explanation, I already reinserted connectors many times (not the SBUS one) moving everything, but I don't have any other clue. Let me add that this "solution" solved also the GeoLink negative readings, once again I don't understand why.
Any hypothesis/alternative explanation is welcome

I'm getting back to the community and possibly to Tomas, as I am not completely satisfied having back my correctly-flying heli, but without having understood the root cause of the previous malfunction(s). Are my clues likely? Is there any additional test I can make?
I am particularly disturbed by the GeoLink behaviour; how can it be influenced by the improperly connected/bound receiver?

THE FINAL CHAPTER.
It happened again. Strange heli movements without command on my side etc.
Building on the previous experience I
1) changed the SBUS cable from FUTABA receiver to the Spirit PRo unit: connector fits tighter as compared to the old one
2) hot glued the connector zone of Spirit Pro unit (see picture) so to secure the connections while leaving the system connection available. The glue can be easily taken away mechanically if needed.
Three batteries flown without any problem: evil defeated.
Hope this helps in case someone experiences something similar

Apologies, I forgot the picture.

Fingers crossed this is now sorted!!
Though I bet you wished you'd changed the SBus cable a little sooner?