Airbus Helicopters H135 – SAS Mode Failure (Video)

Submitted by: Rotary Wing Geek

During pre flight checks (SAS mode), functional check of beeper trim revealed the stick beeped moved backwards with both forward and backward trim inputs. Normal beep behaviour was found when in attitude or upper modes. Switch was working fine. It transpired there was a separate controller board (called the PC Board) that controlled the trim actuator response to beeper input. It was only used by the system when in lower stabilisation modes (eg SAS or SAS off) and so when it failed it was only apparent as a fault when the lower modes were used. The same PC board also contains the controller for the steerable landing light inputs (so if that only goes in one direction it's the same type of fault).

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Maintenance Notes

Outcome: Grounded

Maintenance had never had that component fail before so the symptoms the pilot described were very confusing. The culprit was only discovered after a very deep dive into the maintenance wiring diagrams. Notably the pilot ground school entirely missed the presence of the whole PC board component

These notes reflect reported observations at the time of submission and are provided for educational purposes only. They are not a determination of airworthiness and do not constitute maintenance or regulatory advice.

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