Having blown the sand off a copy of the 105 CBS Flight Manual (English Edition of LBA {Luftfahrt Bundesamt} Approved Flight Manual) from when we purchased 3 nearly 25 years ago- Optional Equipment 30 which deals with "Flights According to Instrument Rules" states the equipment required for IFR flights for both Commercial and Non Commercial. Under Minimum Crew it states "As for the Standard helicopter unless laid down in the applicable operating regulations.
When the stability augmentation system Ferranti (OPT 29) or the helipilot Sperry (Opt 41) is not installed or is inoperative, the minimum crew consists of one pilot and one crew member with rating to carry out the air-ground communications in English during flights according to Instrument Flight Rules. Before commencing the flight, the pilot must satisy himself, that this crew member is capable of providing the required support during the IFR flight"
No idea what Authorities currently require. We certainly operated IFR without SAS, though we were not on a civil register. The ferry flight from Germany was virtually all IFR tho we did have left hand seat occupied by someone who loosely fitted the above requirements.
A very strong, rather underpowered beast that always gave a secure feeling when flying.