Apate - I did say "as far as I know' - The S76D RFM is one I have never had the privilege of reviewing. So in that case, I wind my neck in. By way of a word of caution I would differentiate between the RFM and your company ECL. The former - certainly in that part of the past I am familiar with - put an obligation upon the pilot to accept the fire warning as gospel. Some aircraft (S92?, Super Puma series?) have such a poor record in this respect that it would be unusual if the company ECL did not reflect this. There are some societies where absolute adherence to the book is a given and the lack of any room to avoid arriving at the last line in the drill that invites LAND IMMEDIATELY is problematic.
Yes, the 139 system is pretty reliable but I know from an analysis of over 1500 incident reports relating to the 139 that the three fire warning related incidents were all non-events.
We find that those entering the complex world of the latest generation of helicopters for the first time encounter a problem caused the relative scarcity of (serious) system failures.
Managing over and under reaction is an important element of airmanship. That's why Evidence Based Training using scenario type exercises and properly trained sim instructors has a lot to offer our industry.
The guys in AD did the right thing and I would venture to suggest that this was in no small part down to their (apparently) high level of experience.