Thanks for all the replies, I'm not certain if we've actually obtained a definitive answer though. It would appear that the aural tones can be single and/or double but with no associated caption on the panel, possibly indicating that something isn't right but not pointing to anything in particular - until a caption illuminates. I'm fairly certain that there was no 'momentary' illumination of anything because after the first one I was monitoring the panel like a hawk and I experienced the double bong without anything on the CWP.
The VEMD in particular is not perfect as anyone who flies with them will know and therefore there's every possibility that the aural tones could also be "buggy", although in my case they were clearly suggesting a problem with the engine oil. I may contact Eurocopter/Turbomeca to see if there is a method behind their single/dual bong scenario.
By the way my usual response to anything unusual (aural tone/caption illuminating) is to land, but I've had many discussions with instructors and examiners over the years and that's not always practica.l particularly if you're over water!! I am regularly getting the General Parameter Exceeded warning on my VEMD and last week I had the dreaded "OVER LIMIT DETECTED" which threw me into a total panic only for me to be told that the VEMD "sometimes does that" and you can ignore it. The technology in that equipment is now 15+ years old and the software too. There is more capability in my Apple iWatch these days.
Joel
Last edited by JTobias; 27th Jun 2017 at 10:07.