Class 1 Cat A
Nick Lappos et al
The question I believe was more about what these subjects ARE rather than what one's opinion of their relevance is. Having recently been asked the same question by a customer I had to explain the reality of the situation rather than the academics of what it ought to be.
I have to say that what Nick says makes a lot of sense but as we all know our performance mantras have their origins in the fixed wing world and it is likely to be a while yet before we some common sense creeping into the world of helicopter performance.
What the standards posed by Cat A (Group A if you are a Brit) and Class 1 have done is forced the manufacturers to produce helicopters that are almost able to fly throughout the flight range on one engine. Irrespective of your thoughts about the applicability of 'Cat A' I reckon this is a 'good thing'. I recently saw a picture of Bo105 upside down in the 'oggin' in the GoM after it had suffered a single engine failure but been unable to maintain height at the weight he had elected (been forced to more like) operate at.
So - in the big debate about Cat A , is it a good thing or a bad thing - me, I plump for giving the guys a bit more to play with in an unforgiving and unpredictable world. save the Cat B stuff for the military.
Now I see that I haven't answered his question either and I'm not in the mood to write pages and pages about helicopter performance so I'll leave that to somebody else.