Nick:
I'm sure none of us are without motive; that would be too much to ask and probably boring to boot.
Thanks for the reply and the confirmation - the reason that I raised the quotation and asked the question is that the theme of your post appeared to be taking us away from something we already have - zero exposure to a helideck strike with the majority of modern aircraft in, and about to enter, service. Your figures show that this is even possible for the S92 in the conditions that are present in the Gulf of Mexico.
However, we also know that, for any elevated procedure which has a short vertical section (a TDP of 20’ - 30’) and which relies upon rotor inertia and a 30 second power to achieve deck-edge clearance, there will be a (potential) penalty in drop down; we also know that drop down can be reduced by a favourable density altitude and wind accountability - examination of the S76C+ Category A procedure will confirm this. Drop down is not a bad thing as helidecks are elevated and (in the North Sea) appear to have a mean height of 100’ and are exposed to a mean wind of 20kts.
Onshore elevated heliports and ground level helipads are subject to different conditions but could have the luxury of space to have a back-up procedure, or longer vertical sections which could be traded for drop down.
How can the manufacturers be accused of hiding performance, don’t they publish the Category A procedure; isn’t it more that the operators, pilots and regulators are not capable of asking the correct questions and appear to be satisfied by a statement that the aircraft is Certificated to Category A. Not even FAR 29 requires more - strange then that an interpretation of FAR 29.1(e) appeared to indicate that a Transport Category helicopter should be operated only in Category A - hence the HV graph being in the limitations section (and the lack of performance rules in the current FAR 91 or 135). Are we missing something here, isn’t the class of helicopter that is above 20,000lbs and carries more than 10 passengers mostly used in offshore operations.
For me, and for the reasons that you have stated in your statistical analysis (the calculations look familiar), I am content with PC2 with exposure for offshore operations; but for those States and customers who need to have more assurance built in to their operations (for example when operating in a hostile environment), PC2e appears to give the best of both worlds - zero exposure without the expense of flight trials in the Moray Firth. Looks like a win-win situation to me.