I have no wish to hijack this thread but as Nick and 212man have opened the can, it might be appropriate to provide (my view of) the JAA policy on offshore performance.
When the 1995 version of JAR-OPS 3 was written in the early 90s it was decided that it would have to be in compliance with ICAO Annex 6 Part III; this required (even for Operations in Performance Class 2) the provision of deck-edge clearance and (for operations in a hostile environment) flyaway; which in effect - for the North Sea - was a zero exposure regime; existing operations were grandfathered until 2010.
Around the time of the implementation date of 1995, the discussion on offshore performance was centred on how to show compliance with zero exposure. Informed wisdom at that time was that this could only be achieved with Category A helideck procedures (as one of the requirements was to show the 15’ deck edge clearance). However, such procedures that were in existence (very few at that time) could only provide limited approach/take-off directions with a minimum deck size of 2D (shortly after that Sikorsky provided a S76C+ procedure with a minimum deck size of 1.5D).
With this in mind, working groups extensively explored the problem and decide to concentrate on a solution based upon the concept of ‘exposure time’ -
Not wishing to bore you with safety targets and the compliance procedures, let’s just say that the ‘safety target’ was based around a limited window of exposure (measured in seconds) and a reliability rate based upon 1 failure per 100,000 flight hours.
This was put forward and accepted by all interested parties in 1998 (NPA - 8) but, because of the unease shown by at least one major Authority, the concept was limited until 2010 and a number of statistical procedures were introduced to improve confidence in the methodology. JAR-OPS 3 was amended in 1999 as Revision 1.
One of the major problems with our industry is that our tools are extremely expensive to develop and produce and the launch of new products is rare. We are fortunate to be in one of those rare periods at the moment when exciting products are just about to hit the market. However it must not be forgotten that in 2010, operators will still be using the 332L, the S61 and early marks of the S76.
212man has said that it is a shame that we cannot reproduce the performance of the ETOPS twins that are now the backbone of the transatlantic fleet. None of us would disagree with that but it must be understood that we have in our hands the most flexible aviation tool that has ever been produced and the provision of that flexibility comes at a cost. One of the costs of that (expensive provision of) flexibility is the longevity of equipment; whatever (operational) regulations are specified, they apply to the whole population of helicopters - older helicopters could be protected (grandfathered) but this cannot be to the detriment of newer craft which are by definition safer and more expensive but not necessarily more productive (see the previous discussion on the provision of the crashworthy floor for the EC225).
Another trade-off is the installed power to provide: adequate OEI power in the cruise; fuel consumption to ensure adequate payload/range; and power to eliminate/reduce the exposure to an engine failure on take-off or landing. You will already know that provision of these conflicting features (simplistically) is a trade off between the last two - fuel burn and take-off /landing performance (the AB139 argument put forward by Nick).
Discussions in the JAA over the last couple of years have been concerned with what to do in 2010 when the exposure time concept is due to end. Perceived wisdom now has it that there may be a method of providing zero exposure without reverting to Category A procedures. It would appear that, at least for the later versions of the AS332, B412, S76, EC225, S92 and of course the AB139, zero exposure is possible with the provision of risk assessed take-off and landing procedures giving deck-edge clearance and, for those helidecks that are situated in a hostile environment, a limitation on drop down to avoid ditching. It has been observed that such performance is possible even in ISA nil wind conditions.
Using the inherent environmental conditions that obtain in the North Sea which appear to indicate that:
it can be shown that zero exposure is possible for most of the time without any payload penalty. Because the defining parameter for take-off mass with helideck performance is drop down, for operational theatres with a non-hostile environment (GOM) this does not (have to) come into play and take-off masses can also be slightly higher than they would have been.
Nick’s choice of the - CT7-8X for the S92 was clearly appropriate as it is unlikely that the dash 6 would have been able to provide zero exposure in 2010 - it also has allowed a growth in the operational weight of the S92 to 26,150lbs - not sure that would have been possible with the dash 6. The CT7-8C will also provide additional power margins that might be needed by future contracts yet to be specified. A similar tale exists for the AB139 but for once the (designed in) installed power appears to provide a growth path that we have rarely seen for new helicopters.
As was indicated in a previous post, the provision of regulations is not the bottom line; some customers have a duty of care that extends well beyond compliance with regulations. It has become increasingly clear that ‘standards’ are within the bailiwick of the customer and not the operator; it is those customers who will specify whether the certification, performance, operational equipment and staff training standards are adequate and, with the exception of certification, will ensure that they are raised if they are not!