I hope that readers of this thread are finding it as informative as those of us who have been prepared to post.
Nick, in a previous email warned us to take care with the simple questions about Cat A or not Cat A; I might add my warning to his and use that as justification to clarify the usage of the term Category A. From a close reading of the definition(s) posted on the first page of this thread, it can be seen that the term is restricted to the landing and take-off phases -
there is no such thing as en-route Cat A. FAR 29.67 - 'Climb: One Engine Inoperative (OEI)' is confined to establishing the requirement for first (at 200ft) and second (at 1000ft) segment climb requirements and, subsequent to revision 39, the production of data to establish the climb (or descent) data in the complete operating envelope. Whilst on the subject, there is also no such thing as Cat A Restricted (there is Group A - the UK performance standard, and Group A restricted - which was a less precise form of PC2).
It is therefore (quite rightly) left to operating regulations to stipulate what the en-route climb performance should be. In JAR-OPS 3 that requirement (simply stated) is for a 50ft/min climb performance at an altitude which gives obstacles clearance. Drift down is permitted as is fuel dump:
Fuel jettison is planned to take place only to extent consistent with reaching the heliport with the required fuel reserves and using a safe procedure.
The subtext for fuel dumping was discussed at great length before the words were chosen - in practice it is not as simple or as useful as it first appears; for offshore, if we refer to the previous discussion on one-way-fuel v beach-fuel - with one-way-fuel there is no possibility of use and with beach-fuel there is no need; there are specific onshore cases where fuel dump might be useful but when they exist, they need careful planning.
In FARs in the overwater case, the VFR requirement for en-route climb performance - 50ft /min at 1,000ft - is alleviated if floats are fitted FAR 135,183(d); and for the IFR case:
onshore - requires 50ft/min at the MEA or 5,000ft, whichever is the higher;
offshore - requires 50ft/min at the MEA or 1,500ft MSL, whichever is the higher.
Performance Classes give a much richer operational vocabulary particularly PC2 which describes exactly the points that Nick and others are making about a limited period when engine failure accountability is not provided on take-off and landing. The terms are written objectively and permit any number of methods of compliance.
Whether PC1 is used is a matter of policy for a number of interested parties: society will decide whether ‘exposure’ is permitted in a congested hostile environment (congested area) and customers (oil companies - and some cases like Norway - States) will decide whether zero exposure (PC1 or PC2e) is the standard for operations to helidecks. Provided that a large enough customer base exists for operations in PC1, the manufacturers will provide the equipment and the appropriate procedures. That these zero exposure options come at a cost is not in doubt; for some customers/States the prospect of not specifying zero exposure when it is possible (and it is) and then suffering a failure leading to death or injury is not a justifiable option.
If PC1 is not used (or is too
costly in terms of loss of payload/range), PC2 provides the ability to establish the cost of exposure in a number of currencies. When the calculations are performed, the key elements will be the probability of failure, the consequence of failure and most important of all, whether the subsequent calculation is within the safety target chosen. The calculation for each aircraft type can be standard as the maximum exposure is, as Mars stated above, finite.