Manfromuncle,
The rules were changed at AL5.
The effect on the SNS will depend on the equipment used; for the AW139 there will be no effect at all.
The effect on all NS operations will depend upon the operator's application of the rules. Take-off and landing in Subpart H (PC2) was always divided between: (a) the original ICAO principle of a safe-forced-landing (Pure PC); and (b) the use of Exposure. This did not change with AL5.
Examination of the revised JAR-OPS 3 will show that (both for take-off and landing):
Clause (a)(1) of the rule requires the base-line performance (second segment climb);
Clause (a)(2) is for operations other than with Exposure (with a SFL - i.e. Pure PC2); and
Clause (a)(3) is for operation with Exposure
The operator has the opportunity for application of either Pure PC2 or Enhanced PC2 (PC2e).
PC2e comes within (a)(3) because it is well known that (described in the guidance - as it was in the explanatory material for the NPA) environmental conditions of helideck operations do not always permit a deterministic outcome as prescribed in the Category A procedure. This is one of the reasons why operations cannot be in PC1 (another is the required size of the helideck surface (the TLOF)).
Application of Pure PC2 requires a safe-forced-landing - in the case of helideck operations that implies: (a) no deck-edge strike; and (b) a landing without injury to persons in the helicopter (a safe ditching). It has long been recognised that such a safe landing can be conducted in Sea State 4 and below (from AC 29-2C, significant wave height of 4ft - 8ft and wind between 17kts and 21kts).
Provided that a safe-forced-landing can be achieved, Pure PC2 can be conducted.
Helidecks have to be designed to provide a 180 obstacle free sector - oriented into the prevailing wind. Leaving aside the case of a sea that is running high with a slack wind (which is an issue that
does has to be addressed) it follows that with a reported wind of 21kts or less, a departure or arrival will always be possible within the 180 obstacle free sector
regardless of wind direction. If, for take-off, that is combined with a profile that assures deck-edge clearance, the conditions for Pure PC2 are satisfied. As wind accountability is never built in to the manufacturers procedures other than for drop down, a cross wind has no effect on deck-edge clearance.
Compare that with the pre-AL5 conditions and you can see that (for winds of 21kts or below) the only
additional requirement is the provision of a profile that provides deck-edge clearance. (This does not take cognisance of the provisions that have already been made for low wind operations discussed in the other thread.)
The use of Pure PC2 is tied to a wind speed of 21kts or less (with the rider about significant wave height); this break is hard - i.e. not factored. If that wind is exceeded, then a safe-forced-landing is not assured and the operator has to apply the conditions of the provisions of (a)(3). If the break is hard, it can logically be argued that progression into PC2e should permit full credit for the first 21kts of the wind. Whilst this could not be permitted for a Category A procedure, it can for PC2e because of the flexibility of the provision:
"take-off mass takes into account: the procedure; deck-edge miss; and drop down appropriate to the height of the helideck..."
The situation with institutionalised ditching (albeit tied to a limit of SS4) provides an ethical dilemma for the oil companies; the acceptance of this situation is for them to deal with because it is one of duty of care. Before extensively flaming me for accepting this situation, please examine the status quo - operations with Exposure which encompass both the probability of a deck-edge strike and ditching in an undefined sea state.
In order not to provide a dense post, I will pause at this stage and let you consider what has been said.
I will resume later with: the provision of performance data based upon manufacturers graphs; the situation when the wind is in excess of 21kts
and in the 150 limited obstacle sector; addressing the lack of (explicit) data for the HAPS landing manoeuvre by utilising manufacturer's statements and graphs; and examination of the 'proportion' of operations that may have to be conducted with an exposure element.
Hopefully, by the time the entirety of this has been discussed, you will see that most of HCs apocalyptic predictions are not based upon fact.
Jim