Helimutt,
Unless otherwise stated, the HV diagram - contained in the Flight Manual - applies to all flight manoeuvres except those which are within a Category A procedure or are accepted as being within the bounds of PC1 (as indicated by the latest amendment to JAR-OPS 3). That is why some regulations permit exposure in take-off and landing for operations in PC2 (take-off and landing for twin engine helicopters certificated in Category A).
The HV diagram (if there is only one in the FM) is based upon a set of flight conditions expressed in Parts 27/29 and, as such, is a blunt tool (as an analogy consider a WAT curve that did not take into consideration temperature or altitude and gave one take-off mass for ISA at 7,000ft).
In Europe, penetration into the HV diagram is accepted (an alleviation contained in JAR-OPS 3.005(c)) for a limited period in the take-off and landing phases (because the HV diagram is a limitation of Part 29 helicopters); the limited period is a take-off or landing event -likely to be measured in seconds.
It will be obvious that penetration into the HV diagram, for other than take-off or landing, is likely to place the twin engine helicopter in a situation only marginally better than for a single. It is this marginal benefit that will have to be assessed by the Irish Authority in addressing the recommendation of the Accident Investigators.
Clearly operations such as pipeline inspection could be flown in PC2; however, it is the overall principle that has to be addressed.
At present, the level of protection against commercial activity is provided for: third parties - by the Rules of The Air contained in regulations (in compliance with ICAO Annex 2); passengers - by compliance with the regulation for Commercial Air Transport; and crew members - by Aerial Work regulations. (Obviously some of these are also cumulative.)
If one area of aerial work were to be singled out for special treatment then all areas of aerial work would have to be examined - closely followed by examination of the subdivisions of each task. This for a regulator is the nightmare scenario because it would place the responsibility for each aspect of safe operation with them and not the operator. This would also run counter to contemporary thinking which is to place the responsibility for safer operations with the operator (on the basis that they have the operational experience and would be best placed to run the Flight Safety Program).
This is a heavy recommendation and one which will cause sleepless nights for the Irish Authority - it is to be hoped that it resulted from consultation between the Investigator and Authority and wasn't a unilateral declaration.
It is likely that the Authority will defer any further examination of a change of regulation until after seeing the result of deliberations on Aerial Work by EASA. Any short term policy decision could quite quickly be overturned by a diktat from Europe.
Jim