I'm not sure anyone is arguing for HEC Class D in rescue - to my knowledge, there are no such operations anywhere in the world. What is being pointed out is the liberal use of the term HEC Class D under circumstances where, although persons are being hoisted (or, in fact lifted for short haul), it is not to Class D standards.
The initial question was about the qualification of the Bell 412 for HEC Class D; what was pointed out subsequently is that HEC Class D is tightly defined concept which is used in specific circumstances - mostly 'sea pilot transfer' or 'passenger transfer' under conditions of Commercial Air Transport.
What makes this an interesting discussion is the use of the regulatory language used in Parts 1, 29 and 133. As an example, below are the notes to the table describing the elements of RLC A, B, C and D in AC 29-2C:
NOTES:
1. A person(s), being carried or transported for compensation outside the rotorcraft can only be carried as a Class D RLC.
2. A person who is not being carried or transported for compensation, is knowledgeable of the risks involved, and at some point is required to be outside of the rotorcraft in order to fulfill the mission. These persons are considered as RLC Class A, B, or C HEC as appropriate to the operation.
3. The rotorcraft is approved to the Category A engine isolation requirements of Part 29 and have One Engine Inoperative/Out of Ground Effect (OEI/OGE) hover performance capability, for the requested operating and weight envelopes, to be eligible for certification to the Class D RLC. Reference Paragraph d(12))
4. A Class D RLC operation may be conducted with an external cargo design having a physical configuration that meets the definitions of § 1.1 for RLC Class A, B, or C.
Although these notes are better read along with the table in AC 29-2C, note 4 appears to say that not only in hoisting does HEC Class D apply; if a person is carried for compensation in configurations A, B or C then the condition of HEC Class D should also apply. In fact because almost all conditions of HEC apply equally whether Class D or not, the only additional condition called for would the the performance requirements.
However, my interpretation appears to show a conflict between notes 1 and 4 and also a conflict with the definition of HEC Class D:
(iv) Class D rotorcraft-load combination means one in which the external load is other than a Class A, B, or C and has been specifically approved by the Administrator for that operation (i.e., HEC operations for which the operator is receiving compensation from the person being transported).
or does it?
Jim