Fun Police,
HEC Class D is nothing to do with rescue, it is described in (d) below:
Sec. 133.1
Applicability.
This part prescribes--
(a) Airworthiness certification rules for rotorcraft used in; and
(b) Operating and certification rules governing the conduct of rotorcraft external-load operations in the United States by any person.
(c) The certification rules of this part do not apply to--
(1) Rotorcraft manufacturers when developing external-load attaching means;
(2) Rotorcraft manufacturers demonstrating compliance of equipment utilized under this part or appropriate portions of Part 27 or 29 of this chapter;
(3) Operations conducted by a person demonstrating compliance for the issuance of a certificate or authorization under this part;
(4) Training flights conducted in preparation for the demonstration of compliance with this part; or
(5) A Federal, State, or local government conducting operations with public aircraft.
(d) For the purpose of this part, a person other than a crewmember or a person who is essential and directly connected with the external-load operation may be carried only in approved Class D rotorcraft-load combinations.