14 C.F.R. § 23.2165
(a) An applicant who requests certification for flight in icing conditions defined in part 1 of appendix C to part 25 of this chapter, or an applicant who requests certification for flight in these icing conditions and any additional atmospheric icing conditions, must show the following in the icing conditions for which certification is requested under normal operation of the ice protection system(s):
(1) Compliance with each requirement of this subpart, except those applicable to spins and any that must be demonstrated at speeds in excess of—
[Doc. No. FAA-2015-1621, Amdt. 23-64, 81 FR 96689, Dec. 30, 2016, as amended by Doc. No. FAA-2022-1355, Amdt. 23-65, 87 FR 75710, Dec. 9, 2022]