Text in force at CS23-6: from CS23-5, effective 15 Aug 2017.
(a) The aeroplane design must prevent foreseeable accumulation or shedding of ice or snow that adversely affect powerplant operation.
(b) The powerplant installation design must prevent any accumulation of ice or snow that adversely affects powerplant operation in those icing conditions for which certification is requested.
ED Decision 2017/013/R · Source