CS-E 230 De-Icing and Anti-Icing Precautions

(a)The design of the Engine induction system must be such as to minimise the risk of ice formation adversely affecting the functioning of the Engine and, if necessary, must include provision for the use of a means for ice prevention

(b)Where necessary, provision must be made for the fitting of an induction thermometer or ice indicator, as appropriate for the control of the particular system.