Text in force at CS25-28: from CS25-0, effective 17 Oct 2003.
(a) Each part of the aeroplane near the propeller tips must be strong and stiff enough to withstand the effects of the induced vibration and of ice thrown from the propeller.
(b) No window may be near the propeller tips unless it can withstand the most severe ice impact likely to occur.
ED Decision 2003/002/RM · Source