wrote:
Does anyone know of an airplane manufacturer that specifies engine or
wing anti ice systems need to be activated a set amount of time
(minutes) prior to entering icing conditions? The ones I've seen only
say "prior to entering...", but no requirement given to have it on for
a set time prior in order to heat up the surfaces.

Do far 25 rules testing provide any insights?

Stan

Any heavy iron I flew required that engine anti-ice be on within a range
of temperatures and where there was visible moisture (any cloud is
visible moisture). This policy (invoked by the aircraft manufacturers)
had nothing to do with whether you observed icing.

Wing deice is an entirely different issue. It is "deice." Engine heat
is "anti-ice."