@A33Zab re Probe heating
A33Zab re #551
Described monitoring is task of the installed Probe Heat Computer (3x)
Can you supply a reference to the functionality of the PHCs; and the warning messages they can generate?
My searches have had very limited success so far. However they do not point to any PHC functionality other than ensuring the pitots have voltage applied when appropriate and are drawing reasonable current (i.e. the element is not burning/burned out?).
So far I've not seen any indication that the PHC does anything other than control the normal operation of pitot heating, and monitor for faults.
My suggestion was to infer the presence of high-altitude icing conditions from the pitot's electrical behaviour; which in turn reflects the thermal load on the pitot. I'm delighted if somebody is already doing this, but have seen no indication of it in any of the reports of high-altitude pitot icing I've read.