We don’t have the lower -40 SAT limit so at any temperature below +10 TAT in visible moisture we are required to use it engine ant-ice. It has a very limited impact on performance at the high altitudes however so not a big deal. Wing/Stab boots on with visible ice accretion above -30C.
On our stuff we use OAT on the ground to decide if we use engine/wing anti ice there, and then when in the air we use both TAT and SAT. Below +10 TAT in visible moisture we use anti ice and no longer require it below -40 SAT.
It might interest some readers on how to apply this, but I could be mistaken.
Yes equivalent to TAT (but not compensated for the Ram efficiency). It is a measure of the temperature of the aircraft skin and is used for deciding when to put, for example, engine anti-ice on (+10 RAT and below on the C510). Obviously SAT (Static Air Temperature) is relevant for whether liquid water is found, but whether it sticks is affected by TAT (or RAT).
Equivalent to TAT ?
Should be the meaningful temp to know if inside icing range or not ?
What is the purpose to the pilot of seeing it?
Ram Air Temperature.
What is a “RAT”
It is a G1000 PFD. Yes but -60 is the RAT ie heated by RAM effect. So the SAT would be much colder hence the ISA delta.
