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Mighty cold up there yesterday...

EGTK Oxford

Took me a while to find the -60C. What Garmin product (which actual box) is this?

How is the “ISA – 15C” calculated? ISA

I reckon you were supposed to be at -56.5C.

The coldest I have ever seen was -38C at FL195 which is ISA-14 here

Administrator
Shoreham EGKA, United Kingdom

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.

EGTK Oxford

What is a “RAT”

Administrator
Shoreham EGKA, United Kingdom

Ram Air Temperature.

EGTK Oxford

What is the purpose to the pilot of seeing it?

Administrator
Shoreham EGKA, United Kingdom

Equivalent to TAT ?
Should be the meaningful temp to know if inside icing range or not ?

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).

EGTK Oxford

It might interest some readers on how to apply this, but I could be mistaken.

Administrator
Shoreham EGKA, United Kingdom

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.

United Kingdom
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