OAT

[Bulva]

I'm ashamed to admit, but I don't know where to find information about the OAT temperature ???
Of course there is TAT. I searched on FMC sites (like in 737-800) but can't see OAT ...

[Hotdawg]

FMC Progress page 2

[Hotdawg]

OAT is SAT "Static air temperature"

[Bulva]

Thank you.
Is it possible to switch SAT to TAT in hardware, as it is in the "steam gauge" engine instrument version ???

[Hotdawg]

It has been awhile since I have flown  -400 but your main concern is TAT inflight. 10 degrees TAT or colder and visible moisture inflight is considered icing conditions. On the ground SAT is not accurate unless you have an asperated Rosemount TAT probe. Even then it's better to use current METAR because it's more accurate. The only times pilots really check SAT inflight is during climb or cruise if SAT is below -40 in the clouds you can turn off engine anti-ice and save a little fuel.

Edited November 3, 2022 by Hotdawg
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