737 NGX True Air Temperature way off

[suchw 12]

flying from ybcg to yssy with radar contact and ase real weather cruising at FL300 ASE indicated (-40 celcius i assume) but the TAT on the NGX was only -15 celcius i assume, anybody else had this issue in the NGX with ASE, I have also logged at HIFISIM forum but dont know if its ASE or the NGX thanks

[trisager 2]

The TAT is total air temperature. You should be able to find the outside air temperature in the CDU, although I cannot remember offhand which page it is on.

[suchw 12]

thanks that could explain it i thought it was true air temperature

[Peter James 0]

It's (the REAL outside air temp... is on the 2nd page of the PROG page along with the TAS readout and other stuff like ISA temp deviations etc..) The temp on the engine gauge region is what the airplane senses with speed, compression etc... but not the real ambient air temp... that would be way colder always... the normal temp outiside at FL400 is nearly 80F below zero!!

[trisager 2]

What you are looking for is the static air temperature - it is on PROGRESS page 2. Edit: Peter beat me to it

[suchw 12]

thanks a lot so much to learn loving it