Originally Posted by
Vessbot
Maybe. I fly a different aircraft, where the manual says specifically not to use the aircraft-measured temperature on the ground.
Depends on the aircraft. TAT sensors are heated to prevent them from icing up in flight (getting that heat right - so that it keeps the probe warm enough to prevent ice forming without adversely affecting the temperature measurement - is a very non-trivial engineering challenge).
Some aircraft have TAT probes that are 'aspirated' - air is blown around the probe while on-ground to prevent the probe heat from affecting the TAT measurement statically - but not all aircraft have that feature. IF the TAT probes are not aspirated, on-ground TAT is not considered valid.
The 777 (and all current production Boeings) have aspirated TAT probes that should remain accurate on-ground. Note that there are 'latent' malfunctions that can adversely affect the TAT probe aspiration - debris in the probe being a big one.