Quote from
Lonewolf_50:
The recorded cockpit briefing about temperature not developing as planned/forecasts may be of no moment ... or maybe a clue pointing to TAT readings sensing beginning to degrade as Airspeed sensing began to go wrong?
I'm inclined to think the former. Looking again at that Jetstar A330-200 incident
FDR-trace that mm43 kindly provided us last night (GMT), the TAT down-spike when Mach and CAS collapse is quite small (~5C), whereas the coincident up-spike of SAT is large (nearly 25C), in order nearly to meet the TAT – as you would expect at Mach 0.2.
When looking at the possibility of step-climbs, we look at the decreasing weight and the SAT (and its deviation from ISA), not TAT. Some large jets are limited mainly by buffet margins, others by thrust (the classic examples being respectively the VC10 and B707-320). With its high-bypass turbofans the A330-200 is thrust-limited, so the higher the temperature, the later the step-climb. The crew would have been comparing the SAT readings with the forecast OATs on their computer flight-plan: hence the remark.
Considering your second option, on the other hand: if the CAS/Mach readings had already started insidiously under-reading, causing an over-reading SAT, the A/C would have been actually speeding-up without their knowledge. Not sure if it's possible to prove or disprove that possibility. GS doesn't help because we don't know the wind-component.