Old engineer: Absolutely right, except that measuring the combustor exit temperature is a b***h and except for very limited experimental tests, that temperature must be computed based on fuel/air ratio.
Measuring "EGT" (heh...) at the LPT inlet has at least two advantages:
1) Faster response time, more accurate during transients such as engine starting; and
2) It measures core (HP system) efficiency more directly - and the core is where the bulk of deterioration occurs.
lomapaseo: Absolutely right in the present case, although it serves as a confirming parameter in establishing the timeline of the failure. But it's been a red herring (probably my own fault) in this thread.
