How is online (in-flight) and offline (between flights) health monitoring of large aircraft engines and other essential components done?
As far as I have been told, there are a lot of measured channels (at least for engines), but:
what exactly is measured?
How are the data evaluated during flight?
How are the data evaluated on the ground (from long term point of view or after/before failure)?
EDIT: You can consider Boeing 747 or 787 as a large aircraft (to narrow down the question as requested).