Engines get pulled and sections replaced all the time. So there is no way of knowing how “old” an engine truly is. It is all tracked by hours on EACH sub-component. You might have a cold section that is 800 hours, a hot section that is 1500 hours, a HMU that is 25 hours, a compressor that is 273 hours, etc., all on one engine.
Originally Posted by
WhiskeyKilo
I don't know if it is incidental or not but some of the XJT aircraft that I have flown have a huge disparity in FF on the two engines. Which would signal to me that one got replaced and the other is the old one.