Guess my english isn't as good as u r s.
Could you please clarify WHAT is contrary, and
give me a few more details about u r 2 acf.
Like which one is flying at or closer to optimum level, weight and speed (M#, KIAS, GS) etc.
With regard to old turbofans, the FF will increase about 3-4 % over time.
The biggest loss is in the High Pressure Turbine.
The tip of the turbine blades will get burned away during time, and you get an
increase in the gap between blades and shroud.
The difference in EGT between a new and old HPT and shroud can be 20 deg C.
M
You see below, the only place where a DECREASE in FL
gives a better optimim level on the A310 is above M .80 . Most likely because transonic drag starts
playing tricks.
