Thanks for that.
Can i conclude that when TURBOMECA state the below that N2 is the Ng gage ? It still don't sound right but the number are usable!
When N2 decreases and reaches a value between 85% and 70% then rises above 98%
F2 = 0.1 (engine PRE-MOD TU77)
F2 = 0.3 (engine POST_MOD TU77)
When N2 decreases and reaches a value less than 70%, then rises above 98%: F2=1