(b) Free turbine
The number C2 of reference cycles consumed between one start and the consecutive shutdown is calculated as follows:
C2 = F1 + ∑F2
F1: Complete cycle to the value of 1
F2: Partial cycle (power decrease followed up by a return to nominal rating), related to all the values reached less than or equal to 85%
The value of F2 is counted as follows: after exceeding a minimum value of 98%
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
NOTE this notably concerns the procedure that exists on some aircraft to lock the rotor while keeping the engine in operation (at ground idle), in order to get on board and get off passengers.
This was copied from the TURBOMECA ARRIEL 1 TURBOSHAFT ENGINE MAINTENANCE MANUAL
Can anyone please tell me what they are referring to with N2?
or does N2=Ng gauge
as they don't refer to an N2 anywhere except in the above!
I thought it might be (Rotor tacho = Nr) but then the figures don't line up?:
Thanks in advance.