Wish I could shed some light.
The reply I got from an enquiry to a RWG member was that there is a substantial difference between the centres and Airport Services as to the FPC issue.
The IRC commissioner defined FPC as the attainment of a rating, not the passing of time. Ergo, FPC should become payable when achieving the required ratings in a given group. Ie: if part of an enroute group, then when rated on sectors X,Yand Z you will be FPC.
For us tower rats, the issue is complicated by OCA, and the attainment of same. Swervin Mervin wants to deny us FPC ratings until we get an OCA rating, but this differs at each station as to when and how OCA is given.(at some towers it is a specific check, at others it comes with an ADC rating.)
Under the restructure attainment of FPC entitles FPC pay.
But nothing as yet as to what is FPC.
Hope this confuses the issue for you.
