Seems a bit odd. RAFFCA clubs don't get charged for landing at MOD airfields. I can only speak for my particular club but all of the a/c we have are private and have crown indemnity insurance. Being as I'm not a wheel in that particular area I don't know how it works exactly. If I flew from my other civvy club into a MOD airfield I would get stiffed. There must be a register somewhere of aircraft that belong to a RAFFCA club.