CHC outside of N Sea (not known by me) would have been, before flight - 1. check fms approved database in date (if not, manually enter required locations from published source) 2. check user waypoint database in particular for destination / alternate which is mobile (normally marked with 'X' as first input) against latest customer / rig status sheet and read and crosscheck challenge and response Lat / Long. 3. Confirm correct waypoint routeing. A fixed HLS / platform location in the user database may not necessarily have been checked ........
En route, each leg track and distance should be checked against ops flight plan.