PBN Oceanic Limits RNAV
During oceanic, en route and terminal phases of flight the aircraft is sufficiently far away from the ground that vertical guidance is not necessary. Secondly, angular guidance is not required as during this point the aircraft is not on the approach to a runway. The second of these factors (angular guidance) will change when the approach phase is started; the first (vertical guidance) might change depending on what type of approach is being conducted. The approaches are precision (vertical guidance) or non-precision (no vertical guidance) so vertical guidance is not always given.