parallel ILS approaches

An ATC (air traffic control) procedure permits ILS (instrument landing system) instrument approach operations to dual, triple, or quadruple parallel runway configurations. The ILS/MLS (microwave landing system) are grouped into three classes: parallel (dependent) ILS/MLS approaches, simultaneous parallel ILS/MLS approaches, and simultaneous close parallel (independent) ILS precision runway monitor (PRM) approaches. Aircraft separation during dependent parallel ILS/MLS approaches is ensured by staggered approaches, diagonal radar separation, and ATC information when parallel approaches are in progress. With simultaneous parallel ILS approaches, final monitor controllers are required to ensure that the NTZ (no-transgression zone) is not entered; staggered radar separation is not utilized, and pilots must advise ATC if a simultaneous parallel approach is not acceptable. Approach charts indicate where simultaneous approaches are permitted. With independent simultaneous close parallel ILS PRM approaches, final monitor controllers are required to ensure that no aircraft will enter the NTZ. In this case, PRM is mandatory. In addition, there are also other specific requirements for simultaneous parallel procedures.