chart note stating, “Simultaneous approaches authorized”,  standard separation is used between aircraft on parallel  approaches.  Dual and triple simultaneous independent parallel  instrument approaches, are authorized at certain airports  with specified distances between parallel runway centerlines.  As a part of the simultaneous independent approach  approval, an NTZ must be established to ensure proper flight  track boundaries for all aircraft. Outside of the NTZ, normal  operating zones (NOZ) indicate the operating zone within  which aircraft remain during normal approach operations.  The NOZ between the final approach courses varies in  width depending on the runway centerline spacing. The  NTZ is defined as a 2,000-foot wide area located equidistant  between the final approach courses in which flight is not  allowed during the simultaneous operation. [Figure 4-46]  Any time an aircraft breaches or is anticipated to breach the  NTZ, ATC issues instructions for the threatened aircraft on the  adjacent final approach course to break off the approach to  avoid potential conflict.  A local controller for each runway is also required. Dedicated  final monitor controllers for each runway monitor separation,  track aircraft positions and issue instructions to pilots of  aircraft observed deviating from the final approach course.  [Figure 4-45] These operations are normally authorized  for ILS, LDA and RNAV approach procedures with vertical  guidance. For simultaneous parallel ILS approach operations,  pilots should review the chart notes to determine whether  the non-precision LOC procedure is authorized (in the  event of glide slope equipment failure either in the aircraft  or the ground). An example of a restriction on the use of a  LOC procedure is shown in the notes on Figure 4-24: “LOC  procedure NA during simultaneous operations”. Likewise, for  RNAV (GPS) approaches, use of LNAV procedures are often  restricted during simultaneous operations.  Triple simultaneous independent approaches are authorized  provided the runway centerlines are separated by at least  3900 feet for triple straight in approaches. If one or both  outside runways have an offset approach course of 2.5°  to 3.0°, the spacing between those outer runways and the  center runway may be reduced to 3000 feet.  Simultaneous close parallel (independent) PRM approaches  are authorized for use at designated airports that have  parallel runways spaced less than 4,300 feet apart.  [Figure 4-47] Certain PRM approaches are referred to as  Simultaneous Offset Instrument Approaches (SOIA) and  PRM procedures are the most efficient method of increasing  approach capacity at airports with closely spaced, parallel  runways. Use of PRM procedures increases airport  capacity during periods of low visibility by providing  ATC the capability to monitor simultaneous close parallel  (independent) approaches. These PRM operations reduce  delays and increase fuel savings. Traditionally the PRM  system included a high-update rate radar, a high resolution  ATC radar display, as well as software that can autonomously  track aircraft in close to real time, with visual and aural alerts  that depict the aircraft’s current position and velocity as  well as displaying a ten-second projected position to the  controllers. Today, most PRM operations are conducted  without the need for high update rate radar, so long as all  of the other requirements to conduct such approaches  are met.  are discussed in depth later in this chapter.  There are also special communications and ATC  requirements for PRM approaches. PRM approaches  require a final NTZ monitor controller for each runway, a  separate tower controller for each runway, a PRM tower  frequency, and a runway-specific PRM frequency. Each final  monitor controller will have a dedicated PRM frequency,  and the tower controller will have a separate common PRM  frequency. Pilots transmit and receive on the common  tower PRM frequency, but maintain listening watch on the  final controller’s PRM frequency for their specified runway.  The final monitor controller has override capability on  their PRM frequency. In that way, if the common tower  frequency is blocked, the monitor controller’s instructions  will be heard by the pilot on the monitor controller’s PRM  frequency. Pilot training is prescribed and required for  pilots prior to using the PRM procedures. The FAA PRM  website (http://www.faa.gov/training_testing/ training/  prm/) contains training information for PRM approaches  and hosts PRM training materials for download or viewing  online.”  When pilots or flight crews wish to decline a PRM approach,  ATC must be notified immediately and the flight will be  transitioned into the area at the convenience of ATC. Pilots  who are unable to accept a PRM approach may be subject  to delays.  The approach chart for the PRM approach requires review of  the accompanying AAUP page, which outlines pilot, aircraft,  and procedure requirements necessary to participate in  PRM operations. [Figure 4-48] Pilots need to be aware  of the differences associated with this type of approach.  Differences, as compared to other simultaneous approaches,  are listed below:  Simultaneous Independent Approaches  Simultaneous Close Parallel Precision Runway  Monitor (PRM) Approaches  • Immediately follow break out instructions as soon 4-65