are outlined and listed by specific airport.  Regardless of the type of radar approach in use, ATC  monitors aircraft position and issues specific heading  and altitude information throughout the entire approach.  Particularly, lost communications procedures should  be briefed prior to execution to ensure pilots have a  comprehensive understanding of ATC expectations if radio  communication were lost. ATC also provides additional  information concerning weather and missed approach  instructions when beginning a radar approach. [Figure  4-56] PAR provides both vertical and lateral guidance, as well as  range, much like an ILS, making it the most precise radar  approach available. The radar approach, however, is not  able to provide visual approach indications in the flight  deck. This requires the flight crew to listen and comply  with controller instructions. PAR approaches are rare, with  most of the approaches used in a military setting; any  opportunity to practice this type of approach is beneficial  to any flight crew.  The final approach course of a PAR approach is normally  aligned with the runway centerline, and the associated  glideslope is typically no less than 2.5° and no more than  3°. Obstacle clearance for the final approach area is based  on the particular established glideslope angle and the  exact formula is outlined in FAA Order 8260.3. [Figure 4-57]  ASR approaches are typically only approved when  necessitated for an ATC operational requirement or in an  unusual or emergency situation. This type of radar only  provides heading and range information, although the  controller can advise the pilot of the altitude where the  aircraft should be based on the distance from the runway.  An ASR approach procedure can be established at any radar  Airport Surveillance Radar (ASR)  Precision Approach Radar (PAR)  27L 27R 18L 18R No transgression zone  23L 23R No transgression zone  Simultaneous Dependent Approaches  • Runway centerlines spaced 2,500 feet or greater,  except for specific procedures approved with less  runway spacing  • Final monitor controller  NOT  required  Independent Parallel Approaches  Simultaneous Independent  Approaches  • Runway centerlines spaced 4,300  feet or greater (duals or triples)  • Final monitor controllers required  Simultaneous Independent Close  Parallel Approaches  • Runway centerlines spaced less than  4,300 feet (duals or triples)  • Final monitor controllers required  “PRM” in the approach identification  27  27  • Staggered approaches (diagonal separation) with the  adjacent final approach course  • Standard radar separation between aircraft on the  same final approach course  Simultaneous Dependent Approach Separation  Diagonal separation  Standard separation  Figure 4-43. Classification of Simultaneous Parallel Approaches.  4-72