Simultaneous close parallel ILS approaches are enabled through the implementation of special precision runway monitoring (PRM) equipment operated by ATC at certain airfields for specific runways, titled in 14 CFR Part 97 as “ILS PRM.” ILS PRM approaches are conducted between 4,299 and 3,000 feet parallel runway spacing. Runways 3,400 feet or greater apart utilize two parallel ILS courses, aligned with the runway centerlines (RCLs). For runways spaced less than 3,400 feet, one ILS is offset 2.5° to 3.0°.
