One of the FAA’s less publicized programs to increase airport capacity is the gradual introduction of the precision runway monitor (PRM). Currently commissioned at Minneapolis, St. Louis and Philadelphia, and soon to come online at San Francisco and New York JFK, the PRM allows aircraft to make simultaneous independent approaches to closely spaced dual or triple parallel, or dual converging, runways.
Currently, without a PRM, simultaneous ILS approaches are not permitted in IMC when the centerlines of adjacent parallel runways are less than 4,300 ft apart. This rule came about after analysis showed that there was a statistical possibility, even though remote, that two aircraft approaching simultaneously could inadvertently deviate toward each other and, having no accurate knowledge of the other’s position, create a potentially hazardous situation. In VMC, of course, when the other traffic is clearly in sight, it’s a quite different situation, as operators into San Francisco’s 28L and 28R–separated by just 750 ft–are well aware.
More In ATC
