Study of the geometry of a dependent approach procedure to closely spaced parallel runways

The loss of visual flight rules under instrument conditions results in a substantial loss of throughput to airports with very closely spaced parallel runways (less than 2500 ft). At San Francisco International Airport (SFO), for example, runways 28L and 28R are separated by 750 feet. Use of visual flight rules to runways 28L and 28R allows a typical arrival throughput of approximately 60 landings per hour. During instrument meteorological conditions, a single runway is used, and the arrival throughput is reduced to 30 landings per hour. This loss of throughput can result in significant delays for aircraft intending to arrive at SFO, and can cause backups that have national airspace system (NAS) repercussions as well. To address this loss of throughput during instrument conditions, United Airlines has proposed a procedure for a dependent approach into San Francisco International Airport (SFO). Aircraft would be paired for approach in close longitudinal proximity. Longitudinal separation between paired aircraft would be established and maintained by the use of Automatic Dependent Surveillance Broadcast (ADS-B) combined with a Cockpit Display of Traffic Information (CDTI). The in-trail aircraft of a pair would be required to maintain specific longitudinal separations through the approach for both wake avoidance and collision avoidance purposes. Longitudinal separation between aircraft pairs would be based on standard instrument flight rule separations.