Paired approaches to closely spaced runways: Results of pilot and ATC simulation

Closely spaced parallel runways (CSPRs), i.e.: runways spaced less than 2500 feet and as close as 700 feet, can be used for simultaneous arrivals when visual approaches can be conducted to both of the runways. Under current procedures, when the ceiling drops below a specified level in visual meteorological conditions (VMC), instrument approaches to both runways are not permitted, essentially reducing arrival capacity by half. The paired approach (PA) procedure is designed to enable continued use of both runways, even in instrument meteorological conditions (IMC), mitigating the loss of capacity. The Federal Aviation Administration is developing this capability as part of its NextGen initiative for deployment in the mid-term time frame. In the PA procedure, Air Traffic Control (ATC) pairs eligible aircraft and places them on a final approach course with required altitude separation and within a required longitudinal tolerance. The PA application on the trailing airplane computes and displays speed commands to achieve and maintain a desired spacing goal behind the lead, protecting against potential blunder by lead, or encounter with lead wake. The system also provides alerts if the safe zone is violated. The PA application requires Automatic Dependent Surveillance-Broadcast (ADS-B) position and velocity data from the leading aircraft and knowledge of ownship and lead planned final approach speeds (PFAS) in order to compute the interval required. This paper reports results of two real time simulations designed to assess the initial feasibility of flight crews and controllers, respectively, to conduct the tasks required by the paired approach procedure. Details of the speed guidance algorithms, displays, ATC capabilities, and ATC and flight crew procedures are provided. In both simulations, the flight environment of approaches to San Francisco International Airport was simulated to reflect the operations desired by the procedure. In the first simulation, 10 subject pil- ts with experience in operations at San Francisco International Airport participated in the study. In the second simulation, five controllers and supervisors from the Northern California TRACON (NCT) participated. All were experienced in the closely spaced parallel runway operations commonly used at the San Francisco International Airport (KSFO). Two controllers were current and qualified in the airspace and the rest were supervisory controllers with extensive experience in NCT operations for arrivals into KSFO. The simulation results indicated both the pilots and the controllers were able to perform the tasks expected of them for the conduct of the procedure well within acceptable workload limits. Subjective results for workload and objective results for achieved spacing and capacity are reported. The results suggest a steady state capacity of over 45 aircraft per hour should be possible with this procedure down to Category I minima. Recommendations for next steps are provided.