Anand D. Mundra

Potential benefits of a Paired Approach procedure to closely spaced parallel runways in instrument and marginal visual conditions

This paper discusses a concept called ldquopaired approachesrdquo which is designed to facilitate approaches to closely spaced parallel runways (CSPRs) - i.e., runways separated by 700 ft to 2500 ft, in instrument meteorological conditions (IMC). Such runway pairs experience a significant loss of arrival capacity during IMC and marginal visual conditions because currently, runway pairs like this can only be used for simultaneous arrivals when pilots can provide visual separation. The basic procedure design, operations concept, the required cockpit tools and initial feasibility of the paired approach concept were developed in the 1990psilas and included real time pilot and controller simulations and evaluations. These initial simulations indicated that the paired approach procedure was feasible for both pilots and controllers. This paper focuses on the potential benefits of the procedure. It first provides a brief review of the procedure and prior work. It discusses the variety of procedures currently available for parallel runways, and discusses the magnitude of the delay problem in the National Airspace System (NAS) not addressed by any of these existing procedures or procedures under development, but which the proposed paired approach procedure would address. It presents the potential capacity gain from the paired approach procedure at two representative major airports, and the percentage of time that the procedure could be available. The paper also presents a brief summary of potential infrastructure requirements for implementing the procedure, and concludes by providing an outline of the research and development needed to establish its deployment in the NAS.

Self-separation corridors

This paper describes a concept called self-separation corridors (SSCs). This is an automatic dependent surveillance - broadcast (ADS-B) application that establishes self-separation corridors in high-altitude en route airspace. This concept enables traffic managers to create high-density corridors along specific airspace segments for suitably equipped aircraft for use during heavy sector congestion or limited access due to severe weather. An SSC is defined as a set of parallel routes in close proximity to one another, in which crewmembers accept responsibility for separation from other aircraft in the corridor. While in an SSC, pilots use on-board instrumentation to ensure proper spacing behind the lead aircraft. The on-board instrumentation also provides protection from deviations or blunders by aircraft on the parallel routes. This paper describes the primary SSC concept, proposed solutions, and suggested areas of research.

Evaluation of Near-Term Applications for ADS-B/CDTI Implementation

Two studies are reported that evaluated near-term terminal and oceanic applications for ADS-B/CDTI implementation. A brief description of each application is provided with an emphasis on how a Cockpit Display of Traffic Information (CDTI) capability might help to enhance their operations. In experiment 1, sixteen line pilots flew eight terminal visual approach scenarios with target speed cues and ground track vectors presented on a CDTI. Performance measures revealed closer spacing with the CDTI and a safety benefit with respect to enhanced awareness of proximate traffic speed reductions. In experiment 2, eight additional line pilots flew six oceanic scenarios using a CDTI feature set similar to that used in experiment 1. The scenarios were based on the current In-Trial Climb/ln-Trail Descent (ITC/ITD) oceanic procedures and were modified slightly to take advantage of potential CDTI capabilities. The implications of these findings with respect to the current National Airspace System (MAS) are discussed.

Air ground collaboration through delegated separation: Application for departures and arrivals

Delegated separation is an air traffic management capability in which responsibility for separation from one or more aircraft is assigned to the flight crew by an air traffic controller, in specific tactical situations, to improve operational efficiency in the National Airspace System (NAS). In this human-in-the-loop (HITL) simulation, 8 airline pilots flew departure and arrival scenarios while using a cockpit display of traffic information to maintain separation from a lead airplane. Pilots reported that workload for the departure and arrival tasks was well within acceptable limits and that they would be willing to perform this task with the CDTI as implemented in this study. Objective spacing performance showed reduced spacing compared to the baseline condition where controllers retained separation responsibility. The observed baseline and delegated separation spacing distributions were applied to a fast time simulation to estimate the departure throughput benefit that may result from the application of these procedures. The estimated improvement in arrival rate was about 3 per hour for single runway arrivals, and NN about 4 per hour for single runway departures. Implications for NextGen operational improvement are discussed.

Feasibility analyses for paired approach procedures for closely spaced parallel runways

In current air traffic operations in the U.S., closely spaced parallel runways (CSPRs) separated by less than 2500 feet (ft) can be used to conduct simultaneous parallel operations using visual separation. Once below visual approach minima, such dual runway operations are no longer possible. To address this loss of throughput, several concepts are currently under consideration. This paper discusses a “paired approach” concept which enables use of CSPRs down to Category I and II approach minima. The paper documents Monte Carlo analyses on the feasibility and trade-offs of paired approach procedure variants with and without an escape maneuver. It concludes that both procedure variations require echelon staggering for most airports with runway centerline (RCL) separations below 2500 ft and provides window parameters required for an acceptable Target Level of Safety (TLS). It shows that a value of up to 4000 ft for this echelon spacing is adequate for most CSPRs for an adverse wind threshold of 10 knots; the specific value depending on the concept variation and geometry. Other findings include the ability to achieve abeam positioning with an escape procedure for several runway configurations. Many procedural combinations examined are capable of pairing 95% to 100% of aircraft. Additionally, this paper presents an analysis of wake encounter risk during blunders. The analysis results suggest the non-escape procedure variant has a high probability of wake vortex encounter during blunder. On the other hand, the escape procedure variant with a delay in breakout of 8 seconds or less appears to provide protection from wake encounters even during a blunder. Preliminary considerations for surveillance requirements are presented, including optional 1090 MHz Extended Squitter (1090ES) Automatic Dependent Surveillance-Broadcast (ADS-B) messages and fields that may support the escape procedure variation.

Converging Runway Display Aid in the NAS: Challenges, successes and outlook

The Converging Runway Display Aid (CRDA) is a simple, passive visualization tool that has been available in the terminal automation systems in the National Airspace System (NAS) for about 20 years. CRDA is geared towards simplifying the use of intersecting or converging approaches and paths. Its simplicity has often prompted aviation enthusiasts to hypothesize wider use in the NAS to improve both the safety and capacity of the system. Even so, the tool has not realized wide-spread use in the NAS. Recently, RTCA Task Force V recommended that it be implemented at more sites in the NAS. The Federal Aviation Administration (FAA) has incorporated its wider use as one of its flight plan goals. This has helped its deployment at several new key sites. This paper explores basic factors that contribute to the challenges in deploying CRDA and how they could be addressed. It presents the example of the recent CRDA deployment at Newark Liberty International Airport (EWR) to document and illustrate how this process can and has been applied successfully. It describes the impact of the CRDA use at EWR by analyzing one year of operational data. It concludes with a report on the outlook for CRDA deployment in the NAS.

Predicting Aircraft Approach Speeds for Enhancing Airport Capacity

Today, standards for aircraft arrival separation over the runway threshold must be satisfied regardless of the approach speeds of aircraft as they cross the landing threshold. Aircraft landing speeds vary widely. If expected aircraft speeds could be predicted to some accuracy, more efficient procedures and standards could perhaps be developed. This paper describes examples of airport capacity enhancement concepts that utilize the ability to predict expected aircraft landing speeds. It describes factors that affect aircraft landing speeds such as aircraft weight, design, environmental factors, airline guidance, and individual pilot judgment. It presents an analysis of Flight Operational Quality Assurance (FOQA) data gathered from an airline as related to the ability to predict aircraft approach speeds, to illustrate the possibility of applying this knowledge to concepts of increasing airport capacity. Finally it provides an outline of the main components of the operational implications of using such a method of predicting and utilizing landing speeds.

Wind dependent concepts for wake avoidance: a comparative analysis of capacity benefits and implementation risks

The FAA and NASA are jointly embarking on a multiphased research and development program to develop and implement wake vortex avoidance solutions that can safely reduce separations and improve capacity at airports in the NAS. Many options have been proposed by the wake turbulence community and it is necessary to focus research efforts on the most promising solutions. As part of its WakeVAS initiative, NASA has conducted an investigation of the research difficulty and cost for candidate operational enhancements through a Conops evaluation team (CET). This team included participation by stakeholders from many research, system engineering, system development, pilot, and controller organizations. The operational enhancements that were evaluated included wind-dependent concepts for arrivals to closely spaced parallel runways (CSPRs), departures from CSPRs operated as a single runway, arrivals to single runways, and departures from single runways. To complement this work and help provide the information necessary for NASA to focus their research program toward the most promising concepts, MITRE/CAASD performed an analysis of the potential capacity benefit, opportunity for application, and implementation risk for each arrival and departure concept evaluated by the CET. This paper provides an overview of the direction in which NASA research will proceed and the analysis results that help support this decision.

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 pilots 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.

Capacity enhancements in IMC for converging configurations with down-link of aircraft expected final approach speeds

This paper describes procedures for facilitating increased airport capacity in instrument meteorological conditions for airports with converging and triple converging runway configurations. The concept utilizes existing standards and procedures authorized for dependent converging approaches. It proposes control of the relative approach spacing on two and three runway converging configurations and facilitates safe runway approaches, including missed approaches, by utilizing the down-link of aircraft expected final approach speeds. ADS-B (automatic dependent surveillance broadcast) or CPDLC (controller pilot data link communications) may be capable of facilitating such down-link of required data. The paper presents potential throughput gains, discusses potential controller tools for implementation in the near term, discusses potential certification and authorization requirements, and summarizes required further work to determine the feasibility of the concept and the development required for operational deployment.