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Safe operations in the National Airspace System (NAS) require understanding the individual failure space of avionics technologies, the joint failure space as faults propagate within the distributed environment, and a framework to quantify safety. This paper focuses on the last point, in which the safety assessment framework consists of a set of safety metrics: Loss of Separation (LoS), Traffic Collision Avoidance System (TCAS) II, NASA's Well Clear (WC), and a novel metric called Critical Pair Identification (CPI). The fault space considers the surveillance device Automatic Dependent Surveillance-Broadcast (ADS-B). Using an agent-based model, we demonstrate the framework with a two aircraft example of a perpendicular crossing, in which each aircraft implements self-separation via NASA's Chorus software. We compare three different variations of the crossing: (a) Chorus is absent (open loop), (b) Chorus is operational (closed loop), and (c) Chorus is operational, but one aircraft broadcasts a faulty ADS-B message with a +0.05 deg longitude error (closed loop with a fault). Our results show that the included set of safety metrics cover a variety of dimensions of state information, but may be an overdetermined system for assessing safety. The set or subset appears capable of assessing safety, but requires a detailed case study for understanding faults and their propagating effects within an arbitrary scenario in the NAS.

A method for modeling complex human-integrated systems is presented, in which “critical situations,” which are system configurations where a possible but unexpected control action by an agent in the system can result in an accident in less time than agents need to detect and respond, can be identified. The models are developed from the perspective of the system, and can be demonstrated to be complete. It is argued that, in order to ensure a system is safe, these situations must be controlled, but in many cases such an assurance would render the system impractical or even infeasible. Lastly, it is shown how this method can be used to evaluate the effectiveness of a system, in addition to its safety.

Performance breakdown (PB) has been anecdotally described as a state where the human operator “loses control of context” and “cannot maintain required task performance.” Preventing such a decline in performance is critical to assure the safety and reliability of human-integrated systems, and therefore PB could be useful as a point at which automation can be applied to support human performance. However, PB has never been scientifically defined or empirically demonstrated. Moreover, there is no validated objective way of detecting such a state or the transition to that state. The purpose of this work is: 1) to empirically demonstrate a PB state, and 2) to develop an objective way of detecting such a state. This paper defines PB and proposes an objective method for its detection.

This paper introduces the concepts of metroplex and flexible flight. We focus on the routing part of a complete flexible flight operation. The authors establish a network data structure based on which the optimal routing algorithm is developed for the flexible flights which fly from their original airports to destination metroplexes. Moreover, the metroplex routing algorithm is performed under the dynamic en route traffic congestion constraint, which is rarely studied in literature. We also propose an integrated model which combines the routing and scheduling according to the practical feasible air traffic control procedure. Besides the optimal metroplex routing and the scheduling, we also brief several other functional blocks in the integrated model and illustrate the data flow inside the entire system. Finally we present the simulation results which verify the positive effect of the optimal metroplex routing algorithm and show that the total delay reduction by the integrated system is considerable.

Stream management is a novel air traffic control operational concept in which controllers control streams of aircraft that are functionally equivalent, rather than being responsible for “aircraft in airspace.” One of the potential benefits of stream management is workload reduction for the same amount of aircraft handled. An adaptation of the dynamic density workload measure was used to evaluate stream management operations against current sector based control. This evaluation is completed using FACET software and ASDI data. Stream visualizations and data analysis demonstrate the advantages of stream operations.

A framework has been developed that is focused on providing guidance for the design of procedures and checklists. The framework identifies characteristics of the procedure and environment that could influence procedure following behavior, and formal definitions of those factors are introduced. In addition, tradeoffs between the factors that can be controlled by procedure designers are described. This framework, along with the formal definitions, should help enable provide more concrete guidance for researchers and practitioners concerning the design of procedures for human-machine systems.

A recent experiment has produced evidence that information displays to support the execution of operational procedures can aid performance and increase situation awareness. The experiment involved private pilots flying instrument approach on a desktop flight simulator. The pilots flew six approaches which varied by the entry maneuver required and the presence of dynamic "procedure context" information on an electronic instrument approach display. After each approach subjects were asked a number of questions which tested recall of their adherence to procedure, and this recall was then compared to their control actions while flying the simulator. These two measures were used as an indication of the subjects' situation awareness. The subjects' actual conformance to procedure and their ability to fly a stabilized approach were used as performance measures. All of these measures were significantly affected by the use of the display enhanced with procedure context information. The importance of this finding is reflected in the observation that the control of most systems in safety critical environments is highly proceduralized. While the extent to which procedures impact the work domain has been recognized, there has been little work on understanding how pilots use procedure information or on how to support procedure following. This study provides insight into the use of procedure information during instrument approaches, and suggests a design methodology that may be used for creating information displays to support procedure following. The intent of such displays is to assist operators in not only following operational procedures, but also in comprehending the context of procedures, enabling them to understand why, when, and how to deviate from procedures if necessary.

Changes to air traffic control procedures and requirements for on-board automated systems can be investigated by examining the dynamics of collision potential between two proximate aircraft along closely spaced parallel approaches (CSPA). For these aircraft, there exist relative aircraft positions and trajectories that can-and cannot-provide separation assurance and wake avoidance. These relative positions comprise a "safe zone" (an area in which separation assurance and wake is provided), which depends on aircraft dynamics, pilot performance, alerting system performance, wake transport mechanics, and a determination about the blunders for which protection should be afforded. A systematic evaluation of the dynamics of the safe zone was performed, with implications for the design of paired CSPA procedures.