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An algorithm is presented for computing vertical resolution maneuvers to resolve imminent air traffic conflicts in which loss of separation could occur within two minutes. Several procedures are used, including rejection of altitude amendments that could cause a conflict, temporary altitudes, step altitudes, and critical-level-off confirmation. These methods are tested on archived data from 100 actual operational errors (loss of separation due to controller error), which tend to be more difficult to detect and resolve than routine conflicts that get resolved successfully. Successful resolution was achieved in simulation for 84 of them using vertical maneuvers only. Augmented altitude amendments are then added to the input files to simulate altitude amendments that should have been entered by the controller but were not, or to correct amendments to make them consistent with the pilot's understanding. The number of successful resolutions increased to 94 of the 100 cases. The reasons for the failures are discussed.

This paper presents the framework of a new microscopic simulation model called Virginia Tech airfield simulation model (VTASIM) developed to study aircraft operations at airports. The model presented is designed and built under the concept of the time-based simulation model in which aircraft states are updated at fixed time intervals. By employing a vehicle-following model, VTASIM can portray aircraft movements on taxiways in great detail and with more accuracy than traditional discrete-event based airport simulation models. In order to find efficient taxiing routes between gates and runways, the model employs a time-dependent shortest path algorithm. Another unique feature of the model is its ability to capture the communication activities between pilots and controllers, which may cause delays in airfield operations especially at busy airports. This paper describes the methods and the structure of the model. The model is applied to Ronald Reagan Washington National Airport to illustrate its functionality. CE Database subject headings: Simulation models; Airports and airfields; Air traffic; Computer programming; Time factors.

Very light jets constitute a class of three to eight passenger turbofan-powered aircraft that will enter service in 2006 and will need to be integrated into the National Airspace System. An aircraft performance analysis showed similarities between the predicted performance and capabilities of very light jets and the performance of existing light jets. Based on this, an analysis of operating patterns of existing light jets was used to predict how very light jets will be operated. Using 396 days of traffic data from the FAA enhanced traffic management system, the operating patterns of existing light jets were analyzed. It was found that 64% of all the flights flown by light jets had their origin, destination, or both within the top 23 regional airport systems in the continental United States. This concentration of light jet traffic was found in areas of the air transportation system that are currently exhibiting dense traffic and capacity constraints. The structure of the network of routes flown by existing light jets was also studied and a model of network growth was developed. It is anticipated that this concentration will persist with emerging very light jet traffic. This concentration of traffic at key areas in the system will have implications for air traffic control management and airport activity. For regional airport systems, core airports are expected to saturate and, reliever airports will become critical for accommodating traffic demand. The entry of very light jets will increase the traffic load at the terminal airspace: terminal radar approach control. These impacts need to be taken into account to allow a successful integration of these aircraft in the National Airspace System.

This paper examines issues underpinning the potential move in aviation away fi'om real speech radiotelephony (R/T) communications towards datalink communications involving text and synthetic speech communications. Using a novel air traffic control (ATC) task, two experiments are reported. Experiment 1 compared the use of speech and text while Experiment 2 compared the use of real and synthetic speech communications. Results indicated that generally there were no significant differences between speech and text communications and that either type could be used without any main effects on performance. However, a number of specific differences were observed across the different phases of the scenarios indicating that workload levels may be more varied when speech communications are used. Experiment 2 illustrated that participants placed a greater level of trust in real speech than synthetic speech, and trusted true communications more than false communications (regardless of whether they were real or synthetic voices). The findings are considered in terms of datalink initiatives for future air traffic management, the importance placed on real speech R/T communications, and the need to develop more natural synthetic speech in this application area. Keywords: Datalink; Air traffic management; Flightdeck of the future; Air traffic control; Speech; Text; Communications

Expanding services to some of the 4900 airports not currently served by scheduled air carriers can potentially ease traffic congestion and reduce flight delays at major airports. By developing new avionics and procedures for approach and landing during instrument meteorological conditions, the NASA small aircraft transportation system program demonstrated higher traffic volume general aviation operations at noncontrolled airports, without assistance from air traffic control. This paper proposes revised minimum separations and automated sequencing to help general aviation pilots maintain self-separation and make proper approach timing decisions in a self-controlled airport environment. Total holding time is the measure of merit, and evaluation was conducted with multiple pilots flying simultaneously in a real-time distributed simulation environment. A rudimentary human factors analysis was also conducted to determine the benefits of shifting some spacing functions from the pilot to the onboard systems, for the purpose of reduction in pilot workload. The effect of increased automation on pilot tracking performance was also measured. Results presented in the paper show that the proposed modifications can provide significant reductions in total holding time, thereby avoiding potential bottlenecks and improving efficiency. Reduction in pilot workload was observed, and low-time pilots exhibited improved tracking performance. DOI: 10.2514/1.20637

Methodology for construction and implementation of in-flight trajectory management systems for vehicles participating in future small aircraft transportation systems is considered. The small aircraft transportation systems concept is a modern regional airspace system exploiting integration of key airborne and ground infrastructure technologies to facilitate efficiency and safety improved operations at noncontrolled public-use airports. An area where new trajectory management guidance systems may provide significant benefit is the transition between en route flight and the terminal airspace boundary, or possibly interior terminal airspace navigation fix points, for both approach and departure. Energy state theory and space-time curve geometry are investigated as tools for tailoring time to interface or time to land with traffic constraints. Results imply the trajectory management concepts offer significant design freedom to tailor flight paths and vehicle states for optimum performance and safety in real time. This strategy will also tend to provide practical trajectory profiles while avoiding heavy computational burdens. DOI: 10.2514/1.20960

This paper summarizes findings from the Small Aircraft Transportation System Higher Volume Operations Flight Experiment. The higher volume operations concept improves efficiency at nontowered, nonradar airports in instrument meteorological conditions. The success of the higher volume operations concept is based on pilot acceptability as determined through objective and subjective assessments when compared with the procedural control operations in use today at nontowered, nonradar-controlled airfields in instrument meteorological conditions. Flight experiment data indicate that the concept is viable. The experiment, flown on a general aviation aircraft, used a subset of the Higher Volume Operations Simulation Experiment scenarios and evaluation pilots to validate the simulation experiment results. Results reveal that all 12 low-time instrument-rated pilots preferred Small Aircraft Transportation System Higher Volume Operations when compared with current procedural separation operations. These pilots also flew the higher volume operations procedures safely and proficiently without additional workload in comparison to today's system. Detailed results of pilot flight technical error and their subjective assessments of workload and situation awareness are presented. DOI: 10.2514/1.20403

The Federal Aviation Administration (FAA) is updating the air traffic management (ATM) system to deal with the increasing aviation traffic. The FAA is modernizing the ATM equipment by replacing the ground-based automation equipment and phasing out the ground-based navigation sites. This automation will increase the rate of arriving and departing aircraft and enable free flight. Air-to-ground digital data links will replace air-to-ground voice communication and the space-based Global Positioning System will be used for navigation.

Oceanic Air Traffic Control (ATC) will be advanced during the first two decades of the 21st century to cope with the expected rise in air traffic. Satellites will help in communications, navigation. New hardware and software will be used in the cockpit and on the ground. The FAA will employ several parts of its advanced oceanic automation systems at its oceanic ATC facilities during 1996 to 1999.

Stream Option Manager (SOM) is a proposed concept for automated integration of aircraft separation, merging and stream management, using linear programming techniques. It was developed as part of a research and development initiative for air traffic control (ATC) automation concepts, sponsored by the Federal Aviation Administration (FAA) and performed by MITRE Corporation. SOM is research; it has not been approved by the FAA for use in future ATC. SOM's purpose is to resolve possible problems involving multiple aircraft with given flight paths. Each aircraft must be separated by a minimum distance from every other aircraft at all times, and certain sets of aircraft (e.g., those about to land at a particular airport) must be merged or metered (lined up, or separated in trail by a given distance). Aircraft in sets called streams must be separated in the along-route direction at all times. Each aircraft is also subject to certain speed limits. Given the pilot-preferred flight paths, and separation, metering, stream, and speed requirements, SOM finds modified flight paths for each aircraft that satisfy all the requirements yet stay as close as possible to the pilot-preferred paths. SOM's algorithm is to represent the (x, y, z) positions of each aircraft at future times as variables in a linear program. The requirements are expressed or approximated by linear inequalities or equalities. Pilot preferences are approximated by a linear objective function. The SOM algorithm has been implemented successfully in a prototype simulation in 2D. Scenarios with up to 15 aircraft and 24 separation and/or merging problems have been resolved.