Abstract: The authors present a simple analytic model that explicitly separates the controllable factors that influence delays and propagation of delays in the National Airspace System (NAS) from those factors that are random variables in a given scenario. In this paper, the controllable type of factor is called "fixed" and the random type of factor is called "variable." Simple relationship exists among the fixed and variable factors that characterize NAS delay propagation. We show how the model can be applied to better understand delay propagation from specific NAS airports, especially the effects of flight schedule parameters on measured delay. Recorded data from actual NAS operations are used to derive estimates on key model parameters and to show how delay characteristics vary among different airports.

Abstract: Controller-pilot very high frequency (VHF) voice communication in air traffic control (ATC) relies on amplitude modulation by a carrier frequency of the transmitted analogue voice pattern. This technology is known for its poor voice quality and to be highly sensitive for any kind of noise on the transmission/reception path. On this party-line, pilots have to identify themselves with their call-sign. Human's imperfections in speaking and understanding added to the low channel quality may cause problems to identify without any ambiguity of an aircraft (AC) message without any ambiguity for the controller. The proposed aircraft identification tag (AIT) techniques aim at covering this security lag. The automatic insertion of the supplementary AIT in the transmitted voice communication secures and simplifies the association of a voice message to the specific AC. Supplementary safety increase may be achieved by the mental reinforcement of the audible stimulus (pilot's voice) with a simultaneous visual stimulus in form of e.g. highlighted AC track on the radar screen. Further security increase may be attended from the fact that fake AC VHF transmissions (e.g. jokers, terrorists, ...) becomes mode difficult or even may be impossible by special watermark coding. Simple airfield structures and oceanic high frequency (HF) communication could benefit from such a system, too. AIT technique, therefore, uses proven audio watermark techniques (e.g. used for intellectual property rights for audio CD and digital video). These watermarks are introduced in the voice signal such that, the watermarks are not noticeable. AC and ATC VHF-transceiver need no change. The technique is adapted to the reduced VHF channel spacing of 8.33 kHz. The prototype demonstrator shows very high robustness with a watermark datalink capacity of about 100 bits

Abstract: The paper discusses mode confusion analysis of a flight guidance system using formal methods. The paper describes the use of automated analysis tools, such as model-checkers and theorem provers, to search for potential sources of mode confusion in a representative specification of the mode logic of a Flight Guidance System.

Abstract: An Unmanned Autonomous Vehicle (UAV) is equipped with a nose-mounted camera capable of pan and tilt rotation for the observation of ground targets. The two camera angles are adjusted automatically in order to keep the target in the camera's field of view. While the camera actuators are fast enough to keep up with vehicle motion, the limited range of the camera angles leads to the target getting out of sight. Therefore, target exposure is affected by wind. Furthermore, the relative position of the sun can lead to glare and image overexposure. While the effect of wind can be improved by commanding a sideslip angle, image overexposure is avoided by keeping the vehicle between sun and target. Thus, it is desirable of define maneuvers that result in maximum target exposure, and provide guidance laws to allow path following for these maneuvers. This paper presents initial results, obtained based on circular and elliptical maneuvers. The results were generated using an accurate non-linear Aerosonde UAV representation and environmental dynamic models. Simulated GPS data was used for the path following guidance. The complete path about the target at constant altitude and airspeed is specified simply by the desired orbital segment and course reversals at the segment boundaries. With camera pan limited to the forward 180d, this can achieve long term observation. A camera with minor 'look-back' range can provide continuous observation in a maneuver that employs both circular and elliptical segments.

Abstract: Advanced noise abatement procedures such as the three degree decelerating approach (TDDA) can significantly reduce the noise impact of aircraft during approach. With existing aircraft performance and flight operation uncertainties, however, implementation of the TDDA would require an increase in the initial separation between aircraft that would result in significant reduction in runway capacity. Simulation results indicate that this reduction in runway capacity is on the order of 50%, which is not acceptable for any procedure that must be used n high traffic scenarios. In this paper, we introduce a modified three degree decelerating approach (MTDDA) that provides the same noise benefits as the TDDA with little or no loss in capacity relative to conventional approach procedures. Simulation results indicate that for a representative aircraft mix, the capacity of the MTDDA is within 2% less of the maximum possible capacity using conventional approach procedures.

Abstract: In this paper, the testbed which is built upon the Multi-Modal Immersive Intelligent Interface for Remote Operation (MIIIRO) to support UAV control is presented. The testbed implements a client/server architecture in which UAV operations are simulated on a server that maintains the states of the UAVs. The testbed supports both the route planning and execution of human factors experiments.

Abstract: This paper describes the development of an application of Artificial Intelligence (AI) for Unmanned Aerial Vehicle (UAV) control. The project was done as part of the requirements for a class in AI at NOVA Southeastern University and a beginning project at NASA Wallops Flight Facility for a resilient, robust, and intelligent UAV flight control system. A method is outlined which allows a base level application for applying an Artificial Intelligence method, Fuzzy Logic, to aspects of Control Logic for UAV flight. One element of UAV flight, automated altitude hold, has been implemented and preliminary results displayed.

Abstract: We have developed a formal, executable model of the requirements for portions of the vertical navigation (VNAV) function of a flight management system and have conducted a software safety analysis on the model In particular, we have performed a functional hazard assessment in order to identify the potentially hazardous conditions associated with the VNAV function We then conducted a fault tree analysis and a failure mode effects analysis in order to identify the general categories of errors that relate to safety By comparing these general categories to the system architecture, we were able to develop a list of specific safety requirements for the VNAV function We then used formal methods tools to verify that the VNAV model satisfied the safety requirements We provide an overview of the safety analysis performed to date on the VNAV model, and compare and contrast these results to a similar analysis performed on the mode logic of a flight guidance system Because the flight guidance system model was constructed entirely from Boolean logic it was easily analyzable with model checkers The VNAV model involves continuous logic, (altitude and position values), and requires the use of theorem provers The results of this analysis provide insight into the feasibility of integrating formal methods tools into the safety analysis process in a model based development environment

Abstract: The implementation of Synthetic Vision Systems (SVS) has posed a number of design questions. One of these questions is centered on the minimum required resolution of the Digital Elevation Model (DEM) database. Although a very detailed database may be desirable from a product appeal point of view or for improved representation of the elevation information., there simply may not be enough processing power available to render the high number of polygons with a texture at a high frame rate. Also, there may be a marginal rate of return of increasing DEM resolution when it comes to pilot performance, workload and situational awareness (SA). Another important issue is the choice of texture used on the synthetic terrain images. In the past, researchers and designers have debated about the relative merits of different textures (e.g., photo-realistic, elevation coloring, checkerboard). A third issue concerns the shading model, which may influence performance or SA through the potential for depth perception cues. The Operator Performance Laboratory (OPL) at the University of Iowa conducted a series of three experiments to assess human performance as a function of DEM resolution, terrain texture and shading methods. The DEM resolutions that were studied ranged from 3 arc seconds (best resolution) to 30 arc seconds (worst resolution). Textures included wire-frame (green on black), checkerboard, elevation coloring, contour lines, photo-realistic, and a non-textured plain brown color. Shading models included no shading, Gouraud shading, and flat shading. Part I involved an image identification task, in which the ability of non-pilot participants to recognize terrain features for static (Experiment 1) and dynamic terrain images (Experiment 2) was measured. Part II (Experiment 3) measured pilot performance by cross track error when na

Abstract: The Synthetic Vision Systems General Aviation (SVS-GA) element of NASA's Aviation Safety Program is developing technology to eliminate low visibility induced General Aviation (GA) accidents through the application of synthetic vision techniques. SVS displays present computer generated 3-dimensional imagery of the surrounding terrain to greatly enhance pilot's situation awareness (SA), reducing or eliminating Controlled Flight into Terrain (CFIT), as well as Low-Visibility Loss of Control (LVLOC) accidents. In addition to substantial safety benefits, SVS displays have many potential operational benefits that can lead to flight in instrument meteorological conditions (IMC) resembling those conducted in visual meteorological conditions (VMC). Potential benefits could include lower landing minimums, more approach options, reduced training time, etc. SVS conducted research will develop display concepts providing the pilot with an unobstructed view of the outside terrain, regardless of weather conditions and time of day. A critical component of SVS displays is the appropriate presentation of terrain to the pilot. The relationship between the realism of the terrain presentation and resulting enhancements of pilot SA and pilot performance has been largely undefined. Comprised of coordinated simulation and flight test efforts, the terrain portrayal for head-down displays (TP-HDD) test series examined the effects of two primary elements of terrain portrayal: variations of digital elevation model (DEM) resolution and terrain texturing. Variations in DEM resolution ranged from sparsely spaced (30 arc-sec/2,953ft) to very closely spaced data (1 arc-sec/98 ft). Variations in texture involved three primary methods: constant color, elevation-based generic, and photo-realistic, along with a secondary depth cue enhancer in the form of a fishnet grid overlay. The TP-HDD test series was designed to provide comprehensive data to enable design trades to optimize all SVS applications, as well as develop requirements and recommendations to facilitate the implementation and certification of SVS displays. The TP-HDD flight experiment utilized the NASA LaRC Cessna 206 Stationaire and evaluated eight terrain portrayal concepts in an effort to confirm and extend results from the previously conducted TP-HDD simulation experiment. A total of 15 evaluation pilots, of various qualifications, accumulated over 75 hours of dedicated research flight time at Newport News (PHF) and Roanoke (ROA), VA, airports from August through October, 2002. This report will present results from the portion of testing conducted at Roanoke, VA.

Abstract: Accurate wind magnitude and direction estimation is essential for aircraft trajectory prediction. For instance, based on these data, one may compute entry and exit time from a sector or detect potential conflict between aircraft. Since the flight path has to be computed and updated on real time for such applications, wind information has to be available in real time too. The wind data which are currently available through meteorological service broadcast suffer from small measurement rate with respect to location and time. In this paper, a new wind estimation method based on radar tracks is developed. An Extended Kalman filer extracts the wind information by observation of the radar tracks in turns. After performing many evaluations in realistic framework, our approach is able to estimate the wind vectors accurately. By this mean, each aircraft can be seen as a wind sensor when it is turning. Based on those measurements, a global space-time wind field estimation using vector splines is extrapolated in order to produce wind maps in the area of interest. The underline model for wind field computation is Shallow-Water, which assumes geostrophic wind. The accuracy of this wind map is dependent of the number of aircraft turns in a given zone; then the estimation is better in the terminal area (TMA) than in en-route area because aircraft are tuning more often. Further improvements to the estimation can be made by correlating with meteorological measurements.

Abstract: Building aircraft with navigation and control systems that can complete flight tasks is complex, and often involves integrating information from multiple sensors to estimate the state of the vehicle. This paper describes a method, in which a glider can fly from a starting point to a predetermined and location (target) precisely using vision only. Using vision to control an aircraft represents a unique challenge, partially due to the high rate of images required in order to maintain tracking and to keep the glider on target in a moving air mass. Second, absolute distance and angle measurements to the target are not readily available when the glider does not have independent measurements of its own position. The method presented here uses an integral image representation of the video input for the analysis. The integral image, which is obtained by integrating the pixel intensities across the image, is reduced to a probable target location by performing a cascade of feature matching functions. The cascade is designed to eliminate the majority of the potential targets in a first pruning using computationally inexpensive process. Then, the more exact and computationally expensive processes are used on the few remaining candidates; thereby, dramatically decreasing the processing required per image. The navigation algorithms presented in this paper use a Kalman filter to estimate attitude and glideslope required based on measurements of the target in the image. The effectiveness of the algorithms is demonstrated through simulation of a small glider instrumented with only a simulated camera.

Abstract: Vibration due to flexible modes can be attenuated using a notch filter tuned at the known resonant frequencies of a flexible structure or vehicle. However, there are applications in which those particular resonant frequencies are not known a priori. Further complication arises when those frequencies are not constant in time. The next generation reusable launch vehicle poses such as problem. the X33 concept vehicle, for example, burns up to 90% of its fuel during the first few minutes of flight. The significantly alters the mass distribution and therefore the natural modes of the vehicle. The current work investigates the use of time-varying (TV) notch filters based on the PD-eigenvalue theory Both the notch frequency and the bandwidth of the filter can be adjusted in real time to attenuate the time-varying flexmodes whenever they are excited, and to reduce the undesirable phase lag caused by the filter when the flexmodes are quiescent. Real-time identification of resonant frequencies is performed by a bank of linear, time-invariant (LTI) ban pass filters spanning the entire operating spectrum and a flex-mode detection logic unit. The design principle, as well as some promising simulation results, is given in the paper.

Abstract: This study was conducted to determine the flight technical performance, workload, and situation awareness of pilots flying a low-level curved approach to an austere airfield. This low-level ingress was flown under simulated night IMC with occasional breakouts into VMC. A total of 13 USAF pilots participated in this study. The simulated flights were performed in AFRL's Transport Aircraft Cockpit(TRAC) flight simulator. The simulator was configured using a C-17 aeromodel, and the head-up display showed either conventional commercial symbology (baseline) or one of two synthetic vision pathway configurations with wire-frame terrain. One of the synthetic vision configurations used rectangular pathway elements (pavers) and the other configuration used a square wire-frame tunnel. Speed and altitude information was provided either in the form of tapes or dials in all three configurations. A secondary task was introduced to test the displays under increased levels of workload. The secondary task involved authentication of a 5-digit code. In addition, the pilots had to deal with traffic targets to which they were alerted on the head-down display. The flight technical data clearly indicated that both pathway formats(paver and tunnel) are superior to the baseline symbology format. For all practical purposes the paver and tunnel formats performed equally well. Head-up guidance with terrain and pathway information provided much tighter flight technical performance than conventional head-up guidance. Thus, we conclude that the mission capability of the potential military users could be substantially increased.

Abstract: This paper analyzes the safety benefits of the implementation of PathProx, a runway incursion alerting system. Airport surface incursions have been identified by the National Transportation Safety Board (NTSB) as one of the most significant safety hazards in civil aviation. PathProx is a system development by Rannoch Corporation to help address this problem. It is an aircraft-based runway incursion alerting system, providing runway incursion alerts directly to the pilot(s) in the cockpit. PathProx has undergone a series of simulator and flight tests conducted by NASA over the last 3 years. It is part of the NASA Runway Incursion Prevention System (RIPS). These tests have validated the basic concept and design of PathProx. Several analyses have been performed related to the safety benefits of PathProx implementation. These include analysed of critical runway incursion scenarios and Monte Carlo simulation. The Monte Carlo simulation results indicated that the risk of collisions due to runway incursions could be nearly eliminated through aircraft equipage with PathProx. The simulations and analyses also found that PathProx provides significant improvement in runway safety even without full fleet equipage-where only of the two aircraft involved in a conflict is equipped. Analyses have also been done to compare the safety improvements provided by PathProx with that provided by ground system surveillance and alerting. PathProx provides more timely alerting than provided by ground-based systems, primarily by eliminating the delays associated with having the controller in the loop and associated communications delay.

Abstract: The Attitude Heading Reference System (AHRS) provides data for primary flight instruments, head-up displays, autopilots, and moving map navigation systems. Advances in solid-state MEMS rate sensors, coupled with Kalman Filter algorithms designed to mitigate high drift rates, provide the basis for low cost, high performance AHRS for General Aviation. This paper describes the performance of a low cost, miniaturized AHRS using automotive-grade MEMS sensors. The performance of the system is detailed. The implications for certification of this class of system and fault tolerance are discussed.

Abstract: This paper describes the design of visualizations and interactions within a multidisciplinary framework for the empirical analysis of the applicability of three-dimensional (3D) stereoscopic visualization in Air Traffic Control (ATC). This framework takes into consideration three major components: the design of visualization interfaces, the design of interactivities, and the associated human factors. Flight trajectory is selected as the preliminary subject for analysing. This paper analyzes different ways to model waypoints, flight trajectories and diverse techniques to select, to position waypoints in a 3D stereoscopic environment. We discuss using the polynomial curve for representing 3D flight trajectory. Basing on the analysis of interaction with waypoint, we also propose two new metaphors for selecting objects, various selection and positioning techniques in 3D environment. An experimental approach is also considered to evaluate the performance of different models of flight trajectory and interaction techniques in the end of this paper.

Abstract: This article discusses various methods of improving the detection capability of horizontal and vertical failure modes for a terrain database integrity monitor that is purely based on the inputs from downward looking sensors. Terrain database integrity monitors which use radar altimeter and GPS inputs have previously been proposed for Synthetic Vision Systems (SVS). An SVS provides pilots with either a Heads Down Display (HDD) or a Heads Up Display (HUD) containing aircraft state, guidance and navigation information, and a virtual depiction of the terrain as viewed "from the cockpit." The source used to generate the terrain depicted on these displays is a Digital Elevation Model (DEM). Due to the compelling nature of the displays, it is quite possible for the pilots to use the display for functions other than its original intended function. It may be hard to avoid such a scenario, especially if the system is certified as an advisory system. When using SVS display technology for functions other than advisory it may be necessary to include a DEM integrity monitor whose performance is specified by probabilities of Missed Detection, Fault-Free Detection and Time-to-Alarm. Ideally, the DEM represents the height or elevation of the terrain at corresponding coordinates (e.g. latitude and longitude) expressed in a predefined vertical datum. However, the given elevations deviate from the true elevations due to systematic and blunder errors that are present in the DEM primarily due to the way in which they are generated from different sensor technologies such as photogrammetry, remote sensing, etc. and the manual post-processing process. Another source of error of lesser significance is the flat earth approximation over relatively larger areas, while collecting the data. The described integrity monitor method is based on the compa

Abstract: During the last years DLR has developed an Enhanced and Synthetic Vision (ESVS) test bed, consisting of several imaging sensors mounted onto the DLR's DO-228 test aircraft together with some built-in computing devices for acquiring, storing and displaying the sensor data. The Institute of Flight Guidance of DLR has documented its fundamental experiences and investigations in realtime processing, image analysing, data fusion and the extraction of navigation data especially from millimetre-wave-radar images by publishing several contributions discussing the generation of "useful" displays for the pilot's support. The present document discloses the development of a considerable robust and simple method for the estimation of the relative position of an aircraft with respect to a runway based on camera images only (TV, infrared or PMMW radar). The special feature of this method is, that neither a calibrated camera (referring to focus length and mounting angles relative to the aircraft) is required nor the identification of special points of the runway and their 3-D location has to be known. The only reference to the 3-D world, which has to be known, is the width of the runway stripe. The presented algorithm computes the relative height of the aircraft above the runway stripe and the lateral deviation from the centre line of the runway as well. The robustness and the minimum requirement of real-world 3-D data yield a lower effort for certification, calibration and maintenance of a camera based positioning system. Furthermore, the presented method is not restricted to the ESVS application. The estimation of lateral guidance data for a car driving on a road, is another example for an application. In this case, there is no real world 3-D knowledge about the road required. Solely the data of the mounting height of the camera ab

Abstract: Portable wireless technology provides many benefits to modern day travelers. Over the years however, numerous reports have cited portable electronic devices (PEDs) as a possible cause of electromagnetic interference (EMI) to aircraft navigation and communication radio systems. PEDs may act as transmitters, both intentional and unintentional, and their signals may be detected by the various radio receiver antennas installed on the aircraft. Measurement of the radiated field coupling between passenger cabin locations and aircraft communication and navigation receivers, via their antennas is defined herein as interference path loss (IPL). IPL data is required for assessing the threat of PEDs to aircraft radios, and is very dependent upon airplane size, the interfering transmitter position within the airplane, and the location of the particular antenna for the aircraft system of concern. NASA Langley Research Center, Eagles Wings Inc., and United Airlines personnel performed extensive IPL measurements on several Boeing 737 airplanes. This paper provides a graphical and statistical analysis of IPL data measured onboard two Boeing 737 airplanes. The analysis reveals valuable insight into EMI field propagation characteristics, measurement repeatability, selection of test equipment, and interpretation of measurement data related to IPL.

Abstract: Electronic flight bags (EFBs) are coming into the flight deck, bringing with them a host of human factors challenges. The first step in addressing these challenges was to identify and prioritize them. Good progress has been made on that front by Chandra and Mangold, whose comprehensive document is in active use by industry and the FAA today. Unfortunately, using this document is a daunting task because of its breadth and depth. Our next goal is to develop and test a tool based on the full document that can be used for periodic structured assessments of EFB usability. We expect that this assessment tool will benefit designers, operators, and regulators by providing a structure for EFB human-factors evaluations. Both EFB-specific issues and general user interface topics are covered. The purpose of this report is to document the progress to date on constructing this usability-assessment tool for EFBs. We cover how the tool was developed and tested, what it looks like to date, and how it could be used to help assess and track EFB usability. Further testing is planned to ensure that the tool is usable and to ensure that it adds value to the evaluation process.

Abstract: One goal in the development of a Synthetic Vision System (SVS) is to create a system that can be certified by the Federal Aviation Administration (FAA) for use at various flight criticality levels. As part of NASA's Aviation Safety Program, Ohio University and NASA Langley have been involved in the research and development of real-time terrain database integrity monitors for SVS. Integrity monitors based on a consistency check with onboard sensors may be required if the inherent terrain database integrity is not sufficient for a particular operation. Sensors such as the radar altimeter and weather radar, which are available on most commercial aircraft, are currently being investigated for use in a real-time terrain database integrity monitor. This paper introduces the concept of using a Light Detection And Ranging (LiDAR) sensor as part of a real-time terrain database integrity monitor. A LiDAR system consists of a scanning laser ranger, an inertial measurement unit (IMU), and a Global Positioning System (GPS) receiver. Information from these three sensors can be combined to generate synthesized terrain models (profiles), which can then be compared to the stores SVS terrain model. This paper discusses an initial performance evaluation of the LiDAR-based terrain database integrity monitor using LiDAR data collected over Reno, Nevada. The paper will address the consistency checking mechanism and test statistic, sensitivity to position errors, and a comparison of the LiDAR-based integrity monitor to a radar altimeter-based integrity monitor.

Abstract: The Synthetic Vision Systems General Aviation (SVS-GA) element of NASA's Aviation Safety Program is developing technology to eliminate low visibility induced General Aviation (GA) accidents through the application of synthetic vision techniques. SVS displays present computer generated 3-dimensional imagery of the surrounding terrain to greatly enhance pilot's situation awareness (SA), reducing or eliminating Controlled Flight into Terrain (CFIT), as well as Low-Visibility Loss of Control (LVLOC) accidents. A critical component of SVS displays is the appropriate presentation of terrain to the pilot. The relationship between the realism of the terrain presentation and resulting enhancements of pilot SA and pilot performance has been largely undefined. Comprised of coordinated simulation and flight test efforts, the terrain portrayal for head-down displays (TP-HDD) test series examined the effects of two primary elements of terrain portrayal: variations of digital elevation model (DEM) resolution and terrain texturing. Variations in DEM resolution ranged from sparsely spaced (30arc-sec) to very closely spaced data (1arc-sec). Variations in texture involved three primary methods: constant color, elevation-based generic, and photo-realistic, along with a secondary depth cue enhancer in the form of a fishnet grid overlay. The TP-HDD simulation experiment addressed multiple objectives involving twelve display concepts (two baseline concepts without terrain and ten SVS variations), four evaluation maneuvers (two en route and one approach maneuver, plus a rare event scenario), and three pilot group classifications. Because of the complexity of this experiment, it is not practical to report on every significant aspect of the simulation in this paper. This paper provides a preview of simulation results by evaluating current tech

Abstract: The paper presents the review of pathway displays with pilot awareness, display scaling, navigation performance, tracking displays, certification and recommendations for improvement. The path displays is proposed as an intuitive display format providing tactical situation awareness and good tracking performance. The path and the tunnel displays format provide anticipatory cues about forthcoming flight path. The most compelling advantage of such a format can be found in low visibility landings.

Abstract: This paper describes a fast-time simulation designed to complement real-time human-in-the-loop simulations to support the design of terminal-area (TRACON) spacing and merging concepts. Fast-time simulations allow a variety of experimental conditions to be varied 'Monte Carlo-style.' Human performance models that represent flight crews and ATSPs simulate key interactions. Such simulations enable rapid, iterative concept refinement, and help focus subsequent human-in-loop simulations by identifying test scenarios and experimental conditions likely to provide clear insights. The paper presents preliminary fast-time simulation studies for TRACON spacing and merging concepts. The studies extend prior NASA ATM research, which has generally focused on increasing arrival efficiency (e.g., reducing vectoring) and throughput via ATM concepts that improve traffic flow predictability. In particular, the research has focused on trajectory-oriented operations, with greater information sharing and accompanying ATSP and flight deck automation tools. Following this general approach, the fast-time simulation results presented here principally address arrival scheduling and the ability to use automatically-computed speed adjustments to schedule deviations introduced by TRACON boundary metering fix arrival time and predicted landing speed errors for aircraft flying flight management system (FMS) routes to the runway. However, the paper also considers how this class of concepts relates to other ongoing ATM arrival concept research, the role of simulated agents (in particular, agent fidelity requirements for simulating increasingly refined concepts), and metrics for assessing concept efficacy in complementary real- and fast-time simulations. The remainder of the paper is organized as follows. It first describes the continuous-descent appro

Abstract: Because of its cognitive complexity, the responsibility for operating the National Airspace System (NAS) is distributed among many organizations and individuals An understanding of how this distributed work system functions requires consideration not only of the allocation of control and responsibility, but also of the distribution of data, knowledge, processing capacities and characteristics, goals and priorities It further requires consideration of how alternative architectures for distributing work (as defined by these different dimensions) impact performance on different types of tasks described by P J Smith et al, (1999) Given such a distributed system, one of the most significant challenges is how to plan at a system level in the face of uncertainty, where the level of uncertainty changes over time In this paper, we explore a future vision that allows traffic managers and dispatchers to more fully communicate their beliefs about possible weather and traffic constraints described by P J Smith et al, (2003), and to indicate how they would respond (or would prefer as a response by someone else who has control and responsibility for responding at that point), depending upon the state of their knowledge at the time when they must act Instead of communicating their beliefs about the single most likely scenario (weather at BYP from 1400-1500Z), they would communicate their beliefs about the range of possible scenarios that could potentially occur Then, instead of communicating a single plan, the traffic managers and dispatchers would communicate preferences, constraints or intentions (depending upon whom would have control to make the relevant decision) for each of these contingencies In addition, because the degree of uncertainty about weather and traffic varies over time and often becomes smaller as the

Abstract: This article describes the human factor analysis from flight trials performed in Reno, NV. Flight trials were conducted with a Cheyenne 1 from Marinvent. Thirteen pilots flew the Cheyenne in seventy-two approaches to the Reno airfield. All pilots flew completely randomized settings. Three different display configurations: 1) Elec. Flight Information System (EFIS), 2) EFIS and 2D moving map, and 3) 3D SVS Primary Flight Display (PFD) and 2D moving map were evaluated. They included normal/abnormal procedure evaluation for: 1) Steep turns and reversals, 2) Unusual attitude recovery, 3) Radar vector guidance towards terrain, 4) Non-precision approaches, 5) En-route alternate for non-IFR rated pilots encountering IMC, and 6) Taxiing on complex taxi-routes. The flight trial goal was to evaluate the objective performance of pilots for the different display configurations. As dependent variables, positional and time data were measured. Analysis was performed by an ANOVA test. In parallel, all pilots answered subjective NASA Task Load Index, Cooper-Harper, Situation Awareness Rating Technique (SART), and questionnaires. The result shows that pilots flying 2D/3D SVS perform no worse than pilots with conventional systems. In addition, 3D SVS flying pilots have significantly better terrain awareness, more stable 180ddeg turns, and enhanced positional awareness while taxiing on the ground. Finally, even non-IFR rated pilots are able to fly non-precision approaches under IMC with a 3D SVS.

Abstract: According to historical data, aircraft are subject to a higher accident risk during the landing phase than during other flight phases. With the growth in air traffic volume evaluating safety during the landing phase is an important problem. This article presents an analysis and estimate of two safety metrics at ATL airport: probability of a simultaneous runway occupancy by two landing aircraft and probability of a collision on the runway. We begin with the first order analysis to estimate the simultaneous runway occupancy probability, based on field observations. To obtain a more accurate estimate and to evaluate the runway collision risk, we construct a stochastic model of the aircraft approaching and landing process. The result of Monte Carlo simulation gives an improved estimate for the simultaneous occupancy probability. We then numerically evaluate the runway collision risk using a generalization of the Reich collision model. Finally, we carry out sensitivity analysis to examine the impact on safety and capacity when the separation variance changes.

Abstract: Today's airplane consists of a big network linking embedded controllers to sensors/actuators and communications equipment onboard. Efforts made in recent years to simplify network wirings have resulted in significant reductions in the aircraft weight and labor required to run wiring harnesses. This has often come out at the cost of a more complex data bus architecture (bi-directional protocol instead of unidirectional protocol). As DO-178B is a requirement for certifiable avionics SW design, DO-254 is a set of design guidelines for airborne HW electronics. DO254 considers the use of formal methods and requirements traceability when developing HW to support safety-critical (Level A or B) functions. This article presents a static formal approach that may be used, in combination with requirements traceability features, to apply formal methods in the design and verification of HW controllers to support such protocols as ARINC 429, ARINC 629, MIL-STD-1553B, etc. Model simulation is today's standard practice in verifying HW electronics. A major drawback in simulation is the lack of exhaustive checking, since simulation results are only a function of the testbench scenario defined by the designers. For example, using simulation one cannot guarantee such system behaviors as "the controller shall always respond to a request," "acknowledge shall always arrive no later than N cycles," "the controller shall not drop any data," "the controller shall not lock up," etc. improve-HDL is a formal property checker that complements simulation in performing exhaustive debugging of VHDL/Verilog register-transfer-level HW models of complex avionics protocol controllers without the need to create testbenches. Reqtify is used to track requirements throughout the verification process and to produce coverage reports. Using improve-HDL coupled wit