Air Traffic Control Clearances Research Articles

In-Flight Aircraft Trajectory Optimization within Corridors Defined by Ensemble Weather Forecasts

Today, each flight is filed as a static route not later than one hour before departure. From there on, changes of the lateral route initiated by the pilot are only possible with air traffic control clearance and in the minority. Thus, the initially optimized trajectory of the flight plan is flown, although the optimization may already be based upon outdated weather data at take-off. Global weather data as those modeled by the Global Forecast System do, however, contain hints on forecast uncertainties itself, which is quantified by considering so-called ensemble forecast data. In this study, the variability in these weather parameter uncertainties is analyzed, before the trajectory optimization model TOMATO is applied to single trajectories considering the previously quantified uncertainties. TOMATO generates, based on the set of input data as provided by the ensembles, a 3D corridor encasing all resulting optimized trajectories. Assuming that this corridor is filed in addition to the initial flight plan, the optimum trajectory can be updated even during flight, as soon as updated weather forecasts are available. In return and as a compromise, flights would have to stay within the corridor to provide planning stability for Air Traffic Management compared to full free in-flight optimization. Although the corridor restricts the re-optimized trajectory, fuel savings of up to 1.1%, compared to the initially filed flight, could be shown.

Performance Evaluation of Terminal Airspace System Safety, Delay and Predictability of Muritala Mohammed International Airport, Ikeja Lagos, Nigeria

This paper outlines a multi-dimensional user-oriented performance metrics approach in evaluating the operation of the terminal airspace system to aid in the airport and airspace planning and decision making. Safety, delay and predictability metrics contribute to the analytical framework. From the findings, the occurrence of air incidence has a high severity level at departure, and arrival phases of flight, higher likelihood at the radar room and much of the incidences were as a result of faulty equipment and inherent absence of modern airspace infrastructure. Also, in Lagos terminal airspace, the number of incidences has no close correlation with the level of traffic complexity. Total schedule arrival delay ranges from 1 - 392 minutes representing an average of 7.8 - 17.9 minutes per aircraft that arrived Lagos airport at that period. Besides, the total approach contact time ranges from 1 - 57 minutes, translating to 4.6 - 7.1 minutes per aircraft. However, variability in arrival time of 1 - 5 minutes is common from published airline arrival scheduled time. In the same vein, the variability of 1 - 5 minutes is common from approach contact times of aircraft. These figures indicate sound arrival predictability signature for Lagos airport. Also, departure time variability above 30 minutes is familiar from the ATC clearance time for the various routes under study. However, there is about or more 25% variability of more than 15 minutes, and this indicates possible inconsistency of predicting departure times from the times Air Traffic Control (ATC) clearance was acquired. Above all, the predictability of departure times in Lagos airport is weak compared to those of the arrival. Taken by it, this may be a sign of airspace congestion or ATC deficiencies at the Lagos airport. This is an indication of the lack of users’ confidence in Nigeria’s air transport industry to deliver just-in-time service.

An Examination of Unmanned Aircraft Systems Pilots’ Interaction with Air Traffic Control while Responding to Detect and Avoid Conflicts

New performance standards for a detect and avoid (DAA) system are being developed to support the broader integration of unmanned aircraft systems (UAS) into the National Airspace System (NAS). One subset of these performance standards will address the minimum DAA display requirements to support pilot performance on maintaining well clear of other aircraft. These performance standards must take into account the current air traffic control (ATC) operational environment. In particular, the DAA system, and pilots’ interactions with that system, must account for the requirement for pilots to request a clearance for deviations from their approved instrument flight rules route. A series of human-in-the-loop (HITL) experiments were conducted to help identify the minimum information requirements for DAA displays. As part of these experiments, several pilot-ATC interaction metrics were collected, such as the amount of time it took pilots to request an ATC clearance prior to executing a maneuver to maintain well clear after the appearance of a DAA alert, and the proportion of time that pilots received an ATC clearance prior to maneuvering. The results indicate that while there was no observed effect of different display configurations on pilots’ interactions with ATC, these interactions were affected by the combination of alerting and operational procedures. When pilots received an unambiguous alert to potential well clear violations in conjunction with operational procedures that specified the expected actions to various alert levels, the time that it took for pilots to notify ATC of he need to maneuver dropped substantially, and the rate of obtaining a clearance increased. The implications of these results for developing performance standards for DAA are discussed.

NASA’s UAS Integration into the NAS

In 2011 the National Aeronautics and Space Administration (NASA) began a five-year Project to address the technical barriers related to routine access of Unmanned Aerial Systems (UAS) in the National Airspace System (NAS). Planned in two phases, the goal of the first phase was to lay the foundations for the Project by identifying those barriers and key issues to be addressed to achieve integration. Phase 1 activities were completed two years into the five-year Project. The purpose of this paper is to review activities within the Human Systems Integration (HSI) subproject in Phase 1 toward its two objectives: 1) develop GCS guidelines for routine UAS access to the NAS, and 2) develop a prototype display suite within an existing Ground Control Station (GCS). The first objective directly addresses a critical barrier for UAS integration into the NAS – a lack of GCS design standards or requirements. First, the paper describes the initial development of a prototype GCS display suite and supporting simulation software capabilities. Then, three simulation experiments utilizing this simulation architecture are summarized. The first experiment sought to determine a baseline performance of UAS pilots operating in civil airspace under current instrument flight rules for manned aircraft. The second experiment examined the effect of currently employed UAS contingency procedures on Air Traffic Control (ATC) participants. The third experiment compared three GCS command and control interfaces on UAS pilot response times in compliance with ATC clearances. The authors discuss how the results of these and future simulation and flight-testing activities contribute to the development of GCS guidelines to support the safe integration of UAS into the NAS. Finally, the planned activities for Phase 2, including an integrated human-in-the-loop simulation and two flight tests are briefly described.

Unmanned Aircraft System Response to Air Traffic Control Clearances

In the National Airspace System (NAS), Air Traffic Control (ATC) expects aircraft to complete ATC clearances in a timely manner in order to maintain minimum separation between aircraft. The end-to-end response time for an aircraft to complete a clearance, as measured from the end of ATC instructing the pilot of the clearance to the just noticeable difference (JND) on the ATC display of the aircraft satisfying the clearance (i.e., initiation/completion of an altitude climb), can be referred to as measured response (MR). This MR is not quantified in Federal Aviation Administration (FAA) standards, regulations, or policy; however, as manned aircraft have developed along with the Air Traffic Management System, a shared understanding of reasonable and timely response has evolved. By contrast, the introduction of unmanned aircraft systems (UAS) into the NAS has highlighted this issue. This paper seeks to define MR and its components, and describe a methodology, with an example, that can be used to investigate it.

An Investigation of Flight Deck Data Link in the Terminal Area

The Next Generation Air Transportation System (NextGen) and Europe’s Single European Sky ATM Research (SESAR) concepts require an increased use of trajectory-based operations, including extensive strategic air traffic control clearances. The clearances can be lengthy and complex, which necessitates data link communications to allow for message permanence and integration into the autoflight systems (i.e., "autoload" capability). This paper examines the use of flight deck data link communications for strategic and tactical clearance usage in the terminal area. A human-in-the-loop simulation was conducted using a high-fidelity flight deck simulator, with ten commercial flight crews as participants. Data were collected from six flight scenarios in the San Francisco terminal airspace. The variables of interest were ATC message modality (voice v. data link), temporal aspect of the message (tactical v. strategic) and message length. Dependent variables were message acknowledgement times, communication clarifications, communication-related errors, and pilot workload. Acknowledgement time results were longer in data link compared to voice, a finding that has been consistently revealed in a number of other simulations. In addition, strategic clearances and longer messages resulted in a greater number of clarifications and errors, suggesting an increase in uncertainty of message interpretation for the flight crews when compared to tactical clearances. The implications for strategic and compound clearance usage in NextGen and SESAR are discussed.

Incorporating Human Factors into The Development and Operational Evaluations of Runway Status Lights

The FAA is sponsoring MIT Lincoln Laboratory to conduct human factors assessments of a prototype direct warning system aimed at preventing runway incursions called Runway Status Lights (RWSL). RWSL is comprised of Runway Entrance Lights (RELs), Takeoff Hold Lights (THLs), Runway Intersection Lights (RILs), and the enhanced Final Approach Runway Occupancy Signal (eFAROS), which provide autonomous information as a back-up to verbal air traffic control clearances. Human factors assessment has been essential to both the design and development of RWSL as well as on-going operational evaluations. This safety system has proven effective when both the technical performance and human response is correct according to the designated protocol. Since the commencement of the first field tests of RWSL in 2005, the user outreach, collection and assessment of feedback, and additional human factors assessment techniques have been key to the successful operational concept validation. Specific improvements resulting from system modifications based on human factors assessment will be discussed. Language: en

Monitoring of TCAS Resolution Advisories in Core European Airspace

Downlink and display of Resolution Advisories (RAs) – which are issued by the airborne Traffic alert and Collision Avoidance System (TCAS) – has been proposed as a means of informing the air traffic controller that an RA has been posted onboard the aircraft. Previous research has pointed to a number of operational benefits of RA downlink display, such as an improved controller situational awareness and a smaller likelihood of contradictory clearances to aircraft involved in an RA event. However, these benefits of RA downlink display only pertain to RAs that, if complied with, cause a deviation from the Air Traffic Control (ATC) clearance. In order to investigate the frequency and type of RAs in core European airspace, EUROCONTROL initiated the PASS monitoring study. Within this study, RA downlink data from six Mode-S radars covering a large part of the core European airspace were collected from September 2007 to March 2008. The results of the monitoring indicate that approximately a fourth of the RAs issued are likely to cause a deviation from the ATC clearance. However, because of the low overall number of RA encounters (i.e. 1 RA encounter per 2160 flight hours), the display of all RAs – including those that do not yield a deviation from the ATC clearance – is not likely to cause problems related to screen clutter or controller desensitization. On the basis of the results of the RA monitoring, some concerns are identified and refinements to the operational concept for RA downlink display are proposed.

Pilot Error in Copying Air Traffic Control Clearances

A study investigating the accuracy of pilots' copying air traffic control clearances is described. Twentyfour airline pilots listened to 28 taped clearances and copied them down on an answer sheet using shorthand, longhand, or some combination of these according to their preferences. The copied clearances were analyzed by the number of correctly copied elements, the number of omitted elements, and the number of extraneous elements that were not present in the original clearance. Preliminary results indicate a strong influence of habit and familiar operating environment and procedures on the accuracy of copying unfamiliar information. Common errors included victor-airways copied as jet-airways, low altitudes copied as much higher, and slow speeds copied as much higher. The vulnerability of controller-pilot communications to the effects of unfamiliarity is apparent. A detailed analysis of these data may provide for a better understanding of the shortcomings of controller-pilot communication.

Management by consent in human-machine systems: when and why it breaks down.

This study examined the effects of conflict type, time pressure, and display design on operators' ability to make informed decisions about proposed machine goals and actions in a management-by-consent context. A group of 30 B757 pilots were asked to fly eight descent scenarios while responding to a series of air traffic control clearances. Each scenario presented pilots with a different conflict that arose from either incompatible goals contained in the clearance or inappropriate implementation of the clearance by automated flight deck systems. Pilots were often unable to detect these conflicts, especially under time pressure, and thus failed to disallow or intervene with proposed machine actions. Detection performance was particularly poor for conflicts related to clearance implementation. These conflicts were most likely to be missed when automated systems did more than the pilot expected of them. Performance and verbal protocol data indicate that the observed difficulties can be explained by a combination of poor system feedback and pilots' difficulties with generating expectations of future system behavior. Our results are discussed in terms of their implications for the choice and implementation of automation management strategies in general and, more specifically, with respect to risks involved in envisioned forms of digital air-ground communication in the future aviation system. Actual or potential applications of this research include the design of future data link systems and procedures, as well as the design of future automated systems in any domain that rely on operator consent as a mechanism for human-machine coordination.

A Simulator Study of the Effect of Information Load and Datalink on Crew Error

This study investigated the effects of air traffic control (ATC) induced information load and ATC communication modality on crew error in a fixed-base Boeing 747-400 flight deck simulator. To accomplish this, data from an experiment conducted by Boeing (Logan, et al., 1992) were re-analyzed. In this experiment, flightcrews engaged in two high-fidelity, full-mission scenarios. For this re-analysis, the variability in the amount of information ATC transmitted to the crew in the scheduled clearances was examined as an independent variable. To quantify this measure of information load, each scheduled ATC clearance was decomposed into mutually exclusive informational units called propositions. Each proposition consisted of one discrete “chunk” of information. On average, ATC clearances in the high information load condition contained more than two and a half times as many propositions as clearances in the low information load condition. Flightcrews made significantly more errors, and more errors per proposition, in the high information load condition than in the low information load condition. This indicates that it was the density of the information, or how many propositions were packed into each clearance, and not just the quantity of information which affected crew performance. Another manipulated variable was ATC communication modality. Each flightcrew participated in one scenario using a standard voice communications modality exclusively and in the other scenario using a combination of voice and digital DataLink. Though flightcrew error was significantly lower in the DataLink condition than the voice condition, this tendency was moderated by information load. In the low information load condition, flightcrews committed approximately the same number of errors in the voice and DataLink conditions, but in the high information load condition, flightcrews committed many more errors in the voice condition than the DataLink condition.