C. Borst

Ecological Interface Design for Terrain Awareness

Advanced terrain warning systems, such as the enhanced ground proximity warning system, and safety-enhancing displays, like the synthetic vision system, have proven to play an important role in reducing the number of controlled flight into terrain accidents. Research indicated, however, that terrain collisions may still occur for aircraft equipped with these systems. Synthetic vision allows for perception of the environment, but lacks properties to support understanding and extrapolation of the perceived data. A terrain warning system provides elementary meaning to the environment, but is not well integrated into synthetic vision displays. To further increase terrain awareness and, ultimately, eliminate terrain collisions, synthetic vision should be integrated with a terrain awareness functionality that allows the pilot to be continuously informed about how the external constraints (imposed by the terrain) relate to the internal aircraft constraints (e.g., climb performances). Based on that information, pilots can judge for themselves what an obstacle actually means to them in terms of possibilities to fly over it, and if not, what the alternatives for action are. In this article, the paradigm of ecological interface design is used to analyze the aircraft manual control task in the vertical plane and to develop a more meaningful interface for (vertical) terrain awareness. An abstraction hierarchy is presented, developed for the task of guiding an aircraft through a terrain-challenged environment. The design and experimental evaluation of a vertical situation display are discussed, enhanced with ecological overlays to increase terrain awareness.

Beyond Ecological Interface Design: Lessons From Concerns and Misconceptions

The ecological interface design (EID) paradigm was introduced in the process control domain 25 years ago by Kim Vicente and Jens Rasmussen, as a way to help operators cope with system complexity and events unanticipated in the design of automated control systems. Since that time, this perspective has sparked interest in other safety-critical sociotechnical domains where humans cooperate with computerized systems to ensure safe and efficient system behavior. Many of our own, but also other explorations have, however, resulted in several usability concerns and misconceptions about the EID perspective as a viable design approach. This paper discusses some of these concerns and misconceptions, where the final goal is to get past the EID label and to consider the general lessons relative to the demands and opportunities that advanced information technologies offer and complex systems require. This paper concludes with a preliminary outlook for the future of EID, where it is anticipated that the adjective “ecological” will become increasingly redundant, as the focus on supporting “productive thinking” becomes the dominant paradigm for engineering representations.

Design and Simulator Evaluation of an Ecological Synthetic Vision Display

A synthetic vision display is generally believed to support pilot terrain awareness. Many studies have shown, however, that the bias in perspective views can cause pilots to make judgment errors regarding the relative location, height, and ultimately the avoidance of terrain obstacles. Therefore, alerting systems are required to keep pilots at safe distances from the terrain. These systems provide explicit guidance commands to circumvent terrain conflicts, which is far from optimal regarding pilot terrain awareness as it fails to present the rationale of the terrain separation problem. Consequently, this can affect the trust in and the reliance on these systems and pose a potential safety risk, especially in events or situations unfamiliar to the alerting system. This paper presents the design and evaluation of an extension to a synthetic vision display that aims to make the constraints of the alerting automation more transparent in order to help pilots better understand why, how, and when they should act. A pilot-in-the-loop experiment, using 16 glass-cockpit pilots in a fixed-based flight simulator, showed that the constraint-based overlays indeed improved the overall pilot terrain awareness compared to a command-based display. The decision-making only improved in the unanticipated events introduced in the experiment. The utility of the energy angle was found to be important for recognizing the offnormal events and to prevent terrain crashes. However, the pilot response time, flight safety in terms of low-altitude flying, and pilot workload are better when using the command display. This indicates that a last-resort alerting and advisory system would still be required in operations at the periphery of safe system performance.

Continuous Descent Approaches with Variable Flight-Path Angles under Time Constraints

In order to reduce noise nuisance around Schiphol Airport, a Continuous Descent Approach procedure was introduced in the late ’90s. Unfortunately, because unpredictable individual aircraft behavior lead to increased landing intervals for this procedure, it is currently only applied during night time operations. Time-of-Arrival control in the terminal area could reduce the landing interval for this procedure. The research presented in this paper investigates the influence of multiple segments with different flight-path angles on the time of arrival. A new procedure with Variable Flight-path angle (VFA) involving active planning of the approach from the pilot through a pilot support interface, presented in the Vertical Situation Display. A preliminary pilot-in-the-loop evaluation was conducted, to investigate pilot performance, workload and interface usability. Three scenarios were tested, all with different Required Time of Arrival. Workload was low for all scenarios and performance good for the two scenarios with early arrival times. For the scenario with a late arrival time, performance was mediocre. Changes in representation of the flap and gear cues and the addition of Estimated Time of Arrival information might improve the performance.

Path-Oriented Control/Display Augmentation for Perspective Flight-Path Displays

Flight-path predictor display augmentation and flight-path vector control augmentation concepts have been developed to improve pilot performance and reduce workload with a perspective flight-path display. A recent comparison study conducted at the Delft University of Technology showed a preference for control augmentation, although some improvements could still be made. Pilots command the direction of the aircraft motion and, because in curved trajectories the direction must constantly change, they are required to hold the stick deflected during turns. It is also not clear how much stick deflection is needed during a particular turn. This paper discusses an augmentation concept that addresses these issues. A path-oriented control and display augmentation is described in which the pilot commands the curvature of the aircraft future trajectory, shown as a perspective wireframe on the display. Results of an experiment, conducted in a fixed-base simulator, indicate that although pilot performance improved with this path-augmentation concept, pilot workload and control activity increased. A surprising result of the path-augmentation concept was the relatively large improvement in vertical pilot performance; its primary goal was to improve lateral pilot performance.

Predictive Landing Guidance in Synthetic Vision Displays

In order to improve performance during manual control, synthetic vision displays were augmented with predictive guidance. Little is known on how these predictive guidance concepts can be applied to the landing flare maneuver. This paper discusses the investigation into the applicability of 3D predictive guidance in synthetic vision displays during the final phase of the landing. Two types of predictive guidance were examined, the Flight-Path Predictor that indicates the aircraft’s future position a certain time ahead, and the Flight Trajectory Predictor that presents the future trajectory by interpolating a number of sequential predicted positions. A theoretical investigation and an offline simulation were used to optimize the system for the landing. A pilot-in-the-loop experiment, conducted in a moving-base flight simulator, indicated that predictive guidance supports pilots in manual control. Also, the addition of predictive guidance enhances the pilot’s ability to determine the correct flare initiation time in a way that is comparable to providing a more realistic synthetic vision display with textured surfaces. Even though the flare initiation timing was improved by the addition of predictive guidance, the flare control after initiation was not sufficiently supported and there was no noticeable improvement in landing performance.

Supporting 4D Trajectory Revisions on the Flight Deck: Design of a Human–Machine Interface

To accomplish air traffic growth in a safe and efficient way, future air traffic management concepts require aircraft to accurately execute 4-dimensional (4D) trajectories. A trajectory planned prior to takeoff, might, however, require in-flight revision. To support the flight crew in their task of accurately replanning a flight plan up to a metering fix, in 4 dimensions, a dedicated planning interface has been designed, adopting a cognitive systems engineering approach. The interface allows direct manipulation of the ground track and the descent profile. Constraints on trajectory planning are mapped onto alternative waypoint locations, highlighting the possibilities for acceptable ground track geometry in the horizontal situation display. In the vertical situation display, these constraints are mapped onto candidate top- and bottom-of-descent locations. It is hypothesized that the designed interface enables pilots to efficiently plan suitable 4D trajectories, while allowing for adaptive behavior and supporting situation awareness, even under high workload conditions.

Design and Evaluation of a Safety Augmentation System for Aircraft

This paper presents the design of a safety augmentation system for aircraft that prevents intrusions into a no-fly zone, representing a class of static external hazards. Additionally, when the risk of intrusion is most imminent, the system features an automated fail safe. Different from current alerting systems that only target the visual and aural communication channels, the safety augmentation system also uses the haptic channel to communicate its intent and to provide a smooth transition in control authority from human to machine. The goal of this paper was to investigate what combination of communication modalities would best fit such a system to benefit safety, performance, risk awareness, pilot workload, and acceptance. An experiment with 10 professional airline pilots in a fixed-base simulator showed that safety significantly increased when more communication channels were targeted, in which the visual information contributed most to the pilot’s risk awareness. Haptic feedback showed significant im...

Investigation of Energy Management during Approach - Evaluating the Total Energy-Based Perspective Flight-Path Display

This paper covers an analysis of the energy management task during the approach phase as well as the design of an experiment supporting this analysis. The energy management task is analyzed using the concept of energy rate demand, which expresses the amount of total energy to be lost in comparison to the minimal energy rate the aircraft can attain at the current speed and configuration. Energy rate demand is explicitly defined by the altitude and speed profile and indicates the demand put on the aircraft by the approach trajectory. A number of approach trajectories are analyzed including a conventional approach, a Continuous Descent Approach (CDA) and a new, experimental, Constant Energy Rate Demand Approach (CERDA). An experiment has been carried out using a total energy-based perspective flight-path display. The results are used to assess the benefits of adding energy information to a tunnel-in-the-sky display and to gain more insight into the energy management task by comparing the different types of energy management as well as energy rate demand with workload and performance. The hypothesis that adding energy information to a baseline tunnel-in-the-sky display will increase the pilot’s energy awareness is supported, however, the hypothesis that the workload would decrease with the energy display has been rejected. No relation could be found between energy rate demand, workload, and performance, rejecting the hypothesis that the performance would decrease and the workload increase with increasing energy rate demand.

The Effect of Synthetic Vision Enhancements on Landing Flare Performance

The usage of heads-down, non-conformal synthetic vision displays for landings below minimums has inherent problems during the flare due to minification effects. Literature showed that pilots can use four visual cues to perform a manual flare maneuver. Amongst their strategies, the Jacobson flare method seemed the most suitable to provide flare initiation and flare control cues. Offline, linear simulation results indicated that the Jacobson method was robust and its performance was comparable to an automatic landing system. An enhanced synthetic vision display was designed offering support cues to aid pilots with this landing method. An experiment was conducted in a fixed-based simulator with eight professional pilots and eight novice pilots. The enhanced display was tested against a basic version and conventional primary flight display with outside visuals. Each pilot group was split into two groups with different display orders to check for possible learning effects. The experiment showed that touchdown position was not affected by display type. The enhanced display did achieve softer touchdown sink rates compared to the basic version. The softest landings were done on outside visuals. A strong learning curve was also observed for the group of pilots that first flew with the enhanced display: this translated into better achieved performances with subsequent displays. Therefore, it could be a valuable tool for basic flight training and reduce the number of flight hours required in mastering the landing flare.