No abstract

Terrain awareness enhancing avionics, such as Synthetic Vision Systems and the Enhanced Ground Proximity Warning System, have been developed to reduce the number of controlled flight into terrain accidents. The protection these systems offer, however, is far from optimal. Synthetic Vision Systems only provide pilots with perceptual data, and leave all cognition and interpretation of data to the pilot. With Enhanced Ground Proximity Warning Systems the opposite is true. Here, cognition is hidden in the system and pilots are confronted with compelling advisories and commands. This paper presents a display system, the Emergency Landing Guidance System, which visualizes the functional meaning of surrounding terrain, adopting an ecological interface design approach. The potential benefits of this approach are demonstrated with the case of locating and approaching a suitable landing spot in the situation of a sudden complete engine failure. To evaluate the amount of pilot terrain awareness supported by the new display, an experiment was conducted in a fixed-base flight simulator. Results show that the new display supports pilot terrain awareness much better than present terrain avoidance systems, especially regarding awareness involving the higher levels of cognitive processing. Pilots better understand the meaning of the terrain topology in relation to their goals and constraints.

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. Nomenclatureto-maneuver, m D P = pull-up/push-over distance, m dt = time step, s E kin = kinetic energy, Joule E pot = potential energy, Joule E tot = total energy, Joule g = gravitational acceleration, m=s 2 H = altitude, m H R = radio altitude, m H T = terrain height, m LB, RB = left and right heading constraints, n z = normal acceleration R P = pull-up radius, m R T = turn radius, m T = thrust force, N T L = look-ahead time, s T R = reaction time, m T = time-to-radius, s T = u-turn time, s V a = aerodynamic velocity, m=s V k = kinematic velocity, m=s V w = wind velocity, m=s W = weight, N X, Y = lateral positions, m = vertical flight-path angle, rad E = energy angle, rad M = maneuver angle, rad T = terrain angle, rad = roll lag-time constant, s = roll angle, rad = track angle, rad = heading angle, rad Subscripts a = aerodynamic C = collision k = kinematic min, max = minimum, maximum s, sn = specific w = wind Superscripts OC = optimum climb OG = optimum glide

No abstract

Personal air transportation utilizing small aircraft is a market that is expected to grow significantly in the future. For this segment, "stick and rudder" related accidents should be mitigated to guide this process in a safe manner. Instead of downscaling advanced and expensive fly-by-wire platforms that incorporate flight envelope protection found in commercial aircraft, a low cost solution should be considered. This paper focuses on a flight envelope protection system for small aircraft, to allow carefree maneuvering for the less experienced pilot. Preliminary results are obtained from an empirical comparison study in the time domain, between a PID based control limiting approach, a command limiting approach and a constrained Flight Control Law (FCL) approach using Model-based Predictive Control (MPC), with and without parametric model uncertainties. Investigation of the results reveals that, for this study, command limiting and MPC should be preferred over control limiting and that the practicality of command limiting outweighs the small performance increase of MPC.