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Purpose: The purpose of the paper is to design a nonlinear dynamic inversion (NDI) based robust fault-tolerant control (FTC) for aircraft longitudinal dynamics subject to system nonlinearities, aerodynamic parametric variations, external wind disturbances and fault/failure in actuator. Design/methodology/approach: An uncertainty and disturbance estimator (UDE) technique is used to provide estimate of total disturbance enabling its rejection and thereby achieving robustness to the proposed NDI controller. As needed in the NDI design, the successive derivatives of the output are obtained through an UDE robustified observer making the design implementable. Further, a control allocation scheme consigns control command from primary actuator to the secondary one in the event of fault/failure in the primary actuator. Findings: The robustness is achieved against the perturbations mentioned above in the presence of actuator fault/failure. Practical implications: Lyapunov analysis proves practical stability of the controller–observer structure. The efficacy and superiority of the proposed design has been demonstrated through Monte-Carlo simulation. Originality/value: Unlike in many FTC designs, robustness is provided against system nonlinearities, aerodynamic parametric variations, external wind disturbances and sinusoidal input disturbance using a single control law which caters for fault-free, as well as faulty actuator scenario. [ABSTRACT FROM AUTHOR]

Strategic 4D trajectory conflict-free planning is recognized as one of the core technologies of next-generation air traffic control and automation systems. To resolve potential conflicts during strategic 4D conflict-free trajectory planning, a protection-zone conflict-control model based on air traffic control separation constraints was proposed, in which relationships between expected arrival time and adjusted arrival time at conflicting waypoints for aircraft queues were built and transformed into dynamic linear equations under the definition of max-plus algebra. A method for strategic deconfliction of 4D trajectory was then proposed using two strategies: arrival time adjustment and departure time adjustment. In addition, departure time and flight duration perturbations were introduced to analyze the sensitivity of the planned strategic conflict-free 4D trajectories, and a robustness index for the conflict-free 4D trajectories was calculated. Finally, the proposed method was tested for the Shanghai air traffic control terminal area. The outcomes demonstrated that the planned strategic conflict-free 4D trajectories could avoid potential conflicts, and the slack time could be used to indicate their robustness. Complexity analysis demonstrated that deconfliction using max-plus algebra is more suitable for deconfliction of 4D trajectory with random sampling period in fix air route. [ABSTRACT FROM AUTHOR]

Discontinuity of air routes is a subject that has been analysed in various ways. For example, the complex network approach focuses on network robustness and resilience due to route interruptions during a relatively short period. Also seasonal interruptions of air routes are a well-documented phenomenon in the context of demand variability. However, only recently discussions emerge on the more permanent cessation of air routes, the route churn. Today, European low-cost carriers frequently apply route churn in their networks. To enable early route churn detection in these networks, a regression model is developed in which route characteristics explain the churning likelihood of individual routes. The results of the econometric analysis show that churn rates are higher during an economic downturn, within the Eastern European market, between the Eastern and the Mediterranean market and between primary airports. In addition, we find that distance and the number of seats offered have a significant negative effect on the churn likelihood. The results also show significant effects of market share, seasonality and route age on the chance of cessation. To conclude, the paper demonstrates substantial differences in churn behaviour amongst specific low-cost carriers. [ABSTRACT FROM AUTHOR]