A sensor selection method using a performance metric for phased missions of aircraft fuel systems

Component failures in complex systems, such as aircraft fuel systems, can have catastrophic effects on system performance. There are a large number of components in these systems, each with a number of different failure modes, some of which can cause system failure. In order to detect and diagnose these component failures, sensors that monitor system performance need to be included. However, the number of sensors installed is typically limited by sensor cost and weight. An approach for selecting sensors could be taken considering sensor usefulness for fault diagnostics. In this paper, the sensor performance metric proposed by Reeves et al. [1] is extended to consider a phased mission operation, with component failures occurring at various points in the mission. The performance metric favours sensors that can detect the most failures, the failures that affect the system for longest and the failures that cause system failure. In addition, the performance metric considers the ability of sensors to distinguish between component failures, i.e. to diagnose which components have caused the faults observed by these sensors. The proposed approach is illustrated on the Airbus A380-800 fuel system, where the best combination is found using the performance metric within a Genetic Algorithm method

The Need for Accelerated Integration of the Multifunctional Information Distribution System in the FA-18C Hornet

The FA-18 Hornet is a fourth-generation, supersonic, multi-role aircraft designed and built by the Boeing Aircraft Company, primarily for use as a single-seat US Navy and Marine Corps carrier-based strike/fighter. The Hornet has also been successful in the dual seat variant as both a trainer, and as a land-based aircraft for the Marines. All A through D variants have been marketed internationally as well. While the newer “E” and “F” variants are significantly different from the A through D variants in size and range and endurance capabilities, the avionics suites and capabilities are nearly identical. Except where noted, discussions of operations and aircraft/aircrew workload refer to single seat operation, as that is the majority of the combat operation of the FA-18s currently in the inventory. The purpose of this study was to examine the need (from specific operational experience) in the single seat FA-18 for a jam resistant, long range, high bandwidth datalink for the Strike mission, and how the Multifunctional Information Distribution System (MIDS) and its integration into the Hornet can fill that need. The author‘s operational analysis was done primarily on personal notes and observations during combat operations in Afghanistan October through December of 2001 and combat operations in Operation Iraqi Freedom from February through April of 2003. The capabilities and limitations of the current LINK-4 system in the FA-18, the newer Digital Communication System’s Variable Message Format and finally the MIDS/LINK-16 systems were considered, along with difficulties of MIDS integration into the current FA- 18. This analysis was done partially on data and experience obtained as the Project Officer assigned to the MIDS program, however all conclusions and recommendations are independent of the test program

Automated system design optimisation

The focus of this thesis is to develop a generic approach for solving reliability design optimisation problems which could be applicable to a diverse range of real engineering systems. The basic problem in optimal reliability design of a system is to explore the means of improving the system reliability within the bounds of available resources. Improving the reliability reduces the likelihood of system failure. The consequences of system failure can vary from minor inconvenience and cost to significant economic loss and personal injury. However any improvements made to the system are subject to the availability of resources, which are very often limited. The objective of the design optimisation problem analysed in this thesis is to minimise system unavailability (or unreliability if an unrepairable system is analysed) through the manipulation and assessment of all possible design alterations available, which are subject to constraints on resources and/or system performance requirements. This thesis describes a genetic algorithm-based technique developed to solve the optimisation problem. Since an explicit mathematical form can not be formulated to evaluate the objective function, the system unavailability (unreliability) is assessed using the fault tree method. Central to the optimisation algorithm are newly developed fault tree modification patterns (FTMPs). They are employed here to construct one fault tree representing all possible designs investigated, from the initial system design specified along with the design choices. This is then altered to represent the individual designs in question during the optimisation process. Failure probabilities for specified design cases are quantified by employing Binary Decision Diagrams (BDDs). A computer programme has been developed to automate the application of the optimisation approach to standard engineering safety systems. Its practicality is demonstrated through the consideration of two systems of increasing complexity; first a High Integrity Protection System (HIPS) followed by a Fire Water Deluge System (FWDS). The technique is then further-developed and applied to solve problems of multi-phased mission systems. Two systems are considered; first an unmanned aerial vehicle (UAV) and secondly a military vessel. The final part of this thesis focuses on continuing the development process by adapting the method to solve design optimisation problems for multiple multi-phased mission systems. Its application is demonstrated by considering an advanced UAV system involving multiple multi-phased flight missions. The applications discussed prove that the technique progressively developed in this thesis enables design optimisation problems to be solved for systems with different levels of complexity. A key contribution of this thesis is the development of a novel generic optimisation technique, embedding newly developed FTMPs, which is capable of optimising the reliability design for potentially any engineering system. Another key and novel contribution of this work is the capability to analyse and provide optimal design solutions for multiple multi-phase mission systems. Keywords: optimisation, system design, multi-phased mission system, reliability, genetic algorithm, fault tree, binary decision diagra