Controlled flight for aircraft requires a comprehensive analysis of critical conditions within the flight envelope, providing necessary information to develop a robust control system. These flight conditions are identified, typically where the control system is most active, from which the aircraft is trimmed to a specified steady trim condition. Whilst symmetric flight trims for conventional fixed-wing aircraft are relatively straightforward to determine, those associated with more complex scenarios – multiple redundant control effectors and/or asymmetric flight conditions – can be a particular challenge to solve for. Furthermore, if loci of trim solutions are sought (as one or more parameter varies), this can be a slow numerical process. This paper seeks to address these challenges by proposing a systematic approach that can take account of the above scenarios. It entails a two-stage process, with conventional numerical minimization techniques being used in the first stage to locate initial trim points, with algorithms and software designed to account for generic scenarios such as asymmetric flight. Then, to help ensure that flight conditions between the chosen reference points do not present worse-case scenarios – or indeed to help choose the reference points – the single-point trimming process is used to initialise a continuation algorithm that solves for loci of trim solutions as paramaters are varied. The paper desribes the proposed methodology and its application to a flight mechanics model of a B747 airliner using both straight-and-level and one-engine-out trim examples. These serve to demonstrate the generality and computational efficiency of the process.
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