In-flight cost index optimisation upon weather forecast updates

This paper presents an optimisation framework to compute the altitude and speed profiles of a trajectory in the execution phase of the flight, such that the expected total cost (ETC) of the operation is minimised (i.e. modelling the expected cost of delay and fuel – including arrival uncertainties – at the arrival gate). This is achieved with a two-stage optimisation strategy: a trajectory optimiser that minimises a generalised direct operating cost function, for a given cost index; and an upper-level optimiser, which obtains the best cost index that minimises the ETC. Several case studies are presented for different departure delays, while considering the impact of two different weather forecast updates too: a region with relative high head-winds appearing half way across teh flight; and a cold atmosphere scenario, with a tropopause altitude lower than standard conditions. ETC savings with respect to following the operational flight plan increase with departure delay, as expected. Due to the non-linearity of the cost function, however, the benefits of considering the weather update depend on the actual value of the departure delay, showing the convenience of integrating the proposed approach into a crew decision support tool in order to avoid sub-optimal decisions.