In-flight Profile Updates by Appropriate Cost Index Selection — Operational Perspective*

Abstract

Modern aircraft can generate their optimal flight profile via a flight management computer. The optimality considers both time and fuel costs, and the pilot can set the relative weight factor called a cost index (CI). However, sometimes the flight profile should be updated during flight due to various reasons e.g. passenger boarding delay and airport congestion, and pilots often change the flight profile by changing the CI. Since CI is a relative factor, it is difficult to set the optimal CI in every situation and flight stage. This paper proposes a decision-support algorithm aimed at 1) providing pilots with information on the most appropriate range of CI or flight speed (climb/cruise/descent) and 2) clarifying the relationship between the timing of changing the flight profile and its effect. As for 1), in order to provide the appropriate range of CI or speed, a new metric of direct operating cost bound is introduced. As for 2), it is revealed that descent speed is the most effective parameter to change the flight time and fuel consumption, but the appropriate CI varies with flight phases. The results obtained in this research will help pilots change the flight profile flexibly to achieve greater efficiency.