Examination of excessive fuel consumption for transport jet aircraft based on fuzzy-logic models of flight data

Because the amount of fuel usage is huge, and exhaust emissions of commercial transports is regulated under the Kyoto Protocol, how to reduce fuel consumption is an urgent problem for all airlines. The airlines urgently need a practical method to reduce fuel consumptions within constraints to accomplish the mission. The objective for the present paper is to use a model-based method and flight data to enhance fuel efficiency for commercial transports. The fuzzy-logic modeling (FLM) technique will be employed to establish the reference lift-to-drag (L/D) model. The model is utilized to predict the deficiencies of lift-to-drag ratio through sensitivity analysis to determine the relative contributions from influencing flight variables for the excessive fuel consumption. This method is based on the flight data in quick access recorder (QAR) available in the Flight Operations Quality Assurance (FOQA) program. The process of identifying how flight variables reduce the lift-to-drag ratio of a twin-jet transport aircraft in cruise flight will be presented. The sensitivity derivatives for slow-varying and fast-varying influence variables are analyzed. The factors contributing to the degradation of aerodynamic efficiency (i.e. L/D) in operations are evaluated. The excessive fuel consumption due to the effects of deficiencies will be estimated in the present paper. If all the deficiencies can be improved, the fuel efficiency enhancement will be achieved.