Fuel-Economic Flight Optimization for Descent and Approach Phases

This paper presents a computationally efficient flight optimization method for improving the fuel economy of a fixed-wing aircraft following a landing path during the descent and approach phases. The problem is converted to an optimal control problemwith one energy state variable, subject to state and control input constraints along the path. It is shown that the solution to the energy-optimal path following problemprovides a good approximation to theminimum-fuel problem, hence, it can be used for improving the fuel economy. Compared to standard numerical optimization techniques, the proposed method is more suitable for onboard real-time trajectory optimization because of its guaranteed convergence, and computational efficiency. Numerical examples are presented to demonstrate the validity of the proposed approach, and its capability for improving fuel economy during the landing phase.