Aircraft Route Optimization for Formation Flight

Abstract

We quantify the fuel and cost benefits of applying extended formation flight to commercial airline operations. Central to this study is the development of a bi-level, mixed-integer real formation flight optimization framework. The framework has two main components: 1) a continuous-domain aircraft mission performance optimization and 2) an integer optimization component that selects the best combination of optimized missions to form a formation flight schedule. The mission performance reflects the effects of rolled-up wakes, formation heterogeneity, and formation-induced compressibility. The results show that an airline can use formation flight to reduce fuel burn by 5.8% or direct operating cost by 2.0% in a long-haul international schedule. The savings increase to 7.7% in fuel or 2.6% in cost for a large-scale, transatlantic airline alliance schedule. These results include the effects of a conservative fuel reserve for formation flight. Sensitivity studies show that a modest reduction in the cruise Mach number may be sufficient to manage the impact of formation-induced compressibility effects on system-level formation flight performance. We demonstrate that the potential savings from extended formation flight (an operational improvement using existing aircraft) can approach those claimed for advanced vehicle technologies and unconventional configurations.