Understanding Fleet Impacts of Formation Flight
An operational efficiency concept which is not yet common but could provide significant fuel burn and economic benefits to the air transportation system is formation flight. Formation flight is the practice of flying two or more aircraft in a specific pattern such that the induced drag of aircraft behind the lead aircraft can be reduced. Previous work in this area has been accomplished by a number of researchers, including students at RWTH Aachen and Georgia Tech. This work has been focused on understanding the flight conditions on widely utilized aircraft, such as the Boeing 777, Boeing 757, Airbus A320, and Airbus A300, necessary to maximize the benefits of formation flight. The results of the these vehicle studies by RWTH Aachen have shown that the maximum benefit generally occurs with relatively small spacing of the aircraft, of only a few wingspans. While these vehicle level studies have currently been limited to the aircraft aforementioned, further studies are being conducted for the purpose of generalizing the induced drag and fuel burn reductions achieved during formation flight based on basic geometric and aerodynamic parameters of the aircraft. The ultimate goal of this work is to produce estimates that can be used in fleet level analysis for any combination of aircraft occurring in real world operations. In addition to the work completed between these universities at the aircraft level, the results from these aircraft studies will be included in fleet level estimates of fuel burn. This fleet level analysis provides a starting point for estimation of true benefits with a specific use case. In order to complete these estimates, cost and performance models have been developed, as well as algorithms to determine the optimal meeting and split up points of routes. These tools have been tested to assess potential candidate routes for formation flight for real air carriers. Ultimately, the results generated from these initial studies of formation flight have been limited in scope, and can be expanded upon for more global air transportation considerations. However, based on the results from these studies, it seems likely that fuel burn benefits in the 4-6% range for air carriers could potentially be accomplished if full use of formation flight were to be implemented. While this may be unlikely due to the logistical and regulatory obstacles of implementing such a concept, these estimations still serve as a valid first order estimate of additional benefits that can be achieved through further use of operational efficiency measures.