Automatic Control of Formation Flight in the Upwind Field of the a Proceeding Aircraft

• Applicant: Professor Dr.-Ing. Robert Luckner
• Subject Area: Fluid Mechanics ; Traffic and Transport Systems, Intelligent and Automated Traffic
• Term: from 2012 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 210166512

Aviation has to significantly reduce its emissions in the future. The potential of saving power while flying in formation like migratory birds has long been known, but is still unused. Using this technique, airplanes can save 15-20% of fuel. The trailing aircraft uses the upwind field of the preceding aircraft to reduce thrust and thereby fuel consumption. In several flight tests fuel reductions of 8-15% were successfully demonstrated for different types of aircraft for example in July 2013 using Boeing C-17 transport aircraft on long cruise flight segments. Those flights were performed manually or by using an experimental, relatively simple position control system.In the first project phase it was demonstrated, that tight formation flight using transport aircraft is possible - with fuel reductions of 10% for the following aircraft. The procedure for entering and maintaining the formation in automatic operation was proposed and pilots confirmed it to be feasible. The structure of the control system and its design methods were devised, a control system for seeking the optimal position in the upwind field which is robust against vortex-axes variations was developed. The automatic formation flight can be demonstrated in a flight simulator. To date the investigations are confined to formations of two identical aircraft (homogenous formation), flying steady, straight horizontal trajectories, and limited to flights without failures.Based on the perceptions made so far it can be assumed that formation flight can be used in commercial flight operations (Hypothesis H1). The expected benefits will justify the efforts that are needed to develop necessary systems and procedures (H2). A broad acceptance by aircraft operators and pilots is still missing. It can only be achieved if formation flight is not only cost-efficient but also safe and reliable. To achieve this, an automatic formation flight control system including sensors and displays, which is robust against parameter changes, as well as flight procedures that cover normal flight operations and failures are required (H3).The objective of the second project phase is to clarify, based on the working hypotheses H1 to H3, how and under which conditions the automatic formation flight - including heterogeneous formations - can be safely, efficiently, and comfortably performed so that it can be used in commercial flight operation. The research will be carried out in five steps: 1) definition of procedures, 2) formulation of requirements, 3) development of a concept for sensors and display, 4) design of the control system, and 5) evaluation of steps 1 to 4 in the flight simulator. With the flight simulator SEPHIR which was enhanced during the project an eminently suitable tool is available for research. Results of the project will be coherent operation procedures for both normal and failure cases and a robust concept for the control system. Based on that an integration into future aircraft is possible.

• DFG Programme: Research Grants