Human factors evaluation of mixed reality assistance systems for aerial refueling of fighter aircraft

Abstract The process of transferring fuel from a tanker aircraft to a receiving aircraft is called air-to-air refueling (AAR). This study examines the probe-and-drogue method of AAR, in which a tanker aircraft flies ahead of a receiving aircraft and extends a flexible hose with an attached drogue midflight, allowing the receiver to manually couple its refueling probe with the drogue. In previous research the German Aerospace Center developed two visual, mixed-reality assistance systems to support receiver pilots during contact approach and contact hold by visualizing important, previously unavailable information. One system visualizes the relative speed difference between the probe and the drogue, while the other highlights the drogue’s rim and displays fuel offload information. The second assistance system was only tested in a preliminary state focusing on drogue highlighting without fuel offload and status information. This study examines these assistance systems, though the primary aim is not to evaluate pilot usability and experience, but to assess the effectiveness of the methodology used for evaluating Human Factors (HF) aspects in visual, mixed-reality assistance systems during simulated AAR contact approaches. Conducted in a fighter aircraft simulator, the study involved six experienced fighter aircraft squadron pilots performing multiple refueling contact approaches with and without visual assistance. Alongside simulator flight data, HF aspects such as workload, situation awareness, performance, usability and user experience were recorded and analyzed. The applied methodology proved to be effective for evaluating HF aspects of visual mixed-reality assistance systems for pilots. However, the employed methods did not yield robust statistical findings, as expected given the small sample size. Nevertheless, the findings suggest that visual mixed-reality assistance systems may influence pilot behavior and may facilitate pilot support during manual AAR.