Flying Qualities Prediction Tool for Aerial Refuelling Operational Compatibility Assessment

Air-to-air refuelling is a common operational practise in military aviation, and is used both to extend mission length and reduce total fuel consumption for long-haul missions. Clearing tanker and receiver aircraft pairs for aerial refuelling is an extensive process that requires a combination of analysis and flight testing. In order to develop further tools with which to analyse aerial refuelling, this paper presents the continued development of a fully coupled vortex lattice method representation of two aircraft in close formation flight which is used to calculate the frequency and damping of a receiver aircraft's long period, short period, and Dutch Roll during aerial refuelling. These flight dynamics quantities are then used to predict the flying qualities during air-to-air refuelling. This paper examines the case of a F/A-18 being refuelled by both a C-150 Polaris and C-130 Hercules tanker aircraft. At the refuelling point of both tankers, the results predict a reduction in long period natural frequency, an increase in long period damping, an increase in short period natural frequency and damping, a decrease in Dutch Roll natural frequency, and an increase in Dutch Roll damping. This is predicted to result in Level 2 flying qualities during refuelling.