MH-47G DAFCS Helicopter Aerial Refueling Control Laws

During the development of updated digital control laws for the MH-47G, a focus was placed on reducing pilot workload during aerial refueling. Helicopter aerial refueling (HAR) is a high-workload piloting task that involves aggressive, yet precise flight control inputs in close formation flight behind the tanker aircraft. This paper describes the methodology and control laws that were developed to minimize pilot workload while performing the HAR mission task with the MH-47G Digital Automatic Flight Control System (DAFCS). A real-time HAR simulation task was created with the ability to tailor task difficulty. The simulation was tuned to produce an appropriate level of pilot workload by using feedback from experienced operational pilots. Once tuned, the simulator was employed to evaluate the suitability of proposed response types. Control law parameters were determined using frequency domain techniques. Flight testing consisted of allowing the pilot to select gains from within pre-determined boundaries, then measuring workload with the Cooper-Harper scale. By implementing an attitude-command response type in both longitudinal and lateral axes, pilot workload during aerial refueling is significantly reduced from a borderline level 2/level 3 task to a level 1 task. Flight data are presented.