The innate intelligence of fly-by-wire (FBW) flight controls makes them a natural for reducing the relatively high pilot workload that can come with rotary wings. But to understand what sort of response the pilot expects from control inputs, a standard FBW system needs to be told what phase of flight or environment the helicopter is flying in, reimposing some workload that two research engineers with the Ottawa-based National Research Council Canada Institute for Aerospace Research (aka NRC Aerospace) aim to eliminate.
Bill Gubbels and Kris Ellis have been developing this technology for the past four years, and they are excited about its possibilities. Said Stewart Baillie, director of the NRC Aerospace Flight Research Laboratory, “This new control system architecture gives pilots stability when they need it and agility when [with their primary flight-control inputs] they request it, all without making deliberate ‘mode-choice’ decisions on what the situation demands.” After flying the system in NRC’s technology demonstrator Bell 412, Baillie declared, “I would not want to fly any other way.”
The NRC’s technique blends rotorcraft control response types so that the frequency of the pilot’s input determines the control response applied. With this approach, a pilot making slow or deliberate inputs–for example, those typically used in poor visual conditions–commands the aircraft via translational rate control. A pilot using rapid control inputs, which are more common in an environment providing plenty of visual cues, channels the control inputs to attitude and rate command control systems. The NRC’s control structure combines the stability of a translational-rate-control system with the performance of a rate-command system without requiring discrete mode switching by the pilot.
“The beauty of the control system architecture is that if you move the stick rapidly, the aircraft feels agile and nimble, yet predictable, but move the stick slowly and it’s stable. This gives the pilots the best of both worlds and lets them concentrate on flying the aircraft rather than managing the system,” noted engineer Ellis.
Added fellow engineer Gubbels, “This product is now available to potential licensees, and we believe it’s something that every new and retrofit fly-by-wire aircraft should have installed. The potential for this control architecture to improve operational effectiveness, particularly for military applications, is exponential.” NRC Aerospace is currently seeking partners for the system and invites potential users to contact the department for further explanation of the interface’s applications.