The Bell 525 Relentless, The World's First "Next Generation" Fly-by-Wire Commercial Helicopter

Since its formal launch in 2012, designers of the Bell 525 Relentless have sought feedback and utilized input from a Customer Advisory Panel (CAP) comprised of industry-leading global helicopter operators. The top initiative of this group is to adopt the features of a next generation helicopter that provides enhanced margins of flight safety. In response, the Bell 525 will be the first commercial helicopter to offer full authority fly-by-wire digital flight controls. Helicopter safety reviews have consistently found that human factors and situational awareness are the leading cause of helicopter accidents. With this history, safety clearly points to the need for careful consideration of pilot workload, especially in demanding situations such as hovering near multiple obstacles or performing in Degraded Visual Environments (DVE). Design-for-safety enhancements include Translational Rate Command / Position Hold control laws at low speed, automatic computer assisted entry into autorotation in the event of a dual engine failure, automatic OEI compensation, load alleviation provisions, and control axis decoupling. This paper describes the process of incorporating requirements for modern handling qualities design criteria into the control system design and examines the real-time testing scheduled for the 525's first flight.