Enhancing rotorcraft safety following engine or drive train failures has been a primary concern throughout the history of vertical flight operations. Previous work on autorotation trajectory optimization has shown potential for improved flight control and guidance solutions, and tactile cueing through active flight controls has been investigated to provide autorotation guidance without over-burdening the pilot during this high workload flight condition. This paper examines a notional autorotation tactile cueing system that follows an envelope limiting strategy for the entry, descent, flare, and landing phases to provide greater flexibility to the pilot. Methods for implementation of the guidance cues have been examined that range from adjustable stick force gradients (soft stops) to a surface-mounted appliqué device on the stick grip to provide localized unsteady tactile cues. The latter approach has been examined as a method to provide tactile cueing in legacy aircraft without active flight controls. The development and implementation of a collective axis cueing system is discussed, including supporting optimal autorotation trajectory and control analysis that was used as a design basis for cueing law development. Results are presented on the development and simulation of a prototype collective axis cueing system, development and bench testing of the appliqué cueing device, and pilot-in-the-loop simulation evaluations.
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