Semi-Active Magnetorheological Seat Suspensions for Vibration Isolation of a Helicopter Crew Seat

A magnetorheological (MR) seat suspension system was retrofitted to the MH-60R Seahawk crew seat to provide semi-active control of harmful cockpit vibrations. Current seating systems are designed primarily to meet crashworthiness requirements rather than vibration isolation. Energy absorbing devices within current seating systems will not stroke until a tuned load threshold is reached and therefore act as a stiff link between the seat and the floor during normal rotorcraft vibration. Because of this, these systems provide no isolation to cockpit vibration. In this effort, an MR suspension was implemented in series with the existing energy absorbing devices. Experimental vibration testing results have shown that this system reduces the dominant rotor-induced vertical vibration at the blade passage frequency transmitted to the occupant by over 90%, which is a 86% improvement over the original MH-60R crew seat. Furthermore, full-scale dynamic crash testing performed on this retrofitted seat has demonstrated that crash safety is preserved. Through this dynamic testing in the laboratory, it has been shown that the MR suspension reduces peak lumbar loading as compared to the original MH-60R crew seat from 1,950 lb down to 1,250 lb. This paper presents the results from the system's first set of flight testing.