MULTI-AXIS VIBRATION MITIGATION PROPERTIES OF SEAT CUSHIONS DURING MILITARY PROPELLER AIRCRAFT OPERATIONAL EXPOSURES

摘要

There have been increasing complaints of annoyance, fatigue, and musculoskeletal pain during prolonged exposures to propulsion-generated vibration in military propeller aircraft. The objective of this study was to evaluate the effects of seat cushions on mitigating the higher frequency (>10 Hz) multi-axis vibration associated with Navy E-2C Hawkeye operations. An E- 2C crew seat was used in the laboratory during exposure to a selected operational signal. Triaxial accelerations were measured at the interface between the human and cushion (seat pan and seat back). The most pronounced effects were observed at the blade passage frequency (~73.5 Hz). The highest vibration occurred at the seat pan in the fore-and-aft (X) direction of the subject (lateral direction of the aircraft). Substantial vibration was observed at the seat back in the vertical (Z) direction. Significantly lower levels of fore-and-aft (X) vibration occurred at the seat pan with all cushions as compared to the original E-2C cushion (P<0.05). The largest reduction in the X acceleration was about 40% with a mean reduction of approximately 20% among the cushions. The results raised questions regarding psychophysical effects and whether the vibration mitigation at the blade passage frequency is sufficient for reducing the reported symptoms.