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The detrimental effects of prolonged sitting during long-duration flights include deep vein thrombosis, pressure sores, and decreased awareness and performance. However, the cushion is often the only component of the ejection seat system that can be modified to mitigate these effects. This study investigated the long-duration effects of sitting in four ejection seat cushions over eight hours. Subjective comfort survey data and cognitive performance data were gathered along with comparative objective data, including seated pressures, muscular fatigue levels, and lower extremity oxygen saturation. Peak seated pressures ranged from 1.22–3.22 psi. Oxygen saturation in the lower extremities decreased over the eight hours. Cognitive performance increased over time regardless of cushion with the exception of the dynamic cushion, which induced a decrease in performance for females.

For human motion studies, which are to be used for either dynamic biomechanical analyses or development of human motion simulation models, it is important to establish an empirical motion database derived from efficient measurement and well-standardized data processing methodologies. This paper describes the motion recording and data processing system developed for modeling seated reach motions at the University of Michigan's HUMOSIM Laboratory. Both electromagnetic (Flock of Birds) and optical (Qualysis) motion capture systems are being used simultaneously to record the motion data. Using both types of devices provides a robust means to record human motion, but each has different limitations and advantages. The amount of kinematic information (DOFs), external sources of noise, shadowing, off-line marker identification/tracking time, and setup cost are key differences.

This paper describes the rattle mechanisms that exist in seat belt retractors and the vehicle acceleration conditions that induce these responses. Three principal sources of rattle include: 1) the sensor, 2) the spool, and 3) the lock pawl. In-vehicle acceleration measurements are used to characterize retractor excitation and are subsequently employed for laboratory testing of retractor rattle. The merits and demerits of two testing methods, based on frequency domain and time domain shaker control, are discussed.