Ejection seat cushions in current U.S. Air Force aircraft are not suitable for comfort during extended missions. Specific physiological problems such as buttock, leg and back pain, numbness and tingling in the extremities, and overall fatigue have been documented in past laboratory research and operational use [1,2,3,5,6]. Designing a single cushion to address the physiological problems of the entire aircrew population is a significant challenge. Cushion material selection, cockpit space restrictions, and limited ability to reposition during flight contribute to discomfort during extended missions. Ejection seat dimensions and contours are fixed in most cases, causing accommodation problems for large and small occupants.
A pilot study was performed at the Air Force Research Laboratory at Wright-Patterson Air Force Base to investigate objective test methods for determining cushion comfort. Five volunteer subjects were tested with a variety of operational and prototype cushions. Peak seated pressures, contact areas, and lumbar spinal shapes were measured for each cushion. Tests ranged from six-minute quick looks to gather comparative objective measurements, to four-hour extended seating tests to gather subjective and performance data.
The study showed objective test methods could be used to identify comfort trends for different cushion candidates. Seated peak pressures and contact areas differed among the cushion specimens that were tested. Trends in subject performance and comfort ratings were also shown. Alternate pressure and shape measurement test equipment and data analysis techniques should be investigated. The data also show that the comfort characteristics of current operational equipment could be improved.