Ejection Seat Cushions Static Evaluation for Three Different Installation Rail Angles

Jet fighter missions have been known to last extended period of time. The need for a comfortable and safe seat has become paramount considering that fact that uncomfortable seats can lead to numerous health issues. Several health effects like numbness, pressure sore, low back pain, and vein thrombosis have been associated with protracted sitting. The cushion, and of late the installation rail angle are the only components of the ejection seat system that can be modified to reduce these adverse effects. A comprehensive static comfort evaluation study for ejection seats was conducted. It provides comparison between a variety of operational and prototype cushions (baseline cushion, honeycomb and air-cushion) and three different installation rail angles (14°, 18°, and 22°). Three operational cockpit environment mockups with adjustable installation rail angle were built. Ten volunteer subjects, six females and four males, ages 19 to 35, participated in the seat comfort evaluation. The volunteers fit within the JPATS cases 1-7 range of anthropometry, and all of them tested all cushions in all the three installation rail angles. The volunteer clothing was similar the fighter pilot clothing ensemble (including harness). Each seat comfort evaluation test lasted for six-hours, during which the subjects could not leave the seat. Movement activities in the seat system were reduced as much as possible to reflect flight conditions. The subjective comfort survey and objective data such as seat pressure, blood pressure, and oxygen blood flow were gathered during the sitting period. The test results indicated that for objective methods, rail angle 22° persistently has a lowest seated pressure, while 18° has the highest pressure. An air-cushion has and maintains the lowest seated pressure, while a honeycomb cushion has the highest for all rail angles. The results for blood pressure and pulse rates are inconclusive. However, the oxygen blood flow (basal Sp02) favors the baseline cushion with the highest blood oxygen flow over the period of the testing. When it comes to subjective comfort rating, the baseline cushion has the highest comfort rating, while the air-cushion has the lowest for all rail angles which looks similar to the oxygen blood flow rating.