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Static Comfort Assessments for Ejection Seat Cushions in Three Different Rail Angles

[+] Author Affiliations
Akindeji Ojetola, Landon Onyebueke

Tennessee State University, Nashville, TN

Edward Winkler

The Boeing Company, St. Louis, MO

Paper No. IMECE2010-38839, pp. 509-514; 6 pages
doi:10.1115/IMECE2010-38839
From:
  • ASME 2010 International Mechanical Engineering Congress and Exposition
  • Volume 11: New Developments in Simulation Methods and Software for Engineering Applications; Safety Engineering, Risk Analysis and Reliability Methods; Transportation Systems
  • Vancouver, British Columbia, Canada, November 12–18, 2010
  • Conference Sponsors: ASME
  • ISBN: 978-0-7918-4448-9
  • Copyright © 2010 by ASME

abstract

Aircrew members sit on ejection seats for a long period of time on operational missions. It is paramount for them to be as comfortable as possible within the constraints of this seat system to maximize their operational performance. 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. This comprehensive static comfort assessment for ejection seats provides comparison between a variety of operational and prototype cushions (three in all: baseline cushion, honeycomb and air-cushion) and different installation rail angles (14°, 18°, and 22°) with 18° nominally used as the starting point. Three operational cockpit environment mockups with adjustable rail angle were built. Ten volunteer subjects, six females and 4 males, ages 19 to 35, participated in the comfort assessment. The volunteers fit within the JPATS cases 1–7 range of anthropometry, and each of them tested all cushions in all three installation rail angles. The volunteer clothing was similar the fighter pilot clothing ensemble (including harness). Each comfort assessment test lasted for six-hours, during which the subjects could not leave the seat and 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. 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. The results for blood pressure and pulse rates are inconclusive. However, the oxygen blood flow (basal Sp02) favors the baseline cushion with the highest oxygen flow over the period of the testing, somewhat similar to the comfort rating.

Copyright © 2010 by ASME
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