Citation

Buhrman JR, Andries MJ, Ma D. SAFE J. 1999; 29(1): 29-38.

Affiliation

Air Force Research Lab, Wright-Patterson AFB, OH, USA

Copyright

(Copyright © 1999, SAFE Association)

DOI

unavailable

PMID

unavailable

Abstract

During ejection tower tests conducted by Martin-Baker with a Large JPATS manikin in a simulated Martin-Baker ejection seat (MKUS16LA), the manikin's pelvic region rotated forward under the lap belt and partially out of the seat. This could have serious implications for human occupants due to the potential for spinal misalignment and altered trajectory during ejection. A series of simulated ejections using a biodynamic computer model showed that this phenomenon was due in large part to the inertial properties of the large manikin in combination with the seat pan length and initial leg position. A series of +Gz impact tests on a vertical deceleration tower with the Large JPATS manikin were conducted to verify and more precisely quantify the model results. The tests demonstrated large lap belt loads and excessive hip and knee displacements in the manikin, and identified several contributing factors in the seat/restraint system, including the pre-impact positioning of the manikin's thighs above the seat pan, the length of the seat pan, and the fabric of the flight suit. Modifications were implemented which lowered the initial leg position and extended the seat pan length. Modifications to the manikin which altered the weight and center of mass of the legs were also made in order to more accurately reflect the mean anthropometry characteristics of the large male crewmember. It was found that the seat length and leg positioning modifications when used in combination with the modified manikin were successful in reducing both the loads and displacements.