Tension-bending risk curves for the ATD lower lumbar spine subjected to oblique impact under FAA emergency landing conditions

Abstract With the increasing use of obliquely oriented airline seating configurations, the objective of the present study was to develop injury risk curves for the lower lumbar spine load cell of the FAA-H3 dummy. A new spinal criterion, termed FAA-LLtb, which is a linear combination of tensile load with forward flexion, and lateral bending moments, was developed to predict the injuries occurring to the lower lumbar spine and sacrum regions. The injury definition required for the metric was obtained from the matched PMHS tests. The loading conditions included variations in peak sled accelerations, the presence or absence of an armrest, the belt type (single and dual lap-belt systems), and seat orientation relative to impact vector (45° and 30°). The developed ATD risk curve based on the combined metric represents AIS = 3+ injury probability for the lower lumbar spinal levels. The survival analysis estimated normalized confidence interval size (NCIS) values were in fair and good categories at all levels of probability. At 5%, 25% and 50% risk levels, the combined loading metric values were 1.6, 1.8, and 2.0, respectively. The study estimated that the combination of bending moments and tensile load was a better injury criterion than any individual metric for assessing the injury to the lower lumbar spine and pelvis regions under oblique loading.