Neck Injury Criteria Development for Use in System Level Ejection Testing; Characterization of ATD to Human Response Correlation under Gy Accelerative Input
Increased neck injury risk during ejection due to the increasing mass of modern Helmet Mounted Displays (HMDs) drove Parr et al. (2013, 2014, 2015) to define new neck injury criteria to reduce subjective interpretation of ejection system test results and provide early input to HMD and escape system design. The latest revision of MIL-HDBK-516 includes Multi-Axis Neck Injury Criteria (MANIC) interpretation, as described by Parr et al., to guide HMD and escape system evaluation. This research developed a MANIC(Gy) transfer function to make MIL-HDBK-516 criteria applicable to cost effective Anthropometric Test Device (ATD) escape system testing in the Gy acceleration axis. Statistical analysis of the six primary neck loads for ATDs revealed Mx (side bending) significance, necessitated adjustment to the human MANIC(Gy) calculation developed by Parr et al. before applying it to ATDs. Multiple regression produced models of ATD Six Factor (SF) MANIC(Gy) and human MANIC(Gy) to quantify response differences across the applicable Gy acceleration range. The resulting deltas between the regression models at instantaneous peak-G values defined the transfer function between ATD and human responses. Parametric survival analysis of transformed ATD SF MANIC(Gy) responses produced ATD injury risk curves, indicating 5% risk of AIS 2 injury during Gy accelerations corresponds to a MANIC(Gy) of 0.473 for humans and 0.423 for ATDs.