Development of an Updated Tensile Neck Injury Criterion

Background: Ejection neck safety remains a concern in military aviation with the growing use of helmet mounted displays (HMDs) worn for entire mission durations. The original USAF tensile neck injury criterion proposed by Carter et al. (4) is updated and an injury protection limit for tensile loading is presented to evaluate escape system and HMD safety. Methods: An existent tensile neck injury criterion was updated through the addition of newer post mortem human subject (PMHS) tensile loading and injury data and the application of Survival Analysis to account for censoring in this data. The updated risk function was constructed with a combined human subject (N = 208) and PMHS (N = 22) data set. Results: An updated AIS 3+ tensile neck injury criterion is proposed based upon human and PMHS data. This limit is significantly more conservative than the criterion proposed by Carter in 2000, yielding a 5% risk of AIS 3+ injury at a force of 1136 N as compared to a corresponding force of 1559 N. Discussion: The inclusion of recent PMHS data into the original tensile neck injury criterion results in an injury protection limit that is significantly more conservative, as recent PMHS data is substantially less censored than the PMHS data included in the earlier criterion. The updated tensile risk function developed in this work is consistent with the tensile risk function published by the Federal Aviation Administration used as the basis for their neck injury criterion for side facing aircraft seats.