Side Impact Neck Injury Criteria and Tolerances in Aerospace Safety

The objective of this research is to develop neck injury criteria and injury tolerance levels to be used as a basis for a performance standard for the certification of side facing aircraft seats. This paper presents the results of the first part of this study. A literature review was performed on the neck injuries, kinematics and injury mechanisms in lateral loading and existing injury criteria and tolerance levels. Simulations with a human model were performed to determine the head and neck kinematics of the human body in a side facing aircraft seat and to determine the effect of belts and muscle activity. Injury criteria that seemed to best correlate with neck injuries were the head angle and the head angular acceleration. A few studies also indicated that the upper neck lateral bending moment and upper neck lateral shear force could be related to neck injury. The simulations in which the human model was seated on a rigid side facing couch against a rigid wall at counter side of the impact direction and using a 5-point belt showed the largest head lateral angle and head lateral angular rotation. This ‘worst case scenario’ will be used in future PMHS tests for injury investigation. The phases in the kinematics during lateral loading described in literature coincide with the human model kinematics. The peak head lateral angle and head lateral angular acceleration resulting from the simulations coincide with the literature data. The simulations showed that muscle activity significantly reduces the head lateral angle and head lateral angular acceleration. The simulations showed that at a 16 G triangular impact a neck injury of AIS 2 or more can be expected.