Neck injury criteria formulation and injury risk curves for the ejection environment: a pilot study.
BACKGROUND
Helmet mounted displays provide increased pilot capability, but can also increase the risk of injury during ejection. The National Highway Transportation Safety Administration's (NHTSA's) neck injury criteria (Nij) metric is evaluated for understanding the impact of helmet mass on the risk of injury and modified risk curves are developed which are compatible with the needs of the aviation community.


METHODS
Existent human subject data collected under various accelerative and head loading conditions were applied to understand the sensitivity of the Nij construct to changes in acceleration and helmet mass, as well as its stability with respect to gender, body mass, neck circumference, and sitting height. A portion of this data was combined with data from an earlier postmortem human subject study to create pilot study modified risk curves. These curves were compared and contrasted with the NHTSA risk curves.


RESULTS
A statistically significant difference in the peak mean Nij was observed when seat acceleration increased by 2 G, but not when helmet mass was varied from 1.6 kg to 2 kg at a constant seat acceleration of 8 G. Although NHTSA risk curves predict a 13% risk of AIS 2+ injury for the 8-G, 2-kg helmet condition mean Nij of 0.138, no AIS 2+ injuries were observed. Modified risk curves were produced which predict a 0.91% risk of AIS 2+ injury under these conditions.


CONCLUSIONS
The Nij was shown to be sensitive to changes in acceleration and generally robust to anthropometric differences between individuals. Modified risk curves are proposed which improve risk prediction at lower Nij values.
Air Force Institute of Technology, Wright-Patterson AFB, OH 45433, USA. jeffrey.parr@afit.edu
Jeffrey C
JC
Parr
Air Force Institute of Technology, Wright-Patterson AFB, OH 45433, USA.
Michael E
ME
Miller
Federal Aviation Adminstrartion, Washington, DC, USA.
Joseph A
JA
Pellettiere
Air Force Institute of Technology, Wright-Patterson AFB, OH 45433, USA.
Roger A
RA
Erich
D015998:Abbreviated Injury Scale; D000054:Acceleration; D000060:Accidents, Aviation; D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D006260:Head Protective Devices; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D019838:Neck Injuries; D010865:Pilot Projects; D018570:Risk Assessment / Q000379:methods*; D055815:Young Adult