John R. Buhrman

Biodynamic Testing of Helmet Mounted Systems

New helmet mounted visually coupled systems (night vision devices and helmet mounted displays) which are designed to improve pilot performance may only increase the existing potential for neck injury during emergency escape due to the increase in head supported weight and altered center-of-gravity (CG). Designers need criteria for helmet system mass properties which will not increase the risk of injury above acceptable limits. A research study reviewed and analyzed accident statistics, current literature, and in-house laboratory data. Mass properties of various helmet systems were related to biodynamic responses of instrumented humans and manikins from impact tests conducted on the Armstrong Laboratory Vertical Deceleration Tower. Accident data revealed severe neck injuries are relatively rare in an operational setting. Laboratory studies of head/neck biodynamic response relating compression force at the occipital condyles to head supported weight indicate average forces exceed safe guidelines. The studies also suggest that helmet systems weighing less than 2.27 kg and having a center-of-gravity located only slightly above the anatomical axis origin of the head, will not induce severe neck injury during the catapult phase of ejection compared to current operational helmets.

Evaluation of the Nij neck injury criteria with human response data for use in future research on helmet mounted display mass properties

Technological advances have enabled components to be added to Helmet Mounted Displays (HMDs) that provide increased pilot capability. Future Air Force fighter aircraft are being developed to incorporate added technologies that could result in heavier and bulkier HMDs. The added weight and center of gravity changes to the pilot’s helmet ensemble from these additional components place the neck at an increased risk of injury during ejection. This paper outlines a preliminary research methodology studying the human neck response data from the Air Force Research Laboratory’s extensive human impact testing database using the Nij criteria as an evaluative tool. Initial results are presented.