The modern crew station of Army helicopters uses the helmet as an integral component of the aircraft control systems. What was once viewed as a simple device for crash protection now supports devices including night vision goggles, chemical mask, head-up displays, and weapon aiming systems. These devices combine to increase the biomechanical stress in the neck. This study investigated the effects of increasing helmet torque on the motion of the helmeted head under the conditions of long-duration whole-body vibration exposure. Twelve U.S. Army volunteer aviators were exposed to four hours of whole-body vibration, similar to that found in a UH-60 helicopter, while wearing four different helmets. Helmet torques, as calculated at the point where the head connects to the spine, ranged from a standard aviator helmet to a helmet with a chemical mask and a night vision goggle. Head motion was measured using a three dimensional active infrared marker system attached to a fixture held in the subject's teeth. Results showed no significant differences (p<0.05) in head pitch motion over time for helmets, but significant differences among helmet torques. These results support the existing recommended helmet design of limiting the added helmet torque to 90 Nan for long-duration helicopter flights.

ADA 312122 Approved for public release; Distribution is unlimited. The opinions and conclusions expressed herein are those of the student-authors and do not necessarily represent the views of the U.S. Army Command and General Staff College or any other governmental agency. (References to these studies should include the foregoing statement.)