Effects of Headrest Position and Helmet Weighton Human Dynamic Response During +Gz Impact Acceleration

摘要

Pilot head mobility in the cockpit with a helmetmountedvisually coupled system is importantfor both offensive and defensive maneuvers, andis influenced by the location of the ejection seatheadrest relative to the seat-back. However, thelocation of the headrest may also increase therisk of neck injury during the catapult phase ofejection. An experimental effort was conductedto evaluate the effect of a 1-inch aft headrestposition on human biodynamic response duringvertical impact while wearing a heavy helmetthat simulated the mass properties of a generichelmet-mounted visually coupled system.Vertical impact tests were completed on the AirForce Research Laboratory’s VerticalDeceleration Tower (VDT) with humanvolunteer subjects wearing a 4.5 lb helmet.Tests were also conducted with a baseline HGU-55/P helmet weighing approximately 3.0 lb.The headrest position was varied between thecurrent ACES II headrest position relative to theseat-back, and 1 inch aft of that position.Measured head accelerations and headdisplacement data were analyzed to evaluate theeffects of the headrest position with each helmetconfiguration. Overall, the data indicated thatthere were no significant detrimental changes inthe human response to +Gz impact accelerationas the headrest was shifted aft with either thebaseline HGU-55/P helmet or the heavy helmet.In terms of head dynamics for both helmets, theaft headrest position improved the humanresponse compared to the standard position as was indicated by significant decreases innegative x-axis head acceleration and forwardhead displacement. These results suggest the aftheadrest position may improve pilot neck safetyduring ejection with a helmet-mounted visuallycoupled system.