The Evolution Of A Pretensioning Aircrew Restraint System To Minimize Crash-Related Injuries and Fatalities

Aircrew injuries and fatalities in severe but survivable helicopter crash impacts has been identified as a serious safety concern since the 1960s. Head and upper torso strikes within the cockpit are a primary cause of serious injuries and fatalities in potentially survivable helicopter crash impacts. These injuries are due to excessive occupant displacement, leading to contact with cockpit structure/objects. Crewmembers have a tendency to significantly loosen their restraint system (shoulder straps) to gain comfort and mobility during flight operations. This fact, coupled with other undesirable crash effects (restraint system pay-out, webbing compaction on the inertia reel shaft, strap elasticity or stretch, and seat flexibility/deformation) adversely and significantly increases the occupant flail envelope by 10 inches or more which, in turn, greatly increases the probability of injurious head strikes during the crash event. In survivable crashes, minimizing occupant displacement (flail) is fundamental to sound occupant restraint and the most cost effective way to eliminate aircrew head and upper torso fatalities and injuries due to striking cockpit structure. Restraint enhancements, such as the H. Koch & Sons Co. Pretensioning Aircrew Restraint System (PARS), offer a viable approach to accomplishing this goal. The PARS tightens the restraint at crash onset, in order to maintain the occupant optimally restrained against the seatback, thus minimizing the potential for occupant flail. PARS is a performance-enhancing, restraint supplement which includes the MA-16 inertia reel with its omni-directional locking feature that locks the inertia reel early in the crash event (before significant occupant displacement can occur). This paper describes the historical events that created the impetus for PARS development. The discussion includes the results of full-scale dynamic sled tests of the PARS using Hybrid III manikins conducted over the last 3 years, as well as the additional dynamic tests planned for 2003. These upcoming sled tests will include UH-60 crashworthy seats in a UH-60 cockpit mock-up. The HAWK series rotorcraft represent the worst-case injury threat in a crash because they have a seat stroke capability of up to 17 inches, which is, by far, the most stroke of any military aircraft crashworthy seat. These tests will provide a true and definitive exhibition of PARS performance with regard to its alleviation of the cockpit-structure-strike potential and minimization of the potential occupant injury risk.