A MODIFIED CRASH BRACE POSITION FOR AIRCRAFT PASSENGERS

Background: In 1989, a Boeing 737-400 aircraft crashed at Kegworth, ne ar Nottingham, England. The survivors suffered a large number oi pelvi c and lower limb injuries, and approximately one-third of the passenge rs died. Subsequent research has suggested that the ''brace-for-impact '' position that passengers are advised to adopt prior to a crash land ing might be modified in order to reduce the incidence of such injurie s. The aim of this research was to evaluate biomechanically such a mod ified crash brace position. Hypothesis: A modified brace position woul d help to prevent injuries to some passengers in the event of an impac t aircraft accident. Methods: Impact testing on forward-facing seats w as performed at the Royal Air Force Institute of Aviation Medicine, Fa rnborough, England. Aircraft seats, mounted on a sled, were propelled down a track to impact at -16 Cx. A test dummy was used as the experim ental model. Four dummy positions were investigated: a) upper torso br aced forward and lower legs inclined slightly rearward oi the vertical ; b) upper torso braced forward and lower legs inclined forward; c) up per torso upright and lower legs inclined slightly rearward of the ver tical; and d) upper torso upright and lower legs inclined forward. The impact pulses used were based on Federal Aviation Administration guid elines. Transducers located in the head, spine, and lower limbs of the dummy recorded the forces to which each body segment was ex posed dur ing the impact. These forces were compared for each brace position. Re sults: impact testing revealed that the risk of a head injury as defin ed by the head injury criterion was greater in the upright position th an in the braced forward position. The risk oi injury to the lower lim bs was dependent in part on the flailing behavior of the limbs. Flaili ng did not occur when the dummy was placed in a braced, legs-back posi tion. Conclusions: A modified brace position would involve passengers sitting with the upper torso inclined forward so that the passenger's head rested against the structure in front, ii possible. The legs woul d be positioned with the feet resting on the floor in a position sligh tly behind the knee. The position differs from those previously recomm ended in that the feet are positioned behind the knee. This study sugg ests that such a position would reduce the potential for head and lowe r limb injury in some passengers, given that only a single seat type a nd single size of occupant have been evaluated. Standardization to suc h a position would improve passenger understanding and compliance. Suc h a recommendation should not obscure the fact that an occupant seated in a forward-lacing aircraft seat, restrained only by a lap belt, is exposed to considerable forces during an impact accident. Such forces are capable oi producing injuries in the femur, pelvis, and lumbar spi ne.