Potential Effects of Friction on Injury Measures Computed in Aircraft Seat HIC Analysis Testing

Aircraft seating systems are evaluated utilizing a variety of impact conditions and select injury measures. Injury measures like the Head Injury Criterion (HIC) are evaluated under standardized conditions using anthropomorphic test devices such as those outlined in 14 CFR part 25. An example test involves decelerating one or more rows of seats and allowing a lap-belted ATD to engage components in front of it, which typically include the seatback and its integrated features. Examples of head contact surfaces include video monitors, various plastic and composite fascia, and a wide range of seat back materials. The HIC, and other injury measures such as Nij, can be calculated during such impacts. It has been shown in other safety applications that the friction between a headform and contact surface can affect the test results. A series of finite element simulations of a frontal deceleration pulse with a generalized aircraft seat was performed to determine the variation in HIC and Nij observed based on various friction characteristics between the ATD and select seat components. The results indicate that the level of friction on the test device headform can influence the ability to pass the HIC analysis test. Of particular interest is the change in response due to the use of friction characteristics representative of human skin compared with ATD skin.