United States Department of Transportation
i
Supplemental Injury Risk Considerations for Aircraft Side-Facing Seat Certification
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2017-01-01
[PDF-1008.34 KB]
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NTL Classification:NTL-AVIATION-Aviation Safety/Airworthiness;AGR-SAFETY AND SECURITY-SAFETY AND SECURITY;
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Abstract:Application of FAA Policy Statement PS-ANM-25-03-R1, Technical Criteria for Approving Side-Facing Seats, has revealed a need for additional guidance regarding risk of leg injury, protection of occupants during crashes that are not severe enough to deploy inflatable restraints, and risk of injury due to submarining (belt sliding up onto the abdomen) during rebound. FAA sponsored research has shown that serious leg injury can occur in side-facing aircraft seats during an emergency landing scenario. This research also showed that lower velocity tests are unlikely to result in serious leg injuries, suggesting that the injuries were the result of the inertial force of the unrestrained lower leg. The Civil Aerospace Medical Institute reviewed existing literature and conducted a series of sled tests to provide recommendations addressing questions regarding leg injuries, airbag threshold pulses, and risk of injury during submarining. Based on research data, leg injuries are unlikely to occur for any input acceleration that produces energy below the 28.5 ft/s test case and therefore the 35° leg rotation limit could be exempted for these tests. For the 44 ft/s certification sled test, the maximum femur rotation angle limit should be applied to both the leading and trailing legs, but only during the loading phase as long as the method of mitigation does not return excessive energy to the legs during rebound. The current policy states that the lap belt must remain on the pelvis during both the impact and rebound phases. This has the effect of prohibiting contact between the lap belt and the ATD abdomen. In some seat configurations, the occupant kinematics during the rebound phase of the test result in the belt sliding up onto the abdomen (submarining). Due to the low energy typical of rebound, a lap belt tension limit of 250 lb was identified as a conservative value to limit injury risk as an alternate to the prohibition of contact. These observations may be useful for developing new guidance to address these side-facing seat certification issues.
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