Pre-Impact Seat Rotation for Mitigating Lumbar Injury in Flying Car Crash

Flying cars have already been used in tourism, firefighting, and logistics, and might be soon used for short-distance commute. However, the lumbar spine injury risks in flying car crash accidents have raised safety concerns. This is because the crash load of a flying car is largely aligned with the orientation of the occupant’s spine. This study introduces a countermeasure of actively adjusting seat posture for mitigating lumbar injury in crash events. A flying car crash usually has a few seconds of warning time before collision to ground. The pre-impact warning time is enough to rotate the seat and occupant together using seat motors. Posteriorly rotating seat can alter the angle between the crash load and the spinal axis, thereby reducing lumbar injury risk. Using numerical simulations, the 30g deceleration pulse defined in SAE-AS-8049 was applied to seat of flying car. The THUMS (Total Human Model for Safety) human body model was used to model occupant, sitting in a typical vehicle seat with a conventional three-point seatbelt. Occupant’s responses were simulated under several seat orientations, varied relative to the crash load direction. The results have shown that posteriorly rotating seat before the ground impact can substantially reduce lumbar injury. Compared with the upright posture, mean lumbar injury risk can be decreased by 6.8%, 18.9%, 25.7%, and 40.5% for seat rotation angles of 15°, 30°, 45°, and 60°, respectively. In addition to further revealing the mechanism of the proposed approach, we have also evaluated the influence of various loading directions. All the analyses have indicated that the angle between the crash load direction and the spinal axis is a critical factor influencing the lumbar injury severity. This study has provided a combined active and passive safety protection measure for flying car occupants.