Study of Occupant Model Capability to Quantify Injury Risk for eVTOL Vehicles

Abstract

Researchers at The National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC) previously conducted a full-scale crash test of a Fokker F28 MK1000 aircraft to study occupant injury risks. The goal of the current study was to investigate the injury predictions of the Global Human Body Models Consortium (GHBMC) and Total Human Model for Safety (THUMS) occupant models in the tested aircraft crash condition and explore possible utilization of both human body models (HBMs) in this context. Eight crash conditions were simulated utilizing each of the models. The HBMs were positioned in two postures, a neutral upright posture with hands resting on the legs and feet contacting the floor and a braced posture with head and hand contact with the forward seat back. Head and Neck injury metrics and Lumbar Vertebra axial force were calculated and compared for all simulations. Both HBMs reported similar kinematic responses in the simulated impact conditions. However, the GHBMC model reported higher forces and injury risks in almost all scenarios. The HBMs were compared to previously modeled anthropomorphic test device (ATD) response. The HBMs showed higher loading than the modeled ATDs in two out of eight impact conditions. Relative to the THUMS model, the GHBMC model had more included virtual instrumentation and produced injury metric values which encompassed that of the THUMS model. The THUMS model has additional value in being a free access model. Both models provided valuable insight into the potential response of the human body within the simulated aerospace crash environment. Urban transportation is currently evolving from traditional ground-based vehicles (e.g. cars, taxis, and buses) to include air-based electric vertical take-off and landing (eVTOL) vehicles which can be utilized for on-demand transportation, cargo transport, and emergency services. These new eVTOL vehicles are designed to be small, lightweight, and eventually autonomously operable without user intervention. Safety is a big part of eventual eVTOL adoption; however, gaps in safety features consideration exist. Anthropomorphic test devices (ATDs) are used in aerospace crashworthiness standards to quantify occupant injury risk and develop improved safety designs for emergency landing situations despite their development many decades ago. ATD technology has continued to evolve, leading to a host of newer and more biofidelic ATDs such as the Test Device for Human Occupant Restraint (THOR). Increased computing power has also allowed for detailed computational human body models (HBMs) to be created, such as the Global Human Body Model Consortium (GHBMC). This study aims to assess the capability of both HBMs and new ATD designs to identify injury mechanisms within eVTOL relevant emergency landing conditions. Finite element (FE) analysis was used to expand upon full-scale and seat level impact testing conducted by researchers at the National Aeronautics and Space Administration (NASA) to look at effects of occupant model configurations on injury prediction. The GHBMC HBM and THOR ATD models were simulated in seat level test conditions to characterize differences between these advanced assessment tools and traditional ATDs in the isolated seat loading environment. Of these test conditions, 4 crash pulses were implemented to a rigid seat with 2 of those also being implemented in a generic composite seat and a NASA designed energy absorbing seat. Further exploration was performed by altering the position of the GHBMC into a relaxed and upright position. Results compared the impact response in head, neck, and spinal injury metrics and identified key differences in the responses from each of the models utilized. The GHBMC showed distinctly different biomechanical responses compared to the ATD. As it was expected, the GHBMC models were much more deformable than the ATDs and exhibited higher distribution of forces and increased sensitivity to the duration of acceleration pulses. Both occupant models incorporated into this study identified key mechanisms for injury that should be considered for passenger safety in the development of these novel aircraft. In addition, this study demonstrated the value of FE modelling for running a variety of complex human surrogates to identify potential injury mechanisms for consideration in regulation and development of new aircraft. Continued research in this field to improve validation of these models will only lead to safer aircraft and more comprehensive safety measures.