Occupant injury assessment in an emergency landing condition for a vertical take-off and landing aircraft
In the next few years, the aeronautical industry is poised to change in a way it has not for decades. There has been a rising interest in deploying Vertical Take-Off and Landing (VTOL) aircraft to serve on-demand transportation across urbanized areas. The recent developments in battery and electric motor technologies have opened the path to achieve quieter and more efficient vehicles capable of using compact infrastructure well suited for urban operation. However, this novel concept introduces several aspects that the current airworthiness regulations lack to address, such as the pure vertical crash landing. Scenarios like this are likely to occur since these aircraft need to gain enough altitude to clear the surrounding buildings before reaching higher horizontal velocities for cruising. The tight weight margins require the use of lightweight structures for such aircraft, which can significantly compromise occupant safety since materials such as carbon fiber reinforced plastic are mostly ineffective for energy absorption without the proper design of failure mechanisms. Foreseeing such a challenge, the present study is aimed at evaluating and assessing the sensitivity of occupant injury severity in relation to varying structural parameters defined for the seat, subfloor, and landing skid structural systems. A representative multibody model of the pure vertical crash landing scenario has been developed, validated, and utilized, employing Kelvin restraints to model the structural systems and an FAA Hybrid III ATD model in MADYMO to capture the occupant level of injury. Two case studies are conducted using modeFrontier, where the first uses a linear structural model to describe the stiffness of the structures, while the second case considers a nonlinear definition to account for component failure. The first study yields trends for identifying the driving factors, where the damping of the landing skid is shown to be dominant over other factors to improve occupant safety. The addition of failure variables to the second study is shown to have an improvement in reducing the injury levels. Yet, the added complexity to the model could underline the value of integrated occupant safety design, as effective energy absorption is required to keep low injury levels.