Intermediate Results of Detailed Design Developments for a Crashworthy eVTOL Subfloor Demonstrator

Kurzfassung

This conference paper presents the current status of detailed design developments for a crashworthy eVTOL (electric vertical take-off and landing aircraft) subfloor demonstrator structure that will be manufactured and crash-tested in 2023/2024. The context of this demonstrator test program will be presented and design details explained. The presented subfloor demonstrator is based on an (hybrid) eVTOL aircraft for emergency medical services carrying two occupants (pilot + emergency doctor) in a tandem seat configuration. The vehicle lift and propulsion systems are attached to the airframe upper deck. The airframe structure is designed using a multi-disciplinary approach with researchers from the disciplines design, static sizing, crashworthiness, occupant safety, manufacturing and production. Crashworthiness was defined as a key driver for safe operation of such novel AAM (advanced air mobility) vehicles in particular for the specific flight operational conditions of emergency doctor transportation. The demonstrator structure is designed for crashworthiness while considering manufacturing and industrialization aspects for cost-efficient production of the airframe structure. The DLR-eVTOL subfloor demonstrator continues a series of demonstrator crash tests for VTOL applications performed within the last decades with contributions from DLR. Individual design solutions from past demonstrator programs are taken and combined for the eVTOL subfloor demonstrator, with main priority laid on the integration aspects to prevent unforeseen catastrophic failure – which is a lesson learnt from the past. The crashworthiness aspects considered in the demonstrator design are related to the most relevant and challenging design aspects expected for emergency doctor eVTOLs. Multi-axial crashworthiness is one aspect and considers the capability of an airframe to provide crash safety under off-axis impact conditions as well as under combined horizontal/vertical impact velocities. Multi-terrain crashworthiness is another aspect that provides crash safety for impact on different terrain ranging from rigid surfaces to soft soil and water. Both aspects are related to the flight operational conditions for emergency medical services, with typical flight operations in urban areas, risk of accidental contact with obstacles and landings at unprepared sites. Those operational conditions can result in crash scenarios that require a robust crash design to provide safety to the vehicle occupants. Another aspect is energy storage crashworthiness and the ability to prevent or to contain post-crash fire and other hazards caused by damage or overloading of the energy storage in a crash event. A hybrid propulsion system is considered for the emergency doctor eVTOL to comply with mission duration and turnaround requirements. As a consequence, design solutions need to be developed for crashworthy integration of different types of energy storages: fuel tank and propulsion battery. The subfloor demonstrator is intended to support the overall vehicle design by confirmation of crash design approaches through a crash test. Furthermore, the test data shall support validation of crash simulation models used to develop the eVTOL overall structural design. The demonstrator structure will be crash tested under vertical impactconditions that comply with the 95th percentile of survivable crashes for which the occupants are given every reasonable chance of escaping serious injury. The conference presentation will discuss the crash aspects of the demonstrator design and the detailed design solutions selected for achieving robust crashworthiness under multi-terrain and multi-axial impact conditions as well as for a safe energy storage integration. As a status presentation of ongoing research work, final test and simulation results will not be presented.