In early December, BETA Technologies partnered with the National Institute for Aviation Research (NIAR) and the FAA to conduct a 50ft Code of Federal Regulations (14 CFR) fuel system crash resistance drop test on a full-scale battery system designed for an electric aircraft.
This was the first time the test was attempted at this scale on a representative 800V pack, which absorbed the load with no significant damage at the cell or pack level, demonstrating compliance.
The FAA may adopt this drop test requirement as a baseline means of compliance for battery systems. Essentially, this test was a milestone in the FAA’s research into which methodology to use for evaluating the crashworthiness of battery systems for electric aircraft, as the 50ft drop test is a contender for what it will require from developers.
The results will also help to validate NIAR’s simulation modelling method, refining it for future use by BETA and others to promote safety and scalability in the industry.
This test was also an important step toward informing the FAA certification process for the industry, the company’s own path to certification, and creating a foundation that will enable various types of battery testing in the future.
The FAA tapped NIAR as a partner for additional validation of means of compliance testing, having created a robust simulation designed to model the effect of the drop test on battery systems at the cell and pack level.
Safety is integral to the overall design, development, and operation of eVTOL transport systems. This test is part of an effort to guarantee the safety of this new technology, as it was designed to evaluate and analyse the performance of battery packs that will power eVTOLs during an emergency landing event.
The test was carried out at the new NIAR laboratory facilities at the Jerry Moran Center for Advanced Virtual Engineering and Testing located in Wichita State University. The test and procured results will also inform the FAA’s mission to define future test requirements and minimum obstacle clearance.
To guarantee occupant safety, it is necessary to evaluate and analyse the performance and behaviour of the complete vehicle, including seats, batteries, and the surrounding composite airframe structure), during an emergency landing event.
The primary objective of this test simulation study was to identify the structural, thermal, and electrical behaviour of the battery pack during emergency landing conditions.
This was in order to provide information to the FAA that may be used to define future requirements and how its performance will impact the selection of composite materials for the construction of an airframe capable of providing an adequate level of safety.
Crashworthiness by drop testing is currently regulated for fuel cells and fuel tanks. Due to the prevalence of fuel tanks and the novelty of battery systems in aircraft, EASA has adopted these fuel tank drop test requirements for use with battery systems as a starting point for safety and risk assessment.
Drop testing of fuel systems requires a 50-foot drop of a nearly filled fuel system onto a flat, non-deforming surface, after which the fuel system is monitored for leakage of gas or fluids, as well as fire or explosion.
This test program and simulation studies will provide information regarding the structural performance of the battery and evaluation of load transfer into the cabin and rest of the eVTOL composite airframe structure.
It will evaluate the thermal performance of the battery and the risk of thermal runaway or explosion, whether thermal shielding is required, and whether current composite materials used for constructing the fuselage is acceptable for this use.
Electrical performance of the battery and risk of high-voltage discharge to the surrounding eVTOL structure, occupants, or first response personnel will also be evaluated, and whether advanced materials can be used for the cabin floor to provide shielding during an emergency landing.