Scientists with the National Institute for Aviation Research (NIAR), together with eVTOL developer Beta Technologies, have performed the first-ever drop test of an aircraft battery to study the safety of the vehicle in the event of an emergency landing.
The study, which was sponsored by the FAA, is part of an ongoing crashworthiness evaluation program focused on occupant safety. For this research program, the NIAR will evaluate the performance of eVTOL battery packs and their surrounding structures after being dropped from a height of 50 feet (15 meters)—the same type of testing that fuel cells and tanks made for traditional airplanes and helicopters are required to undergo per federal requirements prescribed in 14 CFR 27.952.
Lithium-ion batteries, which are used in eVTOL aircraft as well as electric road vehicles and most consumer electronics, have a bit of a bad reputation when it comes to safety. Although it rarely happens, lithium-ion batteries have been known to catch fire and even explode in what’s known as a thermal runaway event. Several factors can lead to a thermal runaway event, such as damage to the battery pack or exposure to dangerously high temperatures.
Beta Technologies, a Burlington, Vermont-based start-up developing both the Alia 250 eVTOL aircraft and the supporting charging infrastructure, is no stranger to thermal runaway events. Earlier this year, part of a battery pack that had not yet been extensively tested caught fire inside a shipping container at the company’s headquarters in Burlington. This pack was not intended for installation on the aircraft.
On December 7, Beta became the first eVTOL developer to subject its battery pack to a 50-foot drop test at NIAR's laboratory, located at Wichita State University’s Jerry Moran Center for Advanced Virtual Engineering and Testing in Kansas. A Beta spokeswoman told FutureFlight that the full-scale, 800-volt battery pack was fully charged before it was hoisted 50 feet in the air by a crane and dropped onto a hard surface on the ground. According to the company, the battery pack had “no significant damage at the cell or pack level” after the impact.
“This test proves that our full-scale battery can safely withstand the impact of a 50-foot drop," Beta stated. "As a company, we put a lot of weight and effort behind data capture and real-life testing, and this was a chance to really put our work to the test. The results demonstrate that batteries are safe and largely behave how we predict they will.”
The battery drop test demonstrated the completion of Beta’s means of compliance for its battery system, and it helped to validate NIAR’s simulation modeling methods for eVTOL batteries. The FAA has contracted NIAR to create a tool for simulating the effects of a battery drop test at the cell and battery pack level to assist in the certification process.
The results of the test will help NIAR and the FAA define future requirements for eVTOLs and their batteries. For example, battery performance could impact the selection of composite materials eVTOL companies will be allowed to use in the construction of their airframes. The FAA and NIAR will also consider whether thermal shielding will be required to keep passengers safe from any potential thermal runaway event.
“Occupant safety is an integral part of the overall technical and management processes associated with the design, development, and operation of eVTOL transport systems,” Gerardo Olivares, a senior research scientist at NIAR, wrote in a LinkedIn post. “To guarantee occupant safety, it is necessary to evaluate and analyze the performance and behavior of the complete vehicle (seats, batteries, and the surrounding composite airframe structure) during an emergency landing event.
This story was updated on December 28 to correct some details about a ground fire involving a battery pack inside a shipping container.