Looks At The Power Cells As They Are Used In Aircraft Systems

The NTSB has issued a series of recommendations today related to the evaluation and certification of lithium-ion batteries for use in aircraft systems, as well as the certification of new technology.

The five safety recommendations, all addressed to the FAA, are derived from the NTSB’s ongoing investigation of the January 7, 2013, fire event that occurred in a lithium-ion battery on a Boeing 787 that was parked at Boston Logan Airport.

Investigators found that the battery involved in the Boston 787 fire event showed evidence not just of an internal thermal runaway but that “unintended electrical interactions occurred among the cells, the battery case, and the electrical interfaces between the battery and the airplane.”

The 12-page safety recommendation letter said that the processes used in 2006 to support the certification of the lithium-ion battery designed for the 787 were inadequate, in part, because there is no standardized thermal runaway test that’s conducted in the environment and conditions that would most accurately reflect how the battery would perform when installed and operated on an in-service airplane.

Further, the NTSB said that because there is no such standardized thermal runaway test, lithium-ion battery designs on airplanes currently in service might not have adequately accounted for the hazards associated with internal short circuiting.

In its examination of the challenges associated with introducing newer technologies into already complex aircraft systems, the NTSB said that including subject matter experts outside of the aviation industry “could further strengthen the aircraft certification process” by ensuring that both the FAA and the aircraft manufacturer have access to the most current research and information related to the developing technology.

To address all of these issues, the NTSB asked the FAA to do the following:

• Develop an aircraft-level thermal runaway test to demonstrate safety performance in the presence of an internal short circuit failure
• Require the above test as part of certification of future aircraft designs
• Re-evaluate internal short circuit risk for lithium-ion batteries now in-service
• Develop guidance for thermal runaway test methods
• Include a panel of independent expert consultants early in the certification process for new technologies installed on aircraft

The final report on the January 2013 Boston 787 battery fire investigation is estimated to be completed in the fall.

(NTSB image)

FMI: Recommendation Letter