Lithium-ion batteries pack a lot of power into a small space. This advantage allows airplane manufacturers to replace massive hydraulic systems with lightweight electronics and improve fuel economy. This conversion is termed MEA or “more electrified aircraft”. Examples of MEA include the Boeing 787 Dreamliner and the Airbus A350. While these high-tech batteries rarely fail, when they do, the consequences can be severe.
On 7 January 2013 at Logan Airport in Boston, one of the lithium-ion batteries on a Boeing 787 experienced an uncontrollable increase in temperature and pressure, so-called “thermal runaway”. This was followed by another similar event ten days later in Takamatsu, Japan. These events culminated in the temporary grounding of the Boeing 787 fleet by the U.S. Federal Aviation Administration (FAA). The temporary grounding was lifted by the FAA in late April, 2013.
As a result of these incidents, UL initiated discussions with the National Transportation Safety Board (NTSB) which led to a contract in August 2014, to carry out a post-incident investigation focused on probable cause and assessment of the certification process. One result of the effort was the issuance of a recommendation letter by the NTSB, providing an informed safety strategy to the FAA. This five-part “Safety Recommendation” urged the FAA to take action and implement certification testing for lithium-ion batteries used on commercial airplanes.
The research conducted by UL developed new and innovative forensic testing procedures at the cell, battery and battery-system level that revealed key factors related to the failures. The resulting recommendations include the development of cell-level internal short circuit (ISC) tests, in which manufacturers can evaluate thermal runaway and ISC behavior. With the goal of improving cell, battery and system-level safety performance, enhanced safety standards developed and implemented by independent, third-party experts like UL could help provide confidence in new technologies.
UL is committed to the safe introduction of technology into society. This investigation underscores the importance of involving an independent safety expert at an early stage of the design process.
For more details on the investigation, read NTSB’s Safety Recommendation to the FAA.
Please contact Tom Chapin for further information on lithium-ion battery safety and performance, or on the ongoing NTSB investigation.
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