On January 7, 2014 a JAL B-787 encountered a fire in its auxiliary power unit lithium-ion battery. That led to a highly publicized active NTSB investigation of this incident and on May 22, the Board, in the midst of its review, issued five recommendations directed to the FAA. On December 1, 2014, they issued their final report. There is always urgency in determining what the cause of the failure of a system important to the aircraft’s safety. What is the lesson about the relative merits of a report issued after 35 days versus a 110 page report filed almost 9 months after the event?
The Board opened an investigation on the JAL events and actively pursued the reason why this battery (and others) caught fire. Its May 12 page letter made the following recommendations:
- 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 Acting Chairman said “The history of commercial aviation is one in which emerging technologies have played a key role in enhancing flight safety….This is why it’s crucial that the process by which these technologies are evaluated and certified is as robust and thorough as possible. These recommendations will take us further in that direction.” That’s good advice and was accepted by the FAA.
This early communication noted that the Board would continue its examination of the batteries and delve further into the causes. Now the end result of that work is contained in its final report. At the end of this final analysis, the NTSB recognized that the FAA —
· Develop abuse tests that subject a single cell within a permanently
installed, rechargeable lithium -ion battery to thermal runaway and demonstrate that the battery installation mitigates all hazardous effects of propagation to other cells and the release of electrolyte, fire, or explosive debris outside the battery case. The tests should replicate the battery installation on the aircraft and be conducted under conditions that produce the most severe outcome. (A-14-32)
· After Safety Recommendation A-1432 has been completed, require aircraft manufacturers to perform the tests and demonstrate acceptable performance as part of the certification of any new aircraft design that incorporates a permanently installed, rechargeable lithium-ion battery. (A-14-33)
· Work with lithium-ion battery technology experts from government and test standards organizations, including US national laboratories, to develop guidance on acceptable methods to induce thermal runaway that most reliably simulate cell internal short-circuiting hazards at the cell, battery, and aircraft levels. (A-14-34).
· Review the methods of compliance used to certify permanently installed, rechargeable lithium-ion batteries on in-service aircraft and require additional testing, if needed, to ensure that the battery design and installation adequately protects against all adverse effects of a cell thermal runaway. (A-14-35)
· Develop a policy to establish, when practicable, a panel of independent technical experts to advise on methods of compliance and best practices for certifying the safety of new technology to be used on new or existing aircraft. The panel should NTSB Aircraft Incident Report 83 be established as early as possible in the certification program to ensure that the most current research and information related to the technology could be incorporate d during the program. (A 14-36)
That’s a good report card for quick FAA response.
The Board added other recommendations, such as poor guidance to the FAA staff and the TC holder for certification testing of these batteries. Boeing was told to improve its testing of cascading thermal runaway of the battery as a result of a cell internal short circuit. Boeing’s EPS analysis of the cell failure lacked some technical rigor. It was also was cited for inadequate oversight of the Thales and in turn, Thales review of the battery manufacturer, GS Yuasa. The manufacturing quality of GS Yuasa was also cited as a problem. The Enhanced Airborne Flight Recorder did not function as it was expected.
Iterations of NTSB reports are not common occurrences. In this case, the Board made some tentative findings to which the FAA responded properly. That is good, but what would the consequences be if the latter NTSB review did not support the earlier recommendations? Is sequencing of Board reports to be a permanent practice? If yes, must there be a continuing dialogue between the Board and the FAA about the emerging answers to open questions? Or even more importantly, if the Board’s initial determination(s) begins to lose its technical support, how and when should that change be communicated? Should the “talk” be limited to only the investigative teams? Or should the public be made aware of any such deviation from the original conclusion/hypothesis?
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