NTSB Issues Wake-Up Call on Lithium-Ion Battery Testing. Will the Industry Press the Snooze Button?

This March, I posted an update on the FAA’s all-clear for the Boeing 787 Dreamliner after its issues with lithium-ion batteries. In that post, I pointed out that Boeing seems to have done some clever manoeuvring to get the Federal Aviation Administration (FAA) to declare that they (the FAA) were responsible for inadequate oversight.

At the time, the lithium-ion batteries themselves were still under NTSB (National Transportation Safety Board) review, and there were no conclusions from the investigation.

In my view, the FAA announcement was pre-emptive, intended to show that process controls were put in place which would address problems with the approvals process of the Dreamliner batteries.   This would buffer the blow of whatever the NTSB concluded.  The FAA could point out they have already moved forward with corrective actions.

This was also beneficial to Boeing because, when the NTSB published their report, the findings might already be answered by the aforementioned corrective actions, listed in the FAA’s announcement in March.

And now it would seem that is precisely how this thing has played out. 

Let me begin by confirming that the NTSB addressed all of its recommendations, as a result of their investigation to the FAA, not to Boeing.  Thus, the FAA’s March announcement, wherein they took the full onus of responsibility for lack of approvals oversight on the Dreamliner batteries succeeded in its objectives.

This has become a regulatory matter, to be worked out by the regulators.  Boeing can argue that it has had the all-clear on the 787 Dreamliner, despite the NTSB’s findings, and nothing in the NTSB finding requires Boeing to make any changes to keep existing Dreamliners in service, and continue its production of new units.

But now let’s review those findings:

NB These are preliminary findings.  The Investigations are still ongoing.

The findings thus far documented in a Safety Recommendation Memo issued by the NTSB on May 22, reference A-14-032 through -036, and addressed to the Honorable Michael P. Huerta, Administrator for the Federal Aviation Administration.

Of the January 7, 2013 Japan Airlines 787-8 (JA 829J) fire incident at Logan International Airport, the NTSB states:

One of the eight APU lithium-ion battery cells had experienced an uncontrollable increase in temperature and pressure (known as a thermal runaway) as a result of an internal short circuit. The single-cell failure propagated to adjacent cells, resulting in the cascading thermal runaway of several cells and the release of additional smoke and flammable electrolyte from the battery case. This type of failure was not expected based on the testing and analysis of the APU battery system that Boeing performed as part of the 787 certification program. (emphasis mine)

An Unexpected Failure

Should Boeing and the FAA have expected the failures which occurred?

Lithium-Ion battery runaway risks are a well-established problem, inherent to these cells in all forms and applications.

Short circuits are a known root cause for thermal runaway, though what causes those short-circuits can range from a manufacturing defect to damage to the battery casing and to overcharging, with many points in between.

Was Boeing allowed to establish testing standards for these batteries which would not account for the everyday risks of the cells they would employ?

Here is what the International Federation of Air Line Pilots’ Associations (IFALPA) has to say on Lithium-Ion batteries in a Safety Bulletin which they shared with Flight Chic entitled Safety advice on counterfeit, damaged and recalled batteries:

Since 1991, batteries or battery-powered devices have been involved in over 100 recorded incidents of smoke, fire or explosion in air transportation. In order to be safely transported, batteries are required to undergo testing prescribed by the United Nations (UN) Sub Committee of Experts on the Transport of Dangerous Goods. Additionally, batteries must be designed to prevent short circuit and overcharging, and must be free from damage. 

Lithium-Ion battery flammability issues have plagued these power sources from the beginning.  The causes and dynamics of those failures are many and well-documented.  There are numerous studies, publicly available, and there are accredited, respected laboratories established to evaluate lithium-ion batteries and identify potential failure modes.

Could the FAA and Boeing have been unaware of any or all of these objective third-party experts when certifying the 787 lithium-ion Dreamliner batteries for use on passenger aircraft?

How the Batteries Were Approved in the First Place

Now let’s go back to the NTSB announcement issued on the Boeing battery fires:

In September 2004, Boeing met with representatives of the FAA’s aircraft certification office in Seattle, Washington, to indicate the company’s intent to install lithium-ion technology for the main and APU batteries on the 787 airplane. In response, the FAA reviewed the adequacy of the existing regulations governing the installation of batteries in large transport-category airplanes and determined that the regulations did not sufficiently address several failure, operational, and maintenance characteristics of lithium-ion batteries that could affect the safety of the battery installations.5 As a result, the FAA issued Special Conditions 25-359-SC, “Boeing Model 787-8 Airplane; Lithium-Ion Battery Installation,” which detailed nine specific requirements regarding the use of these batteries on the 787.

While I’ve provided a link to the full SC document, I’d like to highlight some key sections:

The 787 will incorporate a number of novel or unusual design features. Because of rapid improvements in airplane technology, the applicable airworthiness regulations do not contain adequate or appropriate safety standards for these design features. These special conditions for the 787 contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards.

The 787 design includes planned use of lithium ion batteries for the following applications:

Main and Auxiliary Power Unit (APU) Battery/Battery
Charger System.
Flight Control Electronics.
Emergency Lighting System.
Recorder Independent Power Supply.

Large, high capacity, rechargeable lithium ion batteries are a novel or unusual design feature in transport category airplanes. This type of battery has certain failure, operational, and maintenance characteristics that differ significantly from those of the nickel-cadmium and lead-acid rechargeable batteries currently approved for installation on large transport category airplanes. The FAA issues these special conditions to require that (1) all characteristics of the lithium ion battery and its installation that could affect safe operation of the 787 are addressed, and (2) appropriate maintenance requirements are established to ensure the availability of electrical power from the batteries when needed.

Where the requirements of that Special Conditions certification adequate?

The answer is found in the NTSBs preliminary findings:

The intent of these special conditions was to establish additional safety standards that the FAA considered necessary to provide a level of safety that was equivalent to the existing standards for aircraft batteries.

Special condition 2 of 25-359-SC stated, “design of the lithium-ion batteries must preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure.” During the NTSB’s April 2013 investigative hearing on the Boston battery incident, Boeing and FAA representatives testified that only those failure conditions resulting in cell venting with smoke and fire were considered relevant to special condition. The Boeing and FAA representatives also testified that, at the time of the 787 certification, they believed that an uncontrolled increase in temperature or pressure could only occur if a cell or a battery were overcharged. The NTSB’s investigation has not found any evidence to date to indicate that the Boston incident battery was overcharged.

Are we to believe that, despite well established and abundant technical information on the various modes of failure for Lithium-Ion batteries, engineers at Boeing and their corresponding Air Worthiness authorities at the FAA only considered over-charging as a potential risk?

Do the tests Boeing carried out reflect that over-charging was the sole risk of the lithium-ion batteries?

The NTSB report explains the development tests performed by Boeing and the battery manufacturer:

Boeing determined that an internal short circuit in a single cell that resulted in thermal runaway would not propagate to other cells within the battery. This determination was based in part on the results of development (non certification) testing performed in November 2006 by GS Yuasa Corporation of Kyoto, Japan, which developed, designed, and manufactured the battery. This testing involved driving a steel nail through a cell case to penetrate the electrodes of a fully charged single cell within a fully charged, non grounded, preproduction battery to induce an internal short circuit within the cell. The purpose of the test, which was conducted at a temperature representative of the E/E bay operating temperature during a typical flight, was to observe the behavior of the cells near the nail-penetrated cell, observe any release of smoke or initiation of fire, and document any damage to the battery case.

The nail penetration test results showed that the surface temperature of the nail-penetrated cell increased, smoke vented from the cell and the battery case, and the surface temperature of the adjacent cells increased with no venting. On the basis of this development test and field reliability data of a similar cell designed and manufactured by GS Yuasa, Boeing determined that the effects of cell internal short circuiting would be limited to (1) the release of smoke from the battery, which could be effectively handled by the airplane’s ventilation system, and (2) an increase in surface temperature of the short-circuited cell with no propagation of thermal runaway to adjacent cells, damage to the battery case, fire, or explosion. As a result, the 787 electrical power system (EPS) certification plan proposed by Boeing and approved by the FAA did not include a cell internal short circuit abuse test because it was not required for demonstrating compliance with special condition 2.10

So, to recap, despite the previous statement that only overcharging was considered as a risk, damage to the cells was also considered.  However, the airframe manufacturer, Boeing, was allowed to substantiate the safe use of the lithium-ion battery on the Dreamliner based on a nail test.

The NTSB specifically references an inadequacy of the test methodology developed by GS Yuasa, saying:

It appears that the most severe effects of a cell internal short circuit were not demonstrated during GS Yuasa’s 2006 lithium-ion battery development testing for a number of possible reasons, one of which is that the test setup did not include mechanical and electrical interfaces between the battery and the airplane system.18 Thus, the test setup did not fully represent the battery installation on the airplane.

Additionally, The NTSB report says:

Boeing had collaborated with GS Yuasa and Thales Avionics Electrical Systems of France about the development tests to be performed on cells and batteries. (Thales designed the equipment for the 787 electrical power conversion subsystem, which includes the main and APU battery systems and is part of the 787 electrical power system.) Results from this testing helped Boeing determine what types of abuse (thermal, physical, and/or electrical) certification testing and/or safety analyses needed to be performed to show compliance with the applicable battery regulations, including the special conditions. The development tests were not required by the FAA.

The statement that the “development tests were not required by the FAA,” is important here as it reflects two things:  (1) Boeing and associates had to develop the test protocols, because there were no established required regulatory test protocols.  (2) The FAA did not use objective skepticism when looking at the certification tests presented, nor push Boeing or associates to come up with any significant test-validating criteria.

Why was there no test protocol validation?

No third-party objective expert labs were used.  Was this because there aren’t any?  Are there really no established protocols for testing these batteries in the world today?  There is the highly respected United Laboratories (UL), for a start.

UL has developed extensive tests and even computerised thermal modelling techniques to analyse the risk of internal short circuits (ISCs) of Lithium-Ion batteries.  In its Journal report on Lithium-Ion Batteries, UL explains the risks of Lithium-Ion batteries and the benefits of these computational models to predict potential failures as follows:

Lithium-ion batteries are a vital source of sustainable energy and are being used across an expanding array of applications — from portable electronic devices to electric vehicles to stationary energy storage. Importantly, the high energy density that contributes to the performance and popularity of these batteries also makes a small percentage of them vulnerable to internal short circuits (ISCs) that can result in fires or explosions. Computational modeling is a method UL is using to better understand ISCs, along with the mechanisms of heat generation that occur due to the electrochemical reactions within a lithium-ion battery and the primary causes of thermal runaway, which represents the worst-case — and most hazardous — scenario of possible lithium-ion battery failure modes.

UL actually references this recent NTSB report on the Dreamliner batteries on their website, highlighting their contributions to the NTSB’s investigation.

Spoiled for choice on Experts

The NTSB makes mention of various expert opinions in their report.  The experts the NTSB consulted were also available for query at the time of the development of the Dreamliner battery.  They would have been qualified to predict certain risks in the deployment of this power source.  As the NTSB state:

Experts in lithium-ion technology have indicated that the conditions within a cell that lead to an internal short circuit can progress over time while the battery is in use and that these conditions are not readily detectable until an internal short circuit occurs. Depending on its effects, an internal short circuit might not be detected and managed by a battery monitoring system in sufficient time to stop the thermal runaway of a cell and subsequent adjacent cells. For example, between the date that the Boston incident airplane was delivered new to the operator (December 20, 2012) and the date of the incident (January 7, 2013), there were no abnormal indications or maintenance messages related to issues with the incident battery. As a result, it is important for manufacturers to demonstrate, as part of certification testing, that a battery’s design can effectively mitigate the most severe effects of an internal short circuit because the failure conditions that lead to an internal short circuit may not be apparent.

The NTSB’s own tests in this investigation (which they indicated were not “exhaustive”) led to the following determination:

To fully understand the most severe effects that could occur when a single cell within a lithium-ion battery undergoes thermal runaway, various factors expected during normal operations need to be included in aircraft certification tests. In particular, it is important to ensure that installation, environmental, and usage factors are fully accounted for in abuse tests intended to demonstrate the most severe effects of an internal short circuit-induced thermal runaway. The current standard for lithium-ion battery design and safety certification in aviation applications, RTCA document DO-311, “Minimum Operational Performance Standards for Rechargeable Lithium Battery Systems,” includes abuse testing, but the document does not address all of the unique aspects of a battery’s installation on an aircraft. Thus, aircraft manufacturers need to evaluate whether additional requirements and testing are necessary to ensure aircraft-level safety.

The nail hit on the head.

In fairness, the nail test does evaluate one key factor which may lead to battery failure: damage to the cells.  But it excludes other factors which are just as likely to lead to thermal runaway.

The NTSB concludes that aircraft certification tests that induce thermal runaway of a cell in a lithium-ion battery configured as installed on the aircraft would better demonstrate to the FAA that the battery installation could effectively mitigate the potential safety effects of an internal short circuit. As a result, the NTSB recommends 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. The NTSB also recommends that, after Safety Recommendation A-14-032 has been completed, the FAA 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.

In its preliminary report on the Dreamliner Battery, the NTSB found:

Various methods to replicate internal short circuiting within a lithium-ion cell could help manufacturers determine whether they are using appropriate test methods to demonstrate the most severe effects that could result at the cell, battery, and aircraft levels given the battery’s unique design and installation. Guidance on test protocols and methods that reliably simulate the most severe effects of internal short circuiting in lithium-ion batteries could help ensure that this failure mode is properly assessed as part of aircraft certification. As a result, the NTSB recommends that the FAA 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.

More information is available for readers with great technical curiosity on the full NTSB report.

Restating all the points made by the NTSB report would make this article even more burdensome.  Readers who want to are encouraged to click the links to the original report to obtain the full details.

I  list the recommendations at the conclusion of the report, here, as they are key to what comes next, and particularly relevant to my original post on this matter:

  • 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-14-032)
  • After Safety Recommendation A-14-032 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-14-033)
  • 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-14-034)
  • 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-14-035)
  • 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 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 incorporated during the program. (A-14-036)

The responsibility is once again fully on the shoulders of the FAA to take the necessary corrective actions.

One must wonder, in the absence of these new substantiating tests now recommended by the NTSB, whether the FAA will stand by their March 19 Announcement.

It will be interesting to see whether Boeing and associates are asked to run these new tests, recommended by the NTSB, for the existing batteries on the Dreamliner.

It would certainly be in Boeing’s best interest to carry out these tests, as it would help quiet concerns about the Dreamliner batteries.  That would allow Boeing to continue producing and selling the revolutionary and popular 787 Dreamliner, with confidence, for many years to come.

Featured Image Boeing Dreamliner, by Boeing

Marisa Garcia

After working for sixteen years in aviation, specializing in aircraft interiors design and aviation safety equipment, and getting hands-on with aircraft cabins in hangars around the world, Marisa Garcia turned her expertise into industry insight. She has been reporting on aviation matters since 2014. Every day, she's putting words to work.

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  1. […] viewed the report in its entirety, and even recently questioning the process of approval for the Dreamliner’s Lithium-Ion batteries, I can only say that I was surprised to find Al Jazeerah focused so much on allegations from […]

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