Changes in the technology and chemistry of voltaic cells have increased the energy density within the cells. The increased energy density and heightened consumer demand for lithium batteries have both contributed to an increased risk of fire and smoke incidents in transport aircraft.

The objective of this study was to evaluate the effectiveness of various types of shipping materials and configurations to prevent or minimize the propagation of thermal runaway in lithium-ion battery shipments. Tests were performed in square cardboard boxes with a capacity of 16 18650-sized cells. A cartridge heater was placed on the outside corner of the cells to initiate thermal runaway, and a thermocouple was attached to each cell for temperature measurement. The state-of-charge (SOC) of the cells and divider material between each cell was varied. The effectiveness of a packet of water placed above the cells was also evaluated.

Tests showed that thermal runaway propagated when the cells were at a charge level greater than 30% with typical battery package material. Insulative divider materials increased the SOC required for propagation. Conductive divider materials delayed the onset of thermal runaway because there was more heat transfer away from the heater, but decreased the time between thermal runaway events once propagation had begun. The pack of water above the cells prevented thermal runaway propagation at a 50% SOC.

Tests were performed to evaluate the effectiveness of intumescent paint as a method to decrease the propagation of thermal runaway. When exposed to a direct flame, intumescent paint was minimally effective on organic materials and significantly effective on aluminum foil. Intumescent paint was slightly effective when tested against a radiative heat source at a low heat flux, but at higher heat fluxes was unable to deflect the heat away from the organic material. In the tests with lithium batteries, the replacement of cardboard dividers with those coated with intumescent paint or aluminum foil only delayed adjacent batteries from being driven into thermal runaway and did not prevent propagation.

Of the package configurations that were tested, SOCs at 30% and the setup with a pack of water above the cells were the only effective methods to stop propagation. Insulative separation materials helped to reduce the propagation risk, and conductive materials increased the onset time and decreased the propagation time once thermal runaway occurred.

Recent accident experience has raised questions as to whether the design and operational standards of large transport category airplanes, pertinent to water related accidents, might be improved to enhance occupant survival.

This study has been commissioned by Transport Canada and the UK Civil Aviation Authority (henceforth referred to as the Airworthiness Authorities) to carry out a detailed review of accident data and existing research applicable to water related accidents, to determine the need for changes to the relevant regulatory standards, taking into account the cost to industry and the likely benefits to occupant safety.

The study includes ditching and inadvertent water impact accidents involving western built airplanes certified for 20 or more passenger seats (and their cargo variants), that occurred over the period 1967 to 2009. In the context of this study, the term ditching includes planned and unplanned ditchings in which the flight crew knowingly makes a controlled emergency landing in water. Inadvertent water impact accidents are those that might occur during an overrun or undershoot, where the airplane alights on water. The study excludes non-survivable water impacts and accidents involving hijacked airplanes.

The Next Generation (NexGen) burner is a new burner designed by the Federal Aviation Administration (FAA) William J. Hughes Technical Center for the required FAA fire certification tests on power plant components. The objective of this study is to understand the performance of this burner and provide the benchmark to adapt the burner settings for future FAA fire tests. The NexGen burner was found to satisfy the temperature and heat flux requirements under the FAA fire test guidelines. This NexGen burner was modified by adding four tabs to the turbulator in the current study and was found to result in wider and more uniform flames, which increased the burner robustness for the fire test. Calibrations of heat flux and thermocouple (TC) temperature from the NexGen burner were much more sensitive to a change in the fuel flow rate than to a change in the air flow rate. However, the fire test results on the samples were also sensitive to air flow rate. It is recommended that both the fuel and the air flow rate of the NexGen burner be regulated in future FAA fire tests. The influence of TC size on flame calibrations and fire test results was studied. The burner calibrated with the smaller TC size produced less damage on the test sample. It is recommended that the FAA have a narrower tolerance on the TC size used in the temperature calibrations. The performance of the ISO propane burner was also studied. Heat flux produced by the ISO propane burner was found to be much lower than that produced by the NexGen burner, and the damage induced by the propane burner in a horizontal orientation was significantly less than that induced by the NexGen burner. Fire tests were conducted on two different sample sizes. Smaller samples could survive longer under the same burner operating conditions. It is recommended that the sample size be specified in future FAA fire tests.

This report discusses ongoing developmental efforts related to the Nexgen burner. It should be noted that the burner construction and settings discussed in this report are not representative of the most recent that are used on the Nexgen burner. For detailed construction drawings and to view other documentation and presentations that discuss the most up-to-date burner configurations, please see the FAA’s Fire Safety Branch’s website at www.fire.tc.faa.gov.

A previous study of polyetheretherketone showed that the ignitability of this high temperature engineering plastic is sensitive to the presence of absorbed moisture. The present research extends this work to include five other engineering plastics: polycarbonate, polyoxymethylene, polymethylmethacrylate, polyphenylsulfone, and polyhexamethyleneadipamide. Separate batches of each polymer were equilibrated in hot (80°C) water, 50% relative humidity at 20°C, or vacuum dried at 100°C and tested in a cone calorimeter at heat fluxes between 10–75 kW/m2. These hygrothermally conditioned samples were also examined by microscale combustion calorimetry to determine the effect of moisture on the decomposition and combustion properties. It was found that absorbed moisture did not change the thermal decomposition or ignition temperatures significantly, but was released as steam that formed microscopic surface bubbles at or above the softening (i.e., glass transition or melting) temperature of the polymer. The phase change from bound water to steam entrained in the polymer melt (i.e., foam) significantly reduced the ignition time as compared to dry samples. Attempts were made to account for the moisture-sensitive ignition delay in terms of thermal properties and chemical processes governing ignition and in a numerical thermokinetic pyrolysis model.

The use of electronic-tablets (e-tablets) as replacements for conventional in-flight entertainment systems has gained popularity among airlines globally. Innovative methods of storing and charging e-tablets in galley carts have been suggested or are already in service with some airlines.

The danger of thermal runaway in the lithium-ion-pouch batteries that are used in these e-tablets is well known, but the potential fire hazard resulting from e-tablets being stored and charged in galley carts or a similar enclosure has not been established. To examine this potential fire hazard, the Civil Aviation Authority of Singapore and the Federal Aviation Administration conducted a series of tests to investigate the behavior of e-tablet fires.

Tests were conducted within a galley cart and thermal runaway of the e-tablet lithium-ion-pouch battery was initiated by either a heat plate or an external alcohol fire. The arrangement of e-tablets inside the galley cart followed the typical methods of storage proposed by airlines and design organizations. The objectives of the tests were to determine a suitable storage configuration for the e-tablets, which would prevent the propagation of thermal runaway, and to determine the effect that thermal runaway would have on a typical galley cart.

Ten tests were conducted. The results of these tests showed the potential fire hazards associated with bulk storage of e-tablets in a galley cart or similar enclosure. Additional work is recommended to determine the desirable features of galley carts to contain a lithium battery fire and prevent the danger associated with fire, smoke intensity, and explosion.