In today’s world, it is unthinkable to travel without our portable electronic devices (PEDs). In fact, it has been shown that every passenger carries 4-5 devices (average) containing lithium ion cells when travelling. Therefore, it is of interest to Airbus to contribute to gaining knowledge about the fire hazards for the industry.

The pillars of fire safety are passive and active fire protection methods. These are implemented on Airbus aircraft successfully for standard fire hazards which do not involve lithium cells. An example for passive fire protection are intrinsic material properties reducing ignitability and combustibility. Contrarily, examples of active fire protection are fire extinguishing systems in the cargo hold. The same principles and current methods need to be reviewed with new fire characteristics from lithium fire. Fires involving lithium cells (e.g. PEDs, fixed aircraft systems or freight) can have characteristics that go beyond what is considered in standard methods of compliance of flammability and fire requirements: higher temperatures and heat fluxes, explosive behaviour (pressure rise), toxicity and accumulation of unburned combustion gas in dangerous concentrations.

This work explains fundamental phenomena that occur during a thermal runaway event and the applications for abuse testing for the aviation industry. Results from current fire testing activities are highlighted to illustrate the need for lithium battery abuse testing to improve fire resilience of aircraft and inform future rulemaking in the aviation industry.

Results show that lithium fire conditions (peak temperature and heat flux boundary conditions on a target) are greater than what is used for standard fire boundary conditions for the compliance demonstrations of materials. A simplified empirical lithium fire spread rate was derived from thermal runaway propagation data for cylindrical cells with two states of charges (30% and 100% SOC). The fire spread rate for cells at 100% SOC is more than two times that with cells with 30% SOC. A suitable emulation of common PEDs was developed: the artificial fire source (AFS), which is used for standardized comparison tests. This approach allows reduction in uncertainties and increases reproducibility of test results. Gas detection technologies can be specified for targeting gases from thermal runaway events. In the best case, a cell venting phase can be detected to increase the available reaction time for the crew.