The European Union Aviation Safety Agency (EASA) has published a safety information bulletin (SIB) addressing certain brand ELTs to ensure that the presence of fire (in case of a lithium ELT battery failure) cannot propagate from the battery compartment to surrounding material. The specific ELTs in question are approved on various models from H.R. Smith and Techtest Ltd., installed in numerous small and large airplanes and helicopters.
According to the SIB, the affected ELT and battery packs, in case of a thermal runaway, may release gases on fire. As this fire eventually self-extinguishes, the design remains compliant with the criteria of technical standard orders. However, the presence of fire may affect the performance of surrounding equipment if an approved ELT has not been installed under a TC or STC.
Therefore, EASA recommends “operators of aircraft that have any affected ELT or battery pack(s) carried on board which are not part of the approved aircraft type design, or design change, as applicable, to ensure that the presence of fire (in case of an ELT battery failure) cannot propagate to the surrounding material.”
The assessment should “explicitly include the effect of fire or hot gases impingement on any stowed safety equipment installed in proximity of the battery such as life rafts, life jackets or emergency flotation systems.”