The UK AAIB has (Air Accidents Investigation Branch) has issued a special bulletin concerning the investigation into a fire in a Ethiopian Boeing 787 at London Heathrow on 12 July. The AAIB says the investigation has focused on the Emergency Location Transmitter (ELT) located at the rear of the aircraft. Subsequently, the AAIB has issued two safety recommendations.
The AAIB bulletin reads, ‘The ELT model installed in the aircraft contains a set of chemical batteries using a Lithium-Manganese Dioxide (LiMnO2) composition. These allow the ELT, as required by regulation, to operate in an emergency situation entirely independent of the aircraft’s electrical power system.’
‘Detailed examination of the ELT has shown some indications of disruption to the battery cells. It is not clear however, whether the combustion in the area of the ELT was initiated by a release of energy within the batteries or by an external mechanism such as an electrical short. In the case of an electrical short, the same batteries could provide the energy for an ignition and suffer damage in the subsequent fire.’
As a result, the AAIB has ruled that all Boeing 787s switch off an electrical component until further notice. The body also recommended that regulators conduct a safety review of similar components in other aircraft.
At the beginning of this year, all 50 Dreamliners in service worldwide were grounded after two separate incidents concerning batteries.
A statement from Boeing said, ‘The safety of passengers and crew members who fly aboard Boeing airplanes is our highest priority.
‘As a party to the investigation, Boeing supports the two recommendations from the UK Air Accidents Investigation Branch (AAIB), which we think are reasonable precautionary measures to take as the investigation proceeds. We are working proactively to support the regulatory authorities in taking appropriate action in response to these recommendations, in coordination with our customers, suppliers, and other commercial airplane manufacturers.’