Boeing 787-8

A ground fire on Ethiopian Airlines’ parked 787-8 Dreamliner at London’s Heathrow airport in July 2013 was likely to have been caused by short circuiting of the emergency locator transmitter (ELT) battery wires.

According to the UK Air Accidents Investigation Branch (AAIB) report, the short circuit current path could have led to a rapid discharge of the battery,along with the early depletion of a single cell.

The report said: "Neither the cell-level nor battery-level safety features prevented this single-cell failure, which propagated to adjacent cells, resulting in a cascading thermal runaway, rupture of the cells and consequent release of smoke, fire and flammable electrolyte."

Trapped battery wires broke the seal between the battery cover plate and the ELT, which allowed hot gas, flames and battery decomposition products to spread through the cabin and fuselage, investigators stated.

"Neither the cell-level nor battery-level safety features prevented this single-cell failure, which propagated to adjacent cells."

The ELT is designed to transmit a distress signal and identify deceleration in an unexpected crash situation.

During the investigation, the AAIB recommended 14 new safety measures, which the ELT manufacturer will consider when carrying out a design review of the lithium battery-powered equipment.

Boeing was quoted by the Associated Press as saying: "We are committed to a process of continual improvement of our aircraft and we will carefully review the AAIB’s recommendations.

"It is important that any potential changes to the airplane’s design be reviewed with great care, and with due consideration for any potential unintended consequences of any change."

In 2013, the US Federal Aviation Administration (FAA) grounded the entire 787 fleet worldwide after a series of battery-related incidents. Operations resumed after Boeing redesigned the airliner’s battery system.

Image: An Ethiopian Airlines’ Boeing 787-8. Photo: courtesy of Konstantin von Wedelstaedt / Wikipedia.