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Dreamliner 787 Heathrow fire 'may be caused by short circuit' | Dreamliner 787 Heathrow fire 'may be caused by short circuit' |
(35 minutes later) | |
A fire on a parked Boeing 787 Dreamliner jet at Heathrow Airport two years ago was probably caused by a short circuit, air accident investigators have said. | A fire on a parked Boeing 787 Dreamliner jet at Heathrow Airport two years ago was probably caused by a short circuit, air accident investigators have said. |
The fire was likely to have been started by two bare wires touching in a piece of location equipment, the UK Air Accidents Investigations Branch said. | The fire was likely to have been started by two bare wires touching in a piece of location equipment, the UK Air Accidents Investigations Branch said. |
It then spread through the cabin and burnt through the fuselage. | It then spread through the cabin and burnt through the fuselage. |
Investigators recommended tighter testing and certification of devices. | Investigators recommended tighter testing and certification of devices. |
The fire on the Ethiopian Airlines Dreamliner closed down Heathrow for nearly 90 minutes on 12 July 2013. | |
The piece of equipment that caught fire - the Emergency Locator Transmitter (ELT) - was located near the back of the plane, and was made by Honeywell, investigators said. | |
The battery-powered transmitter is designed to detect unusual deceleration, such as the force produced by a crash, and to transmit a distress signal. | The battery-powered transmitter is designed to detect unusual deceleration, such as the force produced by a crash, and to transmit a distress signal. |
The device in the 787 had positive and negative cables that were too long to fit into the box housing the device, and so ended up touching one another. | The device in the 787 had positive and negative cables that were too long to fit into the box housing the device, and so ended up touching one another. |
Testing had predicted that the worst reaction from a short circuit would be the batteries running down. | Testing had predicted that the worst reaction from a short circuit would be the batteries running down. |
Unfortunately, what actually happened was what investigators called "a thermal runaway" - a fire that spread from one battery cell to the next. | Unfortunately, what actually happened was what investigators called "a thermal runaway" - a fire that spread from one battery cell to the next. |
On the ground, the skin of the aircraft was pierced by the heat and the flames. | On the ground, the skin of the aircraft was pierced by the heat and the flames. |
Fire in the air? | |
The location of insulation near the device allowed the fire to spread, investigators said. | |
However, had the aircraft been in the air, the outside of the aircraft would have been cold enough to limit how the fire spread. | |
Cabin crew would have had difficulty locating the fire, as the device is located behind panels. | |
The fuselage would probably have remained airworthy had the fire happened during a flight, but cabin depressurisation would have been a possibility. | |
The toxicity of the fumes was unknown, they added. | |
But the BBC's Jonathan Sumberg says the Dreamliner was built with carbon composite materials which, when burnt, give off toxins. |