They also urged the Federal Aviation Administration to review the use of lithium-powered transmitters in thousands of other planes. Most passenger jets do not have fire suppressant systems in the area where the devices are located. And if a fire occurred in flight, the investigators said, “it could pose a significant safety concern and raise challenges for the cabin crew.”
The recommendations, contained in a three-page interim report on the fire investigation, provided the strongest evidence yet that the emergency locator transmitter that sends out the plane’s location after a crash played a significant role in the fire on the parked Ethiopian Airlines 787 last week.
The findings were good news for Boeing, which was relieved that that the fire centered on a generic piece of equipment that is on many types of planes rather than one of the new systems on the Dreamliner, an innovative plane that is crucial to the future of the company.
Boeing said in a statement that it supported the British recommendations as “reasonable precautionary measures to take as the investigation proceeds.”
The company’s stock was up 2.6 percent in midday trading.
The report, written by Britain’s Air Accidents Investigation Branch, said the most extensive heat damage to the jet’s carbon-composite skin occurred at the spot where the transmitter was attached to the top of the plane near the rear left door. The report said it was not clear if the fire was initiated by a release of energy within the batteries or by an external mechanism like an electrical short.
If a short occurred in the device or its wiring, the battery could have provided the energy for ignition, the report said.
The report said no other systems in that area would have contained enough stored energy to start a fire with the plane’s basic power system turned off. The transmitter, which could broadcast distress signals for many hours after a crash, is designed to operate independently of the jet’s power system.
Still, the investigators expressed surprise that the battery could have caught fire, noting that the manufacturer of the transmitter, Honeywell Aerospace, had produced 6,000 of the transmitters for a wide range of aircraft since 2005, including some Airbus planes, without similar incidents. Honeywell and other manufacturers also make similar devices for thousands of other commercial and business jets.
Industry officials said it might be easier for airlines to temporarily remove the transmitters than to extract the batteries.
Honeywell said that the British recommendations to reduce the risk posed by the devices was “prudent” and that it would help Boeing and the airlines as needed. It also said in a statement that it did not anticipate any material impact on its finances.
But Honeywell also said that with the investigation still under way, it remained “premature to jump to conclusions” about the cause of the fire.
The report indicated that the plane had landed at Heathrow 10 hours before the fire. After the passengers departed, the plane was towed to a remote parking spot and connected to a ground power station. The power source was turned off shortly afterward.
The fire was detected by an employee in the air traffic tower, who noticed smoke coming from the plane. The report said firefighters encountered thick smoke when they entered the middle of the plane, and it became more dense as they moved toward the rear.
Investigators said a hand-held extinguisher did not stop the fire, and the firefighters had to knock down a ceiling panel to get to an upper compartment where the transmitter hung from the inside of the plane’s crown. While the firefighters were then able to put out the blaze with water from hoses, the fire was intense enough that it damaged the plane’s carbon-composite structure in that area and caused the exterior paint to blister and peel.
The high-impact plastic composites are used in about half the structure of the 787 instead of aluminum or other metals. The composites are one of the novel features that helps reduce weight and increase fuel efficiency on the 787.
The plane also has new electric and battery systems, which prompted problems in the early stages of the 787’s service. Still, airlines, attracted by fuel savings of 20 percent, continue to place orders for the aircraft, and Boeing expects to sell thousands of the planes
The transmitter is powered by a small lithium-manganese dioxide battery, a type used in some electric cars and laptop computers. It is much smaller and less flammable than the lithium-cobalt batteries that caught fire or emitted smoke in other areas on two 787s in January.
Those battery problems led to a four-month grounding of the 787s around the world. British investigators have said those larger cobalt batteries were nowhere near where the fire occurred on the Ethiopian jet and played no role in it.
Article source: http://www.nytimes.com/2013/07/19/business/investigators-point-to-transmitter-battery-in-787-fire.html?partner=rss&emc=rss