(AP) - Boeing unveiled its fix for its troublesome 787 battery on Friday and is aiming to wrap up testing within two weeks.
The company hopes to get quick approval from the United States (US) Federal Aviation Administration (FAA) and bring an end to the grounding of the plane that began on Jan 16. Company executives said the plane could be flying again within weeks, although aviation authorities in the US, Japan, and elsewhere will ultimately decide the timing.
Boeing still doesn't know the root cause of the fire on a parked 787 Dreamliner in Boston on Jan 7, or of the smoldering battery that forced an emergency landing in Japan on another 787 nine days later. Boeing executives said they may never know.
Instead, they're building a battery they hope cannot burn.
The battery's eight cells will each be wrapped in an orange tape that won't conduct electricity. A glass laminate sheet protects the cells from the aluminum case. The wires on top are getting extra heat-resisting insulation. And the whole works now goes inside a new sealed steel tub that looks like a kitchen trash can tipped on its side. If a cell overheats, a titanium hose will carry the gases to the outside of the plane through a new inch-and-a-half hole in the fuselage.
The changes make it "very unlikely" that another battery event will happen, said Mr Ron Hinderberger, Boeing's vice-president for 787-8 engineering.
Boeing hopes the new steel box won't just contain a battery fire, but will prevent one from starting at all by choking off the flow of oxygen and venting the battery gases and air inside the box outside of the plane.
The new design was tested before Boeing proposed it to the FAA. It will be retested so it can be certified for use on the plane, Mr Hinderberger said. That should be done within a week or two. After that, approval will be up to the FAA.
He said it would be inappropriate to speculate on how long that would take. Mr Hinderberger's assessment was more cautious than statements from other company officials, who suggested on Thursday that the 787 could be flying within weeks.
Each 787 has two of the lithium-ion batteries. The fix will add 68kg to the weight of each plane, Mr Hinderberger said. Weight is a key issue for the fuel efficiency of any plane, and Boeing has struggled to keep the 787 at the weight that it promised to customers.
Boeing rolled out the changes first in Japan on Friday morning, and then later in a conference call with Mr Hinderberger. All Nippon Airways has 17 Dreamliners - more than any other airline - among the world's fleet of 50. The emergency landing in Japan was an ANA 787, while the battery with the fire in Boston was a Japan Airlines plane. About one-third of each Dreamliner - including the batteries - are made in Japan.
Boeing officials said it's not uncommon for airplane fixes to be applied when the root cause isn't known. The fixes they plan for the 787 should prevent battery fires and runaway heat buildups regardless of the root cause, they said.
Boeing executives downplayed the parts of the incident that have most worried travellers. They said the only fire was on a connector on the outside of the battery box in the Japan Airlines plane, not in the battery itself. The white gas billowing out the side of the plane wasn't smoke, but electrolyte in gas form, they said.
"We have not ruled out a fire in the battery," NTSB spokesman Peter Knudson said after Boeing's comments. The NTSB is leading its own investigating of the Boston fire, and is participating in the investigation in Japan.
"We saw a lot of charring inside the battery. The evidence is consistent with very high temperatures," he said.
Boeing is also replacing the circuitry on the US-made battery charger. The changes will cap the battery's maximum charge, and will also stop draining power sooner, to prevent a so-called deep-discharge. The changes are designed to reduce the amount of energy in the battery, which should reduce its potential to generate heat, Boeing officials said.