Preproduction tests of batteries on Boeing Co. (BA)’s 787 Dreamliner didn’t start a fire during an intentional short-circuit, leading the company to conclude the risks of a blaze were remote, according to a U.S. report.
The National Transportation Safety Board, which released preliminary findings yesterday on a January battery fire, said it will hold an investigative hearing in April on the design and certification of the 787’s lithium-ion battery system.
“It really appears that inadequate testing was done or a failure to anticipate these failure modes,” Patrick Veillette, a pilot and former military accident investigator, said in an interview.
The NTSB report didn’t identify the underlying cause of a short-circuit that, according to safety board investigators, led to a battery fire aboard a Japan Airlines Co. 787 in Boston on Jan. 7.
Boeing’s new aircraft, built with light carbon-fiber materials instead of metal to be more efficient, has been grounded worldwide since Jan. 16 after a second lithium-ion battery failure. It was the first such commercial aircraft grounding since 1979.
The JAL Dreamliner battery caught fire on the ground after landing. An All Nippon Airways Co. (9202) 787 made an emergency landing in Japan nine days later after a battery emitted smoke and fumes.
The NTSB report is “a positive step in the progress toward completing the investigation of the Jan. 7 event in Boston,” Marc Birtel, a spokesman at Boeing’s commercial headquarters in Seattle, said in an e-mail. “The Boeing team has worked tirelessly in support of the NTSB to help develop an understanding of the event and will continue to do so.”
In addition to the investigative hearing, the NTSB plans to hold a forum on lithium-battery safety in April. Fires linked to lithium-based batteries have been involved in three cargo aircraft accidents since 2006.
The U.S. Federal Aviation Administration announced Jan. 11 it was reviewing the 787’s safety to ensure that nothing was overlooked during certification.
In addition to the 787’s carbon skin and frame, Boeing installed unprecedented new electrical systems to further reduce weight and enhance efficiency.
The FAA is preparing for a decision to let Boeing proceed with plans to harden the battery against overheating and fire, and eventually return the plane to service. Administrator Michael Huerta told reporters Feb. 28 that he expected his staff to present recommendations as early as this week.
Boeing presented the FAA with its proposed fix on Feb. 22 in a bid to get the plane airborne again. The agency hasn’t yet ruled on the Boeing recommendations.
Huerta said the Boeing proposal contains three layers: using sensors and circuitry to ensure that none of the eight individual cells within a battery overheats; preventing a failed cell from harming adjacent cells; and protecting the plane from damage if all the cells burn.
Huerta said Boeing’s proposal was “very comprehensive.” In addition to Huerta, Transportation Secretary Ray LaHood, who has said regulators must be “1,000 percent sure” the plane is safe, must also agree.
The first step, according to Huerta, will be a sign-off on Boeing’s plan to re-certify the plane. Commercial flights won’t resume until the batteries pass a series of tests in laboratories and in flight, he said.
The fixes are designed to deal with every possible type of battery failure, Huerta said.
In testing before the 787’s certification, Boeing concluded that the only way the lithium-ion battery could catch fire was if it were overcharged, according to the NTSB. As a result, the company designed multiple layers of circuitry into the charging system to prevent such a failure.
When Boeing engineers triggered a short-circuit in a battery cell by puncturing it with a nail, it didn’t catch fire, only emitting smoke, according to the NTSB.
The safety board didn’t explain why Boeing’s test didn’t produce the type of fire that occurred in Boston.
The nail test can’t always replicate the worst failures in an internal short-circuit, Dan Doughty, a consultant in Albuquerque, New Mexico, who formerly headed battery testing at Sandia National Laboratories, said in an interview.
The test is used because it’s easy and no widely accepted alternative exists, Doughty said. The understanding of how batteries fail has expanded since Boeing performed its tests in the late 2000s, he said.
As a result of Boeing’s initial tests, the company concluded that battery failures creating smoke would occur only about once in 10 million flight hours, the NTSB report said.
Prior to its grounding, the 787 had accumulated fewer than 52,000 hours in flight, according to NTSB. During that time it had two incidents with the batteries, including the fire in Boston.
The NTSB is also investigating separate safety tests conducted on the plane’s electrical system, according to the reports. Those tests often were done without the batteries connected or didn’t test all the battery functions, according to the NTSB.
The fire in an equipment bay in the JAL plane’s belly proved difficult to extinguish, according to the reports.
The smoke and flames didn’t stop when a mechanic used a dry chemical fire extinguisher on the battery, according to the report.
Airport firefighters then used a liquid called Halotron, which knocked down the fire. It later rekindled, according to the report. A fire captain told investigators that the battery continued emitting thick white smoke.
“The captain also reported that the battery was hissing loudly and that liquid was flowing down the sides of the battery case,” investigators said in the report.
The captain was burned on the neck when the battery exploded, the NTSB said in the report.
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