Tougher safety tests of lithium-ion batteries that were implemented after Boeing Co.’s 787 was approved remain inadequate to ensure that the power packs won’t overheat in flight, a U.S. investigation has concluded.
The Federal Aviation Administration’s approval of lithium batteries for other passenger models made by Boeing and Airbus Group NV may have been based on those same tests and should be reviewed, the National Transportation Safety Board said Thursday in recommendations to aviation regulators.
“Researchers have found that current test methods might not reliably produce failure” in the way that occurred last year when batteries on two Dreamliners began chain reactions producing fire-like heat and fumes, the NTSB said.
The safety board makes suggestions for improvements without the regulatory power to implement them. If its recommendations prompt the FAA to change how it approves lithium-ion batteries, manufacturers may need to retest systems that have been in service for years, and future designs may become more expensive.
The NTSB hasn’t concluded what caused a battery aboard a Japan Airlines Co. 787 on the ground in Boston to fail on Jan. 7, 2013. Japanese investigators also haven’t issued findings involving a battery on an ANA Holdings Inc. Dreamliner on Jan. 16, 2013.
After the second incident, the FAA ordered a halt to flights on Boeing’s newest aircraft model, in the longest grounding of a large commercial aircraft by U.S. regulators since jets were introduced in the 1950s.
Before returning the Dreamliner to the air, Boeing did rigorous tests that are “fully consistent” with NTSB’s recommendations, Doug Adler, a company spokesman, said in an email.
“We therefore remain confident in the safety and integrity of the comprehensive battery solution which was developed by Boeing, and approved by the FAA, last year,” Adler said.
Aircraft certification standards should evolve and the company supports NTSB’s effort to enhance testing, he said.
Other aircraft, including the Boeing 777, recent versions of the company’s 737s and the Airbus A380, have smaller lithium-ion batteries that were tested with the same flawed standards, the NTSB said in the letter.
The NTSB recommended that the FAA, which regulates the U.S. aviation industry, review how those other batteries were approved and require additional tests, if necessary.
“The NTSB concludes that the methods of compliance used to certify in-service lithium-ion batteries might not have adequately accounted for the hazards that could result from internal short circuiting,” the agency said in the letter.
Airbus, based in Toulouse, France, is evaluating the NTSB recommendations, Mary Anne Greczyn, a spokeswoman, said in an email.
Thursday’s NTSB letter also offers a glimpse into an investigation that has operated behind the scenes for the past year.
The NTSB, in a series of tests of lithium-battery packs that produced temperatures as high as 707 degrees Fahrenheit, hasn’t been able to fully replicate the failure that occurred in Boston, it said.
Variables such as temperature, the way a battery is installed and how it is used can alter how a battery fails in a test, investigators found.
The agency “is concerned about the reliability and repeatability of such tests,” the letter said.
After the FAA approved the 787’s battery, it adopted an improved testing regime devised by an advisory committee in 2008. NTSB’s tests show those protocols aren’t adequate to prevent battery failures, the letter said.
Tests on the 787 battery before the plane was approved for service were inadequate for the same reasons, the NTSB said. In November 2006, GS Yuasa Corp., the Kyoto, Japan-based manufacturer of the 787 batteries, determined that if one of eight cells shorted out and overheated, it wouldn’t cause adjacent cells to overheat uncontrollably.
That test, which served as a basis for approval of the plane’s safety, was flawed and didn’t show the type of failure that happened in Boston, the NTSB said.
The experience with the 787 shows the need for the FAA to get independent outside technical advice, the NTSB said. The agency should create panels of independent experts to review new technology, it said.
The Dreamliner is the only large commercial jet equipped with lithium-ion batteries as part of its power system. Those cells are part of an electrical system that’s the first to replace traditional hydraulic systems on a commercial plane.
The jet was the first built with a carbon-fiber air frame instead of aluminum and used more electricity than earlier models to produce efficiency gains.
GS Yuasa makes the batteries, which are part of an electrical power conversion system built by France’s Thales SA. United Technologies Corp.’s Aerospace Systems unit supplies the system, which uses 1.45 megawatts of electricity, enough to power 400 homes.
Boeing redesigned the battery during the 787’s grounding to include more protection around the cells to contain overheating, a steel case to prevent any fire from spreading and a tube that vents fumes outside the fuselage.
As Boeing has worked out software flaws that caused false error messages and other issues, the Dreamliner’s performance is approaching that of other wide-body aircraft. Dispatch reliability is about 98.5 percent, although short of the company’s goal of 99 percent, Ray Conner, chief executive officer of Boeing’s commercial aircraft unit, told investors in Seattle Wednesday.
Boeing has delivered more than 143 of the jets to 19 airlines as of May 19, according to its website. The global 787 fleet has performed 97,520 commercial flights, hauling 18.3 million passengers about 184.2 million revenue miles, a capacity measure.
Boeing has learned from the cascading design, supplier and manufacturing miscues that set the original 787 delivery in 2011 more than three years behind schedule. Flight testing on the first of two other planned Dreamliner models has proceeded smoothly, and the jet is on pace to be delivered by mid-year, Conner said.
The FAA concluded March 19 in a review of the 787’s certification and manufacture that the plane is safe. Boeing and the FAA exercised too little quality control over subcontractors during development, the report found.
Boeing and FAA said they had taken steps to follow the report’s recommendations.