In a letter to the Federal Aviation Administration on Thursday, the NTSB criticized the process used by that agency to certify the new jet in 2007. It also recommended that the FAA look outside the aviation industry for technical advice.
The 12-page letter directly conflicts with the FAA’s own internal study released in March, which said the agency had “effective processes in place to identify and correct issues that emerged before and after certification.”
The 787 — also known as the Dreamliner — is the first commercial jet to rely on rechargeable lithium-ion batteries to power key systems. The batteries are lighter, letting airlines save fuel. However, a January 2013 fire aboard a 787 parked at a gate in Boston broke out when one of a battery cell experienced an uncontrollable increase in temperature and pressure, known as a thermal runaway. Nobody was injured, but that fire — and a subsequent smoke condition on a separate plane nine days later — led to a worldwide grounding of the Dreamliner fleet for 100 days.
During the grounding, Boeing redesigned the system. Modifications included more protection around battery cells to contain overheating, a steel case to prevent fire from spreading and a tube that vents fumes outside the fuselage.
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.
Boeing’s primary competitor, Airbus, based in Toulouse, France, is evaluating the NTSB recommendations, Mary Anne Greczyn, a spokeswoman, said in an email.
In its report Thursday, the safety board says the problems go back to September 2004, when Boeing first told aviation regulators of its plans to use lithium-ion batteries on the 787. The FAA was forced to create the first-ever requirements for use of lithium-ion batteries on commercial jets.
One of the nine requirements the FAA came up with was that the “design of the lithium-ion batteries must preclude the occurrence of self-sustaining, uncontrolled increases in temperature or pressure.” In other words, no thermal runaways.
When Boeing and the FAA worked together to set up certification tests in March 2006, they considered the smoke a battery fire might cause but, according to the safety board’s report, “Boeing underestimated the more serious effects of an internal short circuit.” In January 2007, the FAA approved the testing plan proposed by Boeing. It did not include testing for such short circuits.
To avoid such oversights again, the NTSB suggests, the FAA needs to look outside the aviation industry for expertise when approving a new technology. For instance, the Department of Energy has done extensive testing on lithium-ion batteries. If the FAA had reached out to the Energy Department or other experts, the report says, the FAA could have recognized that its tests “were insufficient to appropriately evaluate the risks” of a battery short circuit.
The safety board recommends that the FAA review its lithium-ion battery testing process. Also, any certification of new technology should involve “independent and neutral experts outside of the FAA and an aircraft manufacturer.”
After the FAA approved the 787’s battery, it adopted an improved testing regime devised by an advisory committee in 2008. NTSB 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 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 airframe instead of aluminum and used more electricity than earlier models to produce efficiency gains.
There are now 140 Dreamliners operating around the world. Another 891 have been ordered by airlines.
The FAA has 90 days to respond, but the NTSB’s recommendations are not binding. The safety board makes suggestions for improvements without the regulatory power to implement them.
The NTSB hasn’t concluded what caused the 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 Dreamliner on Jan. 16, 2013.
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