US aviation regulator Federal Aviation Administration (FAA) has approved Boeing's design for modifications to the 787 Dreamliners battery system, a development enabling 787s to return to service upon installation of the improvements.
Designed to address risks at the battery cell level, the battery level and the aircraft level, the changes were approved by the FAA following an extensive review of certification tests.
The redesigned battery system includes improved insulation of the cells, a redesign of the internal battery components to lower initiation of a short circuit within the battery and a new containment and venting system.
Certification tests were designed to validate that individual components of the battery, its integration with the charging system and a new enclosure function as expected during normal operation and failure conditions.
FAA supervised the testing, which was conducted over a month-long period beginning in early March.
FAA stated that next week the agency will issue instructions to operators for making changes to aircraft and will publish in the Federal Register the final directive to allow the 787 to resume commercial flights with battery system modifications.
All airlines that operate the 787s should install containment and venting systems for the main and auxiliary system batteries, and replace the batteries and chargers with modified components, according to the FAA.
US transportation secretary Ray LaHood said safety of the travelling public was the main priority.
"These changes to the 787 battery will ensure the safety of the aircraft and its passengers," LaHood said.
FAA administrator Michael Huerta said: "A team of FAA certification specialists observed rigorous tests we required Boeing to perform and devoted weeks to reviewing detailed analysis of the design changes to reach this decision."
FAA will closely monitor modifications of the aircraft in the US fleet in order to assure proper installation of the new design and will stage teams of inspectors at the modification locations.
The agency noted that any return to service of the modified 787 will only take place after FAA accepts the work.
In addition, FAA will continue to support other authorities worldwide as they finalise their own acceptance procedures.
In mid-January, FAA grounded all 50 787s in-service worldwide following a battery fire on a 787 that landed in Boston's Logan International Airport and another case of an overheated battery, which prompted Japan's All Nippon Airways' jetliner to make an emergency landing.
In addition to battery problems, the 787 has been plagued by several other safety incidents this year, including a crack in the window of a cockpit, an oil leak from a generator inside an engine, a brake problem and fuel spillage, which led to a comprehensive review order by FAA.
Image: The changes to the battery system were approved by the FAA following an extensive review of certification tests. Photo: courtesy of Boeing.