Boeing is preparing to install a modified battery system for flight tests in a 787 in anticipation of the FAA approving its redesign plan, which the manufacturer hopes could come by March 6.

At the same time, the airframer is steeling itself for a lengthy test and qualification period, with regulators already emphasizing the need for extensive testing. Testing and certification of the battery fix now may mean the first 787 does not return to service until late April or May.

Although no firm details of Boeing’s revised battery system have emerged since it was proposed to the FAA on Feb. 22, the manufacturer confirms the plan is for a one-stop permanent solution, and not an interim step. “Our proposal includes multiple layers of protection covering the known potential probable causes of the events,” says Boeing.

While not ruling out further changes to the battery system, Boeing sources indicate these would be made for only economic, rather than safety, reasons. The proposed changes incorporate additional layers of safety to “fully address the safety issues that have been identified,” say company insiders.

According to FAA Administrator Michael Huerta, who gave new details on Boeing’s plan Feb. 27 during testimony to Congress, the proposal outlines three main safety layers. Building on the company’s original safety design philosophy outlined in January by 787 chief engineer Mike Sinnett, the revised configuration prevents individual cells within the battery from overheating. However, if overheating occurs, a second layer of protection in the form of additional space and insulation is being introduced to prevent a failed cell from damaging adjacent cells.

This would prevent the thermal runaway condition identified by the NTSB in the Jan. 7 Japan Airlines battery fire, which first flagged the safety issue.

A new containment and venting system also will be introduced to protect aircraft systems and structure from damage should the battery ignite. Boeing has designed and built initial hardware for flight testing, and by the end of the week will be approaching the 60th ground test run of the revised system.

Work has been conducted at various system and component laboratories around its flight test and development center complex at Boeing Field in Seattle.