The US Federal Aviation Administration (FAA) confirms the agency is close to finalising a comprehensive safety review of the Boeing 787's problematic electrical system.
The agency has completed the detailed technical work for what the FAA now calls the "critical systems review" of the 787. "At this time the report is being finalised," the agency says.
As the US National Transportation Safety Board (NTSB) continues its search for the root cause of the over-heating lithium ion batteries, the public release of the report by the FAA on the overall electrical system could provide new context about the incidents that caused the 787 grounding for four months earlier this year.
It is still unclear if the FAA will call for any design changes or operational restrictions on the 787 as a result of the report's findings.
"Boeing continues to work cooperatively with the FAA as the report on the 787 critical systems review is finalised," the company says. "Until the report has been published, it would be inappropriate for us to comment further."
The report was commissioned by then-Secretary of Transportation Ray LaHood on 11 January, coming in between the two battery incidents that prompted the FAA to order the 787 grounded for four months.
While the lithium-ion battery became the focus of safety probes by the FAA and NTSB, the review initiated by LaHood was designed to consider safety concerns affecting the 787's entire electrical architecture.
The 787 had experienced several electrical problems before the two battery malfunctions in January. In December, Qatar Airways and United Airlines grounded certain 787s due to a faulty batch of circuit boards. Indeed, one United 787 made a precautionary landing in Houston on 4 December after one of the aircraft's six electrical generators failed due to the circuit board problem.
The 787 is the first and still the only commercial airliner that uses electrical power to pressurise the passenger cabin rather than a pneumatic system driven by bleed-air from the engine's compressor stages.
Boeing decided to use more electrical power because of another design choice. By switching from aluminium to a thinner, stronger composite wing, the leading edge of the airfoil could not accommodate the pneumatic hardware. As a result, Boeing was forced to use an electrical power system for the cabin's environmental control system.
As a result, the 787 has the largest onboard electrical powerplant outside of military aviation, generating 1.5MW of total capacity.