First delivery of the 787 will be delayed again to make software and minor hardware changes to the electrical system, but the length of the latest setback will be decided within a "few weeks", Boeing says.
The airframer needs to implement changes to the Hamilton Sundstrand-supplied software that manages and protects power distribution on the aircraft, as well as a minor hardware change to the P100 distribution panel to prevent foreign object debris (FOD) ingestion.
"We have successfully simulated key aspects of the on-board event in our laboratory and are moving forward with developing design fixes," says 787 vice president and general manager Scott Fancher
Boeing says foreign debris "most likely" caused the 9 November fire aboard ZA002 that halted 787 certification operations.
The company adds that "engineers have determined the fault began as either a short circuit or an electrical arc in the P100 power distribution panel", which sits against the left wall of the 787's aft electronic equipment bay and manages power generated by the aircraft's left engine.
Randy Tinseth, Boeing vice president of marketing, says: "Whatever this foreign debris was, it wasn't something big - such as a tool - it was probably something small. We're taking the right steps to ensure the power distribution panels are better protected against foreign debris."
As for the six grounded flight test aircraft, Boeing did not say whether or not the design changes would require implementation before resuming certification activities, saying only: "Boeing is developing a plan to enable a return to 787 flight test activities and will present it to the US Federal Aviation Administration (FAA) as soon as it is complete."
The company says it is now "assessing the time required to complete the design changes and software updates that are being developed".
The first 787 is currently slated for handover to Japan's All Nippon Airways in the middle of the first quarter 2011.