Federal regulators are launching a major review of the safety of the Boeing 787 Dreamliner's electrical systems to be announced Friday at a news conference led by Secretary of Transportation Ray LaHood and new Federal Aviation Administration (FAA) chief Michael Huerta, according to two people with knowledge of the matter.

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Federal regulators are launching a major review of the safety of the Boeing 787 Dreamliner’s electrical systems, according to two people with knowledge of the matter.

The unusual and sweeping review, focused both on the systems’ design and on the manufacturing of their components, will be announced Friday by Secretary of Transportation Ray LaHood and new Federal Aviation Administration (FAA) chief Michael Huerta, the sources said.

Boeing will work with the FAA on the review, which will include scrutiny of its suppliers and their manufacturing processes.

The move comes after a battery fire Monday aboard a parked Dreamliner in Boston, a serious event that came after smaller incidents over six months involving faults in the jet’s electrical panels.

Boeing’s Dreamliners will continue to fly passengers while the broad review of the entire electrical-power system is conducted.

“Nothing suggests there is an imminent safety issue,” said one person familiar with the situation. “But pretty much all the recent incidents have involved the electrical systems, so it’s prudent to take a look.”

Boeing has so far delivered 50 Dreamliners.

The review of the jet’s electrical systems and power-distribution panels is a rare step by the regulatory agency, which more typically uses so-called “airworthiness directives” to mandate specific fixes to known safety problems.

Broader look

The FAA review will be separate but more extensive than the National Transportation Safety Board (NTSB) investigation of the fire at Logan International Airport, which broke out shortly after 183 Japan Airlines passengers and crew had disembarked at the end of a 12-hour flight from Tokyo.

The NTSB will try to determine the cause of that one incident. The FAA review will step back to take an in-depth look at the entire system architecture of the airplane.

The Dreamliner’s cutting-edge design incorporates many new technologies. Its critical systems rely more on electrical power than previous airliners, which typically use more hydraulic and pneumatic power.

In addition, Boeing handed off much of the design of the Dreamliner to its suppliers.

Rather than telling systems suppliers exactly what they needed to build, as it had on other planes, Boeing designed the 787’s top-level architecture and asked suppliers to design the details.

That will complicate the FAA’s review.

Boeing acknowledged this week that last year four Dreamliners — including a United flight from Houston to Newark, N.J., that had to land in New Orleans — suffered electrical faults traced to flawed circuit boards in one of the main power-distribution panels.

The panels were supplied by United Technologies, but a person familiar with the details said the circuit boards were produced by a subcontractor in Mexico.

Three of the four incidents were traced to a single batch of circuit boards, Mike Sinnett, Boeing vice president and 787 chief project engineer, said this week in an interview.

Boeing declined to comment on the FAA review. “While we take each issue seriously, nothing we’ve seen in service causes us to doubt the capabilities of the airplane,” said spokesman Marc Birtel.

Logan battery fire

The NTSB’s investigation into the Logan fire has found that multiple cells in the high-capacity, lithium-ion battery had heated during the fire, according to a person with inside knowledge of the preliminary findings.

That could have led to what’s called a “thermal runaway” — a chain reaction inside a battery whereby one faulty cell goes awry, gets hot, then heats adjacent cells, thus spreading and intensifying any fire.

However, the person said it appeared the liquid electrolytes in the battery had not ignited, suggesting the fire was less severe than it might have been.

Boeing’s Sinnett insisted this week that any such fire in flight could be contained inside the electronics bay, without endangering other critical electrical systems in the compartment.

The 787’s high-energy, lithium-ion batteries, not previously used on a commercial aircraft, prompted the FAA in 2007 to attach special safety conditions governing their use, design and maintenance.

The agency noted they differ significantly from the nickel-cadmium or lead-acid batteries used on other jets and that “lithium-ion batteries are significantly more susceptible to internal failures” and can generate high temperatures “resulting in a self-sustaining fire or explosion.”

Cessna incident

Sixteen months ago, the FAA ordered the urgent removal of lithium-ion batteries from the entire fleet of Cessna Citation 525C jets.

After a recommendation from Cessna, the FAA issued an emergency-airworthiness directive requiring that all 52 of the small-business jets have their lithium-ion batteries replaced within a week.

The FAA said its move was “prompted by a report of a battery fire that resulted after an energized ground power unit was connected to one of the affected airplanes equipped with a lithium-ion battery as the main aircraft battery.”

“We are issuing this (airworthiness directive) to prevent a potential battery fault that could lead to an aircraft fire,” the FAA added.

Asked Wednesday if Boeing might have to change out the Dreamliner batteries, Sinnett said, “We haven’t started looking at something like that.”

He said the lithium-ion battery was the “right choice,” delivering high-density power in a light, compact box.

“Knowing what I know now, I’d make the same choice,” Sinnett said.

However he also said that if Boeing were forced to find an alternative, his engineers would figure it out.

Dominic Gates: 206-464-2963 or dgates@seattletimes.com