When a test of a lithium-ion battery charger turned into an inferno at Securaplane Technologies Inc. in 2006, temperatures reached as high as 1,200 degrees and three waves of firefighters failed to save the building.
An employee of the Oro Valley company blasted the flaming battery with a fire extinguisher to no effect.
Two hours later, the galvanized metal roof collapsed, and the 10,000 square-foot building was a total loss.
It's a fire that federal safety regulators are taking another look at now, since Securaplane provides two key battery components to the Boeing 787 Dreamliner, the start-power and battery-charger units.
While spokespeople from Boeing and Securaplane have said that the 2006 fire is unrelated to the current investigation and the battery charger used in that test is different from what was eventually installed, some aspects of the fire are receiving scrutiny anew.
Golder Ranch records
Records from local Golder Ranch Fire Department, the first of three fire departments to respond to the blaze, describe "an uncontrolled thermal reaction (that) caused the battery to vent and this venting caused the ignition to various items and fixtures throughout the test lab area."
The electrical technician who was performing a test on the battery when it exploded likened the experience to being near a jet after-burner.
Electrolytes from inside the battery were shooting 10 feet into the air, the former Securaplane employee, Michael Leon, said in an interview Friday. "The magnitude of that energy is indescribable."
The fire stands as a graphic illustration of the power stored within energy-dense lithium-ion batteries and the potential consequences if something goes awry.
It also highlights the importance and delicacy of the quality-control measures applied to a novel - and potentially explosive - technology, a technology now allowed, under special conditions, to be used as the main and auxiliary power source of certain aircraft.
The Boeing 787 Dreamliner, the company's newest and most energy-efficient plane, uses two lithium-ion batteries. After two battery-related incidents in the past month, the 50 Dreamliners distributed so far have been grounded.
At least three safety inquiries are under way, and investigators are looking over their shoulder at the Tucson-area explosion that may illuminate the problems smoldering today.
"The fire is a significant event that the NTSB will want to look closely at," said former National Transportation Safety Board chairman Jim Hall.
"The introduction of these batteries is not an insignificant event," he said. "Something in the certification of this aircraft is going to need review."
At a news conference Thursday, NTSB Chairwoman Deborah Hersman said the board would review the Federal Aviation Administration's certification process as well as the supply chain for the batteries and battery components.
She underscored the breadth of the investigation and the importance of determining precisely what caused a fire aboard an empty 787 at a Boston airport Jan. 7.
Hersman said that a visit Tuesday to Securaplane revealed minor issues with the battery charger and start-power units the company supplies for the 787 but the significance was still unclear.
Investigators also traveled to Phoenix to download and examine the memory of the plane's auxiliary power unit controller, produced by Pratt & Whitney Engine Services, she said. The controller, however, was too damaged to provide usable data.
Hersman cited a laundry list of planned tests and unanswered questions and cautioned that investigators are not yet close to establishing the fire's cause.
Questions hover around why the redundant systems designed to prevent a meltdown through multiple independent controls and compartmentalization - the plan approved by the FAA - failed to prevent a fire.
Cause of fire unknown
Tucson fire investigators never did pinpoint the cause of the fire at Securaplane.
The three potential causes identified by Golder Ranch Fire Department were a battery malfunction, a malfunction or miscalibration of the test equipment and human error in the testing process.
The fire investigation dragged on for two years.
Boeing eventually determined that the test was improperly set up, but Leon continues to contest the company's diagnosis.
After the fire, Leon, who was let go by the company, filed a whistleblower complaint to the Federal Aviation Administration.
An administrative law judge found that he was fired for bad behavior rather than his FAA report.
Leon also filed a complaint with Occupational Safety & Health Administration and a series of lawsuits, but his cases have been repeatedly dismissed.
In November he was designated a "vexatious litigant" in Pima County Superior Court and barred from filing further claims.
Still, Leon's technical complaints are getting another look, including his suspicions that he may have been performing tests on a damaged battery when the explosion happened.
Damage a threat
Leon said he brought concerns about the battery to the attention of his supervisors two weeks before the fire.
The battery-monitoring unit that communicates with the battery-charging unit he was testing was not working properly, he said.
Leon also said he saw the battery dissembled by the team producing the start-power unit and he suspected it had been damaged during that team's testing, but supervisors balked at providing a new battery.
Damage to lithium-ion batteries is one of the biggest threats associated with them, battery experts say.
"If they are damaged in some way, there can be a low-level chain reaction that can go undetected and then hit a critical point and start a fire," said Kathleen Almand, executive director of the Fire Protection Research Foundation.
"They have all the ingredients in the battery to sustain the fire," which makes these fires very difficult to put out, she said. "What we're looking at is, When there is a fire, how do we control it?"
The foundation is currently working on a study of firefighting tactics in response to lithium-ion battery fires in vehicles.
Contact reporter Carli Brosseau at email@example.com or 573-4197. On Twitter: @carlibrosseau