Japanese aerospace union officials cast new light on problems with the Boeing 787’s power distribution panels Wednesday, saying one malfunction last year caused a burned circuit board and disclosing two other previously unpublicized incidents.
Power-panel faults, while unrelated to the battery problems that have grounded the 787 jet since mid-January, are another nagging issue with the plane’s innovative electrical system.
On flights in March, April and June of last year, faults in power-panel circuit boards on Dreamliners operated by Japanese carrier All Nippon Airways resulted in error messages in the cockpit, said airline spokeswoman Nao Gunji.
Each time, the panels were inspected after landing. In the case of the fault on an April 7 flight, a circuit board was found to have shorted, causing “slight discoloration” from burning, Gunji said.
All Nippon Airways replaced all three circuit boards, she said.
The Japan Federation of Aviation Workers’ Unions, which represents All Nippon Airways pilots, highlighted the incidents at a news conference in Tokyo Wednesday.
Shozo Tsue, the federation’s secretary-general, said the April 7 incident “was serious and caused damage to the surrounding area,” according to a Bloomberg News account.
Gunji said the purpose of the news conference was to ask the government “to ensure the safety of the aircraft” and take the time to find out what happened.
The union’s account reveals the April 7 incident as one of the four instances of power-panel short circuits cited in January by Boeing Vice President Mike Sinnett in an interview with The Seattle Times. Sinnett didn’t identify the airline at the time, and a company spokesman again declined to do so Wednesday, saying that’s up to the customer.
Sinnett, the 787’s chief project engineer, said that in each of the power-panel incidents electrical arcing inside a circuit board — “a low energy arc that lasted milliseconds, very small” — had damaged the board and shut down some of the plane’s electrical power.
He said the small spark inside the circuit boards produced no safety hazard, only a loss of function that was handled by the plane’s multiple, redundant power systems.
In January, Boeing had not yet found the root cause, but Sinnett said the problems had been traced to a batch of faulty circuit boards inside the power-distribution panels, which are located, like the batteries, inside an electronics bay.
Boeing spokesman Marc Birtel said Wednesday the investigation of the power-panel incidents is still ongoing.
Following the All Nippon Airways power-panel faults, on Dec. 4, another power-panel short circuit occurred on a United flight out of Houston, forcing the pilot to divert to New Orleans.
A few days later, a similar fault occurred on the delivery flight of a Qatar Airways 787 from Everett, Wash., to Doha.
And later in December, a second United jet was grounded after another power-panel malfunction.
Kazuo Harigai, assistant secretary of the Japanese union federation, told Bloomberg News that “there have been lots of problems with the (787) electrical system.”
Boeing’s Birtel said that because the 787 has more electrical systems than other airplanes, “it stands to reason” that component malfunctions encountered in service have been “mostly electrical in nature.”
“We’ve been working hard on improving component reliability on the 787 to improve its in-service performance,” Birtel added.
He also reiterated remarks by Sinnett in January — speaking immediately after the first 787 battery incident, the fire on a parked jet in Boston — that the 787 has in general proved as reliable in service as the 777.