Just when Boeing really needs its engineers, they’re voting on whether to strike.

787 update

Japan’s Civil Aviation Bureau is sending investigators looking into problems with Boeing 787 batteries to Seattle, where the aircraft are assembled.

The Transport Ministry told the Associated Press on Friday that members of the team working on the investigation would leave Tokyo on Sunday for Seattle. It provided no further details.

Boeing’s Seattle-area plant is in Everett, Wash. Company spokesman Marc Birtel said he had no information about the aviation bureau’s planned visit Friday.

The 787 also is assembled in North Charleston. Boeing South Carolina spokeswoman Candy Eslinger said she had no information Friday night whether the investigators also plan to travel to North Charleston. She noted that the plant “has many different visitors at various times and we typically don’t release details on those visits.”

The U.S. Federal Aviation Administration and Boeing earlier dispatched investigators to join the probe in Japan.

All 50 Boeing 787s in use were grounded after a lithium-ion battery in a 787 flight by All Nippon Airways on Jan. 16 overheated, forcing an emergency landing. Earlier in January, a 787 operated by ANA’s rival Japan Airlines suffered a battery fire while parked at a Boston airport. Those planes were made in Seattle.

Investigators in both countries are trying to determine why the batteries have overheated and how to fix the problem.

Staff and wire reports

It’s bad timing for Boeing. The aircraft maker is working around the clock to solve battery problems that have grounded its 787s around the world, and unionized engineers are a big part of that effort.

The vote begins Tuesday and runs through Feb. 19. The union has recommended that its members reject Boeing’s contract proposal, hoping the company offers something better, or they may strike.

The strike threat is growing just as Boeing is dealing with a host of other problems. It must mollify airlines frustrated about buying a $200 million plane they can’t fly, and it needs to fix the battery problem.

Last month a battery on a parked 787 caught fire in Boston. Then on Jan. 16, another 787 had to make an emergency landing in Japan after another battery problem. All 50 787s that Boeing had delivered so far are grounded until the issue is solved.

Boeing has said that fixing the 787 is taking its full effort.

The effort includes hundreds of members of the Society of Professional Engineering Employees in Aerospace, the union’s executive director, Ray Goforth, said Wednesday. The union represents some 23,000 workers at Boeing.

Jim McNerney, Boeing Co.’s chairman and CEO, was asked on Wednesday whether a SPEEA strike would impact the investigation into the battery issues.

“I think we’re going to have enough experts available to keep looking at this issue if it goes that far,” McNerney said after the company reported financial results.

Goforth said the grounding “shifted a lot of leverage to us.” But workers wanted to keep things simple and not take advantage of Boeing’s situation, he said, so they dropped the improvements they had been seeking in favor of extending the contract.

Boeing’s counter-offer — the one the union will vote on — mostly does that. However, Boeing wants to drop traditional pensions for future hires, replacing them with 401k plans. Boeing also declined to make two changes that SPEEA wanted that it said would help preserve current retirement benefits. The union sees those as major give-backs that mean the offer should be rejected.

Boeing calls the proposed contract its “best and final offer.”

The engineers and technical workers in SPEEA work on plans for new planes, as well as solving problems that arise on the factory floor. When a hole gets drilled a millimeter off, or a part is a little too big or too small, a SPEEA member figures out the fix.

The union believes a strike would shut down Boeing production lines in Everett, Wash., where its big planes are made, as well as Renton, Wash., where it cranks out more than one of its widely-used 737s every day.

Goforth believes a strike would also shut down Boeing’s nonunion plant in North Charleston, which makes 787s in addition to those assembled in Everett. That’s because much of the engineering work on the South Carolina planes are done by SPEEA members in Washington, or who are flown in on assignment to South Carolina, he said.

Boeing isn’t saying whether it would keep the plants running through a strike, but it has contingency plans.