Boeing has grounded its 787 fleet temporarily because of a quality problem in the horizontal tails of the 787 Dreamliners built by Italian manufacturing partner Alenia.

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Boeing has temporarily grounded its 787 Dreamliner flight-test fleet while it checks for an assembly flaw in the horizontal tails built by Italian manufacturing partner Alenia.

Within the past week, engineers discovered a quality problem that could lead to cracking at the point where the horizontal tail attaches to the fuselage. Brackets that help hold the horizontal tail, also called a stabilizer, were improperly installed.

In a statement late Thursday, the company said it decided to inspect its five flight-test airplanes before they fly again to ensure any rework is completed as quickly as possible.

Inspections on each of the 23 planes already built are expected to take one to two days. If the inspection reveals a problem, the fix may take up to eight days’ work, Boeing said.

Boeing insisted the planes are not grounded, merely not flying until inspections are completed.

“We made a decision to be prudent and do the inspections before we flew them again,” said Dreamliner program spokeswoman Yvonne Leach.

In a written statement early Thursday, Leach said the “flight test airplanes will be inspected and reworked if necessary over the course of the next several weeks.”

Still, she said the problem won’t cause another delay in completing flight testing and first delivery of the new airplane, which has already been delayed by more than two and a half years.

“We expect that this issue will be addressed within the existing program schedule,” Leach said. “The 787 remains on track for first delivery to ANA by the end of this year.”

Until inspections are completed, Boeing won’t know precisely how many Dreamliners need to be fixed.

“Some have the issue and others do not. We are in the process of scoping the situation,” Leach said.

She said the problem is “regrettable but under control.”

Planes 2 and 3 were due to fly in the next few days. The other three are in ground tests or preparing for future tests.

Leach said the problem should not affect the plan to fly Dreamliner No. 3 to the Farnborough Air Show in England next month.

Focus on brackets

Alenia mechanics in Foggia, Italy, improperly installed brackets used to attach the horizontal tail to the fuselage, according to people familiar with the problem.

The error, discovered during final assembly in Everett, involved small pieces of composite material, called shims, that are used routinely to fill small gaps when assembling structural parts.

The Alenia mechanics also applied too much torque when tightening fasteners through the brackets, Boeing confirmed.

As a result, the shims at the horizontal-tail attachment became compressed and the material degraded. Potentially, this could create a small amount of give in the structural join that would increase localized stresses and could cause fractures that shorten the life of the tail attachment.

“Shims were improperly installed in a manner that could lead to lower-than-expected longevity for a joint within the horizontal stabilizer,” said Leach.

Leach said no actual cracks had been found and that the airplanes can be fixed without taking off the horizontal tail.

“It is not unusual for these issues to arise in the course of production programs,” she said.

When the issue was discovered, Boeing first decided to limit the operating parameters of the flight-test airplanes “to ensure continued safe operation,” she said.

Leach said such restrictions are not uncommon during flight-test programs. They are decided by Boeing and implemented in coordination with the Federal Aviation Administration (FAA), she said.

However, Boeing then decided to ground the flight-test airplanes until the initial inspections are complete “to better understand which airplanes will require rework and understand the sequence of that rework,” she said.

Leach said Boeing expects to maintain its steady march toward certification this fall.

Airplanes that are not part of flight testing and are parked on the flight line in Everett won’t necessarily have to be fixed until later.

After the 787 achieves certification by the FAA, those planes are already required to undergo various modifications due to other late design changes.

This is not the first issue with Alenia’s workmanship.

Exactly a year ago, Boeing issued a stop-work order to Alenia’s other 787 plant in Grottaglie, Italy, after Everett engineers discovered wrinkles in the 787 fuselage skins.

The wrinkles arose because the edges of the fuselage stiffening rods, called stringers, that Alenia had manufactured were way out of the specified thickness.

Big patch

Boeing had to patch 22 completed barrels and strengthened subsequent barrels with thicker skin plies to accommodate the out-of-spec stringers.

Bill Dugovich, spokesman for the white-collar union at Boeing, the Society of Professional Engineering Employees in Aerospace (SPEEA), said the tail problem is “yet another indication that Boeing’s far-flung supply chain is not working.”

Dominic Gates: 206-464-2963 or