Fasteners hold aircraft like the Boeing 787 together. But it looks like incorrectly installed fasteners will further delay the rollout of the aircraft dubbed the Dreamliner.

The 787’s latest problems came in October when Boeing announced it would have to rework up to 3% of the fasteners on the six aircraft at its Everett, Wash., site: A static-test plane, a fatigue-test plane, and four flight-test aircraft in final assembly. Some estimates indicate 3% amounts to thousands of fasteners per aircraft, although Boeing does not disclose fastener counts for competitive reasons.

According to company spokesperson Mary Hanson, Boeing engineers have identified and documented the affected fasteners and are planning to remove and replace each one. Some of Boeing’s major suppliers, which include Vought (Charleston, S.C.), Alenia (Foggia and Grottaglie, Italy), and Kawasaki (Nagoya, Japan), have found similar problems they must rework before shipping their sections of the aircraft to Everett. Boeing would not name suppliers with the problems.

The fasteners in question attach titanium parts to carbon-fiber composite panels or join two carbonfiber parts to each other. Hanson described them as “standard fasteners” routinely used to join composite, titanium, and aluminum parts. Workers insert the fastener’s pin through a predrilled, precountersunk hole, and clamp the joining parts with a nut tightened to a specific torque.

“There are a couple of issues we’re dealing with,” Hanson says. In some cases, drilling burrs keep fastener heads from lying flush against the aircraft skin. In other cases, fastener pins are either too long or too short.

All three defects could impact the structural integrity of the joint. Long pins may not clamp parts with sufficient force. Short pins could provide insufficient shear or pullout strength. And proud fastener heads, those that stick out above the aircraft skin, concentrate loads in the burr area instead of spreading them over the skin.

Hanson said rework would not involve redrilling fasteners holes. But, depending on where fasteners are located, workers may need to move aside already-installed insulation or wiring to complete repairs.

Boeing had instituted extra training in-house and at its partners aimed at preventing a repeat of the problem. In addition, problem specifications that Hanson said were “less clear than they could have been” have been clarified to prevent fastener installers and inspectors from misinterpreting them in the future.

Fasteners were also an issue in 2007, when a shortage in the specified fasteners led to the first supplier produced sections arriving in Everett held together with nonspec temporary fasteners.

Hanson could not immediately estimate the duration or man-hours required for rework. The fastener problem adds to delays announced in November at the end of a seven-week International Association of Machinists strike that idled aircraft production.

The plane’s first flight, originally scheduled for fall 2007, will not take off until sometime next year. And the first production unit may not be delivered until the year after.