All Nippon Airways returned to service the last of five grounded Boeing 787s on July 30, a little more than a week after Rolls-Royce discovered a defect in a batch of Trent 1000 engines installed in the airplanes. ANA had to ground nearly half of its 11 Dreamliners over the weekend of July 21 and 22 after the engine manufacturer found some “minor” corrosion within an external gearbox during product development testing.

“As part of our rigorous approach to product safety and quality, we have identified that a component on Trent 1000 engines on Boeing 787 Dreamliners has a reduced service life,” a Rolls-Royce spokesman told AIN. “As a proactive measure, this component is being replaced in a number of engines.” The remaining four 787s in service—all flying with Japan Airlines and unaffected by the problem—use General Electric GEnx turbofans and, hence, a different gearbox.

For its part, Boeing identified the affected part as crown gears within the Hamilton-Sundstrand-supplied gearbox that corroded as a result of a change to the manufacturing process. Boeing added that it will not deliver any airplanes with the affected parts.

The flawed gearboxes in question appeared in a batch installed in 17 engines, eight of which had gone to ANA. The other nine remained at Boeing's widebody plant in Everett, Washington.

“We don’t expect delivery timing to be affected,” a Boeing spokesman told AIN. “If there are any customers who may be affected within the year, we will work with them privately.”

During the company’s second-quarter earnings call last week, Boeing CEO Jim McNerney reiterated that the gearbox problem would not affect deliveries, although he did acknowledge that aft fuselage production in South Carolina remains a “hot spot.” He added, however, that the residual problems in Charleston would not become a “show stopper” in terms of Boeing’s plans to increase 787 production rates to five per month by the end of this year and 10 per month by the end of next year.

“The last few aft bodies have been delivered to final assembly in Everett and Charleston with significantly improved condition of assembly,” a Boeing South Carolina spokesman wrote in an e-mailed statement. “We're investing in additional tooling and equipment needed to ramp up to the 10-per-month rate to ensure we meet commitments to our customers. For example, in Aft Body we’re completing installation of a fourth Brotje drill and fill machine and have new tooling on order to support composite fabrication.”