All Nippon Airways (ANA) grounded five of its 11 Boeing 787 aircraft on 21 July, after being notified by Boeing that there may be a defect in the gearbox of the Rolls Royce Trent 1000 engine.
"We received a message from Boeing to the effect that there may be an issue with the gearbox on the engines of the 787s in ANA's fleet. No related problems have arisen on our 787s, however we have ascertained that the part at issue is fitted to five of our aircraft," says an ANA spokesman.
It is understood that the issue was first discovered on an engine gear box used for endurance testing on the ground. Some crown gears had shown corrosion, leading to damage to the gear box.
“Boeing is aware of the findings made by Rolls-Royce during engine testing that revealed corrosion in some crown gears within the gear box that had resulted from changes to a manufacturing process,” says a Boeing spokeswoman when contacted.
She adds that no aircraft will be delivered with affected parts.
The five affected aircraft, registration JA802A, JA806A, JA807A, JA808A, and JA810A, have that component. Both engines on two of the aircraft are affected, while the other three have one affected engine each.
The remaining six 787s in ANA's fleet are not affected. Two of the five affected aircraft were repaired and put back into service on 22 July, says ANA.
The remaining three aircraft however will take "another few weeks to fix" as parts have to be flown in, but the carrier is working with Rolls Royce to speed up the process, says the spokesman.
"Working with Boeing, we will replace the part in question and return our fleet to an operating state as quickly as possible," he adds.
The airline had to cancel two domestic services on 21 July due to the grounding, but is now operating all flights as usual using other aircraft.
Japan Airlines, which has four 787s in its fleet which runs on the General Electric's GEnx-1B engine. says its aircraft are unaffected.
"We do not have to ground our Dreamliners for engine inspections," says its spokeswoman.