ANA grounds 5 of 11 Dreamliners

Boeing 787 launch customer ANA has been forced to ground almost half its Dreamliner fleet over an engine defect. (Boeing)

All Nippon Airways has been forced to ground five of its 11 Boeing 787 Dreamliners over an engine defect.

The 787 launch customer said the aircraft were grounded after Boeing discovered an issue with the gearbox of the 787’s Rolls-Royce Trent 1000 engine. ANA said the aircraft were grounded as a precaution but that none had been affected by the issue, which was discovered during Boeing’s ground-based endurance testing of the engine.

“A specific gear showed corrosion due to an issue in the surface treatment at the time of production, which led to damage to the gear box,” ANA said in a statement. “Certain 787 engines within the ANA fleet have gears produced using the same process, that may possibly lead to corrosion.

“Working with Boeing, we will replace the part in question and return our fleet to an operating state as quickly as possible,” the carrier added.

While the extent of the problem remains unclear, the discovery of the engine defect is hardly a welcome development for a program already running years behind schedule.