An Air India Boeing 787-8 is grounded through at least 23 August while GE Aviation inspects a potential fault in the accessory gearbox of both GEnx-1B engines installed on the aircraft, the engine maker says.

GE employees plan to complete the inspection and make replace the gearboxes, if necessary, by 23 August, clearing the aircraft to return to flight status, says a GE spokesman.

The same problem potentially affects a population of eight GEnx-1Bs and GEnx-2Bs with accessory gearboxes made by Avio, which is now a GE subsidiary.

GE recently discovered that eight accessory gearboxes could have been made using an improper heat-treating process during production.

The discovery was made after an accessory gearbox failed on a 5 August flight by a Thomson Airways 787-8, the GE spokesman says. The flightcrew commanded an engine shutdown and made an emergency landing.

The Air India 787-8 is the only such aircraft in service that is equipped with both engines that are among the population of eight with the potential heat treatment problem, the spokesman says.

GE plans to complete inspections and make any necessary replacements within a few days, the spokesman adds.

[UPDATE: Adds the GEnx-2B to the pool of affected engines and clarifies that GE has not determined that all eight gearboxes were made improperly.]