Airlines flying 168 Boeing 787s equipped with two of the same variant of the GE Aviation GEnx-1B engine must rework a fan seal by September or stop flying the aircraft.

The US Federal Aviation Administration will publish a new airworthiness directive on 22 April mandating the rework procedure for operators of 787s powered by two GEnx-1B engines with the performance improvement package (PIP) 2 configuration.

The directive was triggered by a report of an in-flight engine shutdown of a GEnx-1B PIP 2 engine after an ice build-up on the fan inlet suddenly shed. The impact with the ice caused the fan blades to jump forward slightly. The tips of the blades then rubbed against an abradable seal, creating flying shards that damaged the engine so extensively it could not be restarted.

The 787 involved in the incident happened to be powered by one GEnx-1B in the PIP 1 configuration and the other to the PIP 2 standard. The PIP 1 engine sustained damage by the same ice build-up on the inlet, but was able to maintain thrust, according to the FAA.

But the agency is concerned about the risk of dual-engine power loss on 787s equipped with two GEnx-1B PIP 2 engines, so is requiring operators to rework or replace the engines by September or ground the aircraft.

GE has identified a population of 168 787s powered with dual PIP 2 versions of the GEnx-1B, of which about 40 have already been modified. The FAA first issued a warning about the ice shedding problem in March, requiring 787 flight crews to adopt a new procedure if flying into known icing conditions.

The modification involves grinding away the abradable seal layer slightly in front of the blades by about one-tenth of an inch, GE says. The PIP 2 engines feature lower tip clearances between fan blades and the fan case in order to improve fuel efficiency caused by airflow leakage. But the modification is not expected to reduce fuel efficiency, GE says, because the seal layer is being reduced in front of the blade tips.

The FAA says in-flight shutdown incident remains under investigation and further mandates could be issued to address the ice-shedding problem.

Source: Cirium Dashboard