The U.S. Federal Aviation Adminstration (FAA) has adopted a new airworthiness directive (AD) for Boeing 787-8 and 787-9 airplanes powered by General Electric (GE) GEnx-1B engines. The issue requires reworking or replacing engines on a total of 176 aircraft in service with 29 airlines worldwide.

According to the Seattle Times, the action is the consequence of an incident on a Japan Airlines 787 on a flight from Vancouver to Tokyo in January. The FAA says that the incident involved a “significant fan rub event … apparently caused by partial fan ice shedding and a resulting fan imbalance that in turn caused substantial damage to the engine and an in-flight non-restartable power loss.” The event occurred in icing conditions at an altitude of 20,000 feet.

The AD applies only to the Performance Improvement Program (PIP) 2 version of the Genx-1B, featuring modifications designed to improve the engine’s specific fuel consumption (SFC). The AD requires revising the airplane flight manual (AFM) to provide the flight crew a revised fan ice removal procedure and a new associated mandatory flight crew briefing to reduce the likelihood of engine damage due to fan ice shedding.

The second engine on the Japan Airlines plane was an older, PIP1 version of the Genx-1B. According to the FAA, this engine suffered minor damage during the icing event and continued to operate normally. Clearly, an event of this kind on a 787 powered by two PIP2 engines could have catastrophic consequences. As the FAA concludes: “The potential for common cause failure of both engines in flight is an urgent safety issue”.