The US Federal Aviation Administration has ordered immediate inspections of TRW (formerly Lucas Aerospace) full authority digital electronic control (FADEC) systems on Rolls-Royce AE3007A and C series engines after the discovery of failed transistors in some units that could cause in-flight dual engine shutdowns.

The airworthiness directive (AD) requires inspections of installed FADECs "before further flight to be sure that no more than one engine with suspect FADECs is installed on the same airplane, and eventual replacement of all of the suspect FADECs with serviceable units."

The AD was prompted by reports of uncommanded in-flight shut downs of engines powering Embraer ERJ-145s. The affected engines also power ERJ-135s, Cessna Citation X and Northrop Grumman RQ-4A Global Hawk unmanned aerial vehicles.

Rolls-Royce says affected production lots "have been defined and identified, and the failure mode established." It adds that most of the failures occurred in testing prior to delivery, but that some in-flight shutdowns subsequently occurred. Failures occurred because of a failed TR1 transistor in the FADEC, which limits incoming voltage into the unit. Investigations reveal that only engines equipped with FADECs built since March this year are affected, representing around 350 engine control units - or approximately 175 engines. The AD follows two Rolls-Royce service bulletins which instructed operators to swop FADECs around (each aircraft has four), to ensure that no two affected FADECs controlled a single engine, and a second bulletin instructing replacement of transistors from the suspect lot.

• All Rolls-Royce RB211-524D-powered 747 operators have been mandated by the FAA to inspect and repair cold stream nozzle assemblies on their engines after a large section of this part from an engine was lost in-flight.

Source: Flight International