The manufacturer has notified the FAA that 2,176 crankshaft assemblies are subject to the unsafe condition. The FAA estimates that of those 2,176 crankshaft assemblies, 1,632 are installed on aircraft of U.S. registry. The FAA estimates that 544 engines will need to remove one cylinder, 544 engines will need to remove two cylinders, and 544 engines will need to remove three cylinders for compliance with this AD.
This AD was prompted by a report of a quality escape involving improper installation of counterweight retaining rings in the counterweight groove during manufacture. The FAA is issuing this AD to prevent departure of counterweight and retaining hardware from the crankshaft assembly. The unsafe condition, if not addressed, could result in loss of engine oil pressure, catastrophic engine damage, engine seizure, and consequent loss of the aircraft.
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