CF34 Break-up Prompts Emergency AD

The FAA issued an emergency AD on Friday to all owners and operators of GE CF34-3A1, -3B and -3B1 turbofans after NTSB investigators found an electrical arc-out defect in the fan disk of the engine that broke apart on a Mesa Airlines Bombardier CRJ200 during a revenue flight on January 25. The AD requires a one-time visual and tactile inspection of parts of fan disks on 31 specific engines, identified by serial number, within 20 engine flight hours of its receipt. The engines in question power 50- and 44-seat Bombardier CRJs and Challenger 601/604 business jets. After examining pieces of the engine found within a square mile of rural Colorado, the NTSB determined that an electro-chemical etch marking applied during engine assembly to align the fan disk and shaft caused the defect.