CF34 Break-Up Prompts AD

 - March 8, 2007, 4:30 AM

The FAA issued an emergency AD last month to all owners and operators of GE CF34-3A1, -3B and -3B1 turbofans after investigators found an electrical arc-out defect in the fan disk of the engine that broke apart during a Mesa Airlines revenue flight on January 25. Operating as America West Express, the Mesa Bombardier CRJ200 had flown 70 miles west-southwest of Denver and climbed through 24,000 feet when, at 4:50 MST, passengers heard a loud bang. The crew returned the fully loaded 50-seat jet to Denver on one engine and reported no injuries. The NTSB recovered parts of the CF34-3B1’s fan disk, fan blades, engine cowling, thrust reverser, engine spinner and pieces of the fan containment case. Materials specialists quickly identified the origin of the fracture and determined that an electrochemical etch marking applied during engine assembly to align the fan disk and shaft caused the defect. The AD requires a one-time visual and tactile inspection of parts of fan disks on 31 specific engines, identified by serial number. The engines in question power 50- and 44-seat Bombardier CRJs and Challenger 601/604s.