Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that was issued for General Electric Company (GE) CF34- 3A1 and -3B1 series turbofan engines with certain part numbers (P/Ns) and serial numbers (SNs) of stage 5 low pressure turbine (LPT) disks and stage 6 LPT disks. These engines are installed in Bombardier Canadair CL600-2B19 Regional Jet (RJ) airplanes. This proposed AD would add SNs to the affected disk population for RJ airplanes. This proposed AD would also add GE CF34-1 and -3 series turbofan engines with certain P/Ns and SNs of stage 5 LPT disks and stage 6 LPT disks, to the applicability section. These engines are installed in Bombardier Canadair models CL-600-2A12 (CL-601), CL-600-2B16 (CL-601-3A), (CL-601- 3R), and (CL-604) Business Jet (BJ) airplanes. This proposed AD would require initial and repetitive visual and eddy current inspections (ECI) of the affected disk population. This proposed AD would also allow replacement of those disks as optional terminating action to the repetitive inspections. Also, this proposed AD would require eventual replacement of the affected disks as terminating action to the repetitive inspections. This proposed AD results from the discovery of additional suspect stage 5 LPT disks and stage 6 LPT disks. These disks could fail due to low-cycle fatigue cracking that may start at the site of an electrical arc-out on the disk. We are proposing this AD to prevent low-cycle-fatigue (LCF) failure of stage 5 LPT disks and stage 6 LPT disks, which could lead to uncontained engine failure.