AD NUMBER: 2006-04-12
MANUFACTURER: General Electric
SUBJECT: Airworthiness Directive 2006-04-12
SUMMARY: The FAA is superseding an existing airworthiness directive (AD) for General Electric Company (GE) CF34-3A1 and -3B1 series turbofan engines. That AD requires initial and repetitive visual inspections and eddy current inspections (ECIs) of certain stage 5 low-pressure turbine (LPT) disks and stage 6 LPT disks, installed in GE CF34-3A1 and -3B1 series turbofan engines. Those engines are installed in certain Bombardier Canadair Regional Jet (RJ) airplanes. This AD requires the same initial and repetitive visual inspections and ECIs, but adds SNs to the affected disk population for RJ airplanes. This AD also adds GE CF34-1 and -3 series turbofan engines with certain stage 5 and stage 6 LPT disks, to the applicability section. Those engines are installed in certain Bombardier Canadair Business Jet (BJ) airplanes. Also, this AD requires eventual replacement of the affected disks as terminating action to the repetitive inspections. This AD results from the discovery of an additional population of suspect stage 5 LPT disks and stage 6 LPT disks that could fail due to low-cycle fatigue cracking that may start at the site of an electrical arc-out on the disk. We are issuing 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.

FMI: www.faa.gov/regulations_policies/airworthiness_directives/