As part of an interim measure prior to fleet-wide CF34-3 inspections mandate, the Federal Aviation Administration issued an Emergency Airworthiness Directive for General Electric CF34-3A1, -3B and B1 engines for potential fan disk on the Bombardier (BBD) CRJ200. The action was prompted by the investigation into the recent Mesa (MESA) uncontained fan disk failure over Colorado. An inspection of the Mesa engine as well as the recovered segments of the fan disk, found an electrical arc-out defect at the fracture origin site caused by a fault in the electro-chemical etch marking. If the procedure is performed incorrectly, an arc-out defect can occur. The investigation found etching in parts manufacturer was to blame for the incident on the . For Related News 
Inspection of the parts recovered from countryside southwest of Denver, indicated that the fan disk separation was caused by a crack which had developed in the bore of the disk itself. Close inspection of the pieces revealed this had been caused by an electrical arc-out defect which left a blemish on the inside of the bore. The arc-out was caused when the fan disk and shaft was being assembled and aligned using a now-abandoned procedure known as an electro-chemical etch marking (ECM). The process, which was originally used at GE’s CF34 assembly line in Lynn, Mass., was used by operators to mark the positions of the disk and shaft to ensure they were properly aligned. However it was discontinued in 2000 when GE became aware that defects had been caused by a particular operator using the ECM tool in an improper way which resulted in an arc being produced, causing the blemishes.
The AD covers the General Electric CF34-3A1/-3B/-3B1 turbofan engines. It also covers the CL-600-2B16 (CL-601-3R Variant), CL-600-2B16 (CL-604 Variant), and CL-600-2B19 (Regional Jet Series 100 and 440) model airplanes. 2007-04-51 General Electric Aircraft Engines: Docket No. 2007-NE-06-AD.