GE identifies Defective Fan Blades

General Electric will sell, at a heavy discount, CF34-3B1 engine fan blades to Bombardier CRJ operators affected by a service bulletin calling for replacements to be installed during a two-year period. The engine manufacturer identified about 13,000 fan blades from CF34-3B1 engines that power CRJ200 aircraft as being defective. Rough estimates show the blades are present on about 1,500 CF34-3B1 engines. The NTSB issued recommendations to the FAA, citing a safety concern raised by two engine failures on CF34-powered CRJ200s. In both instances a fan blade on a CF34-3B1 turbofan engine fractured, causing a loud bang, severe vibration and, in one case, an engine fire. Examination of the blades showed they failed because of a material defect introduced during the manufacturing process. GE said Teleflex Aerospace machined the titanium alloy blades in Mexico between late 2002 and late 2006 from billets containing a higher percentage of aluminum than was appropriate. "With a higher concentration of aluminum, there is a higher content of hard particles and this makes it more susceptible to cracks," GE said. A number of changes have occurred since the fan blade problem was identified including Teleflex building the fan blades to specification. Teleflex sold its Teleflex Aerospace Manufacturing Group unit to UK aerospace firm GKN in 2007. The NTSB issued six recommendations to the FAA, including that it require GE Aviation to define a reasonable maximum time frame below 4,717 cycles since new for these Teleflex fan blades and require that the blades be removed from service before that limit is exceeded. The NTSB also wants the agency to require GE to include additional testing in the manufacturing process for those blades, and to make modifications in its CF34-1/-3 engine design to ensure that high engine vibrations - such as can happen when a fan blade fractures - will not cause the engine to catch fire.