Thursday, March 06, 2008

NTSB concerned about defects in GE engines for regional jets

NTSB logoThe U.S. National Transportation Safety Board (NTSB) has issued recommendations to the Federal Aviation Administration (FAA) and Transport Canada regarding safety concerns arising from engine failures on two separate Bombardier Canadair Regional Jet CRJ-200 aircraft. According to an NTSB news release issued yesterday, the NTSB has concluded that "a flaw during the manufacturing process for fan blades led to the two engine failures, and the Board wants procedures set up to remove these blades before another incident occurs."

Regarding the incidents which prompted the current recommendations, the NTSB says:
In both instances - a July 27, 2006 engine failure on an Air Nostrum CRJ shortly after takeoff from Barcelona, Spain, and a May 24, 2007 engine failure on an Atlantic Southeast airlines CRJ while in cruise flight from Syracuse to Atlanta - a fan blade on a General Electric CF34-3B1 turbofan engine fractured, causing a loud bang, severe vibration and in one case an engine fire. Both flight crews declared emergencies and landed safely with no injuries.

Examination of the blades showed that they failed due to a material defect introduced during the manufacturing process. The fan blades were manufactured by Teleflex Aerospace Manufacturing Group, located in Mexico. Teleflex has manufactured more than 28,000 of these blades.

"We are issuing this recommendation because we consider the safety risk associated with this condition to be unacceptably high," NTSB Chairman Mark V. Rosenker said.
The ASA fan blade failed very early in its service life -- after only 4,717 cycles and 5,845 hours. Among its recommendations, the NTSB has asked the FAA to require the following of GE Aviation, the manufacturer of the engines:
  • 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
  • to include additional testing in the manufacturing process for those blades
  • 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
In its recommendations to Transport Canada, the NTSB requested that Bombardier, the manufacturer of the CRJ-200 aircraft, be required "to redesign the retention feature of the CRJ 100/-200 engine throttle gearbox to ensure that it can withstand the loads generated by a fan blade separation or similar event."

Here are links to the full-text versions of the NTSB's recommendations regarding GE engines for regional jets:

NTSB Safety Recommendations to the FAA, A-08-04 through -09 - March 5, 2008 (7-page 'pdf' file)

NTSB Safety Recommendation to Transport Canada, A-08-03 - March 5, 2008 (3-page 'pdf file)