NTSB Identification: ENG06IA001.
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Incident occurred Sunday, October 09, 2005 in Madison, WI
Probable Cause Approval Date: 02/28/2008
Aircraft: Cessna Citation 650, registration: N175DP
Injuries: 6 Uninjured.
NTSB investigators traveled in support of this investigation and used data obtained from various sources to prepare this aircraft incident report.
The airplane was in cruise flight when the pilots heard a bang and the left engine lost power. The flight crew made a precautionary landing without incident. An examination of the left engine revealed a hole in the bottom of the cowling, and the LPT 3rd stage blades were broken. Metallurgical examination of the broken blades identified one that had fatigue progressions. By part number, the broken blades had previously been identified as having high stresses that could lead to the separation of the blade through the airfoil section. The interstage transition duct was bulged out around the LPT 3rd stage and had an almost 180 degree split in the bulged out section at the bottom of the duct. The metallurgical examination of the case and its material revealed that it conformed to engineering drawing requirements and material specifications.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The inadequate design of the engine's interstage transition duct that yielded after the LPT stage 3 blades had separated and allowed the uncontained release of turbine debris. A contributing factor was the separation of a turbine blade.
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