NTSB Identification: DFW05IA222.
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Incident occurred Friday, August 19, 2005 in Winnie, TX
Probable Cause Approval Date: 07/31/2006
Aircraft: Air Tractor AT-401, registration: N4545W
Injuries: 1 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
The 18,950-hour commercial pilot reported that that shortly after departure the "engine blew" and he executed a forced landing to a field, and the airplane received minor damage. Examination of the turbine engine revealed that it had experienced an uncontained separation of the second-stage turbine disk as a result of low cycle fatigue. No evidence of deep scratches or gouges were observed on the bore surface or on the forward and aft face of the disk. A review of maintenance records revealed that the engine had been previously installed on an aircraft that was registered in a foreign country, and the maintenance records were not complete. When the operator purchased this engine, he informed the facility that performed his engine maintenance that the second-stage turbine rotor was installed on the engine in 1992 with a total of 730 cycles. The maintenance facility then produced a new life-limit card for the second stage turbine disk. Based on this data, the disk had accrued a total of approximately 1,738 cycles at the time it failed. The rotor had an FAA approved life-limit of 5,400 cycles. However, according to the production records from the manufacturer of the engine, the second-stage turbine rotor had originally been shipped with zero hours and cycles in another, new production engine on January 24, 1973, making the part 33 years old.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The loss of engine power due to the failure of the second-stage turbine wheel as a result of low cycle fatigue. Full narrative available
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