NTSB Identification: CHI01IA047.
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Incident occurred Tuesday, December 12, 2000 in ST. CLOUD, MN
Probable Cause Approval Date: 09/06/2001
Aircraft: Cessna 172S, registration: N582SP
Injuries: 2 Uninjured.

NTSB investigators used data provided by various sources and may have traveled in support of this investigation to prepare this aircraft incident report.

The outer 14 inches of one of the propeller blades separated during takeoff at an altitude of 400 to 500 feet above the runway. The certified flight instructor was able to land the airplane on a parallel taxiway without incident. The propeller had 236 hours total time at the time of the incident. Metallurgical examination revealed that about 60 percent of the fracture surface contained features typical of fatigue cracking which emanated from the flat face of the blade arm, near the trailing edge. The examination also revealed the microstructure was normal with the exception that the grain flow pattern followed the surface of the scallop region and not the surface of the blade. Chromium present in the scalloped region of the fracture and not on the fatigued surface indicated that the chromic anodized solution penetrated the indication during the anodizing process prior to the blade being painted.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

the fatigue failure of the propeller blade during the initial takeoff climb. The failure was a result of a material defect, which occurred during the manufacturing process and the manufacturers failure to detect the defect.

Full narrative available

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