NTSB Identification: NYC06IA143.
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Incident occurred Tuesday, June 06, 2006 in Lawrence, MA
Probable Cause Approval Date: 08/30/2007
Aircraft: Cessna 172S, registration: N2138W
Injuries: 2 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 commercial pilot was conducting a practice missed approach under instruction, when a propeller blade separated. The flight instructor took control of the airplane and shut down the engine to prevent further damage. He then made a Mayday call and glided the airplane to a successful runway landing. A postflight examination of the airplane revealed that the propeller blade was separated about 12 inches from the center of the hub. Metallurgical examination of the remaining fracture face revealed fatigue cracking that emanated from an indentation at the blade's leading edge. The fatigue crack propagated through approximately 50 percent of the fracture face, and beyond that, there was a band of overstress cracking. There was no evidence of corrosion, and a chemical analysis of the propeller blade revealed that the hardness and chemical composition of the blade met the requirements of the applicable engineering drawing. The flight instructor stated that during the airplane's preflight inspection, both he and the commercial pilot visually inspected the propeller blade, and ran their hands along the leading and trailing edges with no anomalies noted. The most recent maintenance inspection of the propeller occurred about 1 month before the incident.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: Foreign object damage to the leading edge of the propeller blade, which resulted in fatigue cracking and subsequent blade failure. Full narrative available
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