NTSB Identification: ANC00IA083.
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Nonscheduled 14 CFR
Incident occurred Tuesday, July 04, 2000 in DEADHORSE, AK
Probable Cause Approval Date: 07/10/2001
Aircraft: Cessna 207A, registration: N73100
Injuries: 1 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 certificated airline transport reported that about 10 minutes after departure, while in cruise, level flight, he noted a light sheen of oil forming on the windshield, and he elected to return to his departure airport. He noted that by the time he was within two miles of the airport he was having difficulty seeing though the windshield due to a heavy accumulation of oil. He said that while on approach to the airport, the propeller rpm increased for about 20 seconds, followed by the propeller detaching from the engine. He said that he was able to glide the airplane to the runway, and land without further incident. A postincident investigation revealed that the engine had been rebuilt/zero-timed by Teledyne Continental Motors, 9.0 hours of operation, and 3 days before the incident. A Safety Board metallurgist examined the fractured crankshaft flange, and reported that his initial visual examination revealed that about one-half of the fracture was on a flat plane and contained crack arrest positions, features indicative of fatigue cracking. He added that the primary fatigue initiation appeared to be from a very large number of individual initiation sites in the center of the fatigue region.

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

An in-flight fracture of the engine crankshaft propeller flange. A factor associated with the accident was the manufacturer's inadequate quality control standards.

Full narrative available

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