NTSB Identification: ANC09LA065
Nonscheduled 14 CFR Part 135: Air Taxi & Commuter
Accident occurred Saturday, July 11, 2009 in Akiachak, AK
Probable Cause Approval Date: 05/11/2010
Aircraft: NOORDUYN UC-64A, registration: N225BL
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The airline transport pilot was on a Title 14, CFR Part 135 passenger flight. The pilot said during cruise flight he heard a loud bang, and the engine started running rough. He said he diverted to the nearest airport, but the engine quit completely, and he was unable to reach the runway. The airplane subsequently collided with terrain, sustaining substantial damage to both wings and the fuselage. An examination of the engine revealed that a locking screw had backed out of one of the anti-vibration counterweights on the crankshaft, scoring the interior back surface of the engine case. The unsecured counterweight then moved from its position in the crankshaft, and was likely struck by the engine's master rod, which shattered the weight, and liberated it from its normal location. The liberated counterweight was struck by internal moving parts, creating several component failures, and ultimately an engine seizure.

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

The loss of engine power due to the failure of a crankshaft component, resulting in an off-airport landing.

Full narrative available

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