Crash of a Noorduyn Norseman IV in Akiachak
Date & Time:
Jul 11, 2009 at 1300 LT
Operator:
Registration:
N225BL
Survivors:
Yes
Schedule:
Bethel – Tuluksak
MSN:
542
YOM:
1944
Crew on board:
1
Crew fatalities:
Pax on board:
1
Pax fatalities:
Other fatalities:
Total fatalities:
0
Captain / Total hours on type:
100.00
Aircraft flight hours:
15729
Circumstances:
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.
Probable cause:
The loss of engine power due to the failure of a crankshaft component, resulting in an off airport landing.
Final Report:
