Pilot Debrief

NOORDUYN UC-64A near Akiachak, AK — 2009-07-11

Final reportANC09LA065
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Date
2009-07-11
Location
Akiachak, AK, USA
Aircraft
NOORDUYN UC-64A
Registration
N225BL
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Climb

Probable cause

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

NTSB narrative

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.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have returned to Bethel instead of diverting to Akiachak.

NTSB coding

Evidence available

  • 2 docket documents
View NTSB final reportView NTSB docket

Docket documents2

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