Pilot Debrief

DEHAVILLAND BEAVER DHC 2 near Thorne Bay, AK — 2013-07-24

Final reportANC13LA068
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Date
2013-07-24
Location
Thorne Bay, AK, USA
Aircraft
DEHAVILLAND BEAVER DHC 2
Registration
N4787C
Category
Airplane
Highest injury
Serious
Fatalities
0
Phase of flight
Cruise

Probable cause

The failure of the No. 1 linkrod bushing or the bottom portion of the linkrod, which resulted in a total loss of engine power.

NTSB narrative

The pilot reported that, while the float-equipped airplane was in cruise flight about 1,200 ft above ground level, the engine made a loud noise and lost partial power, so he maneuvered the airplane to land on a nearby lake. During the approach, the engine lost total power, and the airplane descended into an area of trees before reaching the lake, which resulted in substantial damage to the wings, fuselage, and empennage. The operator reported that the engine had been overhauled (zero-timed) 31 hours before the accident. A postaccident engine examination revealed metal fragments and heavy gouging damage to the rotating components within the crankcase. The bottom portion (crankshaft end) of the No. 1 linkrod and its respective bushing were missing from the No. 1 linkpin; the oil sump contained metal debris consistent with heavily damaged remnants of these (and other) components. The No. 2 cylinder barrel and linkrod and the No. 3 linkrod showed deformation to the left (in the direction of engine rotation). Based on the damage observed in the engine, it is likely that the event that initiated the engine failure involved either the the No. 1 linkrod bushing or the bottom portion of the No. 1 linkrod; however, the extensive damage to these components precluded determination of the failure mode.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have performed an emergency landing sooner after first engine issue.

NTSB coding

Evidence available

  • Photos
  • 7 docket documents
View NTSB final reportView NTSB docket

Docket documents7

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