Pilot Debrief

BEECH 35 B33 near Urbana, IN — 2013-09-24

Final reportCEN13LA557
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Date
2013-09-24
Location
Urbana, IN, USA
Aircraft
BEECH 35 B33
Registration
N8910M
Category
Airplane
Highest injury
Serious
Fatalities
0
Phase of flight
Cruise

Probable cause

The failure of the crankshaft following several overheating events that had led to a stress crack and the subsequent fracture forward of the No. 6 rod journal.

NTSB narrative

The pilot reported that, while in cruise flight, he noticed a change in the engine sound and a 100-rpm increase on the tachometer. He adjusted the propeller control to lower the rpm, but the rpm immediately increased to over 3,500, which is above the red line. The pilot reduced the propeller and throttle controls, but the propeller continued to overspeed. The propeller then separated from the airplane, and engine oil covered the windscreen. The pilot subsequently made a forced landing to a soft bean field, which resulted in substantial damage to the fuselage, wings, and engine mounts. A postaccident examination of the engine revealed that the crankshaft was fractured forward of the No. 6 rod journal across the oil transfer collar area and that the No. 6 rod had separated from the crankshaft. An examination of the fracture revealed evidence of several overheating events at the surface of the crankshaft next to the oil transfer collar hole. A crack had formed adjacent to the overheated surface, and the surface crack led to a stress crack, which formed the surface of the main separation fracture.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have conducted a precautionary landing before engine failure.

NTSB coding

Evidence available

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

Docket documents6

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