Pilot Debrief

BELLANCA 17-30A near Arden Hills, MN — 2020-12-03

Final reportCEN21LA073
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Date
2020-12-03
Location
Arden Hills, MN, USA
Aircraft
BELLANCA 17-30A
Registration
N28067
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Climb

Probable cause

Incorrect connecting rod installation, which resulted in the failure of the nos. 5 and 6 connecting rods and subsequent total loss of engine power.

NTSB narrative

The pilot reported that he heard a loud “bang” and the engine began to vibrate and ultimately lost complete power. He executed a forced landing to a highway during which the airplane struck a car and a highway divider which resulted in substantial damage to both wings. Postaccident engine examination revealed that the Nos. 5 and 6 connecting rods had failed. Further examination revealed two undamaged rod nuts within the oil pan that had no remnant of a rod bolt within the threaded portion of the nut. Additionally, a rod bolt, although damaged, was complete from bolt head to threaded shank and did not have a nut on the threaded portion. Review of maintenance records revealed that the Nos. 1, 4, and 6 cylinders had been removed and replaced due to low compression about 8 years and 396 hours before the accident, but it is not known if the connecting rods were removed at this same time. The most recent engine overhaul was completed 16 years before the accident, and it had accumulated about 1,296 hours time-in-service since the overhaul. Based on the available evidence, the loss of engine power was likely due to improper connecting rod installation that resulted in the loss of connecting rod bolt torque, separation of the rod bolt nuts, and subsequent failure of the Nos. 5 and 6 connecting rods.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Perform thorough engine inspection before flight after previous maintenance issues.

NTSB coding

Evidence available

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

Docket documents4

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