Pilot Debrief

BELL 206L-3 near Abilene, TX — 2009-03-29

Final reportCEN09IA234
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Date
2009-03-29
Location
Abilene, TX, USA
Aircraft
BELL 206L-3
Registration
N708M
Category
Helicopter
Highest injury
None
Fatalities
0
Phase of flight
postflight

Probable cause

The formation and propagation of a fatigue crack in the trailing edge of the main rotor blade due to interconnected porosity and resultant corrosion. The area of interconnected porosity was due to a manufacturing defect which was not detected during the manufacturing process.

NTSB narrative

Following the post-flight inspection of a repositioning flight, the pilot noted a crack in the trailing edge of the rotor blade. He had characterized the previous flight as turbulent, but otherwise unremarkable and without any mechanical anomalies. An examination of the main rotor blade revealed a path of interconnected porosity between the lower trailing edge skin, trailing edge strip, and epoxy that allowed for the introduction of moisture and resultant corrosion. The failure was due to insufficient squeeze-out of the epoxy layer between the lower skin and the trailing edge strip during manufacture. The corrosion pit allowed the formation of a fatigue crack with a resultant crack along the blade surface.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Detecting the crack during preflight or maintenance could have prevented the issue.

NTSB coding

  • Unknown or undetermined · Unknown

Evidence available

  • 3 docket documents
View NTSB final reportView NTSB docket

Docket documents3

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