Pilot Debrief

BELL 206L-1 near Greensburg, IN — 2008-08-31

Final reportCHI08FA269
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Date
2008-08-31
Location
Greensburg, IN, USA
Aircraft
BELL 206L-1
Registration
N37AE
Category
Helicopter
Highest injury
Fatal
Fatalities
3
Phase of flight
Climb

Probable cause

The in-flight separation of a main rotor blade due to a fatigue failure of the blade spar, rendering the helicopter uncontrollable, and the manufacturer's production of main rotor blades with latent manufacturing defects, which precipitated the fatigue failure of the blade spar.

NTSB narrative

The emergency medical services crew had attended a local fundraising event and was returning to the helicopter/crew base when the accident occurred. Witnesses reported that the helicopter made a normal departure. They subsequently reported seeing components separate from the helicopter before it descended and impacted the ground. The helicopter came to rest in a corn field approximately 1.2 miles from the departure point. A postaccident examination of the helicopter revealed that an 8-foot section of one of the main rotor blades separated in-flight rendering the helicopter uncontrollable. Metallurgical examination determined that the blade failed as a result of fatigue cracking. The origin of the fatigue crack coincided with a large void between the blade spar and an internal lead weight. Further investigation determined that the presence of residual stresses in the spar from the manufacturing process, in combination with excessive voids between the spar and the lead weight, likely resulted in the fatigue failure of the blade. The manufacturer issued an alert service bulletin that identified main rotor blades that may have been affected by the combination of residual stresses and excessive voids between the spar and the lead weight. The service bulletin also called for supplemental inspections in order to maintain the continued airworthiness of the affected blades.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have aborted the flight after hearing low rumble and vibration.

NTSB coding

Evidence available

  • ADS-B / radar
  • Photos
  • 29 docket documents
View NTSB final reportView NTSB docket

Docket documents29

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