Pilot Debrief

BELL 47D1 near Lake Ozark, MO — 2013-06-28

Final reportCEN13LA396
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Date
2013-06-28
Location
Lake Ozark, MO, USA
Aircraft
BELL 47D1
Registration
N78900
Category
Helicopter
Highest injury
None
Fatalities
0
Phase of flight
Cruise

Probable cause

The improper rebuild and maintenance of the helicopter and inadequate subsequent inspections, which resulted in undetected fuel contamination and a subsequent total loss of engine power during cruise flight.

NTSB narrative

The pilot stated that, during the preflight inspection, he observed no contamination in the fuel sumped from the helicopter. During the helicopter's second air tour flight of the day, it experienced a total loss of engine power during cruise flight. The pilot performed an autorotation to a field, which resulted in damage to the tailboom and main rotor blade. The helicopter had been in a previous accident and was subsequently rebuilt; it was sold to the operator about 6 months before the accident. During the rebuild, parts were sand and bead blasted. The pilot stated that, about 2 months before the accident, fuel samples from the helicopter showed contamination. He described the contaminated fuel as "discolored…from sitting." The operator drained and replaced the fuel, ran the engine on the ground, and performed numerous sumps until the fuel was "clean" and up to the operator's standards. The helicopter was then flown for about 12 hours before the accident flight occurred. During postaccident examinations, a substance consistent with silicon-glass blasting was found within the carburetor bowl, carburetor screen, and fuel sump. No other anomalies were found that would have precluded normal operation of the helicopter. It is likely that the fuel was contaminated by the blasting substance at the time of the rebuild and that the substance was not found during subsequent preflight inspections, which resulted in a total loss of engine power during cruise flight.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Properly inspect and maintain fuel system to prevent contamination.

NTSB coding

Evidence available

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

Docket documents18

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