Pilot Debrief

BELL 206 - B near Mammoth Lakes, CA — 2012-09-19

Final reportWPR12LA426
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Date
2012-09-19
Location
Mammoth Lakes, CA, USA
Aircraft
BELL 206 - B
Registration
N222GR
Category
Helicopter
Highest injury
None
Fatalities
0
Phase of flight
Climb

Probable cause

The pilot’s inability to maintain sufficient main rotor rpm while maneuvering in high density altitude conditions, which resulted in a precautionary landing and subsequent rollover.

NTSB narrative

While performing an aerial survey of transmission structures and wires in mountainous terrain at an elevation of about 7,500 feet mean sea level, the pilot initiated a climb to clear a ridge ahead. When he realized that there was no response to an increase in collective, and, with the torque nearing 100 percent, he chose to maneuver the helicopter left of a set of wires, avoid approaching terrain, and establish an approach for a precautionary landing to a dirt road. The pilot reported that, during the approach, he was unable to arrest the helicopter's descent, and, at the same time, he heard a noise that he assumed was the low rotor rpm warning. The helicopter subsequently impacted terrain just short of the road, rolled over on its left side, and was consumed by the postcrash fire. A postaccident examination of the airframe and engine revealed no mechanical anomalies that would have precluded normal operation. At the time of the accident, the nearest weather reporting facility, which was located 10.5 miles west of the accident site, reported wind at 4 knots, gusting to 14 knots, and a temperature of 24 degrees C. The calculated density altitude for the conditions was about 9,742 feet, which would have affected the helicopter's climb performance.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have considered density altitude in preflight planning.

NTSB coding

Evidence available

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

Docket documents15

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