Pilot Debrief

BELL 206 near Rolling Fork, MS — 2017-11-07

Final reportWPR18LA029
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Date
2017-11-07
Location
Rolling Fork, MS, USA
Aircraft
BELL 206
Registration
N93PH
Category
Helicopter
Highest injury
Minor
Fatalities
0
Phase of flight
Maneuvering

Probable cause

An uncommanded yaw and subsequent loss of main rotor rpm for reasons that could not be determined.

NTSB narrative

The pilot was conducting an aerial application flight. He reported that he was almost finished spraying a river when he suddenly felt the helicopter yaw right then left. Subsequently, he raised the helicopter’s nose up and right to clear a line of trees that ran parallel to the river. When the helicopter reached the height of the treetops, the pilot realized that the airspeed was slow, so he held the collective down to start an autorotation. He then pulled full collective just as the skid impacted the ground hard. The helicopter then came to rest on its right side. Examination of the helicopter revealed that flight control continuity was established. The tailboom was found fracture separated, consistent with main rotor blade contact. Both main rotor blades exhibited impact damage and warping due to slight spanwise deflection opposite direction of rotation but with low inertia. The 1st-stage compressor inlet and blades exhibited damage consistent with foreign object ingestion. Foreign object damage was also noted in the compressor, and the case was pierced in several areas. Black, sludge-like material that contained aluminum debris was found throughout the gas path from the compressor to the combustor and turbine inlet, and it was mostly along the inner surface of the outer combustion case, consistent with splatter during N1 rotation. The ingestion of material throughout the engine and foreign object damage to the compressor is consistent with engine operation during the impact sequence. The reason for the uncommanded yaw could not be determined based on the available information because postaccident examination of the airframe, engine and fuel system revealed no evidence of any mechanical malfunctions or failures that would have precluded normal operation.

Analysis

Primary failure mode
Loss of control
First missed decision gate
Pilot could have initiated a controlled descent earlier to avoid trees.

NTSB coding

Evidence available

  • 6 docket documents
View NTSB final reportView NTSB docket

Docket documents6

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